straight line of travel

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How far is it? - Distance Calculator

This tool enables you to calculate the straight line distance between two locations or two cities, "as the crow flies". As you can share your location, it will let you know easily how far you are in a straight line from any point of interest. Here are the steps to use it:

Enter the address or the city of the first location.
Enter the address or the city of the second location.
Click on the "Calculate the distance" button.

How far is it? The result of the geodesic distance calculation is immediately displayed, along with a map showing the two points linked by a straight line.

Geodesic distance calculator

Our formula integrates the curve of the earth to calculate as best as possible the distance as the crow flies. It is extremely accurate, especially for shorter distances.

Click on the button to use your geolocation instead of manually entering an address.

First location

Second location

Straight line missions

2.1 Choosing a location
2.2 Mapping a straight line
2.3 Choosing when to travel
3.1 Buying supplies
3.2 Stash points
4 The mission
5.1 Private property
5.2 Health concerns

Straight line missions are a form of travel in which the adventurer aims to cross an entire park, region, or country in a straight line, typically on foot. The goal of such travel is to introduce the adventurer to remote or offroad areas that are typically overlooked, but when done on scale it often requires extensive planning and preparation. Such a route necessitates leaving roads and paths and traveling directly through forests, hedges, and terrain obstacles.

History [ edit ]

YouTube adventurer and blogger Tom Davies made the first attempt to cross a country ( Wales ) in a straight line in 2019, triggering a wave of interest in the form of travel. After local travel restrictions during the COVID-19 Pandemic, particularly in Scotland , prevented further successful missions, the easing of restrictions led others to attempt straight line missions in the Cairngorms National Park and the Isle of Man .

Planning [ edit ]

Choosing a location [ edit ].

First you will need to decide where to attempt your straight line mission. For hikers and mountaineers, the most feasible challenge will be crossing a preserve or park. Doing so is the easiest way to avoid private property but may necessitate crossing difficult terrain.

Consider the length of the mission. As you will not be following a path and will not be turning to the left or right to avoid obstacles and terrain, you won't be able to go as far in a day as you would along a hiking trail. The British Isles' terrain features hedges and gorse bushes in rural areas, and these will slow your travel greatly. Don't expect to travel more than 10 miles (16 km) each day, and don't plan for a route that is more than 50 miles (80 km) (about five days of missioning) without somewhere you can deviate from the line to rest and recuperate. As a result, long but narrow countries such as Norway or Wales are the only ones realistic for country-crossing missions. For a first mission, you may want to consider a smaller region with public access to become used to the complicated maneuvering associated with missioning.

The ideal regions for such missions are uninhabited but not too-remote. While you will need to avoid homes and gardens (in some countries all private property), remote areas with no phone service create risks in the case of medical emergencies. In remote areas there may also be nature reserves, military areas and other off-limits places.

You may want to check your provider's cell phone service coverage for the area in question, and will definitely want to bring one, if not multiple devices with you on your journey.

Mapping a straight line [ edit ]

You will need a suitable mapping application (or equivalent maps) to plan your route. Google Earth, for instance, allows you to edit its satellite imagery by adding paths in order to measure distances and terrain. Although your line will of course include only a beginning and end point, with no curves or deviations, it will need extensive tweaking in order to be practically feasible. You will need to avoid private property, depending upon right to roam laws in your respective country, and any other off-limit areas. Some maps are better and more complete in the marking of areas to avoid than others.

If more than a day in travel time, the route will need to contain "stash points," such as campsites, staging points or roads where you can either stash food and water or arrange for someone to meet you at a specified time with necessities. As an added bonus, you may be able to find a short stretch of your route that follows a road or path, which will give you some respite between areas of more difficult terrain.

You will need to check the "terrain" or "altitude" feature of the maps or software you are using to ensure that there are no cliffs along your route. Even the best software has limited elevation detection qualities, though, so you will need potential trouble spots before traversing the route in order to ensure that there are no small (and therefore undetectable in satellite's macro view) banks following rivers or mountainsides. Forests, in particular, can be poorly judged by imaging software and can conceal steep embankments. Regular maps, often based on overlapping photos taken by aircraft at lower altitude, and sometimes manually edited, may make a better effort to be usable for ground navigation. For some countries, the photos are available on the net, even in 3D versions. Dense forests pose a problem also there.

Beside topography, you will need to ensure that your straight line does not cross other forms of dangerous untraversable, or exhausting terrain, such as some glaciers, some types of bogs and block fields. In some areas, these features are seasonal, and conditions on the ground will likely not match satellite imagery in this regard. A good terrain map may be better at showing seasonal features. People used to hiking through rough terrain in the region may be good at identifying probable challenges from hints on maps and photos.

Make sure there are no live rail lines or highways that you will need to cross on your route (unless your route goes through a proper railroad or road crossing, of course). These could be easily missed or overlooked as you obviously can't turn to the left or right to find a crossing. Crossing a live rail line is a serious criminal offense and is a must-avoid in any straight line mission.

When your straight line is mapped and is do-able, you will need to save and download the line and upload it to the mapping software on your GPS tracking device. Make sure your route is aligned entirely with the route you drew on your computer software or paper map and that the location reader on the GPS is precise.

Choosing when to travel [ edit ]

Cities and farms have elaborate drainage systems in place in order to prevent flooding and to make the ground composition suitable for development or agriculture. However, rural and off-road areas haven't seen this level of human intervention and therefore can be impassable during parts of a year if not year-round. Planning the time of year to travel will be essential to the success of a mission. Rural areas of the British Isles, for example, can become overgrown by gorse bushes and other thorny plants during the summer, making travel much more difficult if not impossible. On the other hand, seasonal flooding can turn solid ground during one part of the year into a flooded bog or swamp.

While winter is likely a better time to attempt a straight line mission in many temperate climates, be aware of temperature differences along the route, particularly due to elevation changes. Remote mountain valleys can become dangerously cold in winter, may be avalanche traps and often don't contain weather stations to monitor conditions, so you will need to bring spare clothes, considering that balance between warmth and the weight of your backpack.

Preparation [ edit ]

Make sure you're physically well and fit before you leave. Make sure you're able to cope with the conditions and climate of the place where you are traveling and that you're comfortable hiking with a heavy backpack.

Buying supplies [ edit ]

You will need a GPS tracking system and perhaps a satellite phone to attempt a straight line mission. Bring batteries from different battery packs that all fit your devices, as you will likely need to replace batteries on a multi-day mission. While it is convenient to bring one pack of batteries for the GPS, one pack of faulty batteries could leave your GPS tracking device powerless and prematurely end your expedition.

If you're planning to film the journey, in order to validate it, you will need to capture the entire route. The best tool for this is a highly portable and adaptable camera such as a GoPro camera. These can become glitchy in damp conditions, so you may want to bring a backup. That said, consider the weight of everything you bring in your backpack; make sure the total weight is do-able on tough mountain slopes and in hedges/bushes before you leave for the trip.

Food and water supplies are essential but may need to be stashed along the way (see below) depending upon the length of the journey. As with any backpacking mission, other essentials like toilet paper or essential medicines will need to be considered as well.

You will need some tough clothes, particularly in temperate areas which are likely to contain thick undergrowth, thistles, and thorny bushes such as gorse. A couple pairs of thick gloves will come in handy. In an area with potentially dangerously wildlife, you may want to bring some form of protection such as bear spray.

If your route crosses a river or lake which you can't cross on foot, that may be workable if you can bring – or even better, arrange for support crew to bring – a kayak to cross the body of water. If you're going alone, however, you will have to consider stash points and where you will dispose of the kayak once you've crossed the water body as it will be too heavy to carry for a distance. For still water, a raft made from your backpacks, walking sticks and a tarp may be an option, at least if the body of water is narrow enough that you can pass one at a time and use a line to get the raft back.

Stash points [ edit ]

If your expedition will take longer than a day, you will need to prepare stash points along your route. Ideally, you will have a support crew who will know your stash points and arrange to meet you there. Find some points where your straight line crosses a road or campsite (or adjust your line to include them per above) and allocate these as stash points with food, water, and a tent. Consider multiple locations for stopping each night, with different locations along the route depending upon how far you travel that day. An unforeseen bank, forest undergrowth, or patch of bushes could cause you to travel less distance than expected and force you to use your nearest stash point. Be flexible!

Stash points allow carrying less equipment, which certainly is nice in rough terrain. However, if you are used to carrying tent and other equipment and can manage carrying them also in the terrain ahead, then there is no need to have such arrangements for every night. However, food for more than a few days is heavy. You may also want to have a chance to get help if the terrain was worse than you anticipated or if you had an accident. If phone coverage is weak along your route, this may be a real safety issue.

The mission [ edit ]

Once your stash points are prepared and you're ready, you can begin the mission! Make sure you are familiar with how your GPS functions, such as whether it faces north or in the direction that you're traveling. You may need to program this in your settings in order to avoid deviations.

Terrain features will make it difficult if not impossible to stay "bang-on line" so deviations will likely be necessary; the goal is to make the deviations as small as possible. This is why it's so important to have both your current location and your planned route programmed precisely into your GPS software. On a multi-day expedition, deviations within 25 metres (82 ft) are ideal, but you may be forced to deviate up to 50 metres (160 ft). Deviations of 50 metres (160 ft) to 100 metres (330 ft) are the maximum you can realistically take before entirely compromising the point of the mission. Take your deviations from the route wisely and only when absolutely needed, as every deviation will subtract from your mission's Burdell Score, which takes into account even the smallest deviations from the route and calculates a percentage grade out of 100 based upon the accuracy of your route to the straight line. After the mission, you can upload your actual travel route from your GPS device to a score-calculating website such as the Straight Line Project to receive your score.

Precautions [ edit ]

Private property [ edit ].

One of the most important considerations for straight line travel is private property. Right to access in the Nordic countries makes straight line missioning in these countries much easier, but you will still need to take care to avoid traveling on a line that takes you into gardens or sensitive property areas such as farmers' fields. In areas without right to roam such as England and particularly the U.S., crossing private land without permission may go against civil or criminal law. Outside of right to access countries, you are best advised to stick to public access areas such as parks and public preserves.

Be careful about crossing fences, or hedges in the British Isles. Although barbed wire fences are crossable if you have gloves and you know what you're doing, there are two problems with this. First, by doing so you are likely entering private property where your access is restricted. Although trespassing is a civil rather than criminal issue in some countries, it's still likely to result in confrontation and ejection from their land, and not in a straight line! If there is no right to access in the country, a landowner or farmer will likely direct you to leave their property in a route that takes you off a straight line. Second, many fences are electrified and while probably not to an extent that would be fatal, being shocked or electrocuted by a fence is obviously not ideal. In summary, take great care to avoid private property without the express consent of the owner.

Take into account travel restrictions before traveling. As travel restrictions are typically enforced via checkpoints on highways, you will be bypassing those checkpoints on your expedition and could be inadvertently breaking the law. Likewise, make sure the country in which you are traveling is politically stable with robust rule of law and protections outside urban areas.

Health concerns [ edit ]

Don't attempt a straight line mission if you have an underlying health condition that could become a serious risk in areas where you cannot receive immediate help. A straight line mission may take you through areas that would be difficult for emergency crews to access. When planning and traveling on your route, be aware of the remoteness of the location and the accessibility of the site. On the other hand, be aware of potential routes to safety if you need to leave the route. Your GPS device and satellite phone are extremely important for such a scenario as well as being useful along the route.

Why Are Great Circles the Shortest Flight Path?

Why do you fly over Greenland in an airplane flight?

Or why is it that when you see flight paths on a map they always take a curved route between 2 cities?

It’s because planes travel along the shortest route in a 3-dimensional space.

This route is called a geodesic or great circle route . They are common in navigation, sailing, and aviation.

But geodesics can be confusing when you’re looking at a 2-dimensional map as they follow quite the odd flight path. Let’s dig into this concept a bit deeper.

Great Circle Routes Explained

In a flight path from New York to Madrid, if I asked you which line is shorter, you’d say the straight one, right?

However, a straight line in a 2-dimensional map is not the same as a straight line on a 3-dimensional globe .

This is why flight paths travel along an arc between an origin and a destination.

Now here’s what the same flight paths look like on a sphere. Remember that the straight line in the Mercator map above followed the 40° latitude line.

This paints quite a different story, doesn’t it? It’s deceiving to the human eye.

The takeaway is this:

A route that looks longer on the map is because of the distortion created by map projections like the Mercator Projection . In navigation, pilots often use great circles (geodesic) as the shortest distance flight.

Great circles vs small circles

Now that you have a visual understanding of great circles. Here’s a definition of what a great circle is:

A great circle is a circle on the globe such that the plane passing through the sphere’s center is equal to the circumference of the Earth.
Alternatively, a great circle is where the radius is equal to that of the globe representing the shortest distance between two points on the surface of the earth.

In basic terms, imagine you’re cutting into an orange. You can cut them at any angle – north-south, east-west, diagonally. As long as you cut two identical portions, then the circle where the cut was made is a great circle.

For example, the equator is a great circle because it’s the maximum possible circle:

You could also cut it at the north and south poles. This longitudinal line also cuts two equal portions. Any meridian line is a great circle as well.

From New York to Madrid, here’s how the plane creates two equal segments.

A great circle generates two arcs with the shorter one being the shortest path. Here is the shortest path and how the plane is angled to create the shortest path.

How about when you follow along the 40° latitude line? Anywhere that it doesn’t cut two equal pieces is a small circle .

While a rhumb line track is at a constant azimuth, a geodesic line changes direction all the time.

This fundamental difference in navigation concepts can have a significant impact on long-distance sea voyages.

READ MORE : Rhumb Lines: Setting it Straight with Loxodromes

How Geodesics Work

Planes travel along the shortest route in 3-dimensional space. This route is called a geodesic or great circle .

While map projections distort these routes confusing passengers, the great circle path is the shortest path between two far locations.

This is why pilots fly polar routes saving time and distance . And this is why pilots often fly over Greenland.

Have any questions? Please let us know in the comments section below.

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35 comments.

Buy a globe and figure it out.

I’m trying to figure out what flight path an LTA aircraft (Larger than Goodyear Blimp) would take from England to Idaho. It’s part of a novel I’m writing. Any suggestions?

You’re definitely on the right path and to use a great circle.

I am a layman. Please describe the route from Mumbai to New York and San Fransico to Tokyo through a diagram to show why airlines prefer polar routes?

A great circle connecting two points is the shortest distance but it requires frequent heading changes throughout the journey. A straight line (rhumb line) drawn on a Mercator projection map produces the constant compass bearing to follow for the same journey; which is easy to draw and much easier to follow. Over a short distance the difference between a great circle and a rhumb line route is negligible so the simple rhumb line route is used. However, over a very long journey the difference in distance will be quite significant so a great circle route is preferred.

In navigation latitude is the angle above (north) or below (south) of the equator. Longitude is the angle east or west of the prime meridian (ie the Greenwich Meridian). Both of these angular measurements are derived from the centre of the global earth mass. 0 degrees latitude, 0 degrees longitude is the intersection of the prime meridian and the equator (just south of Ghana West Africa).

When you try to draw a flat map to depict the surface of a globe there is a huge problem; imagine taking the peel off of an orange and trying to lay it out flat.

On the surface of global earth the horizontal distance measured between two meridians along the equator (0 degrees latitude) will be greater than the distance between the same two meridians measured along any other latitude because the circumference of each latitude gets smaller toward the poles so the meridians are closer together near the poles. However, the distance measured between two latitudes on the same longitude is the same distance on other longitudes because they will lie on a great circle.

For marine navigation the map solution generally accepted is the Mercator projection because of its unique property of representing any course of constant bearing as a straight segment that can easily be drawn on a flat map. Such a course, known as a rhumb line, is preferred in marine navigation because it is easier for a ship to sail in a constant compass direction to reach its destination even though it will be a bit further than a great circle route. For short distances the difference between the rhumb line and great circle route is negligible. For aviation the distance is more critical since it directly affects time, fuel and load. A simple solution is, where possible, create a sequence of short rhumb lines along the corresponding great circle route. In the modern era all of these positioning problems have been overcome by GPS satellite navigation.

These days we all take degrees latitude and degrees longitude for granted because they have been successfully used for over 2,000 years. Around that time there were early attempts to measure the circumference of the global earth. Early mariners setting off on long voyages either came ‘back’ or never returned; which for millenniums gave rise to the flat earth notion. The first circumnavigation of the earth was accomplished by the Magellan fleet sailing westward 500 years ago. I’ve personally used latitude and longitude to circumnavigate the earth 5 times.

I’ll finish with a reminder that latitude and longitude are both angular measurements derived from the centre of the global earth mass. If the earth were flat then for positioning on it there would be only one angle from the centre and a linear distance measurement from it… an idea that has never ever been tried and proven.

Taking all of the info from this page into consideration, how could it be used to strengthen flat earth theory? I was directed here because I wanted to learn what constitutes a “great circle” and I now understand. I seriously want to know how anyone could reach that conclusion.

High-altitude flying brings another problem to the fore. It is called “coffin corner” where if you fly slower you will stall, and if you fly faster you will also stall.

It actually makes sense if you go back to the comparison of cutting an orange. Again understanding how to navigate along a 3-dimensional globe while looking at a 2-dimensional picture is why it seems so confusing. And No Cari it doesn’t support the flat earth theory. Not even its own theory supports it. lol. The entire point of this is because of it’s a globe. If it were flat none of this would be necessary. Not to mention the Japanese would still be en route to Pearl Harbor if it were a flat earth. That’s an exaggeration but still, it would have been quite a long flight. One that those little planes would never have been capable of making. In fact, if the earth were flat many lives at Pearl Harbour as well as at both Hiroshima and Nagasaki would have been spared. It’s a shame that the earth is in fact round.

You have supported the theory of a flat earth. Thanks.

My wife just left Dallas for Tokyo. I looked on the flight plan and it goes up through Montana and Canada and over the edge of Alaska. I don’t see how this could be the shortest route to Tokyo from Dallas. It seems more like they are trying to avoid flying directly over the vastness of the Pacific Ocean in case there is a mechanical problem.

Having read all the above I’ve decided to go by boat.

Odd! I was told that because of centrifugal force, the Earth was compressed at the poles, thus making it wider at the equator. The great arc is a navigational compensation!

Meanwhile, the Egyptians, who started all this, still could not figure out the height of the pyramids even though they had Pythagoras. Not to mention that even today there is no certain way to measure the partial volume of a cylinder.

The Earth is flat and south polar centered. That’s it.

What about the direction of the route? Nobody can convince me that Madrid lies to the north of Newyork as they are saying now.

Maybe thats how they conclude it but its wrong, even if it works. the real reason is because of difference of rotational velocity of a shorter vs longer circumference. if you draw two lines from the center of a circle, each come out of the destinations. then draw two lines, one at altitude and the other at ground level. clearly the one at altitude is longer. it doesn’t matter if these lines are curved or not. what matters is the velocity the earth rotates at. the length of a circumference increases by 2 pi r. this means that at greater radius per starting location, the rotational velocity of a shorter radius vs a larger are varied. at a great altitude, though you are traveling at a perceived pace relative to the motor function, but you are multiplying that velocity by the increase in circumference relative to the ground’s. or vice versa, you can say the ground it traveling quicker as well since two point in the circumference have less distance to travel compared to the greater altitude. but what this really does is multiply the distance you travel at altitude relative to the ground. so one minute of flight at ground level vs one minute of flight at altitude results in greater distance. but its only if you fly against earth’s rotation. the earth is rotating at a constant speed, but the circumference between the greater height points travels at length over time just as the shorter one. but the shorter circumference then has less length to travel in that time, so its technically traveling slower. so as you increase height from the center of a circle, the increase in circumference, with earth’s rotation increase your velocity. if earth wasn’t rotating, then height wouldn’t matter and straight line would. 3 dimensions or 2… sure, you could look at it that way, but its over complicated…

Because the time it takes to fly to the higher altitude is not commensurate to the time lost by not climbing.

Let P = pressure, d = density, R = gas constant, T = temperature, h = height, g = gravitational acceleration.

By Ideal Gas Law PV = nRT -> d = n/V = P/RT

By the law of hydrostatic pressure

dP/dh = -d*g = P*g/RT

We know have a first-order separable differential equation. Solving this, we get:

Integral dP/P = Integral -g/RT dh log(P) – log(P0) = -g*h/RT -> P = P0*exp(-g*h/RT) d = P/RT = P0/RT*exp(-g*h/RT)

Therefore, as you go higher, the weight of the air column decreases reducing atmospheric pressure and density. However, the air also gets colder slightly increasing density. In the Stratosphere, temperatures increase with altitude instead of decrease. However, this layer of the atmosphere is above the troposphere where we live, so it has to be less dense. Thus, the weight of the hydrostatic pressure of the air column has a larger effect on atmospheric pressure and air density at least less than 10 km above sea level.

In the real world of long distance air navigation, great circle routes are *not* the shortest *flight* path, but they do make a good start on figuring out what will be the shortest flight path. The article fails to understand that aeroplanes travel in the air, which is moving, rather than fixed in relation to the earth. The origin and destination are fixed to the earth, if the sea and the air were likewise fixed, a great circle would yield the shortest path. A longer path with regard to the earth can yield flight path savings in the order of 30% to 50%, the classic example being North Atlantic flights in the forties, where savings of this order resulted from using Bellamy drift derived constant heading paths instead of great circle routing.

Aircraft need to travel the shortest route in the air, not in three dimensional space. Sometimes that will be the same thing, but not very often. For an air routing, you could use the barometric pressure at origin and destination plus the latitudes. Using these, you can calculate the drift for the entire flight due to pressure differences and Coriolis effect, the net geostophic winds. However, there may be jetstreams at less optimum altitudes that could provide considerable net improvement, even if more fuel is used per air mile (meaning movement through the body of air, not the 3D relationship with the earth), but lets not go there. Having derived a constant heading, it is flown, and neglecting political geography, with no concern for the position with respect to the position on earth below, other than the destination and not bumping into things.

To help with the lay understanding, imagine a rectangular table top, with a dot at each end. Over the top you have a much larger piece of perspex. You have a toy car which can travel at a speed equal to the distance between the dots over one hour. Over the course of an hour, the perspex moves half that distance to the left of the direct track, then half that distance to the right. If we attempt to stay on the “shortest” path from A to B, at the end of an hour, we will still be at A. If we calculate the net drift between A and B, which in this example means following a constant heading equal to the direct heading at the start of the journey, our path will be much longer than the direct path, a loop heading out to the left. However, after an hour, we will be at B. If we change the total distance moved by the perspex to half A-B, purely left and right, it will still take us one hour on the constant heading, but if we follow the direct path on the table top, we will get there, having taken considerably more than an hour to do so.

On shorter journeys in the real world, there are few wind reversals – there is also little difference between a rhumb line course and a great circle, so you may as well fly a rhumb line. Longer journeys are where this counts, and also where the great circle should be of use, but often is not, due to winds aloft.

The correct term is “Density altitude” which is a calculation of pressure altitude corrected for nonstandard temperature. As temperature and altitude increase, air density decreases. All aircraft have a flight “ceiling”, an altitude above which it cannot fly. As an airplane ascends, a point is eventually reached where there just isn’t enough air mass to generate enough lift to overcome the airplane’s weight. This is why (depending on the airplane) you might not be able to take-off from a high altitude airport on a particularly hot day. I have experienced this (pilot) myself several times.

If you depart from the North Pole with a plane along a meridian, directly from the rotation point (rotation axis) where speed is 0, to a destination at the equator where the rotation speed is around 1660 km / h , would the plane still reach its destination? From North Pole direct to Brazil(circular arc over meridian 60 W).

Thinner air does not give better engine performance. The reason flying high is more economical compared to flying at low altitude is because the TAS is higher due to density. Thus the amount of fuel burned per nm travel is lower.

You have such great figures. May I use one of them in a presentation to illustrate great circle routes?

Yes, you can. But please give credit by referencing to gisgeography.com

Chris, you are wrong. For air, D=PM/(RT), where D=mass density, P=pressure, M=molecular weight average, R=ideal gas constant, & T=absolute temperature. This is why you need to fill your tires with air in the winter. The temperature drop compresses the air, which means you have to add air to fill in the same amount of relative space.

There are many other atmospheric factors in play such as humidity, wind speed, and wind direction to consider as well.

…and yes, thinner colder air is better for fuel efficiency, but bad for lift. The higher you go, the harder it is to maintain altitude, so like everything else, there is a trade-off. Airplanes are designed to take advatange of the thickness of the air at a certain altitude. That altitude is not fixed relative to the ground, but depends on the weather. So on a hot day, they can fly higher. On a cold day, they.have to fly lower. But there is always an optimum “temperature altitude” for any given plane on any given day. You can’t just keep going up forever. You need pressure under the wings, or you’re flying a brick.

Airplanes need air pressure to fly, it doesn’t matter how dense the air is if there’s no pressure, and pressure and altitude have a consistent relationship. Does that make sense?

Actually, you’re all right, but you’ve each only got two-thirds of the puzzle. There is no direct relationship between temperature and density. There IS a relationship between PRESSURE and temperature and density.

In aviation, there is a concept called “termperature altitude.” So the actual relationship is between all three of them, but the focus is only on the two. The higher you go, the colder and thinner the air gets because the pressure is dropping. For every 1000 feet you go up, there is an expected drop in temperature and pressure, and this remains constant. So flying through colder air is like flying higher. The colder air makes the pressure go down while the density remains the same. The airplane acts as if the air is less dense. Got it?

I too, like Mr. Bir, noticed that there was something wrong with the explanation regarding the density of air. Yes, as air gets colder it gets denser, that’s why to start a cold gasoline engine you have to activate the ‘choke’ which in turn will supply the fuel-air mixture with an extra amount of fuel in order to compensate the leanness that otherwise would not start a combustion.

J Bir, unlike liquids the viscosity of gases inceases with increasing temperature. This can be explained using the kinetic theory of gases.

Mr Bir has it right on, as soon as I read it, I questioned it. But we appreciate your explanation of the great circle route. Good article.

Let me correct you. As the air gets colder, it gets denser, not thinner. However, as you increase in altitude, the air gets thinner and colder. Pilots will always want to fly higher as the low density of the air reduces drag and thus increases the efficiency of the fuel.

Every airline in the world has a business route. This route determines where the aircraft can and cannot fly. For example certain routes over the Atlantic are more costly to make but much faster, the final determination is down to the pilot, in regards to how much fuel he has on board, how delayed the aircraft is, in respect to flying faster than he normally would. This is a very significant thing when determining which transatlantic route to take, because there are at least a dozen of which only 3 of those routes are the fastest and most economical, the rest vary with flight cost. In respect to flying over Greenland, there was a very valid reason to do so especially during the winter and early spring months. As the air gets colder, it gets thinner, and the air thins it gets more and more difficult for an aircraft to stay in the sky. This meant under aviation rules, those aircraft with only 2 Jet Engines had to make the shortest distance between land masses, incase an engine stopped working. This way the pilot could make an emergency landing. Aircraft such as the 747 had no such problems, and could easily fly the quickest transatlantic routes. However over the decades Jet Engines have become increasingly reliable, so much so, that they too can now fly over the Arctic to whatever destination. There are very few airlines who actually use Arctic routes, because these routes are extremely expensive to use. An example of a flight from Helsinki (EHFK; HEL) to Barcelona (LEBL, BCN) does not use a Great Circle nor a Small circle, it uses a direct path from point A to B.

Small circles are not always used for short distances, infact they are seldom used in Europe. Instead most short distances are literally from A->B.

Why are small circles used in short distance trips and not the latter?

This Is the Longest Straight-Line Ocean Path Around the Earth

But don’t go hauling your boats out just yet

Julissa Trevino

In 1519, Ferdinand Magellan set sail on a greuling and dangerous quest: the first-ever voyage around the world. But since that first daring adventure, advances in sailing technology and navigation have made the trip much more common. Today, even families— children and all —have accomplished the lengthy venture.

But there is at least one ocean path that's likely never been traveled: the longest straight-line sailable path on Earth. This 19,940-mile trip runs from the Pakistan coast through the passage between Madagascar and Africa and around to northeastern Russia—and is the longest straight-line someone could (theoretically) sail without touching land.

As David Schultz reports for Science , this straight-line path has just been scientifically verified for the first time thanks to work by Rohan Chabukswar, a physicist at United Technologies Research Center Ireland, and Kushal Mukherjee, an engineer at IBM Research India in New Delhi.

The path was first mapped five years ago by Reddit user Patrick Anderson, who goes by the screenname kepleronlyknows. To create the map, Anderson used a set of coordinates that appeared in a Wikipedia entry titled “Extreme points of Earth.” This was supposedly the longest straight line on Earth that can be sailed without hitting land.

Interested in testing the route, Chabukswar and Mukherjee used data from the National Oceanic and Atmospheric Administration’s ETOPO1 Global Relief model of Earth, which can map features down to about a mile in size. As Schultz reports, this gave the scientists relative certainty that the points of the map were all within the ocean.

To calculate the possibilities, they first found the number of great circles on Earth. Great circles are the paths around a sphere whose distance is equal to the circumference of that sphere. Following one of these paths across the Earth is the shortest distance between two locations, but because our planet is circular, the path does not appear as a straight line on a 2-D map. They are used for many types of navigation, such as helping pilots find the shortest distance between two cities.

But there’s hundreds of millions of different possible great circles, each with tens of thousands of points to verify. In total, that would require examining more than 5 trillion possible points, Schultz writes . So instead, they turned to the “branch-and-bound” algorithm, a computer program that tests only a few possibilities of the longest path before tweaking the search again for the best possible line.

In just 10 minutes of using this program, the researchers had support that the Wikipedia entry and Anderson’s map were correct. They detail their work in a study that they uploaded to the preprint server arXiv .

As the scientists write in the paper, the original map sparked lots of debate about whether Anderson was right. It also led to some attempts at finding the longest distance on land without hitting a major body of water.

Chabukswar and Mukherjee also tested to find the longest drivable straight-line path. This time, it took the computer 45 minutes, but it found a 6,985-mile path that started in eastern China and ended in western Portugal.

Unfortunately, Gabart probably won’t be sailing the newly verified path anytime soon. In fact, the researchers don’t recommend that anyone sail or drive these paths since the algorithm analysis does not ensure safe conditions along these tracks.

As they write in their paper: “The problem was approached as a purely mathematical exercise.”

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Julissa Trevino | | READ MORE

Julissa Treviño is a writer and journalist based in Texas. She has written for Columbia Journalism Review, BBC Future, The Dallas Morning News, Racked, CityLab and Pacific Standard.

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Light Travels in Straight Line

An Introduction

Light is one form of energy that plays a vital role in our life. We cannot imagine a world full of darkness. Light makes our vision possible and enhances the beauty of everything around us. Light is playing an important role in both art and science. Light is one of the important tools in science that helps scientists to observe things around the world.

Some theories of science are saying it is particles and some of them are saying light is a wave . If the light is a wave, how does light travel and what is the medium of propagation? Light travels in a straight line. The straight-line path of light is very much evident when light travels through a dusty atmosphere. In this article, we will be discussing the straight line motion of light.

How does Light Travel?

Light can travel through both in a medium and in a vacuum . But in a vacuum, there will not be any particles light can not reflect by hitting it. Hence, in a vacuum, light is invisible. In air, light can be reflected by hitting dust or some other particles, hence light is visible in the air.

Light can be considered as waves. Light waves travel in different wavelengths and depending on the wavelength, different light has different colours. For example, the high wavelength light in visible light has a red colour and the shortest wavelength of light has a violet colour. Being a wave light can show properties of waves such as interference and diffraction .

The answer to the question of how light normally travels is that light travels in a straight line. But the actual answer is light seems to travel in a straight line because of the smaller diffraction effect of light. Diffraction is the bending of waves around an object such that it spreads out and illuminates an area where a shadow is expected.

For light, the wavelength is in the order of nanometers. This wavelength is too small and obstacles of this size cannot be determined by our naked eyes. Hence, we feel that light travels along a straight line. The straight-line motion of light is also called rectilinear propagation of light .

Experiment for the Straight Line Motion of Light

Since the diffraction effect of light is too small, normally light travels along a straight line. By using a simple experimental setup, we can prove that light travels along a straight line.

Place three cardboard sheets back to back in front of a candle on the tabletop. Make sure that the cardboard sheets and the candles are placed in a straight line. Light the candle and make a pinhole on each cardboard sheet. The holes should be made at equal height such that the flame of the candle is visible through them. Now look through the holes and observe light travels in which line. The light flame will be visible along the straight line of holes. Now move one of the cardboard sheets to either side and observe the flame. Can you see the flame? On moving the cardboard sheet, the flame will not be visible. Now, again place the cardboard sheet back in its position. The flame is visible now.

From this experiment, we can conclude that light travels along a straight line and this experiment diagram is given below.

Examples of Straight Line Motion of Light

Light travels in straight line examples are as follows:.

Light comes out from a torch or train or lamp follows a straight line path.

A straight line path of light is visible when Sunlight comes out through the small holes in a dusty atmosphere.

When we place any opaque object in front of the object, we observe that the object will be invisible. It is because light cannot bend through the corners of the opaque object.

Interesting Facts

Sunlight can reach a depth of 80m in the ocean.

Paul Dirac proposed a theory in explaining the dual nature of light in 1927.

Particles of light are called photons.

The scientist Euclid Catoptrics in 280 BC found light travels in straight-line inhomogeneous media.

Key Features

Light travels along a straight line.

The straight-line motion of light is due to its small diffraction effects.

Light comes out from the train, torch, and lamp are examples of straight line motion of light.

FAQs on Light Travels in Straight Line

1. What is rectilinear propagation of light?

Light travels along a straight line. The straight-line motion of light is called rectilinear propagation of light.

2. Explain why light travels in a straight line?

Light is a wave exhibiting the property of diffraction. The phenomenon of diffraction is observed only if the wavelength of the wave matches the size of the particle it collides with. Light has wavelengths in the order of nanometers. Usually, an object of nanometer size can not be seen by the naked eye. Hence, the diffraction effect of light is too small to be considered. So, light appears to travel along a straight line.

3. Why is light invisible in a vacuum?

Light can travel through a vacuum. Since in a vacuum there are no particles, light can not reflect. Hence, light is invisible in a vacuum.

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Bridge Course Class 7th Science

Course: bridge course class 7th science > unit 4, light travels in a straight line.

Light and its Characteristics

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Video transcript.

Light Travels In a Straight Line

Light travels in a straight line can be observed by keeping an object in the path of light. In an atmosphere which is bit dusty, we can see light traveling in a straight line. Light emerging from the torch, train and lamps always travel in a straight line. Let us study in detail how does light travel in a straight line.

Browse more Topics under Light

Reflection of Light
Sunlight – White or Coloured
Images Formed By Lenses

Now if suppose we displace the center of the CD’s we observe that we are not able to see the flame of the candle. Why does that happen? This is because the light gets blocked. If the light could have the ability to take a curve and travel, we could have seen the lightwave. But since light travels in a straight line, we were unable to see the flame of the candle when the CD is displaced. This proves that light travels along a straight line.

(Source: Wikipedia)

In the above picture, we can clearly see that light coming through the holes in the window travel along a straight line.

Questions For You

Q1. The phenomenon in which the moon’s shadow falls on earth, or the earth casts its shadow on the moon, is known as

Lateral deviation

Answer: C. The phenomenon in which the moon’s shadow falls on earth or the earth casts its shadow on the moon is known as an eclipse. During a solar eclipse, moon’s shadow falls on the earth. During a lunar eclipse, earth’s shadow falls on the moon.

Q2. Two examples of non-luminous objects are

Stars and Moon
Burning candle, glowing bulb
The moon, a spoon
Stars, a spoon

Answer: C. Non-luminous objects are those that do not emit light. The moon and the spoon do not emit light. So these two are good examples of non-luminous objects.

Q3. We can see the objects only when

Reflected light from the object reaches our eye.
The objects absorb all the light.
When the objects allow all the light to pass through them.
None of these.

Answer: A. Objects can only be seen when light falls on the object and are reflected back to our eyes.

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A Nationwide Comparison of Driving Distance Versus Straight-Line Distance to Hospitals

Francis p. boscoe.

New York State Cancer Registry

Kevin A. Henry

New Jersey Cancer Registry

Michael S. Zdeb

University at Albany School of Public Health

Many geographic studies use distance as a simple measure of accessibility, risk, or disparity. Straight-line (Euclidean) distance is most often used because of the ease of its calculation. Actual travel distance over a road network is a superior alternative, although historically an expensive and labor-intensive undertaking. This is no longer true, as travel distance and travel time can be calculated directly from commercial Web sites, without the need to own or purchase specialized geographic information system software or street files. Taking advantage of this feature, we compare straight-line and travel distance and travel time to community hospitals from a representative sample of more than 66,000 locations in the fifty states of the United States, the District of Columbia, and Puerto Rico. The measures are very highly correlated ( r 2 > 0.9), but important local exceptions can be found near shorelines and other physical barriers. We conclude that for nonemergency travel to hospitals, the added precision offered by the substitution of travel distance, travel time, or both for straight-line distance is largely inconsequential.

Numerous geographic studies have analyzed the distances between residential locations and locations of features in an effort to identify risks, gaps, shortages, and disparities. These include emergency services, such as distances from fire stations or ambulance response times ( Jones and Bentham 1995 ; Lyon et al. 2004 ; Liu, Huang, and Chandramouli 2006 ; Nicholl et al. 2007 ; Schuurman et al. 2009 ); medical services, such as distances and travel times to primary care physicians, hospitals, or specialists ( Luo 2004 ; Wang and Luo 2005 ; Patel, Waters, and Ghali 2007 ; Ludwick et al. 2009 ); and proximity to amenities such as schools, playgrounds, and greengrocers ( Pearce, Witten, and Bartie 2006 ; Pearce et al. 2007 ; Larsen and Gilliland 2008 ; Sharkey 2009 ). There are also a host of studies that look at spatial proximity to adverse features such as gambling centers, liquor stores, and pollution sources ( Burdette and Whitaker 2004 ; Cradock et al. 2005 ; Pearce et al. 2008 ; Hart et al. 2009 ; Hay et al. 2009 ; Kearney and Kiros 2009 ). The preponderance of these studies has found that distance is a relevant explanatory variable, with shorter distance corresponding to higher utilization or exposure.

In many of these studies, geographic distance is the single measure of accessibility or exposure. Others incorporate additional measures involving population size, density of features, and choice among competing options ( Guagliardo 2004 ), but even for these more complex analyses, distance is a necessary component. A majority of studies define distance as the straight-line distance between locations, using either Euclidean distance with projected coordinates or spherical distance with latitude and longitude coordinates. Locations are often first aggregated to some geographic unit for which the data have been collected, such as postal codes or census-defined areas. An advantage of this approach is that calculations are straightforward, not necessarily requiring specialized geographic information systems (GIS) software. A smaller number of studies measure distance using actual road network distances or automobile travel times. This approach offers greater sophistication and precision, although traditionally at the expense of purchasing and managing specialized GIS software or street network data. In our experience, we have found that driving distances and times are perceived to be substantially more precise than straight-line distance. For example, this perception was a major impetus for the recent development of a shortest path calculator by the North American Association of Central Cancer Registries and the University of Southern California GIS Research Laboratory (2009) .

Recent technological advances have essentially eliminated the cost of using street-network distance in analyses. There are now at least five commercial Web sites offering precise driving directions between nearly all locations in the developed world (Google, Yahoo!, Mapquest, Bing, and Rand McNally). Simple programs written in open-source programming languages such as Python can be used to make repeated calls to these sites to obtain the travel time and distance information for any number of locations. In this article, we make use of this functionality to conduct a large-scale comparison of straight-line distances and travel times and distances for the fifty states of the United States, District of Columbia, and Puerto Rico. Our aim is to assess the extent to which using travel time or distance confers a genuine advantage over straight-line distance and to identify locations where differences between the two are most pronounced.

Interest in this question dates at least to the 1960s and research on network models in geography ( Haggett 1967 ). Cole and King’s (1968) Quantitative Geography defined the ratio of travel distance to straight-line distance as the “detour index” and reported typical values of 1.2 to 1.6 for rural areas in various parts of Britain, with the calculations done by having students trace roadways on paper maps. This ratio has been applied in other fields ranging from ecology to computer science where travel over networks is measured, often under different names such as the “index of circuitry” or “route factor” ( Cardillo et al. 2006 ; Bebber et al. 2007 ; Buhl et al. 2009 ).

Several studies have found that the correlation between straight-line distance and road-network distance or time is extremely high and that substituting one for the other is unlikely to have a substantial impact on analytic results ( Martin et al. 2002 ; Wood and Gatrell 2002 ; Jordan et al. 2004 ; Fone, Christie, and Lester 2006 ; Apparicio et al. 2008 ). In particular, a New York State study considering travel from postal ZIP codes to hospitals via state highways found a near-perfect correlation between straight-line distance and road-network distance ( Phibbs and Luft 1995 ). In contrast, a study of access to renal units in England reported the use of road-network distance represented a “significant improvement” ( Martin et al. 1998 ), and a Spanish study found that travel distance offered better predictors of transit ridership than straight-line distance ( Gutierrez and Garcia-Palomares 2008 ).

It is sensible that the correlation between straight-line distance and road-network distance would be very high in the United States given the overall density of roads. Of course, it is not a perfect correlation. Islands, points along an irregular coastline or lakeshore, and locations separated by uncrossable lakes, rivers, and mountains would be expected to have higher-than-expected travel times. This was the case for many locations in a study of hospital access in rural British Columbia ( Schuurman et al. 2006 ). In the New York State study just cited, points on opposing sides of the Hudson River where there were no nearby bridges were among the largest outliers. In this article, we evaluate the magnitude of these deviations throughout the United States and the extent to which they argue for the standard use of travel distance in social scientific research.

We developed a population-based nationwide sample of travel paths by selecting one point from each census tract as origins and locations of community hospitals as destinations. Census tracts are designed to be demographically homogeneous and roughly equal in population, with an average of about 4,000 people per tract. There were 66,125 census tracts containing at least one road in the fifty states, District of Columbia, and Puerto Rico according to the 2000 Census. The geographic centroid of each tract, derived from the Census cartographic boundary files, was snapped to the nearest vertex of the nearest road, and this was taken to be a representative location in the tract. 1

The straight-line distance, travel time, and travel distance between these points and the nearest community hospital were then calculated. Community hospitals consisted of the set of hospitals categorized as general acute care hospitals ( N = 5,111) by the Centers for Medicare and Medicaid Services (2009) as of March 2009. These are nonfederal, publicly accessible hospitals that mirror the population distribution generally, with 40 percent located outside metropolitan statistical areas. Geocoding of hospital locations was done using QualityStage Geolocator software, version 2.0.1, and the Dynamap street reference file, version 9. Hospitals that could not be geocoded (< 1 percent) were manually reviewed and geocoded using Google Maps ( Google 2009 ).

The nearest hospital was found by first identifying all candidate tract–hospital pairs within one degree of latitude and longitude of each other, calculating the straight-line distance for each pair, and retaining the minimum distance. For tracts not within one degree of latitude and longitude of a hospital, the search was expanded to two degrees, and so on. This method reduced the number of potential calculations by 98 percent. Straight-line distances were computed as great circles assuming a spherical earth. Results summarizing the difference between the predicted and actual driving distances for all tracts were viewed on a scatterplot, basic statistics were calculated, and the magnitude and locations of substantial outliers were noted.

Travel distance and travel time were obtained through repeated calls to the Google Maps Web page using the SAS FILENAME URL method in SAS version 9.1 ( Helf 2005 ; Zdeb 2009 ). Each call generates a vast amount of HTML code from which the travel distance and travel time can be extracted using character string functions. (Walking time and distance can also be obtained in this manner, along with driving time during peak traffic periods and public transportation time for selected metropolitan areas. These were explored but not used in this study.) The SAS code is available from the authors.

Once straight-line distances, driving distances, and driving times were obtained for all tracts, the linear relation and correlations between these three measures were assessed using ordinary least-squares regression. The model was fitted using a zero intercept given that a trip of zero distance requires zero travel time. The ratio of driving distance to straight-line distance was defined as the detour index. The difference between the actual driving distance and the predicted driving distance as derived from the regression equation was calculated for all tracts and used to examine outliers. The “predicted” travel distance or travel time was defined as the straight-line distance multiplied by the slope of the regression line. Except where noted previously, all analyses were performed using SAS version 9.1 and ArcGIS version 9.3.

There were 66,011 census tracts with a valid driving route to a hospital. The 114 remaining tracts mainly consisted of islands without ferries or bridges, along with a very small number where the selected point fell within a gated residential community. 2 Straight-line distance predicted travel distance very well in nearly all locations, with the r 2 for the United States as a whole equal to 0.94. The largest outliers were disproportionately located in Alaska, which has significant roadless areas and locations connected by ferry, but excluding Alaska did not alter the r 2 . The detour index was 1.417 for the entire data set. Straight-line distance also predicted travel time very well, with r 2 = 0.91 for the United States as a whole—reasonable given that travel distance and travel time are themselves highly correlated ( Table 1 ).

Correlations between straight-line distance (km), travel distance (km), and travel time (min) for the fifty states of the United States, District of Columbia, and Puerto Rico (N = 66,011)

The r 2 values are presented merely to establish that they are extremely high; their exact interpretation is confounded by the spatial autocorrelation of the observations. Of greater interest is identifying the number and location of tracts where the straight-line distance is a poor predictor of driving distance. Both the absolute and relative differences between the actual and predicted driving distances were used to measure this ( Table 2 ). Over 90 percent of the tracts have good agreement using thresholds within 10 percent or 5 kilometers. For the remainder, positive relative errors represent locations where the actual driving distance exceeds the predicted driving distance; negative values represent the converse. Large positive relative errors are found near irregular shorelines, on islands, in very low-population-density wilderness areas, adjacent to other impassable physical features, or some combination of these. Large negative relative errors are in locations that are not close to a hospital but that have a very straight drivable route to the nearest one. The lowest possible relative error is 41.7 percent, the situation when a route follows exactly the shortest straight-line distance.

Differences between actual and predicted travel distance for the fifty states of the United States, District of Columbia, and Puerto Rico (N = 66,011)

Note: Predicted Travel Distance = Straight-Line Distance * 1.417.

The most extreme difference between straight-line distance and travel distance is found between Grand Marais, Minnesota, and Houghton, Michigan ( Figure 1 ). Here, an 8.5-hour drive through three states is required to cover a distance that via straight line is just 155 kilometers, yielding a detour index of 3.4. This example also misassigns the hospital that is truly closest, as the hospital in Duluth, Minnesota, would be reached before the one in Houghton. Other large differences are found at other locations in the western Great Lakes; between the eastern end of Long Island, New York, and Connecticut; and in remote parts of western states such as Utah and Idaho. The same type of pattern can be found within urban areas, albeit on a much reduced scale. In New York City, there is a section of Queens close to the East River where the closest hospital is 1.1 km across the river in Manhattan. With no bridge immediately nearby, driving this route requires traveling 9.4 km, a detour index of 8.5, but there are hospitals in Queens closer than this.

An external file that holds a picture, illustration, etc.
Object name is nihms436252f1.jpg

Example of incorrectly determined nearest hospital using straight-line distance.

The differences between straight-line distance and travel distance are further illustrated by mapping the outliers in Nevada, a state with some of the largest outliers ( Figure 2 ). The map reveals longer-than-expected travel distances in the mountainous suburbs west of Reno, where roads are sparse and serpentine. Meanwhile, in the small town of Elko, travel distances are shorter than expected owing to a very direct route to the nearest hospital—albeit one that is in an adjacent state, roughly four hours away. Overall, though, the two measures agree to within 10 kilometers for over 90 percent of the tracts.

An external file that holds a picture, illustration, etc.
Object name is nihms436252f2.jpg

Outliers in predicted travel distance based on straight-line distance, state of Nevada.

In terms of computational complexity, few studies involving geographic distance use as many points as we have used here (66,000 origins and 5,000 destinations). For studies larger than this, processing time could become an issue. In our study, identifying the nearest hospitals from each sample point and calculating the straight-line distances took about 1.5 hours using a desktop computer with dual 3.16 Ghz processors, 3.3 GB of RAM, and 250 GB of free drive space. Finding the travel times via the repeated calls to Google Maps took about five hours. Our approach would be inappropriate for the calculation of travel-distance or travel-time buffers, where very large numbers of travel routes would need to be evaluated. In contrast, the calculation of buffers based on straight-line distance is trivial.

Discussion and Conclusions

In nearly all locations within the United States, the straight-line distance is an adequate proxy for travel distance, after applying a detour index of about 1.4. Exceptions are limited to areas located near uncrossable physical features such as lakes, rivers, and mountains and in wilderness areas of the western United States and Alaska. If errors up to 5 kilometers or 10 percent are tolerated, then the two distance measures are equivalent for over 90 percent of the population; relaxing the threshold to 10 kilometers or 10 percent raises this figure to over 96 percent. These are conservative tolerances in the area of nonemergency medical care, where variations in travel of less than thirty minutes generally do not pose significant barriers ( Lee 1991 ).

These results strongly suggest that the many past studies where straight-line distance was used remain valid, and they contradict the widespread perception that travel distance or time represent a tremendous improvement in precision that should be pursued even at significant cost. But because the cost of obtaining travel distance and travel time has become negligible, we do recommend incorporating their small added precision into future studies that relate residential location to geographic features. In the area of emergency response, where results are sensitive to even small differences, such inclusion is essential. Although we focused on community hospitals, we do believe that our findings logically extend to other geographic destinations of varying densities and spatial scales such as parks, schools, and shopping centers that typically involve car travel. They would not necessarily extend to fine spatial scales where driving is unlikely ( Okabe and Kitamura 1996 ). Our results assume the accuracy of the route choices and drive-time estimates using Google’s database. Although we find these data reliable, we are unaware of any formal evaluation of this. The many comments that have been posted online on this subject tend to describe inaccuracies of several hundred meters at most.

Finally, we call attention to the observation that the nationwide detour index of 1.417 is virtually equal to the diagonal of a unit square (1.414). This means that, on average, traveling from an arbitrary address in the United States to the nearest community hospital is equivalent to the maximum possible Manhattan distance between those two points (that is, the distance measured along the two equal axes of an isosceles right triangle). We leave as a future project the determination of whether this is merely an interesting coincidence or a theoretically meaningful result.

Biographies

FRANCIS P. BOSCOE is a Research Scientist at the New York State Cancer Registry, 150 Broadway, Suite 361, Menands, NY 12204. : .su.yn.etats.htlaeh@10bpf His research interests include cancer and chronic disease epidemiology, medical geography, environmental health, spatial methods, and data visualization.

KEVIN A. HENRY is an Associate Director and Research Scientist at the New Jersey Cancer Registry, The Cancer Institute of New Jersey, UMDNJ-Robert Wood Johnson Medical School, 120 Albany Street, Tower II 5th Floor, New Brunswick, NJ 08901. : [email protected] His research interests include geographic analysis of disease, applied methods in health geography, and socioeconomic disparities in cancer stage at diagnosis, treatment, and survival.

MICHAEL S. ZDEB is an Assistant Professor in the Department of Epidemiology and Statistics at the University at Albany School of Public Health, Rensselaer, NY 12144. : .ude.ynabla@30zsm His research interests include biostatistical methods, data visualization, and analysis of vital records data

1 The alternative of choosing a random location in the tract does not impact the results. The average resulting displacement from the centroid is about 1 kilometer and is independent on the hospital locations.

2 The Google Maps database structure does not allow these points to be connected to the greater road network. This database characteristic was introduced into the Google Maps database during the course of our research, and it is unclear whether this was an intended feature or a bug. We considered using a competing database, but the number of problematic locations was small enough to have no impact on our results.

Contributor Information

Francis P. Boscoe, New York State Cancer Registry.

Kevin A. Henry, New Jersey Cancer Registry.

Michael S. Zdeb, University at Albany School of Public Health.

Literature Cited

Apparicio P, Abdelmajid M, Riva M, Shearmur R. Comparing alternative approaches to measuring the geographical accessibility of urban health services: Distance types and aggregation-error issues. International Journal of Health Geographics. 2008; 7 :7. [ PMC free article ] [ PubMed ] [ Google Scholar ]
ArcGIS, version 9.3. Redlands, CA: ESRI; [ Google Scholar ]
Bebber DP, Hynes J, Darrah PR, Boddy L, Fricker MD. Biological solutions to transport network design. Proceedings of the Royal Society B. 2007; 274 (1623):2307–15. [ PMC free article ] [ PubMed ] [ Google Scholar ]
Buhl J, Hicks K, Miller E, Persey S, Alinvi O, Sumpter D. Shape and efficiency of wood ant foraging networks. Behavioral Ecology and Sociobiology. 2009; 63 (3):451–60. [ Google Scholar ]
Burdette HL, Whitaker RC. Neighborhood playgrounds, fast food restaurants, and crime: Relationships to overweight in low-income preschool children. Preventive Medicine. 2004; 38 (1):57–63. [ PubMed ] [ Google Scholar ]
Cardillo A, Scellato S, Latora V, Porta S. Structural properties of planar graphs of urban street patterns. Physical Review E. 2006; 73 (6):066107. [ PubMed ] [ Google Scholar ]
Centers for Medicare and Medicaid Services. [last accessed 10 January 2010]; National Provider Identifier Standard: Overview. 2009 http://www.cms.hhs.gov/NationalProvIdentStand/
Cole JP, King CAM. Quantitative geography. London: Wiley; 1968. [ Google Scholar ]
Cradock AL, Kawachi I, Colditz GA, Hannon C, Melly SJ, Wiecha JL, Gortmaker SL. Playground safety and access in Boston neighborhoods. American Journal of Preventive Medicine. 2005; 28 (4):357–63. [ PubMed ] [ Google Scholar ]
Dynamap/Transportation Street Layer, version 9.0. Lebanon, NH: Tale Atlas; [ Google Scholar ]
Fone DL, Christie S, Lester N. Comparison of perceived and modelled geographical access to accident and emergency departments: A cross-sectional analysis from the Caerphilly Health and Social Needs Study. International Journal of Health Geographics. 2006; 5 :16. [ PMC free article ] [ PubMed ] [ Google Scholar ]
Guagliardo MF. Spatial accessibility of primary care: Concepts, methods, and challenges. International Journal of Health Geographics. 2004; 3 :3. [ PMC free article ] [ PubMed ] [ Google Scholar ]
Google. [last accessed 1 October 2009]; Google Maps. 2009 http://maps.google.com .
Gutierrez J, Garcia-Palomares JC. Distance-measure impacts on the calculation of transport service areas using GIS. Environment and Planning B. 2008; 35 (3):480–503. [ Google Scholar ]
Haggett P. Network models in geography. In: Chorley RJ, Haggett P, editors. Integrated models in geography. London: Methuen; 1967. pp. 609–68. [ Google Scholar ]
Hart JE, Laden F, Puett RC, Costenbader KH, Karlson EW. Exposure to traffic pollution and increased risk of rheumatoid arthritis. Environmental Health Perspectives. 2009; 117 (7):1065–69. [ PMC free article ] [ PubMed ] [ Google Scholar ]
Hay GC, Whigham PA, Kypri K, Langley JD. Neighbourhood deprivation and access to alcohol outlets: A national study. Health and Place. 2009; 15 (4):1086–93. [ PubMed ] [ Google Scholar ]
Helf G. Extreme Web access: What to do when FILENAME URL is not enough. In: Nelson GS, editor. Proceedings of the Thirtieth Annual SAS Users Group International Conference. Cary, NC: SAS Institute, Inc; 2005. [last accessed 23 May 2011]. http://www2.sas.com/proceedings/sugi30/toc.html . [ Google Scholar ]
Jones AP, Bentham G. Emergency medical-service accessibility and outcome from road traffic accidents. Public Health. 1995; 109 (3):169–77. [ PubMed ] [ Google Scholar ]
Jordan H, Roderick P, Martin D, Barnett S. Distance, rurality and the need for care: Access to health services in South West England. International Journal of Health Geographics. 2004; 3 :21. [ PMC free article ] [ PubMed ] [ Google Scholar ]
Kearney G, Kiros GE. A spatial evaluation of socio demographics surrounding National Priorities List sites in Florida using a distance-based approach. International Journal of Health Geographics. 2009; 8 :33. [ PMC free article ] [ PubMed ] [ Google Scholar ]
Larsen K, Gilliland J. Mapping the evolution of “food deserts” in a Canadian city: Supermarket accessibility in London, Ontario, 1961–2005. International Journal of Health Geographics. 2008; 7 :16. [ PMC free article ] [ PubMed ] [ Google Scholar ]
Lee RC. Current approaches to shortage area designation. Journal of Rural Health. 1991; 7 (4):437–50. [ PubMed ] [ Google Scholar ]
Liu N, Huang B, Chandramouli M. Optimal siting of fire stations using GIS and ANT algorithm. Journal of Computing in Civil Engineering. 2006; 20 (5):361–69. [ Google Scholar ]
Ludwick A, Fu RW, Warden C, Lowe RA. Distances to emergency department and to primary care provider’s office affect emergency department use in children. Academic Emergency Medicine. 2009; 16 (5):411–17. [ PubMed ] [ Google Scholar ]
Luo W. Using a GIS-based floating catchment method to assess areas with shortage of physicians. Health and Place. 2004; 10 (1):1–11. [ PubMed ] [ Google Scholar ]
Lyon RM, Cobbe SM, Bradley JM, Grubb NR. Surviving out of hospital cardiac arrest at home: A postcode lottery? Emergency Medicine Journal. 2004; 21 (5):619–24. [ PMC free article ] [ PubMed ] [ Google Scholar ]
Martin D, Roderick P, Diamond I, Clements S, Stone N. Geographical aspects of the uptake of renal replacement therapy in England. International Journal of Population Geography. 1998; 4 (3):227–42. [ Google Scholar ]
Martin D, Wrigley H, Barnett S, Roderick P. Increasing the sophistication of access measurement in a rural healthcare study. Health and Place. 2002; 8 (1):3–13. [ PubMed ] [ Google Scholar ]
Nicholl J, West J, Goodacre S, Turner J. The relationship between distance to hospital and patient mortality in emergencies: An observational study. Emergency Medicine Journal. 2007; 24 (9):665–68. [ PMC free article ] [ PubMed ] [ Google Scholar ]
Okabe A, Kitamura M. A computational method for market area analysis on a network. Geographical Analysis. 1996; 28 (4):330–49. [ Google Scholar ]
Patel AB, Waters NM, Ghali WA. Determining geographic areas and populations with timely access to cardiac catheterization facilities for acute myocardial infarction care in Alberta, Canada. International Journal of Health Geographics. 2007; 6 :47. [ PMC free article ] [ PubMed ] [ Google Scholar ]
Pearce J, Mason K, Hiscock R, Day P. A national study of neighbourhood access to gambling opportunities and individual gambling behaviour. Journal of Epidemiology and Community Health. 2008; 62 (10):862–68. [ PubMed ] [ Google Scholar ]
Pearce J, Witten K, Bartie P. Neighbourhoods and health: A GIS approach to measuring community resource accessibility. Journal of Epidemiology and Community Health. 2006; 60 (5):389–95. [ PMC free article ] [ PubMed ] [ Google Scholar ]
Pearce J, Witten K, Hiscock R, Blakely T. Are socially disadvantaged neighbourhoods deprived of health-related community resources? International Journal of Epidemiology. 2007; 36 (2):348–55. [ PubMed ] [ Google Scholar ]
Phibbs CS, Luft HS. Correlation of travel times on roads versus straight line distance. Medical Care Research and Review. 1995; 52 (4:5):32–42. [ PubMed ] [ Google Scholar ]
QualityStage GeoLocator, version 2.0.1. Ascential Software; Westboro, MA: [ Google Scholar ]
SAS, version 9.1. Cary, NC: SAS Institute; [ Google Scholar ]
Schuurman N, Bell NJ, L’Heureux R, Hameed SM. Modelling optimal location for pre-hospital helicopter emergency medical services. International Journal of Health Geographics. 2009; 9 :6. [ PMC free article ] [ PubMed ] [ Google Scholar ]
Schuurman N, Fiedler RS, Grzybowski SCW, Grund D. Defining rational hospital catchments for non-urban areas based on travel-time. International Journal of Health Geographics. 2006; 5 :43. [ PMC free article ] [ PubMed ] [ Google Scholar ]
Sharkey JR. Measuring potential access to food stores and food-service places in rural areas in the U. S American journal of preventive Medicine. 2009; 36 (4 Suppl):S151–S155. [ PubMed ] [ Google Scholar ]
University of Southern California GIS Research Laboratory. [last accessed 1 October 2009]; Shortest path. 2009 https://webgis.usc.edu/Services/ShortestPath/Default.aspx .
Wang F, Luo W. Assessing spatial and nonspatial factors for healthcare access: Towards an integrated approach to defining health professional shortage areas. Health and Place. 2005; 11 (2):131–46. [ PubMed ] [ Google Scholar ]
Wood DJ, Gatrell AC. Equity of geographical access to inpatient hospice care within North West England: A geographical information systems (GIS) approach. Lancaster, UK: Institute for Health Research, Lancaster University; 2002. [ Google Scholar ]
Zdeb MS. [last accessed 1 October 2009]; Driving distances and drive times using SAS and Google Maps. 2009 http://www.sascommunity.org/wiki/Driving_Distances_and_Drive_Times_using_SAS_and_Google_Maps .

Light Travels Along a Straight Line

Introduction.

One type of energy that is essential to our existence is light. We are unable to envision a world without light. Light improves the beauty of everything around us and allows us to see. In both science and art, light is a crucial element. One of the crucial scientific instruments that enable scientists to examine things all across the world is light.

Some scientific theories claim that it is made up of particles, while others assert that it is made up of waves. What is the medium of propagation if the light is a wave? How does light move? We shall find answers to some of these questions in this article.

How does Light Travel?

Light can pass through a medium and in a vacuum. However, there won’t be any particles in a vacuum that light can’t reflect off of. Therefore, light is invisible in a vacuum. Light can reflect in the air when it strikes dust or other particles, making light visible in the atmosphere. Light may be thought of as having waves. Different light waves have varied wavelengths, and different light has different colours based on the wavelength. For instance, the shortest wavelength of light has a violet colour, whereas the highest wavelength of visible light has a red colour. Light, being a wave, may exhibit wave characteristics like diffraction and interference.

The answer to the question of how light typically moves is that it moves straightforwardly. However, the truth is that light’s smaller diffraction effect is the reason it appears to move in a straight line. The spreading out and the illumination of an area where a shadow is anticipated is known as diffraction, which is the bending of waves around an object. The wavelength of light is on the order of nanometers. We cannot see impediments of this size with our unaided eyes because the wavelength is too narrow. As a result, we see that light moves in a straight path. Rectilinear propagation of light is another name for the way that light moves in a straight line.

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Experiment with the Straight Line Motion of Light

Normal light travels in a straight line because there isn’t enough diffraction to cause any noticeable effects. We demonstrate that light moves in a straight line using a basic experimental setup. In front of a candle on the tabletop, arrange three cardboard sheets back to back. Ensure that the candles and cardboard sheets are arranged in a straight line. On each cardboard sheet, poke a pinhole after lighting the candle. To allow for the visibility of the candle’s flame, the holes must be made at equal heights. Now, observe which line light travels in by looking through the holes. Along the slender line of holes, the thin flame will be visible. Now move one of the cardboard sheets to either side and observe the flame. Can you see the flame? The flame won’t be seen when you move the cardboard sheet. Reposition the cardboard sheet in its original location. The flame may now be seen. The experiment diagram is shown below. From this experiment, we may infer that light moves in a straight line.

Straight Line Motion of Light Experiment

Examples of Straight-Line Motion of Light

When a lamp, torch, or another source of light emits light, it travels in a straight line.
When sunlight enters a dusty environment through tiny holes, a straight-line trail of light is apparent.
The object will become invisible when an opaque object is placed in front of it. The reason for this is that an opaque object prevents light from bending through its corners.

The light rays move in a straight line. The minimized diffraction effects of light facilitate the propagation of the light in a straight path. Examples, where the light rays travel in a straight line, are the light ray that comes from a train, a torch, and/or a lamp.

Frequently Asked Questions

1. what is rectilinear propagation of light.

Ans: The motion of the light rays in a straight line is termed the rectilinear propagation of the light.

2. Explain why Light Travels in a Straight Line?

Ans: Diffraction is a wave characteristic of light. Only when the wavelength of the light wave is of the order of the dimension of the size of the particle it collides with, and the phenomena of diffraction take place. The wavelengths of light are on the order of nanometers. Typically, a nanometer-sized item is invisible to the human eye. Light’s diffraction impact is therefore too modest to be taken into account and travels in a straight-line path.

3. Why is Light Invisible in a Vacuum?

Ans: Light can travel through the vacuum, however, since there are no particles available in the vacuum, light cannot reflect in a vacuum and therefore light is invisible in a vacuum.

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23. Straight line travel

Travel in a straight line across the surface of the Earth in any direction. After approximately 40,000 kilometres, you will find you are back where you started, having arrived from the opposite direction. While this sort of thing might be common in the wrap-around maps of some 1980s era video games, the simplest explanation for this in the real world is that the Earth is a globe, with a circumference about 40,000 km.

It’s difficult to see how this sort of thing could be possible on a flat Earth, unless the flat Earth’s surface were subject to some rather extreme directional and distance warping— that exactly mimics the behaviour of the surface of a sphere in Euclidean space . While this is not a priori impossible, it would certainly be an unlikely coincidence. Occam’s razor suggests that if it looks like a duck, quacks like a duck, and perfectly mimics the Euclidean geometry of a duck, it’s a duck.

This could be a very short and sweet entry if I left things there, but there are a few dangling questions.

Firstly there’s the question of exactly what we mean by a “straight line”. The Earth’s surface is curved, so any line we draw on it is necessarily curved in the third dimension, although this curvature is slight at scales we can easily perceive. The common understanding of a “straight line” on the Earth’s surface is the line giving the shortest distance joining two points as measured along the surface. This is what we mean when we talk about “straight lines” on Earth in casual speech, and it also matches how we’re using the term here.

In three dimensions, such “straight lines” are what we call great circles . A great circle is a circle on the surface of a sphere that has the same diameter as the sphere itself. On an idealised perfectly spherical Earth, the equator is a great circle, as are all of the meridians (i.e. lines of longitude). Lines of latitude other than the equator are not great circles: if you start north of the equator and travel due west, maintaining a westerly heading, then you are actually curving to the right. It’s easiest to see this by imagining a starting point very close to the North Pole. If you travel due west you will travel in a small clockwise circle around the pole.

Great circles on a sphere. The horizontal circle is an equator, the vertical circle is a meridian, the red circle is an arbitrary great circle at some other angle.

Secondly, how can we know that we are travelling in such a straight line? The MythBusters once tested the myth that “It is impossible for a blindfolded person to travel in a straight line” and found that with restricted vision they were unable to either walk, swim, or drive in a straight line over even a very short distance[1]. We don’t need to keep our eyes closed though!

When travelling through unknown terrain, you can navigate by using the positions of the sun and stars as a reference frame, giving you a way of determining compass directions. Converting this into a great circle path however requires geometric calculations that depend on the spherical geometry of the Earth, so this approach is a somewhat circular argument if our aim is to demonstrate that the Earth is spherical.

A more direct method to ensure straight line travel is to line up two landmarks in the direction you are travelling, then when you reach the first one, line up another beyond the next one and repeat the process. This procedure can keep your course reasonably straight, but relies on visible and static landmarks, which may not be conveniently present. And this method is useless at sea.

Modern navigation now uses GPS to establish a position accurate to within a few metres. While this could be (and is routinely) used to plot a straight line course, again this relies on geometrical calculations that assume the Earth is spherical. (It works, of course, because the Earth is spherical, but render this particular line of argument against a flat Earth circular.)

Before GPS became commonplace, there was a different sort of navigation system in common use, and it is still used today as a backup for times when GPS is unavailable for any reason. These older systems are called inertial navigation systems (INS). They use components that provide an inertial frame of reference—that is, a reference frame that is not rotating or accelerating—independent of any motion of the Earth. These systems can be used for dead reckoning , which is navigating by plotting your direction and speed from your starting location to determine where you are at any time. They can be used to ensure that you follow a straight line path across the Earth, with reference to the inertial frame.

Inertial navigation systems can be built using several different physical principles, including mechanical gyroscopes, accelerometers, or laser ring gyroscopes utilising the Sagnac effect ( previously discussed in these proofs ). These systems drift in accuracy over time due to mechanical and environmental effects. Modern inertial navigation systems are accurate to 0.6 nautical miles per hour[2], or just over 1 km per hour. A plane flying at Mach 1 can fly a great circle route in just over 32 hours, so if relying only on INS it should arrive within 32 km of its starting point, which is close enough that a pilot can figure out that it’s back where it started. So in principle we can do this experiment with current technology.

A great circle on our spherical Earth is straightforward. But what does a great circle path look like plotted on a hypothetical flat Earth? Here are a few:

The equator.

Great circle passing through London and Sydney.

Great circle passing through Rome and McMurdo Station, Antarctica.

As you can see, great circle paths are distorted and misshapen when plotted on a flat Earth. If you follow a straight line across the surface of the Earth as given by inertial navigation systems there’s no obvious reason why you would end up tracing any of these paths, or why you would measure the same distance travelled (40,000 km) over all three paths when they are significantly different sizes on this map. And then consider this one:

Great circle passing through London and the North Pole.

This circle passes through the north and south poles. If you travel on this great circle, then you have to go off one edge of the flat Earth and reappear on the other side. Which seems unlikely.

Travelling in a straight line and ending up where you started makes the most sense if the Earth is a globe.

References:

[1] “MythBusters Episode 173: Walk a Straight Line”, MythBuster Results, https://mythresults.com/walk-a-straight-line (accessed 2019-08-20).

[2] “Inertial Navigation System (INS)”, Skybrary, https://www.skybrary.aero/index.php/Inertial_Navigation_System_(INS) (accessed 2019-08-20).

straight line of travel

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This Is the Longest Straight-Line Ocean Path Around the Earth

An Introduction

How does Light Travel?

Experiment for the Straight Line Motion of Light

Examples of Straight Line Motion of Light

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A Nationwide Comparison of Driving Distance Versus Straight-Line Distance to Hospitals

Kevin A. Henry

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Light Travels Along a Straight Line

How does Light Travel?

Experiment with the Straight Line Motion of Light

Examples of Straight-Line Motion of Light

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2. Explain why Light Travels in a Straight Line?

3. Why is Light Invisible in a Vacuum?

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