how far can radio waves travel in space

Galactic Map of Every Human Radio Broadcast Reveals How Isolated We Are

Those aliens better be nearby.

This map designed by Adam Grossman of The Dark Sky Company puts into perspective the enormity of these scales. The Milky Way stretches between 100,000 and 180,000 light-years across, depending on where you measure, which means a signal broadcast from one side of the galaxy would take 100,000 years or more to reach the other side. Now consider that our species started broadcasting radio signals into space only about a century ago. That's represented by a small blue bubble measuring 200 light-years in diameter surrounding the position of the Earth. For any alien civilizations to have heard us, they must be within the bubble.

The very first experimentation with electromagnetic radiation was conducted some 200 years ago, when Danish physicist and chemist Hans Christian Ørsted discovered that electric currents create magnetic fields. This research was expanded by scientists including Michael Faraday , and it eventually resulted in James Clerk Maxwell 's theory of electromagnetism outlined in 1865 and demonstrated by German physicist Heinrich Hertz's experiments more than two decades later. Even then, it wasn't until Italian inventor and electrical engineer Guglielmo Marconi developed long-range radio transmission technologies around the turn of the 20th century that our species really started broadcasting its existence out into the void.

.css-2l0eat{font-family:UnitedSans,UnitedSans-roboto,UnitedSans-local,Helvetica,Arial,Sans-serif;font-size:1.625rem;line-height:1.2;margin:0rem;padding:0.9rem 1rem 1rem;}@media(max-width: 48rem){.css-2l0eat{font-size:1.75rem;line-height:1;}}@media(min-width: 48rem){.css-2l0eat{font-size:1.875rem;line-height:1;}}@media(min-width: 64rem){.css-2l0eat{font-size:2.25rem;line-height:1;}}.css-2l0eat b,.css-2l0eat strong{font-family:inherit;font-weight:bold;}.css-2l0eat em,.css-2l0eat i{font-style:italic;font-family:inherit;} Even if you threw 100 darts, it's a near certainty that none would land in the little blue bubble of our radio waves

If we are optimistic, and we assume an advanced extraterrestrial species has the technological capabilities to detect humanity's very first radio waves (and distinguish them from the general background noise of the universe), we can estimate our farthest signals are a little more that 100 light-years away. If you threw a dart at the map of the Milky Way, and wherever that dart landed is where an advanced alien species resides, there would be a cosmically small probability that they live close enough to be aware of our existence. Even if you threw 100 darts, it's a near certainty that none would land in the little blue bubble of our radio waves.

The search for extraterrestrial intelligence (SETI) institute is constantly listening with our most capable radio telescopes , and they are broadcasting messages from us as well. But given the sheer size of the galaxy, SETI will likely have to listen and transmit for tens of thousands of years at least to have a chance of making contact with another intelligent species—and even that might not be long enough. Perhaps, in the meantime, we should contemplate Carl Sagan's next line in his Pale Blue Dot speech:

"In our obscurity, in all this vastness, there is no hint that help will come from elsewhere to save us from ourselves."

Source: Planetary Society

Jay Bennett is the associate editor of PopularMechanics.com. He has also written for Smithsonian, Popular Science and Outside Magazine. 

.css-cuqpxl:before{padding-right:0.3125rem;content:'//';display:inline;} Space .css-xtujxj:before{padding-left:0.3125rem;content:'//';display:inline;}

NASA Is Creating an Artificial Star (On Purpose)

Can We Detect the Grav Waves of Alien Warp Drives?

Scientist Just Spotted a Black Hole 'Waking Up'

Microwave-Emitting Object Is a New Space Mystery

Could This Hole Be Humanity’s Martian Home?

Life May Have Kicked Off Earlier Than We Thought

A Missing Piece in the Big Bang Theory Has Arrived

The Physics of Wormholes Is Absolutely Metal

The World’s Biggest Rocket Just Got Closer to Mars

A Researcher Says There Could Be an Anti-Universe

This Is the World's First Wooden Satellite

• Subscribe to BBC Science Focus Magazine
• Previous Issues
• Future tech
• Everyday science
• Planet Earth
• Newsletters

How far from Earth could aliens detect our radio signals?

Asked by: Anna Briggs, Plymouth

Robert Matthews

While commercial radio broadcasts began around 100 years ago, these early transmissions used frequencies that were either mopped up by the atmosphere or drowned out by radio emission from the Sun.

In contrast, military radar transmissions set up during the Cold War to detect incoming ballistic missiles have the power and frequency characteristics to be detected over hundreds of light-years – and have already broadcast our existence to any aliens within around 60 light-years of the Earth.

• The thought experiment: What would happen if aliens contacted us?
• How could we talk fluently to aliens?
• How far do we travel through space every day?
• Could we ever detect other universes?

Subscribe to BBC Science Focus Magazine for fascinating new Q&As every month and follow @sciencefocusQA on Twitter for your daily dose of fun facts.

Share this article

• Terms & Conditions
• Privacy policy
• Cookies policy
• Code of conduct
• Magazine subscriptions
• Manage preferences

• Skip to main content
• Keyboard shortcuts for audio player

Scientists have picked up a radio signal 'heartbeat' billions of light-years away

Ayana Archie

This image released by NASA on Tuesday, July 12, 2022, combined the capabilities of the James Webb Space Telescope's two cameras to create a never-before-seen view of a star-forming region in the Carina Nebula. Captured in infrared light by the Near-Infrared Camera (NIRCam) and Mid-Infrared Instrument (MIRI), this combined image reveals previously invisible areas of star birth. NASA, ESA, CSA, STScI via AP hide caption

This image released by NASA on Tuesday, July 12, 2022, combined the capabilities of the James Webb Space Telescope's two cameras to create a never-before-seen view of a star-forming region in the Carina Nebula. Captured in infrared light by the Near-Infrared Camera (NIRCam) and Mid-Infrared Instrument (MIRI), this combined image reveals previously invisible areas of star birth.

Astronomers at the Massachusetts Institute of Technology have picked up repetitive radio signals from a galaxy billions of light-years from Earth.

Scientists have not been able to pinpoint the exact location of the radio waves yet, but suspect the source could be neutron stars, which are made from collapsed cores of giant stars.

The signals have been occurring steadily and last up to three seconds, researchers say. Most fast radio bursts, or FRBs, only last a few milliseconds.

"Within this window, the team detected bursts of radio waves that repeat every 0.2 seconds in a clear periodic pattern, similar to a beating heart," MIT said in a statement .

On Dec. 21, 2019, researchers at the Dominion Radio Astrophysical Observatory in British Columbia, Canada, picked up a signal of a potential FRB, according to the MIT statement.

"Not only was it very long, lasting about three seconds, but there were periodic peaks that were remarkably precise, emitting every fraction of a second — boom, boom, boom — like a heartbeat," said Daniele Michilli, a postdoctoral researcher in the Massachusetts Institute of Technology's Kavli Institute for Astrophysics and Space Research. "This is the first time the signal itself is periodic."

Data on the bursts, including their frequency and how they change based on where the source is located in proximity to Earth could help researchers determine at what speed the universe is expanding.

The announcement about the repetitive radio signals follows the release earlier this week of the first images of the universe from the James Webb Space Telescope. Those images reveal some galaxies formed more than 13 billion years ago.

• Massachusetts Institute of Technology
• massachusetts institute

Suggested Searches

• Climate Change
• Expedition 64
• Mars perseverance
• SpaceX Crew-2
• International Space Station
• View All Topics A-Z

Humans in Space

Earth & climate, the solar system, the universe, aeronautics, learning resources, news & events.

Hubble Examines an Active Galaxy Near the Lion’s Heart

NASA Prepares for Air Taxi Passenger Comfort Studies

Alphabet Soup: NASA’s GOLD Finds Surprising C, X Shapes in Atmosphere

• Search All NASA Missions
• A to Z List of Missions
• Upcoming Launches and Landings
• Spaceships and Rockets
• Communicating with Missions
• James Webb Space Telescope
• Hubble Space Telescope
• Why Go to Space
• Commercial Space
• Destinations
• Living in Space
• Explore Earth Science
• Earth, Our Planet
• Earth Science in Action
• Earth Multimedia
• Earth Science Researchers
• Pluto & Dwarf Planets
• Asteroids, Comets & Meteors
• The Kuiper Belt
• The Oort Cloud
• Skywatching
• The Search for Life in the Universe
• Black Holes
• The Big Bang
• Dark Energy & Dark Matter
• Earth Science
• Planetary Science
• Astrophysics & Space Science
• The Sun & Heliophysics
• Biological & Physical Sciences
• Lunar Science
• Citizen Science
• Astromaterials
• Aeronautics Research
• Human Space Travel Research
• Science in the Air
• NASA Aircraft
• Flight Innovation
• Supersonic Flight
• Air Traffic Solutions
• Green Aviation Tech
• Drones & You
• Technology Transfer & Spinoffs
• Space Travel Technology
• Technology Living in Space
• Manufacturing and Materials
• Science Instruments
• For Kids and Students
• For Educators
• For Colleges and Universities
• For Professionals
• Science for Everyone
• Requests for Exhibits, Artifacts, or Speakers
• STEM Engagement at NASA
• NASA's Impacts
• Centers and Facilities
• Directorates
• Organizations
• People of NASA
• Internships
• Our History
• Doing Business with NASA
• Get Involved
• Aeronáutica
• Ciencias Terrestres
• Sistema Solar
• All NASA News
• Video Series on NASA+
• Newsletters
• Social Media
• Media Resources
• Upcoming Launches & Landings
• Virtual Events
• Sounds and Ringtones
• Interactives
• STEM Multimedia

NASA Announces Winners of Inaugural Human Lander Challenge

In Space Production Applications News

NASA Shares Two New Moon to Mars Architecture White Papers

Unity in Orbit: Astronauts Soar with Pride Aboard Station 

The 1998 Florida Firestorm and NASA’s Kennedy Space Center

Climate Interactives

NASA@ My Library and Partners Engage Millions in Eclipse Training and Preparation

Mapping the Red Planet with the Power of Open Science

NASA’s Mars Odyssey Captures Huge Volcano, Nears 100,000 Orbits

Pillars of Creation Star in New Visualization from NASA’s Hubble and Webb Telescopes

Hubble Captures Infant Stars Transforming a Nebula

An Eclipse Megamovie Megastar

Hypersonic Technology Project

NASA Engineer Honored as Girl Scouts ‘Woman of Distinction’

Amendment 22: Heliophysics Flight Opportunities in Research and Technology Final Text and Due Date

Augmented Reality Speeds Spacecraft Construction at NASA Goddard

Slow Your Student’s ‘Summer Slide’ and Beat Boredom With NASA STEM

NASA Kennedy Team Recognized During White House Sustainability Awards

Astronauta de la NASA Frank Rubio

Diez maneras en que los estudiantes pueden prepararse para ser astronautas

Astronauta de la NASA Marcos Berríos

Space communications: 7 things you need to know.

Katherine Schauer

1.     the basics, 2.     ground networks, 3.     space relays, 4.     bandwidth, 5.     data rates, 6.     latency, 7.     interference.

Movies and television shows can make communicating with space look easy. Astronauts on far off planets video chat with loved ones on Earth with crystal clear quality and no delay.

Do these imagined communications capabilities match reality? Not really.

Communicating to and from space is a challenging endeavor. Fortunately, NASA has the experience and expertise to get space data to the ground.

NASA’s Space Communications and Navigation (SCaN) program enables this data exchange, whether it’s with astronauts aboard the International Space Station , rovers on Mars , or the Artemis missions to the Moon.

Let’s look at some of the challenges of space communications alongside the technologies and capabilities NASA uses to overcome them.

At its simplest, space communications relies on two things: a transmitter and a receiver. A transmitter encodes a message onto electromagnetic waves through modulation, which changes properties of the wave to represent the data. These waves flow through space toward the receiver. The receiver collects the electromagnetic waves and demodulates them, decoding the sender’s message.

Consider a Wi-Fi router and networked devices around the home. Each device receives signals from the router, which transmits data from the internet. At its heart, the complex task of communicating with space resembles wireless communications in the home – only on an enormous scale and at incredible distances.

Communicating from space involves more than pointing a spacecraft’s antenna at the Earth. NASA has an extensive network of antennas around the globe — over all seven continents — to receive transmissions from spacecraft. Network engineers carefully plan communications between ground stations and missions, ensuring that antennas are ready to receive data as spacecraft pass overhead.

Ground station antennas range from the small very high frequency antennas that provide backup communications to the space station to a massive, 230-foot antenna that can communicate with far-off missions like the Voyager spacecraft , over 11 billion miles away.

In addition to direct-to-Earth communications, many NASA missions rely on relay satellites in order to get their data to the ground. For example, the space station communicates through Tracking and Data Relay Satellites (TDRS), which transmit data to ground stations in New Mexico and Guam. The recently launched Mars 2020 Perseverance rover will send data through orbiters around Mars, which forward the data to Earth.

Relays offer unique advantages in terms of communications availability. For example, the placement of TDRS at three different regions above Earth offers global coverage and near-continuous communications between low-Earth orbit missions and the ground. Rather than waiting to pass over a ground station, TDRS users can relay data 24 hours a day, seven days a week.

NASA encodes data on various bands of electromagnetic frequencies. These bandwidths — ranges of frequencies — have different capabilities. Higher bandwidths can carry more data per second, allowing spacecraft to downlink data more quickly.

Currently, NASA relies primarily on radio waves for communications, but the agency is developing ways to communicate with infrared lasers . This type of transmission — dubbed optical communications — will offer missions higher data rates than ever before.

NASA’s Laser Communications Relay Demonstration (LCRD) will showcase the benefits of optical communications. The mission will relay data between ground stations in California and Hawaii over optical links, testing their capabilities. NASA will also furnish the space station with an optical terminal that can relay data to the ground via LCRD.

Higher bandwidths can mean higher data rates for missions. Apollo radios sent grainy black and white video from the Moon. An upcoming optical terminal on the Artemis II mission will send 4K, ultra-high definition video from lunar orbit.

But bandwidth isn’t the only constraint on data rates. Other factors that can affect data rates include the distance between the transmitter and receiver, the size of the antennas or optical terminals they use, and the power available on either end. NASA communications engineers must balance these variables in order to maximize data rates.

Communications don’t occur instantaneously. They’re bound by a universal speed limit: the speed of light, about 186,000 miles per second. For spacecraft close to Earth, this time delay — or communications latency — is almost negligible.

However, farther from Earth, latency can become a challenge. At Mars’ closest approach — about 35 million miles away — the delay is about four minutes. When the planets are at their greatest distance — about 250 million miles away — the delay is around 24 minutes. This means that astronauts would need to wait between four and 24 minutes for their messages to reach mission control, and another four to 24 minutes to receive a response.

As NASA prepares to send humans to the Red Planet , communications engineers are developing ways for astronauts to stay connected with Earth while recognizing delays will be a part of the conversation.

As communications transmissions travel over long distances or through the atmosphere, the quality of their data can deteriorate, garbling the message. Radiation from other missions, the Sun, or other celestial bodies can also interfere with the quality of transmissions. To make sure that mission operations centers receive accurate data, NASA uses methods of error detection and correction. Methods of error correction include computer algorithms that interpret noisy transmissions as usable data.

While Hollywood dreams up stories that connect people across the galaxy with ease, NASA engineers endeavor to turn those dreams into reality. NASA is developing technologies and capabilities that address the real-world challenges of space communications, while empowering science and exploration missions with robust communications services.

Explore More

It might appear featureless and unexciting at first glance, but NASA/ESA Hubble Space Telescope observations…

Who knew Earth’s upper atmosphere was like alphabet soup? NASA’s Global-scale Observations of the Limb…

Surprising Phosphate Finding in NASA’s OSIRIS-REx Asteroid Sample

Chapter 6: Electromagnetics

Page One | Page Two | Page Three | Page Four | Page Five | Page Six

Chapter Objectives

Upon completion of this chapter you will be able to describe in general terms characteristics of natural and artificial emitters of radiation. You will be able to describe bands of the spectrum from RF to gamma rays, and the particular usefulness radio frequencies have for deep-space communication. You will be able to describe the basic principles of spectroscopy, Doppler effect, reflection and refraction.

Full image and caption

Electromagnetic Radiation

Electromagnetic radiation (radio waves, light, etc.) consists of interacting, self-sustaining electric and magnetic fields that propagate through empty space at 299,792 km per second (the speed of light , c ), and slightly slower through air and other media. Thermonuclear reactions in the cores of stars (including the Sun) provide the energy that eventually leaves stars, primarily in the form of electromagnetic radiation. These waves cover a wide spectrum of frequencies. Sunshine is a familiar example of electromagnetic radiation that is naturally emitted by the Sun. Starlight is the same thing from "Suns" much farther away.

When a direct current (DC) of electricity, for example from a flashlight battery, is applied to a wire or other conductor, the current flow builds an electromagnetic field around the wire, propagating a wave outward. When the current is removed the field collapses, again propagating a wave. If the current is applied and removed repeatedly over a period of time, or if the electrical current is made to alternate its polarity with a uniform period of time, a series of waves is propagated at a discrete frequency. This phenomenon is the basis of electromagnetic radiation.

Electromagnetic radiation normally propagates in straight lines at the speed of light and does not require a medium for transmission. It slows as it passes through a medium such as air, water, glass, etc.

The Inverse Square Law

Electromagnetic energy decreases as if it were dispersed over the area on an expanding sphere, expressed as 4pR 2 where radius R is the distance the energy has travelled. The amount of energy received at a point on that sphere diminishes as 1/R 2 . This relationship is known as the inverse-square law of (electromagnetic) propagation. It accounts for loss of signal strength over space, called space loss .

The inverse-square law is significant to the exploration of the universe, because it means that the concentration of electromagnetic radiation decreases very rapidly with increasing distance from the emitter. Whether the emitter is a distant spacecraft with a low-power transmitter or an extremely powerful star, it will deliver only a small amount of electromagnetic energy to a detector on Earth because of the very great distances and the small area that Earth subtends on the huge imaginary sphere.

Discover More Topics From NASA

Asteroids, Comets & Meteors

Kuiper Belt

• Become A Member
• Gift Membership
• Kids Membership
• Other Ways to Give
• Explore Worlds
• Defend Earth

How We Work

• Education & Public Outreach
• Space Policy & Advocacy
• Science & Technology
• Global Collaboration

Our Results

Learn how our members and community are changing the worlds.

Our citizen-funded spacecraft successfully demonstrated solar sailing for CubeSats.

Space Topics

• Planets & Other Worlds
• Space Missions
• Space Policy
• Planetary Radio
• Space Images

The Planetary Report

The exoplanet issue.

The expanding frontier of discovery.

Get Involved

Membership programs for explorers of all ages.

Get updates and weekly tools to learn, share, and advocate for space exploration.

Volunteer as a space advocate.

Support Our Mission

• Renew Membership
• Society Projects

The Planetary Fund

Accelerate progress in our three core enterprises — Explore Worlds, Find Life, and Defend Earth. You can support the entire fund, or designate a core enterprise of your choice.

• Strategic Framework
• News & Press

The Planetary Society

Know the cosmos and our place within it.

Our Mission

Empowering the world's citizens to advance space science and exploration.

• Explore Space
• Take Action
• Member Community
• Account Center
• “Exploration is in our nature.” - Carl Sagan

Bruce Murray Space Image Library

Extent of human radio broadcasts

For full functionality of this site it is necessary to enable JavaScript. Here are instructions on how to enable JavaScript in your web browser .