• Fri. Feb 23rd, 2024

No, radar technology doesn’t prove Earth is flat

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The claim: Radar technology wouldn’t work if the Earth was a globe

An April 20 Instagram post (direct link, archived link) features an image of a world map on a radar screen.

“You think radar works on a ball?” reads the text in the post. “Think again.” 

The post garnered more than 1,000 likes in four days. 

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Our rating: False

Scientists say the post’s logic is flawed and that radar technologies account for the Earth’s curvature. Furthermore, the curvature of the Earth plays into some of the limitations of radar technology. An abundance of evidence demonstrates the Earth is spherical in shape – including images of the planet taken from outer space.

Scientists say radar technology accounts for Earth’s curvature 

Radar technology utilizes radio waves to detect and track objects in the atmosphere. Radar technology has a broad range of uses, including tracking weather and precipitation, monitoring airspace for aircraft and airborne weapons, tracking ships at sea and calculating the speed of moving objects. 

Radars are made up of an antenna and a large rotating dish. As the dish turns, the antenna sends out beams of energy, called radio waves, into the atmosphere. The antenna can send out beams of energy at slightly different angles as it rotates, ranging a few degrees above and below the horizon line. 

When the wave hits an object, like a water droplet or airplane, the beam of energy is scattered and reflects some of that energy back toward the radar dish. The radar is able to calculate the size of the object and how far away it is by analyzing the strength of the reflected signal.

Radar technology factors in the beam’s angle and the Earth’s curvature in its calculations to determine the location of the objects it detects, according to Jessica Schultz, deputy director of the National Weather Service Radar Operations Center.

Ground-based radars are usually aimed skyward to a small degree, depending on their location and purpose. Especially in the case of long-range weather radar, the radar beam will get higher as it travels further away from the radar site due to the angle of the beam and the curvature of the Earth, Schultz said. 

As a result, weather radars can “overshoot” certain areas and have difficulty detecting precipitation closer to the ground level at long distances. Airplanes and other airborne objects can take advantage of this to evade detection by air traffic control and other radars, Doerry said, noting that this is the premise of the colloquialism “flying under the radar.” 

Armin Doerry,  a radar researcher at Sandia National Laboratories, acknowledged this in a 2013 report on the effects of the Earth’s curvature and atmospheric refraction on radar signals.  

“The earth isn’t flat, and radar beams don’t travel straight,” Doerry wrote. “This becomes more noticeable as range increases.”

Both Schultz and Doerry told USA TODAY radar beams do not travel in perfectly straight lines as the atmosphere is not uniform in density, moisture or temperature. Generally, the atmosphere is less dense at higher altitudes, which causes the radar beam to bend along the Earth’s surface.

The Ancient Greeks were the first humans to theorize the Earth may be spherical in nature, according to the American Physical Society. Modern scientists have discovered ample evidence confirming this is the case in the millennia since then. 

For example, Polaris – also known as the North Star – would always be visible in the night sky if the Earth was a level plane, physicist Jason Steffen previously told USA TODAY. But that’s not the case, as people in the Southern Hemisphere are unable to view the star, Steffen said. 

USA TODAY previously debunked an array of flat Earth posts, including those that claim a laser test proves the Earth is flat and that Antarctica is really an ice wall, not a continent.

Fact check roundup: Debunking the flawed science behind flat Earth claims

USA TODAY reached out to the Instagram user who shared the post for comment but did not receive an immediate response. 

Our sources:

  • USA TODAY, Dec. 7, 2022, Fact check roundup: Debunking the flawed science behind flat Earth claims
  • USA TODAY, Dec. 7, 2022, Fact check: Laser beam tests done over water are skewed by refraction, don’t prove Earth is flat
  • USA TODAY, Nov. 17, 2022, Fact check: Ample evidence the Earth is round and rotating, contrary to persistent social media claims
  • American Physical Society, June 2006, This Month in Physics History
  • Armin Doerry, April 27, Phone interview with USA TODAY 
  • Bureau of Meteorology, accessed May 5, How Radar Works
  • Encyclopedia Brittanica, updated Feb. 20, Radar
  • Jessica Schultz, April 25, Phone interview with USA TODAY 
  • KYFR, July 20, 2022, Morse Code of Weather: limitations of weather radars, including radar gap in far western ND and how that’s addressed
  • Laser Interferometer Gravitational-Wave Observatory, accessed March 23, Ultra-High Vacuum  
  • National Center for Atmospheric Research, accessed May 5 How Do Radars Work
  • National Weather Service, accessed May 5, NWS Radar: How Does the Radar Work? 
  • National Weather Service, accessed May 5, JetStream Max: Radar Beams 
  • NOAA, April 3, How radar works 

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