What are Dyson spheres? Former NASA chief scientist Dr. Jim Green explains the significance of "megastructures" in search for extraterrestrial life

Former NASA chief scientist Dr. Jim Green dove deep into the organization's search for extraterrestrial life in a recent appearance on This Week in Space podcast. The Arthus S. Fleming Award winner explained the significance of finding technosignatures like Dyson spheres and other megastructures in space.

Speaking about them in an episode released on March 8, 2025, Dr. Jim Green explained to hosts Rod Pyle and Tariq Maik:

"We are still doing research in technosignatures. It is not just radio - it is looking for structures, megastructures. What are the options in megastructures? Well, Freeman Dyson in the 60s wrote a wonderful paper about really advanced technologies and civilisations that are gonna wanna capture all the energy from its dying Sun. That would be called a Dyson sphere."

A Dyson sphere is a concept that was designed as the ultimate solution to the energy crisis for an advanced civilization. It was first theorized by British American physicist Freeman Dyson. It is essentially imagined as a shell of mirrors or solar panels that completely encompasses a star, thereby harnessing all its energy.

Dyson connected this concept with an advanced extraterrestrial civilization in a 1960 paper where he stated:

“One should expect that, within a few thousand years of its entering the stage of industrial development, any intelligent species should be found occupying an artificial biosphere which completely surrounds its parent star.”

In the paper, Dyson also explained that the spheres would exude waste heat, which would be detectable as infrared radiation. Therefore, looking for technosignatures like these would be a logical way of searching for extraterrestrial life.

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Dr. Jim Green opened up about NASA's history of receiving funding to aid its search for extraterrestrial life

National Aeronautics and Space Administration - Source: Getty

During the discussion on This Week in Space podcast, Dr. Jim Green explained how NASA was looking for alien life through radio signals during the 1990s. He also explained that human civilization uses radio signals everywhere because of our use of gadgets like radio, television, etc. Therefore, it was wise for the organization to keep an eye out for those signals in space as a technosignature for life.

“The key to that is to have them on, look out and gather that data and see if we can find a civilization that's doing that. Because we do that, you know, know, when we created tv and radio and all those radio waves leave earth…” he said.

Dr. Green added:

“So we're, we're, you know, we're just leaking radio waves like crazy. So it's a good idea, uh, and and started in the 90s and NASA started working in that direction."

However, he claimed that NASA got Congressional direction to quit that field of research. Thereafter, SETI went into the hands of the private sector. For the unversed, SETI stands for Search for Extraterrestrial Organisms.

Congressman Lamar Smith was the major force behind getting the organization involved in SETI again, as per Dr. Green.

"What was happening is there was a big push in Congress, particularly by Lamar Smith, to help fund SETI, to really get NASA more involved, bring NASA back into the search for extraterrestrial intelligence,” he said.

The push resulted in the organization securing funding of $10 million and continuing its research on SETI.

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NASA's fiscal budget has seen a constant rise over the years. For FY 2025, the President's budget request for the organization stands at $25.4 billion, marking a 2% increase over last year's budget.