Stephen Hawking gets it right again

Sep 18, 2025

Join gravitational-wave researcher Alberto Vecchio from Birmingham University as he discusses a groundbreaking LIGO detection, confirming Hawking's area theorem with the merging of two black holes. Vecchio highlights how this elegant math has withstood rigorous testing. The podcast also explores an ambitious ESA plan to catch a pristine comet on its first visit to the inner solar system, supported by insights from Colin Snodgrass and Meg Schwamb about upcoming space missions. Discover the future of cosmic exploration and its exciting possibilities!

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INSIGHT

Clearest Test Of Black Hole Mathematics

LIGO's January 2025 detection was exceptionally loud and clear, allowing precise tests of black hole theory.
The merger confirmed Hawking's prediction that the total event horizon area increases after two black holes merge.

INSIGHT

Black Holes Reduced To Two Numbers

Black holes appear deceptively simple: general relativity predicts they are described only by mass and spin.
Measuring those numbers from gravitational waves lets scientists compute the black hole horizon area and test theory.

ANECDOTE

UK-To-Sweden Scale Analogy

Vecchio gave a vivid scale analogy: the pre-merger horizon area equalled roughly the area of the United Kingdom.
After the merger, the resulting horizon roughly doubled to the size of Sweden in his analogy.

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Gravitational waves show two black holes merge just how Hawking predicted. Plus, a space mission without a target. And a Space probe without a confirmed budget.

In January 2025 the LIGO gravitational wave observatories witnessed two distant black holes spinning into each other. In the ten years of LIGO’s operations, that’s not a first. But the instruments have been improved to such an extent that this time some very important predictions of General Relativity and out understanding of black holes could be tested. As Birmingham University’s Alberto Vecchio says, the elegant simplicity of the mathematics of black holes has passed a test, in particular Stephen Hawking’s prediction that the surface area of merging black holes can only be increased.

Space craft have met comets before. But because spaceflight takes so long to plan and fund, we’ve only sent them to comets with human-lifetime orbital periods so far, because we know when they’re arriving. ESA wants to meet one we’ve never seen before, one that has never or seldom been in close to the sun, and never been barbecued and seared by the radiation. Colin Snodgrass of the University of Edinburgh explains the plan to launch and park a comet chaser in space to wait for one of these elusive extraterrestrial objects to come in from the cold.

That, says Meg Schwamb of Queen’s University Belfast, is going to be much easier in the next few years as the Vera Rubin Telescope begins its ten year survey cataloguing anything in the sky that changes. The type of sky survey it will provide will identify, it is hoped, many candidate first-time comets for the small fleet of spacecraft to intercept.

Having a spacecraft ready in position rather than having to launch a new one anytime you want to do some science is a good place to be, one would think.

NASA’s Juno mission has been delivering science from Jupiter since its launch, and is still functioning and able to deliver more. Yet NASA funds are under considerable threat, and as Scott Bolton tells Roland, at the end of this month Juno could be left slowly spiralling into the gas giant, silently collecting data but with no budget to keep the science going.

Presenter: Roland Pease Producer: Alex Mansfield Production Coordinator: Jana Bennett-Holesworth