Why Your Body Needs Gravity

The Rest Is Science

Does space travel make astronauts younger?


Professor Hannah Fry and Michael Stevens explore Einstein’s twin paradox, time dilation and NASA’s famous Twins Study with astronauts Scott and Mark Kelly.


After Scott Kelly spent 340 days aboard the International Space Station, he returned milliseconds younger than his identical twin. But microgravity had also affected his eyesight, bones, blood, gut microbiome, body temperature, genes and telomeres.


So what exactly happens to the human body in space, and which changes remain after astronauts return to Earth?


In this episode, Hannah and Michael discover how deeply the human body depends on gravity. Along the way, they uncover why your head ages faster than your feet, what a 63 day cave experiment reveals about our sense of time, and whether future humans could ever truly adapt to life beyond Earth.


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For more information about Cancer Research UK, their research, breakthroughs and how you can support them, visit ⁠https://www.cancerresearchuk.org/our-research/rest-is-science


Cancer Research UK is a registered charity in England and Wales (1089464), Scotland (SC041666), the Isle of Man (1103) and Jersey (247). A company limited by guarantee. Registered company in England and Wales (4325234) and the Isle of Man (5713F). Registered address: 2 Redman Place, London, E20 1JQ.


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Find The Rest Is Science all over the internet by ⁠⁠clicking here.⁠⁠


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Video Producer: Teo Ayodeji-Ansell 

Animator: Sam Benson

Video & Social: Bex Tyrrell

Assistant Producer: Lucy Lipscombe

Producer: Simona Rata

Senior Producer: Lauren Armstrong-Carter

Chief Digital Officer: Samuel Oakley

Exec Producer: Neil Fearn

Learn more about your ad choices. Visit podcastchoices.com/adchoices

More description

Does space travel make astronauts younger?


Professor Hannah Fry and Michael Stevens explore Einstein’s twin paradox, time dilation and NASA’s famous Twins Study with astronauts Scott and Mark Kelly.


After Scott Kelly spent 340 days aboard the International Space Station, he returned milliseconds younger than his identical twin. But microgravity had also affected his eyesight, bones, blood, gut microbiome, body temperature, genes and telomeres.


So what exactly happens to the human body in space, and which changes remain after astronauts return to Earth?


In this episode, Hannah and Michael discover how deeply the human body depends on gravity. Along the way, they uncover why your head ages faster than your feet, what a 63 day cave experiment reveals about our sense of time, and whether future humans could ever truly adapt to life beyond Earth.


-------------------


For more information about Cancer Research UK, their research, breakthroughs and how you can support them, visit ⁠https://www.cancerresearchuk.org/our-research/rest-is-science


Cancer Research UK is a registered charity in England and Wales (1089464), Scotland (SC041666), the Isle of Man (1103) and Jersey (247). A company limited by guarantee. Registered company in England and Wales (4325234) and the Isle of Man (5713F). Registered address: 2 Redman Place, London, E20 1JQ.


-------------------


Find The Rest Is Science all over the internet by ⁠⁠clicking here.⁠⁠


-------------------


Video Producer: Teo Ayodeji-Ansell 

Animator: Sam Benson

Video & Social: Bex Tyrrell

Assistant Producer: Lucy Lipscombe

Producer: Simona Rata

Senior Producer: Lauren Armstrong-Carter

Chief Digital Officer: Samuel Oakley

Exec Producer: Neil Fearn

Learn more about your ad choices. Visit podcastchoices.com/adchoices

2026-09-13 43 min
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