London Daily

Focus on the big picture.
Friday, Aug 22, 2025

Here's why astronauts age slower than the rest of us here on Earth

Here's why astronauts age slower than the rest of us here on Earth

The next time you find yourself wishing the weekend would last longer, stay low to the ground and move really fast.

Time feels like one of the only constants in life — it passes day after day at the same pace.

Then Albert Einstein had to go and ruin that for us.

We've all heard the phrase that "time is relative," but it can be difficult to wrap the mind around what that actually means.

The phrase came from Einstein's Theory of Relativity that joined space and time and created the idea of a fabric that permeates the whole universe: "space-time."

We all measure our experience in space-time differently. That's because space-time isn't flat — it's curved, and it can be warped by matter and energy.

So depending on our position and speed, time can appear to move faster or slower to us relative to others in a different part of space-time. And for astronauts on the International Space Station, that means they get to age just a tiny bit slower than people on Earth. 

That's because of time-dilation effects. First, time appears to move slower near massive objects because the object's gravitational force bends space-time.



The phenomenon is called "gravitational time dilation." In a nutshell it just means time moves slower as gravity increases.

That's why time passes slower for objects closer to the center of the Earth where the gravity is stronger.

That doesn't mean you could spend your life in a basement, just to outlive the rest of us here on the surface. The effect isn't noticeable on such a small scale. If you became a basement hermit, then across your entire lifetime you'd only age a fraction of a second slower than everyone else above ground.

But this concept gets pretty crazy when you start thinking about it:

 *  A watch strapped to your ankle will eventually fall behind one strapped to your wrist.

*  Your head technically ages more quickly than your feet.

*  Time passes faster for people living on a mountain than those living at sea level.

Time gets even weirder though.

The second factor is something called "relative velocity time dilation" where time moves slower as you move faster.

The classic example of this is the twin scenario. One twin blasts off in a spaceship traveling close to the speed of light, and one twin stays behind on Earth. When the space-traveling twin returns to Earth, she's only aged a couple years, but she's shocked to find that her Earth-bound sister has aged over a decade.

Of course no one has performed that experiment in real life, but there's evidence that it's real. When scientists launched an atomic clock into orbit and back — while keeping an identical clock here on Earth — it returned running ever so slightly behind the Earth-bound clock.

Then time gets even more complicated because gravitational time dilation and relative velocity time dilation can happen at the same time. A good way to think about it is to consider the astronauts living on the International Space Station.

Currently, an international crew of seven live and work aboard the ISS, orbiting Earth about every 90 minutes, according to NASA.

They're floating about 260 miles above, where Earth's gravitational pull is weaker than it is at the surface. That means time should speed up for them relative to people on the ground. But the space station is also whizzing around Earth at about nearly five miles per second.

That means time should also slow down for the astronauts relative to people on the surface.

You'd think that might even out, but actually their velocity time dilation has a bigger effect than their gravitational time dilation, so astronauts end up aging slower than people on Earth.

The difference isn't noticeable though — after spending six months on the ISS, astronauts have aged about 0.005 seconds less than the rest of us.

That means that when former NASA astronaut Scott Kelly returned home in 2016 from his history-making, year-long stay on the ISS, he technically was 0.01 second younger than his twin astronaut brother — and now US senator — Mark Kelly who stayed on Earth.

So the next time you find yourself wishing the weekend would last longer, stay low to the ground and move really fast. It won't feel like your weekend got any longer, but technically you may gain a teeny, tiny fraction of a fraction of a second.

Remember, time is relative.

Newsletter

Related Articles

0:00
0:00
Close
After 200,000 Orders in 2 Minutes: Xiaomi Accelerates Marketing in Europe
Ukraine Declares De Facto War on Hungary and Slovakia with Terror Drone Strikes on Their Gas Lifeline
Animated K-pop Musical ‘KPop Demon Hunters’ Becomes Netflix’s Most-Watched Original Animated Film
New York Appeals Court Voids Nearly $500 Million Civil Fraud Penalty Against Trump While Upholding Fraud Liability
Elon Musk tweeted, “Europe is dying”
Far-Right Activist Convicted of Incitement Changes Gender and Demands: "Send Me to a Women’s Prison" | The Storm in Germany
Hungary Criticizes Ukraine: "Violating Our Sovereignty"
Will this be the first country to return to negative interest rates?
Child-free hotels spark controversy
North Korea is where this 95-year-old wants to die. South Korea won’t let him go. Is this our ally or a human rights enemy?
Hong Kong Launches Regulatory Regime and Trials for HKD-Backed Stablecoins
China rehearses September 3 Victory Day parade as imagery points to ‘loyal wingman’ FH-97 family presence
Trump Called Viktor Orbán: "Why Are You Using the Veto"
Horror in the Skies: Plane Engine Exploded, Passengers Sent Farewell Messages
MSNBC Rebrands as MS NOW Amid Comcast’s Cable Spin-Off
AI in Policing: Draft One Helps Speed Up Reports but Raises Legal and Ethical Concerns
Shame in Norway: Crown Princess’s Son Accused of Four Rapes
Apple Begins Simultaneous iPhone 17 Production in India and China
A Robot to Give Birth: The Chinese Announcement That Shakes the World
Finnish MP Dies by Suicide in Parliament Building
Outrage in the Tennis World After Jannik Sinner’s Withdrawal Storm
William and Kate Are Moving House – and the New Neighbors Were Evicted
Class Action Lawsuit Against Volkswagen: Steering Wheel Switches Cause Accidents
Taylor Swift on the Way to the Super Bowl? All the Clues Stirring Up Fans
Dogfights in the Skies: Airbus on Track to Overtake Boeing and Claim Aviation Supremacy
Tim Cook Promises an AI Revolution at Apple: "One of the Most Significant Technologies of Our Generation"
Apple Expands Social Media Presence in China With RedNote Account Ahead of iPhone 17 Launch
Are AI Data Centres the Infrastructure of the Future or the Next Crisis?
Cambridge Dictionary Adds 'Skibidi,' 'Delulu,' and 'Tradwife' Amid Surge of Online Slang
Bill Barr Testifies No Evidence Implicated Trump in Epstein Case; DOJ Set to Release Records
Zelenskyy Returns to White House Flanked by European Allies as Trump Pressures Land-Swap Deal with Putin
The CEO Who Replaced 80% of Employees for the AI Revolution: "I Would Do It Again"
Emails Worth Billions: How Airlines Generate Huge Profits
Character.ai Bets on Future of AI Companionship
China Ramps Up Tax Crackdown on Overseas Investments
Japanese Office Furniture Maker Expands into Bomb Shelter Market
Intel Shares Surge on Possible U.S. Government Investment
Hurricane Erin Threatens U.S. East Coast with Dangerous Surf
EU Blocks Trade Statement Over Digital Rule Dispute
EU Sends Record Aid as Spain Battles Wildfires
JPMorgan Plans New Canary Wharf Tower
Zelenskyy and his allies say they will press Trump on security guarantees
Beijing is moving into gold and other assets, diversifying away from the dollar
Escalating Clashes in Serbia as Anti-Government Protests Spread Nationwide
The Drought in Britain and the Strange Request from the Government to Delete Old Emails
Category 5 Hurricane in the Caribbean: 'Catastrophic Storm' with Winds of 255 km/h
"No, Thanks": The Mathematical Genius Who Turned Down 1.5 Billion Dollars from Zuckerberg
The surprising hero, the ugly incident, and the criticism despite victory: "Liverpool’s defense exposed in full"
Digital Humans Move Beyond Sci-Fi: From Virtual DJs to AI Customer Agents
YouTube will start using AI to guess your age. If it’s wrong, you’ll have to prove it
×