# Astronauts age slower than people on Earth?

#### edro

##### Lifer
If an astronaut is orbitting the Earth at a speed of twice per 24 hour period... would his time be on a different scale than that of Earth?

Lets say over a 30 day period. He would have gone around the Earth in 30 days, but the people on Earth would only have gone around for 15 days... right?

I don't really know where I'm going with this... but... umm... anyone have any info or input on this topic?

#### Kalvin00

##### Lifer
Aging has nothing to do with revolving of the Earth...

#### kritical

##### Senior member
No because you're aging is dependent on physical conditions. It really has nothing to do with with.

no

#### PowerMacG5

##### Diamond Member
He is technically aging slower in reference to the Earth because he is moving at a high velocity (17,000 mph). This has to do with Einstein's theories. If the astronaut had an identical twin on earth, and the astronaut went into space for a little bit, he would be slightly younger (a few seconds) than his brother.

#### TheBoyBlunder

##### Diamond Member
As far as I understand it, you'd have to be going near the speed of light to age noticeably slower than someone on earth. KrazyKid's explanation is pretty good as well.

#### Kelvrick

##### Lifer
Only thing I can think of is because he is moving at a faster velocity, hence closer to the speed of light, time passes slower for him then for us. For him, say, 5 years passes, but on Earth, 10 years have passed. Its not to say he can have an extra 5 years, time just passes slower and so he ages slower.

Its all in perspective.

EDIT: Damn, beaten.

#### Siddhartha

##### Lifer
There are relativistic effects involved but they are pretty small.

#### JawaJedi

##### Senior member
I only remember some rudimentary physics from my undergrad classes, but I think edro13 is right. The faster you go, the slower things are, in relation to your original time. But orbiting around the earth at twice the speed is way too slow to have a noticeable difference, even if the astronaut were to spend his entire life in space. THe difference would be so small it wouldn't even matter.

But if somebody were to go at near the speed of light, there would be a big enough difference... right? I mean the astronaut wouldn't be aging slower, but in relation to how old he'd be if he had spent the same amount of time in regular time... he'd be younger. Isn't that how relativity works? Maybe not.

#### WinkOsmosis

##### Banned
It's like when superman reversed time by flying around the world backwards.

##### Platinum Member
i think he's refering to time dilation

#### MikeMike

##### Lifer

it was the russian astronaut who was in space for a few years. and they said he was a fraction of a second younger because he was moving so quickly for so long.

MIKE

#### Antoneo

##### Diamond Member
I remember reading an article where an airplane had an atomic clock onboard sychronized with an atomic clock on ground and after flying for a while, they told slightly different times (with the onboard clock being behind).

#### niwi7

##### Golden Member
i dont understand this at all

when you say aging are you talking about time or physical conditions?

because if your talking about time then ok i understand, but if you are talking about physical conditions....i just dont see how going fast can make you "age" faster?

#### Xenon14

##### Platinum Member
Originally posted by: Antoneo
I remember reading an article where an airplane had an atomic clock onboard sychronized with an atomic clock on ground and after flying for a while, they told slightly different times (with the onboard clock being behind).

Was just going to say that. I saw that too; after thousands of miles of nonstop flight at supersonic speeds the difference was in milliseconds. So yes, astronauts age slower relative to those on earth, but a few months in the space station would probably not even yield a second difference.

#### PowerMacG5

##### Diamond Member
Originally posted by: Antoneo
I remember reading an article where an airplane had an atomic clock onboard sychronized with an atomic clock on ground and after flying for a while, they told slightly different times (with the onboard clock being behind).

Yeah, there was a few thousandths of s second difference.

#### PowerMacG5

##### Diamond Member
Originally posted by: niwi7
i dont understand this at all

when you say aging are you talking about time or physical conditions?

because if your talking about time then ok i understand, but if you are talking about physical conditions....i just dont see how going fast can make you "age" faster?

Going faster makes the local time-space within the ship actually go slower than a point of reference (Earth for instance), so you would in essence age slower.

#### BurnItDwn

##### Lifer
thats not enough velocity to really make a difference with time dilation. Now if he was going like 1/3 or 1/4 the speed of light, than that would be enough for a measurable difference..

Originally posted by: BurnItDwn
thats not enough velocity to really make a difference with time dilation. Now if he was going like 1/3 or 1/4 the speed of light, than that would be enough for a measurable difference..

There is direct evidence. They flew an atomic clock on the concorde, and it was then behind the one that was on the ground.

#### Looney

##### Lifer
Originally posted by: Kalvin00
Aging has nothing to do with revolving of the Earth...

Not with the revolution of Earth, but he means according to Einstein's theory that as you approach the speed of light, time slows down. When you're in revolution around the Earth, you're travelling faster than people on earth, so time affects you differently. Of course, 30 days in space isn't going to save you 15 days on Earth. Maybe seconds.