Can the earth twin experence the space twins date?

[Mr Skeptic]

But his body is also a clock, and also runs slower. Consider if your watch were to run slower than regular earth time when you are here on earth. Usually this is a few seconds in quite a while, but say your watch ran much slower. Eventually, you compare your watch to everyone else's and decide to synchronize. You could change your watch to match everyone else's, or everyone else's to match yours. Changing the clocks either way will not magically transport you to the past or future.

 

Now imagine if every way you had of telling time, be it aging of your body, rate of decay of your deceased pet goldfish, burn rate of your candle, radioactive decay of the Americium in your smoke detector, how fast you think, every way of measuring time that you possibly can have inside a spaceship, disagreed with every possible way of measuring time on earth. Again, changing you watch is not going to transport you to the past or the future.

[Moontanman]

From the point of view of the space ship twin wouldn't it be the earth twin who's time was slowed down? Since from his point of view it would be the rest of the universe that was time dilated?

[cameron marical]

yes.

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but, in reality, he was the one moving, so he was the one who was affected abnormally compared to earth. i think thats how it works.

[swansont]

yes.

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but, in reality, he was the one moving, so he was the one who was affected abnormally compared to earth. i think thats how it works.

 

It's not the motion. The system is symmetric — each sees the other's clock as being slow — until one of them undergoes an acceleration, and that's the only way they can get into the same inertial frame. The acceleration is the key.

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I have no objections, I am just trying to understand how the twin is in the year 2000 in his time frame yet steps into the year 2010 on earth. I can only think that he is really ageing his with his twin and only his clock runs slower.

 

As Mr Skeptic has commented, the body is also a clock. This is an effect on time, which is measured by clocks. Time runs slower for the twin that makes the trip. Not as many days have passed.

 

Timekeeping is an exercise in bookkeeping. If my Google-fu is working, I see that this is the year 5769 according to the Jewish calendar. But it's the year 2009 according to the Gregorian calendar, and that would be ~13 days off from the Julian calendar (meaning it would be March 2). When the change was made from the Julian to the Gregorian calendar, the people "lost" 11 days, but they didn't really lose any time. What your clock or calendar reads does not dictate what will happen. It's only a matter of convenience so that we can make comparisons from the same perspective. But that assumes time runs at a constant rate, an assumption which fails to hold in relativity.

 

If the twins were 20 years old when the journey started in 1990, and they live for 80 years and drop dead from some congenital defect, the earth twin will die in 2050, and the space twin will die in 2060. The space twin only experienced 10 years while in the rocket, while the earth twin experienced 20.

[cameron marical]

As Mr Skeptic has commented, the body is also a clock. This is an effect on time, which is measured by clocks. Time runs slower for the twin that makes the trip. Not as many days have passed.

 

Timekeeping is an exercise in bookkeeping. If my Google-fu is working, I see that this is the year 5769 according to the Jewish calendar. But it's the year 2009 according to the Gregorian calendar, and that would be ~13 days off from the Julian calendar (meaning it would be March 2). When the change was made from the Julian to the Gregorian calendar, the people "lost" 11 days, but they didn't really lose any time. What your clock or calendar reads does not dictate what will happen. It's only a matter of convenience so that we can make comparisons from the same perspective. But that assumes time runs at a constant rate, an assumption which fails to hold in relativity.

 

If the twins were 20 years old when the journey started in 1990, and they live for 80 years and drop dead from some congenital defect, the earth twin will die in 2050, and the space twin will die in 2060. The space twin only experienced 10 years while in the rocket, while the earth twin experienced 20.

 

but in the twins paradox, at least the one i read about, it talked about a clock measured by a photon ticking across some mirrors making a little second by second thing. i understand the light traveling slower for that clock, but we dont have those in our bodys.

[Moontanman]

Ok, I'm not trying to be obtuse here, i am really trying to understand. I understand that from the stand point of both twins their own clocks are running at the normal rate. Both see the other as having a distorted time frame. Both see the other as foreshortened, more massive and time slowed. Why is reality the of the twin who is moving the only reality that turns out to be real? it's all relative, neither twin can say who is moving until one of them stops. Why is one reality real the other not?

[Sisyphus]

Ok, I'm not trying to be obtuse here, i am really trying to understand. I understand that from the stand point of both twins their own clocks are running at the normal rate. Both see the other as having a distorted time frame. Both see the other as foreshortened, more massive and time slowed. Why is reality the of the twin who is moving the only reality that turns out to be real? it's all relative, neither twin can say who is moving until one of them stops. Why is one reality real the other not?

 

They’re both real. The reason they’re different “when one of them stops” is because starting and stopping involves acceleration, which means that the situation is not symmetrical. Take a look at the Wikipedia article on the Twins Paradox, which explains it in some detail in a few different ways:

 

http://en.wikipedia.org/wiki/Twins_paradox

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but in the twins paradox, at least the one i read about, it talked about a clock measured by a photon ticking across some mirrors making a little second by second thing. i understand the light traveling slower for that clock, but we dont have those in our bodys.

 

But we do have all sorts of other "clocks," everything that happens in your body and mind that takes an amount of time. Which is to say, everything that happens in your body and mind. The reason light traveling back and forth is especially useful is because the speed of light is constant no matter what, so it’s a straightforward and reliable way to measure how much time is really passing, and because it’s a good way to show why time in different frames must be different.

[swansont]

but in the twins paradox, at least the one i read about, it talked about a clock measured by a photon ticking across some mirrors making a little second by second thing. i understand the light traveling slower for that clock, but we dont have those in our bodys.

 

That's to demonstrate that it's not because of some mechanical effect (or defect) in the clock. The rate at which time passes has changed, so it affects everything.