Twin Paradox

Consider the traveling twin. Suppose you seal him in a craft and tell him that he will be sent into low earth orbit, brought home in a day or two, and then spend the next ten years in complete isolation. Unbeknownst to him, however, once he takes off from earth and experiences multiple g’s for a few minutes, weightlessness for a short period when he thinks he’s in Earth orbit, which may or may not be the case, and then accereration again as he supposes that he is returning to earth and finally one g as he thinks he is back on earth. He is not, though. Instead, the spacecraft has been accelerated to produce the effect, finally accelerating at one g to produce the illusion of earth’s gravity. As the speed of light is approached, forward acceleration is reduced and rotation of the spacecraft produces an angular acceleration of one g. Meanwhile, our hero has been watching videos and eating pizza and drinking good beer. He does this for ten years. Now he is told by the computer which is running the whole show that he’s going into space again. The spacecraft has been approaching earth and decelerating at one g. Now the acceleration is manipulated in such a way as to produce the illusion of taking off from earth into orbit (multiple g’s). The craft slips into orbit, real this time. He is told that he will now return to earth, for real this time. He experiences multiple g’s again and finally returns to earth. He steps out of the spacecraft for the first time in ten years and “Holy Shit!”; he’s millions of years in the future.

Is this a possible scenerio?

Probably not, just because of the difficulty of accelerating to light speed. At one g, it would take a long time to do so, and he would probably notice. I think the rest of it is plausible, though I’d await the opinion of a physicist.

We are not talking about “accelerating to the speed of light”, only approaching it.

I think that is a somewhat exaggerated demonstration of time dialation, yes. “Millions of years” is the problem. :slight_smile:

Why is he a twin?

If two twins experience identical accelerations, one due to gravity and the other due to artificial gravity via rocketry, they will both age at the same rate. The actual speed of the second twin is irrelevant!

The “Twin Paradox” is one of the reasons we have “Special” and “General” relativity. Do a Google on these terms and do some reading.


I was chatting with a surgeon at the hospital. When we finished, I left and immediately ran into him again in the corridor. I looked back to where I had been, and sure enough he was in two places at the same time. Turned out to be a twin pair o’ docs!!! :smiley:

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