A long long time ago in a place far far away, well maybe not so far away but it was a long time ago, I read a book entitled, “Understanding Einstein”, I don’t remember who the author was but it was a very interesting book because it went through Einsteins various thought experiments and how they lead to his theory of general relativity.
After reading the book, and I had at least thought I had comprehended it, I thought to myself, this is the same logic that lead people to believe that faster than sound travel was impossible, until we did it.
Moreover, things appeared to be mainly a perspective problem. That is, if you were able to watch the clock of someone receding from you of course their clock would appear to be running shorter, because the time it takes the light to travel from the clock back to you is getting ever longer because they are traveling away.
I ran into a bit of a logical non sequitur, because as I understand it, Einsteins theory of general relativity just specifies the motion relative to you, it doesn’t matter if it’s coming or going, the clock still goes slower as observed from your frame of reference. Trying to visualize it the way I was would have the clock going faster if someone was speeding to me at a significant fraction of the speed of light.
So I concluded I really couldn’t make sense of things at all. I read a bunch of physics books and they all made interesting implications as well.
You see, as I understood general relativity, based upon my reading Understanding Einstein, I was under the impression that if I watched someone moving relative to me at .87c, then I would see their clock run at half speed, their ruler become half as short, etc. But, from their perspective, their clock would be running at the normal speed, their ruler would be the correct length, but my clock would appear to be running slow and my ruler short.
I read various physics books, and articles like Alice in Quantum Land, and they give the impression that the moving person experiences their own clock running slow and their own ruler short. If I was running into a non sequitur before, now I’m really lost. That makes no sense at all because then everybody’s clocks would be out of whack equally and it would be as if nothing had happened. Alice in Quantum Land also makes the assertion that one second of time is equal to 186,000 miles of physical space. I don’t understand how that logic follows anymore more than one second of time is equal to 761 miles of physical space based upon the speed of sound.
Think about the classical example, someone takes a trip to a distant star system at a significant fraction of the speed of light, they get there in the expected time frame for them, let’s say Alpha Centauri at 4.3 light-years at .99c so the traveler would experience a trip duration of just over 4.3 years, but when they returned to earth, hundreds of years would have gone by, because relative to us their clock was going way slow.
But wait a minute, motion is relative, there is no absolute frame of reference. So someone traveling to Alpha Centauri at .99c, that’s exactly equivalent to them remaining stationary and the Earth, and Alpha Centauri and the rest of the stars moving towards the traveler at .99c, and then in that case, their clocks, all the clocks on earth would be running slow compared to the same traveler.
So if that is the case, if there is no absolute frame of reference, and I was under the impression that the Michelson-Morley experiment proved that, then from each others perspective, each others clocks ran slow, and so everyone is really still in sync and nothing magical happened in terms of time going bonkers. Most of his friends and relatives would still be alive and hundreds of years would not have passed.
You see none of this really is making good sense to me right now. My latest physics read, “The Dancing Wu-Li Masters“, it gets me back into the “the person in motion relative to me, their clock is going to appear to run slow to me, their ruler short, their mass heavy”, but to them everything is normal. And since everything is relative, likewise my clock, ruler, and mass will be affected in the same manner from their perspective.
Can someone help me make sense of this? I’m going to have a hard time sleeping now.