[OK I have to go now as guests are arriving so this may need some editing still. Hopefully it kinda makes sense]
A few of my problems with relativity, both of which might expose my extreme leymanish understanding of relativistic issues! Both problems are about the relatativistic effects of velocity.
I am sure we’ve all heard the example of time dilation due to velocity where a space ship heads away from the earth to alpha centuri at close to the speed of light and, due to its velocity, we’d see time slowing down due to relativity …
My problem with that whole example is this:
To the people on the spaceship, they would be the stationary observers and the earth would be moving away relative to them at close to the speed of light and hence (surely) they’d see time slowing down for us.
a. Is this the case?
b. If so then how can the two simultaneously be true in any traditional layman’s view of what time is?
c. When physicists say ‘time slows down’ for an object are they talking about the observed rate at which time passes for the object rather than whats actually happening to it? i.e. we see things happening more slowly on the object rather than them actually slowing down?
I assume all of the above would be true of the theoretical claim that an object ‘travelling faster than the speed of light’ would travel backwards through time.
Realtive to what? The earth I assume. Surely to any observer on the object would ‘see’ (for want of a better word) the earth relative to them moving faster and so perceive that moving backwards through time.
Is what the physicists are actually describing the fact that we would see what happened to the object in reverse order - i.e. we would see it moving backwards through time? This makes sense to me, for an object approaching the observer at least.
This would be my understanding of the situation, but I’d thought I’d ask for an expert opinion.
As far as I know although we have some physical evidence of relativity due to gravitation (flying clocks around the world etc) there’s none for relativity due to velocity, other than that it correctly predicts what we as ‘stationary’ observers can expect to see (i.e. it correctly predicts what will be observe in certain situations NOT what is actually happening).
Essentially relativity seems to map the universe on to a space which describes what we observe, and thus the models are dictated by or choice of viewing media. We have the conceit of believing all there is to the universe is what we perceive … and I have a real problem with this.
Imagine, if you will, a race that evolved to an enlightened state without knowledge of EM radiation, lets say in the dark seas of Europa.
Without light they no eyes, no perception of EM radiation at all all sensory input comes from sonar. They develop a perfectly good working model of their perceived universe, with relativity based around the speed of sound, perhaps a little earlier in their history than us, given that any perceived distortions due to velocity would exaggerated and more easily measured than those of light.
As a result, europan science correctly predicts that as the velocity of an object approaches the speed of sound the mass of the objects approach enourmous proportions (supersonic travel is well beyond the current capabilities of Europan science).
We, on the other hand, with our extra weapon of observation through light, would see no such thing. Europans science merely adds extra mass to the object so that, at the velocity they perceive it moving at (due to their choice of viewing medium) the object’s mass etc fits their other perceived experimental data.
What their science predicts is what they will observe, not what is actually happening, and the same, I believe is the case with Relativity.
(Not a perfect analogy I know … but you understand my my point I hope).
Surely a better approach for either science (human/europan) to take would be to understand the behaviour of their viewing media, take this in to account when making observations, but then, when they have their observations, do a little more work and create a model of the universe as it actually is.
At the very least physicists should be aware of what they’re doing (i.e. predicting what might be observed) and stop disappearing up their navels, making idiotic predictions about the universe about such things as time travel!
Such an approach would certainly save a lot of red faces on both europa and planet earth… (Note: unable to perceive ‘redness’ as such, traditional Europan scientists would describe such a phenomena as ‘time dilation due to embarrassment’, the speed of sound accelerated by the warmed fluid around the cheeks joke).
Anyhoo comments/answers please. I may be completely wrong in my understanding of this whole field. As I have said I don’t have an in depth knowledge of these issues!