It’s so we know what time ‘Lost’ is on… oh well… I guess it is sort of useless now.
A clock for space travellers would be useless. What time zone would you set it to?
Don’t ask “What good are clocks?”. Ask “How do clocks behave?”. Physics will answer that question. Then figure out what you can do with that behavior. Clearly, lots of nice things can be done with that behavior; you know what clocks are and you’ve clearly found them of great use to you before. Just because they don’t happen to behave exactly the way you naively thought they did in all conditions doesn’t mean the behavior they actually have can’t still be useful to you, as clearly it often has been.
Then why do GPS satellites have to factor in both special and general relativity in their time calculations? If relativity is wrong, why does it work?
Nevermind about that. One can always play semantics games to make it so, but let’s cut to the heart of the matter, the brute observable facts. What do you suppose would happen if we took two clocks (garden-variety, off-the-shelf, just-what-you-think-a-clock-is clocks), synchronized them, then let one sit around at home, and sent the other off in a very fast rocket far out and then back? Would the two clocks have the same reading upon the reunion?
As I understand it, such experiments have been performed and the result has been that two clocks no longer have the same reading upon reunion. Accordingly, if you claim they will, well… sorry, but you’re wrong. That’s not what happens. Any theory that strives to accurately describe the world will have to account for this.
So go on, explain what force is acting on the digital or mechanical components of a clock, that would make the device record time differently?
Would it always be faster? Slower? Is there any variation?
Suppose you had two cars with synchronized odometers, then drove them along two very different paths from point A to point B. You probably wouldn’t be very surprised to discover that the odometer readings of the two cars at B might not be the same. Would you ask what force is acting on the mechanical components of the odometer to cause this? That’s not where the answer is found; the answer is just “One car took a longer path from A to B than the other”.
Well, that was just concerning points and paths in space, but the same thing happens with points and paths in spacetime. Different ways of getting from one location and moment to another location and moment can cause a clock to increase by different amounts, just as different ways from getting from one location to another location can cause an odometer to increase by different amounts. That happens to be the way the universe works, and we even know very precise mathematics describing the manner in which it happens, as experimentally verified. Many people have a model in their mind of how the universe works where this phenomenon would not occur, but that just means the model they have in their mind is inaccurate, insofar as experiments give different results from it.
I know about the tests they have done with clocks, and I don’t think they are accurate. I think it’s an observation of finding an idea that might correlate with the results, but doesn’t actually explain the cause.
If I drove two identical cars using at the same speed along two different routes to reach the same destination, but arrived at one destination faster than the other… you might assume that one route is faster than the other, but maybe it’s a mechanical problem, that one odometer said I was going so fast when I really wasn’t. Thus, I went slower without realizing it down a path that might actually be just as fast.
Maybe these clocks say time was passing more slowly, but it really wasn’t. Maybe it’s a deceptive behavior based only on speed and gravity, and even space, but maybe time is not a factor like we think it is.
I think FTL communication will happen, and we’ll find out then.
If we never question science, then it becomes a religion.
We are not measuring the distance it has travelled, we are measuring the time it has been travelling. Are you suggesting there are “short cuts” or “scenic routes” in time? How does that work?
I’m saying, yes, not all routes from point A in spacetime to point B in spacetime cause clocks to increment by the same amount. Such is the way the world works. The math isn’t even that hard: suppose from person A’s point of view, person B moves by distance d and time t at a constant speed. Then, person B’s clock will actually tick forward by sqrt(t^2 - (d/c)^2) over that movement, which will be less than t so long as d is greater than 0. Add this up over every (possibly infinitesimal) constant-speed leg of person B’s journey and you’ll know how much person B’s clock ticks.
For example, suppose, from person A’s point of view, person B blasts away at half the speed of light for 50 seconds, then blasts back at half the speed of light for 50 seconds. By the time of reunion, person A’s clock will have ticked 100 seconds off; however, person B’s clock will have only ticked 50 * sqrt(3) ~= 86.6 seconds off.
(Physicists, and people who know what they’re talking about in general, please correct me if I’m getting any of this wrong)
Can you describe a practical application of this theory that doesn’t involve equations?
We constantly question science. That’s called ‘doing experiments’. All experiments so far (with clocks, cosmic rays, interferometry, GPS measurements etc.) so far agree with special relativity. To say ‘yeah, well, I still think it’s wrong’, especially without having a viable alternative, isn’t healthy scepticism, it’s simply stubbornness.
Why does there have to be a “viable alternative”? What is so hard for scientists about saying “We don’t know and this is just our best guess.”? When the most highly educated people on the planet believed that the Earth was the centre of the universe*, it was wrong whether there was a viable alternative, or not. They just didn’t know how or why they were wrong.
- Although, in their usual bullshitting way, some are now saying we are the centre of the universe…and so is everywhere else!
Well, that’s what the word ‘theory’ means…
The problem is that in order to admit you’re wrong, you have to know that you’re wrong – i.e. you need contrary evidence at least.
In order to admit you are wrong, you have to accept that you might be, and it would seem that a lot of scientists are heavily invested in their current beliefs. This is an asset if they are on the right track, but if they are not, it can be very difficult to get them to switch rails.
Um, it tells you what actually happens in these situations? Is that not enough? What sort of thing would you be looking for?
Something more realistic than people flying about at speeds that are not even possible, would be nice. The way I see it, if something can only be understood with reference to numbers, I’m calling BS on it as a real explanation.
As has been said, GPS wouldn’t work, or at any rate be less precise, without taking into account both special and general relativity.
What’s so impossible about half the speed of light? I mean, a fourth, a millionth, whatever you like, the same example works, mutatis mutandis. Anyway, at speeds negligible in comparison to the speed of light, the theory is negligibly different from Newtonian mechanics; its whole raison d’etre is to give calculations accurately describing the observed experimental results concerning higher-speed phenomena.
Where is the cut-off line for “high speed phenomena”? 50,000mph? 50,000mps?
What would/could travel at half the speed of light? Something with half the energy? What would that be?