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Can you explain the speed:time phenomenon?

There are a lot of pasoti-ites far brighter than me, so can you explain something I can’t get my head around.

We all learned at school Einstein’s principle contained within his theory of relativity that the faster you travel, so time slows down. So, if I travel at the speed of light to some distant constellation and return when you are 12 months older, I may have aged by only 6 months or less. I’ve read several explanations of the cause, including Hawkins’ book, but frankly I still don’t understand it.

Until now my ignorance didn’t bother me. That is until 2 weeks ago when I read that because the satellites which transmit our TV signals and Satnav are travelling through space faster than we are, then time for these satellites is running slower, and constant fine tuning is therefore required to keep the satellite on exactly our clock and make sure you don’t get your satnav direction to turn right 20 seconds after you needed it.

Here’s my question. If I sit in my back garden on a cloudless night I can watch a satellite pass over in, say, 3 minutes, horizon to horizon. However I now know it’s doing that exact journey in 2.99999etc minutes. So how can the time I spent watching it be different from the time it spent doing it, whilst I was watching it?
 

MickyD

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Dec 30, 2004
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The time that passes "locally" for the satellite is also exacty 3 seconds, but from its viewpoint - because it's moving faster than you - the time you took observing it was 3.00000000000000000000......1 seconds. It's exactly the same in principle as the trip to the distant star and back (although the time dilation would be vastly greater than six months): local time, both on Earth and in the spacecraft, passes "normally", but relatively speaking, for the body at the far higher velocity (the spacecraft), time passes far more slowly than it does for you back on Earth. The nearer the speed of light relative to one another, the greater the time dilation. (Not that any physical object with mass can get anywhere near the speed of light in Einsteinian phsyics anyway, because the energy required would approach infinity.) Clear as mud? You have to think in terms of four-dimensional spacetime, not boring old three-dimensional space plus time.

And if you think Relativity is weird and counter-intuitive, try getting into quantum physics! And while I'm on the subject, nobody has yet found a way to make the macroscopic Relativity work with the microscopic Quantum Theory, which means that there's much more yet to be discovered and worked out. There's hope for string theory, and an idea known as quantum gravity, but it seems there's some way to go yet - and it will take something far more powerful than CERN to test them.

If that ever happens, we'll finally have a GUT - Grand Unified Theory - that will marry together the four fundamental forces as we currently understand tham: the strong nuclear force; the weak nuclear force; electromagnetism; and gravity.

PS And to be pedantic :D : you can't travel to a constellation, because the stars that comprise it might be thousands of lightyears apart as measured from Earth. It's just human pareidolia that shapes them into animals and mythical characters and so on, as if projected onto a flat background when those stars actually exist in vast three-dimensional space.
 

MickyD

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Dec 30, 2004
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Brighton
Glad it helped.

Maybe there should be a Pasoti Pals board, a bit like the now-defunct Yahoo! Answers :thumbup:

On second thoughts, though... no. It would soon devolve into a thinly-disguised opinions board, with threads beginning with rhetorical questions.
 
Apr 3, 2008
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Westerham Kent
You might enjoy Project Hail Mary, written by The Martian Author Andy Weir....

He uses a lot of these concepts in the plot of this book and it kind of helps to see them in the process of reading the story rather than in the abstract....
 

GreenThing

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I’ve had the thought that this tiny time difference could be the reason behind deja vu. You get the feeling that you’ve been there before, and you have, a fraction of a nanosecond ago.
 

The Doctor

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I’m not surprised you didn’t get much out of a book by Stephen Hawking. His books are garbage. I read a stat once that said that only a tiny fraction of the people who had bought the bestselling ‘A Brief History of Time’ had got beyond the first 20 pages or so…
 
Jul 15, 2006
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The Doctor":1327b15p said:
I’m not surprised you didn’t get much out of a book by Stephen Hawking. His books are garbage. I read a stat once that said that only a tiny fraction of the people who had bought the bestselling ‘A Brief History of Time’ had got beyond the first 20 pages or so…

I read it all :greensmile:
 

Willis88

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Quinny":17skhe0c said:
The Doctor":17skhe0c said:
I’m not surprised you didn’t get much out of a book by Stephen Hawking. His books are garbage. I read a stat once that said that only a tiny fraction of the people who had bought the bestselling ‘A Brief History of Time’ had got beyond the first 20 pages or so…

I read it all :greensmile:

Ditto, although re-read a few chapters to get my head around some bits.

Currently working through Chaos by James Gleick that's a bit easier to follow.
 

MickyD

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Dec 30, 2004
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Quinny":1ldq1gwd said:
The Doctor":1ldq1gwd said:
I’m not surprised you didn’t get much out of a book by Stephen Hawking. His books are garbage. I read a stat once that said that only a tiny fraction of the people who had bought the bestselling ‘A Brief History of Time’ had got beyond the first 20 pages or so…

I read it all :greensmile:
I read it in a day :whistle: but I was already quite familiar with its contents, having helped him to write it having read similar stuff before.

As for the 20 pages: I suspect that's probably true of many "classic" books: War and Peace, Moby-Dick, what have you. I got about two pages into War and Peace myself, but I'd never planned to read it: my parents had bought it for me for some reason. I'd never shown the slightest interest in bleedin' epic Russian literature, so maybe they'd seen it in a WH Smiths bargain bin or something.
 

MickyD

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Dec 30, 2004
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Brighton
Willis88":b69781tl said:
Quinny":b69781tl said:
The Doctor":b69781tl said:
I’m not surprised you didn’t get much out of a book by Stephen Hawking. His books are garbage. I read a stat once that said that only a tiny fraction of the people who had bought the bestselling ‘A Brief History of Time’ had got beyond the first 20 pages or so…

I read it all :greensmile:

Ditto, although re-read a few chapters to get my head around some bits.

Currently working through Chaos by James Gleick that's a bit easier to follow.
Great book - I read it when it first came out. I got hold of a fractal program for my pre-internet computer (running Windows 3.1, I think) and it absolutely blew my mind.
 

The Doctor

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Yes, Gleick’s book ‘Chaos’ is very good.

For a really good general overview of science I think it is hard to beat Bill Bryson’s ‘A Brief History of Nearly Everything’. Bryson isn’t a scientist (at all) so he took a lot of time to get to grips with the content and puts it across in a very approachable way.

Carlo Rovelli’s book ‘Seven Brief Lessons on Physics’ is good to read too. He’s got a wonderful, almost novelistic way of writing.