SPEED OF LIGHT

The non amateur stuff. Hawking, black holes, that sort of thing

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Gregger
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Post by Gregger »

Cant agree with that. Some of the facts may be correct but asuumptions surely not

I live in Derby. If my brother in Derby travlsl to London and when he gets there sends a postcard back it will take a day to reach me. We were at the same time when he posted it but just because the post takes a day to relay the message doesn't mean his clock is slower than mine?
A clock up in a plane runs faster than one at the stronger gravitationally held ground. Fact
Yes , I've read that in a book too. Thats what you mean by fact. Whose seen the paper, understood it , worked out the maths and stats with it and agrees. Whose actually read Einsteins actual work and understands it. Its all well beyond me and I suspect nearly everyone else. But thta doesn't neccesrily mean its gospel
Gregger
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Post by Gregger »

I'm not totally sure what happens when a body ages but I guess its molecular strucure must alter.

So by moving quicker we can alter atoms and molecular strucure?
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Post by joe »

Hi Gregger,

It's a fact in the sense that two synchronised clocks can be compared after one has gone up on a plane. The one that stayed on the ground shows a shorter time has passed. The amount is miniscule and it is necessary to use accurate atomic clocks or something like that but it has been measured. Now, as you say, I've only read that in a book and haven't performed the experiment myself but it makes sense. It's the same with your brother, you don't see the difference because it is miniscule. If your brother's clock was running 0.00000000005% less than yours your not going to notice. You have to get close to the speed of light to actually see the effect. I have read many accounts of Relativity and while I cannot do the maths I don't think you have to in order to understand the concepts, even though they are tricky.

I'm afraid my posting rambled a bit but perhaps you can agree that if a person travels to a star five light years away at half the speed of light it should take him ten years, in theory. Now if you on Earth look through your telescope after ten years to see him reach the star you won't see it happen. He will still be only part of the way through his journey. If it does take ten years for the trip then once the astronaut has reached the star, the light from that event has to take five years to return to our telescope. Ten plus five years = 15 years for a ten year journey. Einstein's formula for time dilation (don't ask :? but it's the same one involved with the plane above and it has been tested thousands of times) will give a reading on the clock on board the rocket that is less than ten years when it arrives at the star, say eight years for the trip. So you on Earth see the rocket reaching the star after 15 years when you know that it has taken 10, and you see on the rocket's clock that it reads eight years!

The bottom line here is that as two clocks travel away from each other the time taken for the time information (light) to travel between the two progressively increases so something has got to give. The light from your clock reaches your eye immediately but the light from the other can take weeks or years. It is impossible for them to look the same or tell the same time.

Regards,
Last edited by joe on Sat Feb 26, 2005 7:50 pm, edited 2 times in total.
200mm Newtonian, OMC140, ETX90, 15x70 Binoculars.
joe
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Post by joe »

Hello again Gregger,

I think aging affects the chemical structure rather than molecular. Motion does not affect anything in your local timeframe. It's only with comparison to someone else's. Unless you get accelerated to 20G then it probably will have a lasting effect on your body! :twisted:

You are right to highlight the difference between real slowing of time and apparent slowing. But the very important point is that you have to travel to experience both. To travel you have to accelerate which means increasing the gravitational field around you which physically slows time. I obviously won't convince you 'cos I don't know enough maths to prove it here. If only astrophysicists answered questions on forums. And I might add thousands of people have read the paper, understood it, tested it and explained their results. The GPS system for example can only work when the effects of relativity are factored in as they contain clocks of the kind that can measure miniscule differences of the kind involved in weak gravitational fields like the one associated with the Earth.
200mm Newtonian, OMC140, ETX90, 15x70 Binoculars.
Gregger
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Post by Gregger »

The GPS system for example can only work when the effects of relativity are factored in
I guess thats where it must work. An awful of of technology works using relativity theory, so there must be some sense behind it!
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Post by joe »

Yes there must.
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Gregger
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Post by Gregger »

If only astrophysicists answered questions on forums
I'd have thought they're the worst people to explain it!

"Brief History of Time" for example. I've tried it twice and got to page 60 so far before putting it back on the shelf!
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