Time dilation?

[Zico]

I just cant get my head around the concept of time dilation.. It was touched on in Physics at college this morning, I looked it up on various sources only to read things like..

"Time dilation would make it possible for passengers in a fast-moving vehicle to travel further into the future while aging very little, in that their great speed slows down the rate of passage of on-board time. That is, the ship's clock (and according to relativity, any human travelling with it) shows less elapsed time than the clocks of observers on Earth. For sufficiently high speeds the effect is dramatic. For example, one year of travel might correspond to ten years at home. Indeed, a constant 1 g acceleration would permit humans to travel through the entire known Universe in one human lifetime.The space travellers could return to Earth billions of years in the future."

?!?!?

Now that is a headmincer and a half !



I'd always believed time was a constant. For me... time slowing down for a person travelling at 99.9% of the speed of light must be an illusion relative to the stationary observer only. I'd compare it to the 'Doppler effect' where the tone of a sound wave will appear to change to a higher note as it moves towards you or a lower note as it moves away from a stationary observer... or am I looking at this from the wrong perspective?

I can be a bit thick at times I freely admit.. Are there any former phyisics students on here that can help me get my head round this?

[EuroTroll]

I'm no good at Physics, but I know that even for satellites orbiting the Earth, time moves at a different rate. Clocks on GPS satellites have to be adjusted for this, or your GPS would be way off.

[Mark]

No time is relative to the observer, the only real constant thing is the speed of light.

This affect applies to every moving object, someone travelling in a car will experience a slightly different time (were talking trillionths of a second) to a person not moving.

I've heard it explained as if you are moving away from a clock at half the speed of light, you'd observe the clock to be running half as fast as the light from the clock takes twice as long to reach you as in effect it's trying to catch up with you. If you go at 100% the speed of light the time on the ticking clock will appear to stop.

[schmenke]

I'm no good at Physics, but I know that even for satellites orbiting the Earth, time moves at a different rate. Clocks on GPS satellites have to be adjusted for this, or your GPS would be way off.

Makes sense. The faster an object travels, the greater the time dialation.
GPS satellites are traveling, continuously for years, at thousands of miles per hour.

[Mark]

Crucially for GPS satellites the positioning system relies on them having hyper accurate clocks and the GPS receivers work out the position on the earth due to the difference in the timestamps transmitted, so the smallest inaccuracy with the clocks mean GPS won't work.

The clever thing is that Eisenstein worked this all out without experimental evidence.

[Knock-on]

That explains it. I was down the pub having a game of pool the other day and I swear I was only there for about 1/2 an hour but Mrs Knockie gave me hell for being out most the night.

I will calmly and logically explain to her that as it was quite a slow game, time actually slowed down relative to the clock in the Kitchen and therefore she's in the wrong for having a go. In fact, if we have a really slow game, I could be out all the night without actually having entered the pub in the first place!!

Sweet little filly will probably struggle with the concepts but I'll just pat her on the head and let her get on with the washing.

:D

[Breeze]

No time is relative to the observer, the only real constant thing is the speed of light.

This affect applies to every moving object, someone travelling in a car will experience a slightly different time (were talking trillionths of a second) to a person not moving.

I've heard it explained as if you are moving away from a clock at half the speed of light, you'd observe the clock to be running half as fast as the light from the clock takes twice as long to reach you as in effect it's trying to catch up with you. If you go at 100% the speed of light the time on the ticking clock will appear to stop.
So, if you doubled back at the speed of light would the effect be reversed so that you arrived only shortly after you left? And if you are moving away from one object, aren't you moving toward another so that when you arrive there all the girls are old and wrinkled?

[Mark]

So, if you doubled back at the speed of light would the effect be reversed so that you arrived only shortly after you left? And if you are moving away from one object, aren't you moving toward another so that when you arrive there all the girls are old and wrinkled?

Nah, not as simple as that, never as simple as that.

[Breeze]

That explains it. I was down the pub having a game of pool the other day and I swear I was only there for about 1/2 an hour but Mrs Knockie gave me hell for being out most the night.

I will calmly and logically explain to her that as it was quite a slow game, time actually slowed down relative to the clock in the Kitchen and therefore she's in the wrong for having a go. In fact, if we have a really slow game, I could be out all the night without actually having entered the pub in the first place!!

Sweet little filly will probably struggle with the concepts but I'll just pat her on the head and let her get on with the washing.

:D

Its strategy like that which allowed Wellington to put the smackdown on Bonaparte.

[Breeze]

Nah, not as simple as that, never as simple as that.

AAhhhhrrrrrggg. Brainfreeze! :s

[schmenke]

So, if you doubled back at the speed of light would the effect be reversed so that you arrived only shortly after you left? And if you are moving away from one object, aren't you moving toward another so that when you arrive there all the girls are old and wrinkled?

It’s the other way around isn’t it?

Time is relative to the observer.
If, say, Edgar travels to a distant galaxy at close to the the speed of light, and it takes him 5 years there and back, then he has aged 5 years. Time is constant relative to his reference.
However, an observer on earth, sitting on a porch, say in Savannah Georgia, would experience time relative to his reference, i.e. travelling at a speed of zero. Hence, he would have aged far more. Upon Edgar’s return, who is now 5 years older, the observer in Savannah would be an old geezer still chasing unwrinkled skirts.

I think... :erm:

[Knock-on]

Its strategy like that which allowed Wellington to put the smackdown on Bonaparte.

More likely allow Mrs Knockie to smackdown on my butt!!

[Mark]

Which is fine until you consider the prospect of travelling to the nearest galaxy at the speed of light, which takes 5 years. When the nearest galaxy is 2 million light years away. :D

[Breeze]

So as I understand it, for a traveller moving near the speed of light, time slows down tremendously. And has some math whiz sorted by how much? Would the traveller's movements also be in slow motion? Would the cells in his body and his metabolism know he was travelling that fast and slow down correspondingly? After all, if the clock slowed everything moving at that speed would slow, no? How long would it take to chew a piece of gristle? Or brush your teeth afterword? Or have an orgasm!

Head officially minced.

[Knock-on]

Which is fine until you consider the prospect of travelling to the nearest galaxy at the speed of light, which takes 5 years. When the nearest galaxy is 2 million light years away. :D

Why only c1? Why not c10, c100 or even forget about the speed at all and just folding space?

[schmenke]

This thread is getting too deep for me.
I have a hard enough time just finding a folded pair of trousers in the morning :s

[Mark]

So as I understand it, for a traveller moving near the speed of light, time slows down tremendously. And has some math whiz sorted by how much? Yes, of course, Albert Eisenstein, you may have heard of him.



Would the traveller's movements also be in slow motion? Would the cells in his body and his metabolism know he was travelling that fast and slow down correspondingly?

No, as far as he's concerned everything is normal.



After all, if the clock slowed everything moving at that speed would slow, no? How long would it take to chew a piece of gristle? Or brush your teeth afterword? Or have an orgasm!

Depends on how fast you are going..

[Mark]

Why only c1? Why not c10, c100 or even forget about the speed at all and just folding space?

Cos it was specified that the speed of light was the travel speed ;)

[EuroTroll]

Albert Eisenstein

If you cross Albert Einstein and Sergei Eisenstein (http://en.wikipedia.org/wiki/Sergei_Eisenstein), what do you get? :p :

[edv]

The 4th of these 4 comics is relevant:

Actually, this is how I picture schmenke as a father.....

http://i.imgur.com/w10md.jpg

[Zico]

I'm no good at Physics, but I know that even for satellites orbiting the Earth, time moves at a different rate. Clocks on GPS satellites have to be adjusted for this, or your GPS would be way off.

Is this to do with time dilation or is it just natural timing acuracy differences between two devices that require to be fully sychronised to ensure the GPS positions can be calculated acurately?



No time is relative to the observer, the only real constant thing is the speed of light.

This affect applies to every moving object, someone travelling in a car will experience a slightly different time (were talking trillionths of a second) to a person not moving.

I've heard it explained as if you are moving away from a clock at half the speed of light, you'd observe the clock to be running half as fast as the light from the clock takes twice as long to reach you as in effect it's trying to catch up with you. If you go at 100% the speed of light the time on the ticking clock will appear to stop.

You seem to be agreeing with my understanding of the concept in the first paragraph.. not in the second one but are again in the third?

If you could somehow view a clock face as you moved away from it at close to the speed of light I can understand how the clock timing would appear to slow down in the same principle as my anology to the doppler effect where sound waves will be heard at a lower tone (slow down to a lower frequency ) ie an ambulance siren sounds an octave lower as it moves away from you.


The theory that a person that travelled at the speed of light would age less relative to a stationary person is what I'm struggling with.

The earth rotates at aprox one thousand mph and rotates round the sun at 67,000 mph so we are all travelling through space and time at the same rate.... are they saying that we would all age far quicker if (somehow) the earth and the planets were stationary? :D

If that is what Einstein is saying/said, he's got this one wrong! ;)


Good stuff guys, keep it coming....

[J4MIE]

I remember there was a program on the BBC a while back and it was all about time and how it is different for everyone. Can't remember what program or who it was but I'll let you know when I watch it next week.

[Breeze]

This thread is getting too deep for me.
I have a hard enough time just finding a folded pair of trousers in the morning :s

Schmenke and I will be down at the local pounding beers. Just call if you need us.

[donKey jote]

So that's how it took god only seven days to create everything ! :idea:

[janvanvurpa]

Einstein had a great saying on the idea of time being totally subjective--depending on where the observer of time was and what he was doing:

10 minutes sitting on the top of a hot stove would be a very long time indeed.
But an hour in the arms of your lover is but a moment.

He was a genius. Nuff said.

[Rollo]

Why only c1? Why not c10, c100 or even forget about the speed at all and just folding space?

Professor Sinclair proved that C5 was slower than the speed of smell.

[airshifter]

Schmenke and I will be down at the local pounding beers. Just call if you need us.

You go right ahead. I'll join you after I get my head around how this time thing works. I figure I can get in several days of drinking before last call if I move fast enough. :D

[Tazio]

Carl Sagan does a very good job of demonstrating the concept. However at the end of the video he admits that only atomic particles traveling near the speed of light do decay more slowly than stationary ones do. This is crucial in our understanding of time dilation. For obvious reasons it can't be tried with a person until a vehicle is developed that can do 95% the speed of light

http://www.youtube.com/watch?v=yirQ4YXZZVk

I'm not sure, but I think the idea of looking back at a clock while travelling a relatively long distance at close to light speed would be subject to the time it takes light to travel that distance. So just like every other object in space, a snapshot of the clock will show the time it is on the clock minus the two years light takes to reach from the clock to the traveler.

In the following video Sagan goes on to explains the speed of light, and traveling near the speed of light and elaborates on time dilation

http://www.youtube.com/watch?v=BgpcqiiTM8A&feature=related

[EuroTroll]

Is this to do with time dilation or is it just natural timing acuracy differences between two devices that require to be fully sychronised to ensure the GPS positions can be calculated acurately?

I think it must be to do with time dilation, as Mark and Schmenke explained. As I understand it, the atomic clocks on these satellites are so precise that they wouldn't otherwise need adjustment.

[Zico]

Thanks guys..

Studiose- I remember reading years ago about an atomic clock that had been flown around the earth in the stratosphere at great speed.. after return to earth, like you say...there was a time difference between an atomic clock on earth, I had rubished the idea that time itself could have altered putting it down to particle behaviour at a sub atomic level (Quantum physics) somehow altering to cause a timing discrepancy due to the reduced effects of gravity. It turns out that that my prediction is actually true to some extent..

"According to Einstein's theory of gravity and space-time -- called "general relativity" -- clocks in strong gravity tick slower than clocks in weak gravity. Because gravity is weaker on the ISS than at Earth's surface, PARCS should accumulate an extra second every 10,000 years compared to clocks ticking on the planet below. PARCS won't be there that long, but the clock is so stable that it will reveal this effect in less than one year. (Strayer notes that clocks on GPS satellites experience this relativistic phenomenon, too, and that onboard systems must correct for it.)"


Tick-Tock Atomic Clock - NASA Science (http://science.nasa.gov/science-news/science-at-nasa/2002/08apr_atomicclock/)


Great videos Mr Alkatraz, thank you. I'm still not convinced though.. :/ The distortion created by 'Red shift' is perfectly understandable due to visible light over the spectrum frequency range of aprox 405 THz to 790 THz, if we somehow broke that down to one frequency/wavelength to remove the distortion wouldn't the photons reaching our eyes (whilst travelling backwards close to the speed of light) have slowed substancially to make it appear that the time on that clock had slowed down?... therefore is it not just an illusion?

This is too much for a Saturday morning eh? :D

[Brown, Jon Brow]

http://download.lardlad.com/framegrabs/9F22/126.jpg

[Tazio]

Great videos Mr Alkatraz, thank you. I'm still not convinced though.. :/ The distortion created by 'Red shift' is perfectly understandable due to visible light over the spectrum frequency range of aprox 405 THz to 790 THz, if we somehow broke that down to one frequency/wavelength to remove the distortion wouldn't the photons reaching our eyes (whilst travelling backwards close to the speed of light) have slowed substancially to make it appear that the time on that clock had slowed down?... therefore is it not just an illusion?

This is too much for a Saturday morning eh? :D
I thought that someone raised the question of what time the stationary clock would read. I was careful to use the word snapshot so the view would be instantaneous I also said I wasn’t sure. (It’s been 39 years since I took Freshman Physics) :( However when you look at something like a star that is 2 light years away you are seeing the star as it appeared 2 years ago. It could have gone Super Nova a month earlier but it will not appear that way until two years have passed from when the event happened. That clock will read roughly what it did when you left if you traveled in a straight line at the speed of light. Remember it is the the watches on the vehicle that would be slowing down. Two light years is two light years and you would see the clock as it appeared two years ago. Actually the clock would have gained some time since the vehicle could approach light speed, however it cannot attain it.
Cheers

[D-Type]

Don't try to understand it - just accept it.

You thought that time was constant. Now your teacher tells you it isn't constant but varies with where you are and what speed you are travelling at. It may seem strange to you but all you can do is accept it. And understand how the new rules work without asking why.

It's happening all the time. We are constantly adding to the body of knowlege. When I was a student some 40 years ago, Continental Drift was considered a crackpot fanciful notion. Now it is a fundamental principle of geology.

We were, and I believe still are, taught at school that friction is independent of the contact area. This isn't true - just look at the wide tyres on racing cars. But the basic assumption is nearly true for a variety of situations and gives the right answer.

[Mark]

Well it's also certainly true that relativity does explain everything it breaks down in certain areas but these are often explained by Quantum theory. Which is often at odds with relativity.

If you thought the likes of time dilation was strange Quantum theory is just plain odd.

[schmenke]

...If you thought the likes of time dilation was strange Quantum theory is just plain odd.

Yep, I recently watched an entertainnig PBS (Nova, I think) series about Quantum Mechanics and it was mind-boggling stuff. They started going on about string theory and I've never looked at my shoe laces the same since :crazy:

[donKey jote]

Was it Billy's missus used to teach G-string theory, or was it only black holes ?