#1
Ok I'm reading about absolute time and this passage is a little ambiguous, so if anyone out there knows any general relativity can you clear this up for me. The paragraph goes:

"Consder a pair of twins. Suppose that one twin goes to live on the top of a mountain while the other stays at sea level. The first twin would age faster than the second. Thus if they met again one would be older than the other."

So to me that made it seem like the twin on the mountain top would age faster, however he then goes on to explain that in space when one flies around and approaches the speed of light, time relative to ones self will speed up so everyone on earth will be older in comparison. Now here's the confusion, does it mean flow of time is inversely proportional to or proportional to gravity. The way he explained it makes it seem like it's inversely proportional but I always thought it was the other way around, I thought if you live on the top of an apartment building you'd be younger than the people on the bottom. If anyone could enlighten me that'd be swell.
#3
Your hypothesis regarding the two components being directly proportion is interesting and perhaps even plausible, but I think you're forgetting the fundamental question here...




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#4
yeah...right....well..then...you see...i have no idea...link to the site?
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#5
I knew that light moves so fast that it only moves through space and when you approach the speed of light you age a lot slower but i've never heard the mountaintop thing.

I know this doesn't help at all but i'm curious to understand this too.
“Science cannot solve the ultimate mystery of nature. And that is because, in the last analysis, we ourselves are part of nature and therefore part of the mystery that we are trying to solve.”


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#6
Gravity has nothing to do with timeas far as i know.

The concept of the twins aging at different rates would probably be a consequence of the air (air's thinner at high altitudes), humidity, and temperature (higher places have lower temps).

Seems like a bad choice of example IMO.
Originally Posted by evening_crow
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#7
Quote by yawn



WHO CARES?!


well, I do, the idea that there is no absolute time or position seemed pretty interesting to me. Hoping somebody else out there does too.

and to evening crow, you kidding or not? I'm not sure.
#8
Quote by farcry
well, I do, the idea that there is no absolute time or position seemed pretty interesting to me. Hoping somebody else out there does too.
The minute difference in the aging process as a result of slight elevation distance isn't really a process of much significance. Interesting in theory perhaps, but of little value in terms of practicality.
#9
Quote by evening_crow
Gravity has nothing to do with timeas far as i know.

The concept of the twins aging at different rates would probably be a consequence of the air (air's thinner at high altitudes), humidity, and temperature (higher places have lower temps).

Seems like a bad choice of example IMO.

Relativity does say something about gravity and time just like speed and time. Black holes, with a gravitational pull of infinity ripping through space, do the same thing as the speed of light.
“Science cannot solve the ultimate mystery of nature. And that is because, in the last analysis, we ourselves are part of nature and therefore part of the mystery that we are trying to solve.”


-Max Planck

☮∞☯♥
#10
Quote by farcry
Ok I'm reading about absolute time and this passage is a little ambiguous, so if anyone out there knows any general relativity can you clear this up for me. The paragraph goes:

"Consder a pair of twins. Suppose that one twin goes to live on the top of a mountain while the other stays at sea level. The first twin would age faster than the second. Thus if they met again one would be older than the other."

So to me that made it seem like the twin on the mountain top would age faster, however he then goes on to explain that in space when one flies around and approaches the speed of light, time relative to ones self will speed up so everyone on earth will be older in comparison. Now here's the confusion, does it mean flow of time is inversely proportional to or proportional to gravity. The way he explained it makes it seem like it's inversely proportional but I always thought it was the other way around, I thought if you live on the top of an apartment building you'd be younger than the people on the bottom. If anyone could enlighten me that'd be swell.

I was sure it was the other way around - the twin at the mountain should be aging slower than the one at sea level.

I wrote an article about this, it's in my blogs. You might be interested in readin it. In short, the relativity theory says the closer you are to light speed, the less gravity applies to you, and gravity is what causes time to flow (and time causes people to age). In your case, the twin at the mountaintop would age slower (might've misread/miswritten something?) because he's further away from the Earth's gravitational pull-centre.
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#11
ahhhhh!!! people talking about science in a very sophisticated english!!!

*runs away*
#12
no I read it right raziel, it's right from Stephen Hawking's book. And to Yawn, if you knew anything about quantum mechanics or general relativity the relavence would be clear. Physicists are searching for a unified theory to explain existance, a theory of everything, seems pretty relavent if you ask me.
#13
Quote by .smudged.
ahhhhh!!! people talking about science in a very sophisticated english!!!

*runs away*
Would you prefer Piglatin?
#14
Quote by farcry
no I read it right, it's right from Stephen Hawking's book. And to Yawn, if you knew anything about quantum mechanics or general relativity the relavence would be clear. Physicists are searching for a unified theory to explain existance, a theory of everything, seems pretty relavent if you ask me.

String Theory FTW!

11 dimensions!

Infinite Universes where anything and everything happens!

woohoo!
“Science cannot solve the ultimate mystery of nature. And that is because, in the last analysis, we ourselves are part of nature and therefore part of the mystery that we are trying to solve.”


-Max Planck

☮∞☯♥
#15
Quote by farcry
no I read it right raziel, it's right from Stephen Hawking's book. And to Yawn, if you knew anything about quantum mechanics or general relativity the relavence would be clear. Physicists are searching for a unified theory to explain existance, a theory of everything, seems pretty relavent if you ask me.
Pfft. Clearly one must only chain a baby to ground level and chain a baby to the top of mountain and just wait a few decades to see. Unethical? Yes. Scientifically invaluable? You betcha.
#17
Quote by yawn
Pfft. Clearly one must only chain a baby to ground level and chain a baby to the top of mountain and just wait a few decades to see. Unethical? Yes. Scientifically invaluable? You betcha.


I'm teetering between laughing and thinking you're an absolute moron. You have a weird sense of humour if that's what you're doing.
#18
Quote by yawn
Pfft. Clearly one must only chain a baby to ground level and chain a baby to the top of mountain and just wait a few decades to see. Unethical? Yes. Scientifically invaluable? You betcha.

No. Just no...

We need more babies to make sure the results are valid.
Originally Posted by evening_crow
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#19
Quote by evening_crow
No. Just no...

We need more babies to make sure the results are valid.
Did someone say necrophilic pedophilic baby bonanza???

Quote by farcry
I'm teetering between laughing and thinking you're an absolute moron. You have a weird sense of humour if that's what you're doing.
I'm most definitely the latter. I resent being called weird!
#20
Quote by yawn
Did someone say necrophilic pedophilic baby bonanza???

LMAOSAURUS!!!!

Can i get that with some whipped cream and cherry on top?
Originally Posted by evening_crow
Quoting yourself is cool.


WARNING: I kill threads.
#21
Quote by Raziel2p
I was sure it was the other way around - the twin at the mountain should be aging slower than the one at sea level.

I wrote an article about this, it's in my blogs. You might be interested in readin it. In short, the relativity theory says the closer you are to light speed, the less gravity applies to you, and gravity is what causes time to flow (and time causes people to age). In your case, the twin at the mountaintop would age slower (might've misread/miswritten something?) because he's further away from the Earth's gravitational pull-centre.



well, technicaly, time doesnt cause people to age, the wearing down of the body through cell replication is what causes you to physicaly age. Time is just the way we measure the amounts of such things that occur consecutively.
#22
Quote by toshiro umezewa
well, technicaly, time doesnt cause people to age, the wearing down of the body through cell replication is what causes you to physicaly age. Time is just the way we measure the amounts of such things that occur consecutively.


Excellent observation. I would be thinking that the person up the mountain would age less as they are constantly moving at a greater speed than the person down the bottom and gravity is of no consequence to time.
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#23
Quote by toshiro umezewa
well, technicaly, time doesnt cause people to age, the wearing down of the body through cell replication is what causes you to physicaly age. Time is just the way we measure the amounts of such things that occur consecutively.

"Time" these days is measured by the number of vibrations in quartz atoms, and gravity makes atoms move around more. Aging is indeed the physical wear-down of the body, but it makes sense that the more atoms are allowed to move around, the faster the cells can replicate etc. Just like a cloth worn often will be quickly worn down, a body more exposed to gravity will age quicker. That's my view of it, anyways.
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#24
Quote by the_random_hero
Excellent observation. I would be thinking that the person up the mountain would age less as they are constantly moving at a greater speed than the person down the bottom and gravity is of no consequence to time.

Oh, that might be it. In his twin paradox, Hawkings might have been referring to the fact that on a mountain, you'll be moving slightly faster than you would be at sea level. In which case, gravity probably isn't what's being dealt with here, it's movement/speed.
I'm a communist. Really.
#25
Quote by the_random_hero
Excellent observation. I would be thinking that the person up the mountain would age less as they are constantly moving at a greater speed than the person down the bottom and gravity is of no consequence to time.


I did some more looking, flow of time is inversely proportional to strength of gravitattional field. I'm not talking about the biological changes of a human, stop thinking of it like that, think of it like clocks, the one on the mountain will be ahead of the one at sea level if you bring them close enough to look at them both at the same time.

edit: it's called gravitational time dilation
Last edited by farcry at Oct 13, 2007,
#26
Basically moving away from a stationary observer at speeds relative to the speed of light causes time dilation to occur. In other words, time slows down for the person in the rocket, relative to the observer.

EDIT: Gravitational time dilation only works with a stationary reference frame that takes the two into account because it's still to do with acceleration, as above. There'll be a tiny effect due to the differing gravitational potential slightly changing spacetime, but it'd only be obvious if an object fell down this potential and gained near-light speeds.
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Last edited by Yakult at Nov 30, 2007,
#27
Yeah Yakult's got it right.

Time dilation only occurs at speeds close to speed of light so the difference between the 2 dudes on the mountain will be minimal at very best as Yakult has said.

Look up the twin paradox, thats all about time dilation and special relativity.
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#28
yea, the mountain thing is a bad example of time dilation because even if the person fell off the mountain and accelerated to their terminal velocity (the fastest you can fall in the presence of air resistance) the speed of falling would be nowhere near the speed of light. the two people would age at relatively the same rate

as for the twins in the space ship, if the ship was flying near the speed of light, like at 99% of the speed of light, for example, the twin on earth would age much more quickly than the one in the ship

the way i think of it is every object has a 'total speed' which is the total of its speed through space and its speed through time. the total speed is always the speed of light - this means the faster you are moving through space, the slower you must go through time to compensate ('travelling' through time is the same as aging)

when the twin got back to earth, they would feel as though time had been moving just as it always does. however they would be a lot younger than everyone who was the same age as them when they left

i cant believe i just typed that, and also that you read it. im going back to learning the sweet child solo
#29
This effect has been verified with very sensitive clocks placed in satellites, (I believe I read that this effect has a practical application in the GPS network) and time does pass 'faster' closer to a massive body, but the effect is tiny, milliseconds per century.

I think in relation to velocity the faster you go, the more mass you have so if it was possible for an object with mass to travel at the speed of light it would have infinite mass and the energy needed to reach light speed would also be infinite, this doesn't apply to light itself (photons) because they don't have mass
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#30
Age is in proportion to your position within the atmosphere and the gravity inside it. This is due to more properties living lower down ageing you i believe. For example, more bactiria etc lives closer to sea level. Now you may say, doesnt that mean if we went into space we wouldnt age. No because humans would still at least require some form of gravity to live, just maybe in space we would age slower...
#31
well from what i understand from that example is the the person on top of the mountain ages fast beacause in a year he travels a slightly greater distance through space due to the fact that being on a mountain slightly increases the distance he revolves aroung the core. I think i may be looking at it too simply but mabey not and i have read steven hawkins book so i am a qualified scientist
#32
Quote by Feel bad inc.
Age is in proportion to your position within the atmosphere and the gravity inside it. This is due to more properties living lower down ageing you i believe. For example, more bactiria etc lives closer to sea level. Now you may say, doesnt that mean if we went into space we wouldnt age. No because humans would still at least require some form of gravity to live, just maybe in space we would age slower...

ageing is the result of many many many copie of cells like when you record something thats distorted it gets more distorted. thats what happens to our bodies our cell slightly distort ocasionaly and the aded up effects of this is aging. Its kind of like a slow form of cancer....its not....but.....kind of :P
#33
Quote by farcry
no I read it right raziel, it's right from Stephen Hawking's book. And to Yawn, if you knew anything about quantum mechanics or general relativity the relavence would be clear. Physicists are searching for a unified theory to explain existance, a theory of everything, seems pretty relavent if you ask me.

I'm reading that book at the moment, and have actually tried to explain this to someone else before, I think it's a book I'm gonna have to read twice.

But yeah, the bit on quantum mechanics is completely confusing and mind-blowing.
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#34
They are both still rotating at the same speed so they would be the same age. The one on the mountain is rotating faster than the person on the ground but the person on the ground is close to the center so it cancels itself out. They would be the same age.
#36
It's not to do with gravity, its due to velocity. Your velocity (through space and such) is higher on top of a mountain than at the bottom, because the earth is spinning and therefore the outside moves faster. When you go faster, according to relativity that is, time passes slower for you.

But then.. the bottom one should be older?!

I'm stuck

EDIT: Upon actually reading the thread, I've realised that its actually a case of gravity time dilation rather than velocity time dilation. Excellent, I do enjoy physics. (haha)
Last edited by shigidab0p at Nov 30, 2007,