6

Fri 2 Apr, 2010 10:53 pm
From what i understand of this theoretical experiment. There are two twins, one goes at the speed of light, one doesn't, and then after all is said and done, one twin is older. My question is, isn't the twin only visually older? The light cannot catch up to the twin therefore the light cannot portray any time or age on the twin. yet the cells continue to age. Is this only a visual illusion? Light is only visual and doesn't effect the rate of growth of anything organic.

I haven't read up on this much, i just had an interesting discussion in English. I could be totally off on this one and if i am, please forgive me .
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kennethamy

1
Fri 2 Apr, 2010 11:00 pm
@Yogi DMT,
Yogi DMT;147706 wrote:
From what i understand of this theoretical experiment. There are two twins, one goes at the speed of light, one doesn't, and then after all is said and done, one twin is older. My question is, isn't the twin only visually older? The light cannot catch up to the twin therefore the light cannot portray any time or age on the twin. yet the cells continue to age. Is this only a visual illusion? Light is only visual and doesn't effect the rate of growth of anything organic.

I haven't read up on this much, i just had an interesting discussion in English. I could be totally off on this one and if i am, please forgive me .

If it were true that one twin only looks older then there would be no paradox. I don't know enough about relativity theory to explain why one twin is older, but that is what Einstein claimed. I am sure it has to do with his view that time is relative to the system the inertial system the perceiver is in.
Yogi DMT

1
Fri 2 Apr, 2010 11:06 pm
@Yogi DMT,
Put everything in a big box and put a clock beside it. Watch the clock go by and watch the objects in a box. That's how i like to think of it, not sure if the metaphor will work for you.
kennethamy

1
Fri 2 Apr, 2010 11:10 pm
@Yogi DMT,
Yogi DMT;147713 wrote:
Put everything in a big box and put a clock beside it. Watch the clock go by and watch the objects in a box. That's how i like to think of it, not sure if the metaphor will work for you.

But the things in the box are all in the same inertial system, so the analogy is not a good one, since the twins are not in the same inertial system. That is the point.
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Yogi DMT

1
Fri 2 Apr, 2010 11:13 pm
@Yogi DMT,
What if the box contains two inertial systems (which i'm not quite sure what this means). All i'm saying is if you look at the huge picture, why would time be any different in any particular place.
kennethamy

1
Fri 2 Apr, 2010 11:17 pm
@Yogi DMT,
Yogi DMT;147717 wrote:
What if the box contains two inertial systems (which i'm not quite sure what this means). All i'm saying is if you look at the huge picture, why would time be any different in any particular place.

Bu the box could not contain two inertial systems. Einstein is discussing physics, and physics need not be commonsense. You really would have to look this matter up. Why not try Googling "the twin paradox"?
Yogi DMT

1
Fri 2 Apr, 2010 11:20 pm
@Yogi DMT,
kennethamy

1
Fri 2 Apr, 2010 11:22 pm
@Yogi DMT,
Yogi DMT;147723 wrote:

Well, discussions in ignorance usually don't lead anywhere much.
Yogi DMT

1
Fri 2 Apr, 2010 11:25 pm
@Yogi DMT,
Agreed. (16 characters)
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jeeprs

1
Sat 3 Apr, 2010 05:54 am
@Yogi DMT,
No, that is not it. There are some Time Life explanations of how relativity works that might help you. It would be easier with a diagram but here goes. Two spaceships, right? You're on one and George is on the other. Relative to you, George goes by at quite a few million miles an hour. Woosh.

Now in each spaceship, there is a clock. The clock works by firing a beam of light at the mirror on the floor once a second. This is how it keeps time. The clock on George's spaceship does this too. But, relative to you, the mirror in George's spaceship has actually travelled quite a few thousand miles between the time the beam left the roof, and hit the mirror on the floor, and then another few thousand miles on the return trip.

From where George is standing, the light has just made a standard round trip of a few meters. From where you are standing, the light has travelled a few thousand miles. Light always travels at the same speed.

Therefore the time taken for the light beam on George's spaceship has taken longer relative to you than it does, relative to George.

So the clock is actually running slower on George's spaceship.

hope that helps.
kennethamy

1
Sat 3 Apr, 2010 05:58 am
@jeeprs,
jeeprs;147801 wrote:
No, that is not it. There are some Time Life explanations of how relativity works that might help you. It would be easier with a diagram but here goes. Two spaceships, right? You're on one and George is on the other. Relative to you, George goes by at quite a few million miles an hour. Woosh.

Now in each spaceship, there is a clock. The clock works by firing a beam of light at the mirror on the floor once a second. This is how it keeps time. The clock on George's spaceship does this too. But, relative to you, the mirror in George's spaceship has actually travelled quite a few thousand miles between the time the beam left the roof, and hit the mirror on the floor, and then another few thousand miles on the return trip.

From where George is standing, the light has just made a standard round trip of a few meters. From where you are standing, the light has travelled a few thousand miles. Light always travels at the same speed.

Therefore the time taken for the light beam on George's spaceship has taken longer relative to you than it does, relative to George.

So the clock is actually running slower on George's spaceship.

hope that helps.

But "what" is not it? Time is relative to different inertial systems.
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jeeprs

1
Sat 3 Apr, 2010 06:05 am
@Yogi DMT,
Sorry, what I meant was, the OP doesn't understand relativity.

In the example I gave, if you set a watch, and put it on both ships, and then after a while, they came back together, both watches would be telling different times, but both would be correct.

It is just a simple way to illustrate how it works - as I said, a Time Life books example.
wayne

1
Sat 3 Apr, 2010 06:08 am
@jeeprs,
jeeprs;147808 wrote:
Sorry, what I meant was, the OP doesn't understand relativity.

In the example I gave, if you set a watch, and put it on both ships, and then after a while, they came back together, both watches would be telling different times, but both would be correct.

It is just a simple way to illustrate how it works - as I said, a Time Life books example.

Does a mechanical clock actually run slower, or does this only affect the light clock?
kennethamy

1
Sat 3 Apr, 2010 06:08 am
@jeeprs,
jeeprs;147808 wrote:
Sorry, what I meant was, the OP doesn't understand relativity.

In the example I gave, if you set a watch, and put it on both ships, and then after a while, they came back together, both watches would be telling different times, but both would be correct.

It is just a simple way to illustrate how it works - as I said, a Time Life books example.

But not unless the two ships were in different inertial systems.
0 Replies

TheRealFeeny

1
Sat 3 Apr, 2010 12:56 pm
@Yogi DMT,
The mechanical clock is no different. All clocks work on the same principle, an object moves a known distance in a known time at regular intervals. The light clock is just given as a more visible example. But you can also think of the gears on a clock moving instead of the beam of light.
0 Replies

jeeprs

1
Sat 3 Apr, 2010 02:44 pm
@wayne,
wayne;147809 wrote:
Does a mechanical clock actually run slower, or does this only affect the light clock?

TIME actually slows down on George's ship. If he goes far enough, fast enough, 30 years for him will be 150 years on earth. But it is all theoretical. We don't have the technology, or the energy, to actually realise this effect, but the principle is clear. Time slows down the faster you go, relative to a stationary observer.
Yogi DMT

1
Sat 3 Apr, 2010 05:16 pm
@jeeprs,
jeeprs;147808 wrote:
Sorry, what I meant was, the OP doesn't understand relativity.

In the example I gave, if you set a watch, and put it on both ships, and then after a while, they came back together, both watches would be telling different times, but both would be correct.

It is just a simple way to illustrate how it works - as I said, a Time Life books example.

Is this because the light hasn't caught up to one of the watches so it's visually delayed?
jeeprs

1
Sat 3 Apr, 2010 05:49 pm
@Yogi DMT,
Not exactly. In the time it takes the light to travel two meters on your ship, it has travelled thousands of meters on George's ship. Visualize George's ship going past you - you're both in space, you can see it coming from 10,000 kilometers away. Lightbeam leaves origin point on George's ship, by the time it hits the mirror on the floor, the ship has moved several hundred thousand meters. And even though light moves pretty quickly, that difference is measurable.

So again, if George's ship is moving at millions of kilometers an hour, relative to you:

• From George's viewpoint, he sees the beam go straight down and straight back up
• From your viewpoint, if you could see the lightbeam in George's ship, you would see it travel obliquely for several hundred thousand meters in each direction, to 'keep up' with the motion of the ship
• So the distance the light beam has to travel, according to your frame of reference, is not two meters, but two hundred thousand meters (say)

And even though light is fast, the speed is finite, so it takes longer, from your frame of reference, for the beam on George's ship to make its return journey.

So time is actually moving slower on George's ship. it is not an illusion, an appearance, or the way the clocks work. The faster you go, the slower time is for you, relative to a stationary observer.
YumClock

1
Sat 3 Apr, 2010 06:27 pm
@Yogi DMT,
Yogi DMT;147989 wrote:
Is this because the light hasn't caught up to one of the watches so it's visually delayed?

If this was to happen, one watch would have to exceed the speed of light. Einstein's theories state that nothing can exceed the speed of light, and relativity is observed at speeds near this.

Perhaps your thought of visual delay is related to theories of the event horizon of a black hole.

Time actually slows down. At extreme speeds, space curves, and time curves along with it. As the shortest distance between two points is a straight line, an uncurved portion of space will reach a point in time before the curved portion of space, and thus the uncurved portion of space will be older.
prothero

1
Sat 3 Apr, 2010 06:52 pm
@YumClock,
YumClock;148004 wrote:
If this was to happen, one watch would have to exceed the speed of light. Einstein's theories state that nothing can exceed the speed of light, and relativity is observed at speeds near this.

Perhaps your thought of visual delay is related to theories of the event horizon of a black hole.

Time actually slows down. At extreme speeds, space curves, and time curves along with it. As the shortest distance between two points is a straight line, an uncurved portion of space will reach a point in time before the curved portion of space, and thus the uncurved portion of space will be older.
It is not just the clock that runs slower. Everything runs slower all of the chemical reactions and biological processes of aging run slower. The traveling twin actually is younger in every way. It has to do with the affect of acceleration and gravity not only on space time but on all other physical process as well. Time is change and not only does time slow down but so does ALL other changes as well. It is not a trick or an illusion it is physical law. It is only counterintuitive because it is outside our ordinary experience. We do not encounter such speeds or effects (except in particle accelerators) here on spaceship earth. Interestingly this change in the lifetime of elementary particles based on fractional light speed has been repeatedly confirmed. Particles decay more slowly when traveling at near light speeds.
It is a confirmed theory, therefore more like a fact.

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