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Author Topic: How would you age at the speed of light?  (Read 15440 times)

Offline ultimatebeast

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How would you age at the speed of light?
« on: 07/01/2013 22:55:43 »
I was wondering if one were to travel at the speed of light, how fast or slow would they age. Would they age at the same speed as on Earth because the speed of light is relative or would they age slower due to time dilation thanks for the replies
« Last Edit: 25/01/2013 17:15:01 by JP »


 

Offline RD

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« Last Edit: 07/01/2013 23:43:53 by RD »
 

Offline Pmb

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Re: How would you age at the speed of light
« Reply #2 on: 08/01/2013 01:55:24 »
I was wondering if one were to travel at the speed of light, how fast or slow would they age. Would they age at the same speed as on Earth because the speed of light is relative or would they age slower due to time dilation thanks for the replies
Since its impossible to travel at the speed of light the question is without meaning .. or to be more precise, there is no answer.

In any case, when speaking of aging one has to ask with respect to what clock one is aging with reference to.
« Last Edit: 08/01/2013 01:57:07 by Pmb »
 

Offline Airthumbs

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Re: How would you age at the speed of light
« Reply #3 on: 08/01/2013 04:39:09 »
Nothing is impossible just highly improbable.... therefore in the extremely unlikely event it is possible to travel at the speed of light, say by switching off the Higs field for example, then I would be saying hello to me again?
 

Offline evan_au

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Re: How would you age at the speed of light
« Reply #4 on: 08/01/2013 08:53:18 »
If you were traveling "Very Fast*" in a straight line with no acceleration, an observer (say, on Earth) seeing you pass would think that you aged more slowly than them. http://en.wikipedia.org/wiki/Time_dilation#Relative_velocity_time_dilation

However, it gets a lot more complicated if you start on Earth and accelerate to reach the very fast speed, then decelerate and reverse to return to Earth.

*With our current understanding, "Very Fast" is always less than the speed of light in a vacuum. If your speed is closer to the speed of light, the observed rate of time passing gets closer to zero (from the viewpoint of an observer on Earth).

The Twin Paradox arises because from your viewpoint as a traveler, time for the observer on Earth is passing more slowly than for you.
 

Offline AndroidNeox

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Re: How would you age at the speed of light
« Reply #5 on: 08/01/2013 20:45:41 »
To accelerate an object with non-zero rest mass, no matter how little, to the speed c would require infinite energy. Honestly, some things ARE impossible and this is one of them. That's probably why I've always been drawn to physics... it has some, few, rules that are utterly absolute for all observers under all possible circumstances. Most of these are represented as physical symmetries in Schrödinger’s equation. But, the speed c is an absolute constant for all observers under all circumstances.
 

Offline Pmb

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Re: How would you age at the speed of light
« Reply #6 on: 09/01/2013 21:57:31 »
Nothing is impossible just highly improbable....
That's clearly wrong. and without basis. We know of things that are impossible, not merely improbably. E.g. suppose I were to ask you if it were  possible for you to be wrong? :)
 

Offline flr

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Re: How would you age at the speed of light
« Reply #7 on: 10/01/2013 17:28:05 »
I was wondering if one were to travel at the speed of light, how fast or slow would they age. Would they age at the same speed as on Earth because the speed of light is relative or would they age slower due to time dilation thanks for the replies

The speed of light is not relative, it is an absolute constant.

Only photons (having zero rest mass) can travel at the speed of light.
It may be tempting to say that photons appear 'timeless' or 'out of time' or 'time does not flow for photons', because the faster an object move relative to us the more time dilated it appears to us.

However, that may be incorrect for the particular case of a photon.
In order to asses the time-dilation (and any other special relativity effects) one have to compare 2 frames of reference.
In other words I have to compare my local clock with photon's local clock and see (from my frame) how much the photon appears slowed down.
The problem is: it is unclear how to define a local clock (and ruler) for a photon. That means: you don't have a second frame (local to photon). If so, then we cannot apply the relativity to answer your  question.

 

Offline ultimatebeast

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Re: How would you age at the speed of light
« Reply #8 on: 11/01/2013 17:19:48 »
Hi, you guuys thanks for all of the responses but I just want to know if someone traveled at the speed of light for 100 years how much he would age. Would he age the same or would he age slower. Thanks
 

Offline Pmb

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Re: How would you age at the speed of light
« Reply #9 on: 11/01/2013 19:30:13 »
Hi, you guuys thanks for all of the responses but I just want to know if someone traveled at the speed of light for 100 years how much he would age. Would he age the same or would he age slower. Thanks
Since nobody can travel at the speed of light for any amount of time, your question has n answer.
 

Offline Airthumbs

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Re: How would you age at the speed of light
« Reply #10 on: 14/01/2013 23:39:35 »
I could not help notice that my example of switching off the Higs field has been ignored.......  if the Higs field is responsible for giving objects mass and you switched it off somehow then surly that opens up new possibilities? 

PMB; if we fully understood our universe then I would fully agree with you........
« Last Edit: 15/01/2013 00:14:11 by Airthumbs »
 

Offline Pmb

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Re: How would you age at the speed of light
« Reply #11 on: 15/01/2013 00:51:32 »
I could not help notice that my example of switching off the Higs field has been ignored.......  if the Higs field is responsible for giving objects mass and you switched it off somehow then surly that opens up new possibilities? 

PMB; if we fully understood our universe then I would fully agree with you........
It is wrong to think that because we don't fully understand the universe that what we do understand must be wrong. Physicists assume certain thing when addressing questions and giving answers and those things are that the laws of physics as we know them are valid in the domain that they've been tested in. Again, there is no basis to assume that Nothing is impossible just highly improbable.... . How do you know that's true? Why would you assume that it's true? On what basis are you suggesting that the Higgs field could be switched off? Why would you believe that it could be done? If you say "Well we really don't know everything so we should not trust anything so that everything is possible" then that not only gets you nowhere but it also suggests that you're assuming that there is a Higgs field. I can, for the same reasons you've been using, that there's no such thing as a Higgs field.

My point is that it you say "We don't understand the universe" and take that to mean that all the laws of physics are wrong or shouldn't be trusted or could all be wrong then you might as well make up anything yhou wanted to without using any reason at all. Just whatever fantasy that comes to mind "could be true" etc.

That and $1.50 will get you cup of coffee.
 

Offline AndroidNeox

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Re: How would you age at the speed of light
« Reply #12 on: 15/01/2013 01:48:49 »
Hi, you guuys thanks for all of the responses but I just want to know if someone traveled at the speed of light for 100 years how much he would age. Would he age the same or would he age slower. Thanks

The simple answer is, anything moving through space at c, equal to the speed of light in a vacuum, experiences zero time flow. If you were to travel at the speed of light, you would experience no time.

Actually, if you consider matter and energy in spacetime... EVERYTHING always travels through spacetime at c. An inertial observer, experiencing zero acceleration or force, will have a perspective that moves along its time axis at c, experiencing time at the maximum rate but no motion through space (from its own perspective). A light beam, or you, ultimatebeast, in this case, would be moving through space at c and would experience zero time.
 

Offline Pmb

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Re: How would you age at the speed of light
« Reply #13 on: 15/01/2013 02:01:13 »
Quote from: AndroidNeox
The simple answer is, anything moving through space at c, equal to the speed of light in a vacuum, experiences zero time flow. If you were to travel at the speed of light, you would experience no time.
That kind of response is considered to be flawed since for it to have any meaning one would have to measure it and there’s now way to make a clock travel at the speed of light. Otherwise we’d have given this trivial answer long ago. Nobody and no thing can experience moving at the speed of light so the question is really meaningless. Especially since the OP referred to “someone” traveling at the speed of light. We know that no person can move at the speed of light. That’s why we’ve given the responses that we’ve given.

Quote from: AndroidNeox
Actually, if you consider matter and energy in spacetime... EVERYTHING always travels through spacetime at c.
That’s not true and is based on the misconception of a spacetime interval being identical to “distance” and then incorrectly calculating velocity by dividing a spacetime interval by the spacetime interval with a factor of c not canceling out. You can call the result you get  anything you’d like with the exception of “speed” or “velocity” or “traveling at c” since all these things already are well defined and already have well defined answers which are different than you’ve given. You just can’t say that its moving through spacetime with speed c. Those terms are already defined and cannot be redefined in the same breadth.
 

Offline simplified

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Re: How would you age at the speed of light
« Reply #14 on: 15/01/2013 17:59:15 »
I was wondering if one were to travel at the speed of light, how fast or slow would they age. Would they age at the same speed as on Earth because the speed of light is relative or would they age slower due to time dilation thanks for the replies
Only your travel relatively of gravitational bodies makes your time slower.Your travel relatively of light doesn't make your time slower. :P
 

Offline AndroidNeox

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Re: How would you age at the speed of light
« Reply #15 on: 15/01/2013 20:43:48 »
That’s not true and is based on the misconception of a spacetime interval being identical to “distance” and then incorrectly calculating velocity by dividing a spacetime interval by the spacetime interval with a factor of c not canceling out. You can call the result you get  anything you’d like with the exception of “speed” or “velocity” or “traveling at c” since all these things already are well defined and already have well defined answers which are different than you’ve given. You just can’t say that its moving through spacetime with speed c. Those terms are already defined and cannot be redefined in the same breadth.

The speed that we perceive to be c is a function of the angle between the space axis and the time axis. We only see a 3-space cross section of the 4-space trajectory and the tangent, distance/time = c.
 

Offline Pmb

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Re: How would you age at the speed of light
« Reply #16 on: 15/01/2013 20:56:52 »
Quote from: AndroidNeox
The speed that we perceive to be c is a function of the angle between the space axis and the time axis. We only see a 3-space cross section of the 4-space trajectory and the tangent, distance/time = c.
Sorry but I can't even imagine what that's supposed to mean.

Speed is defined as distance traveled divided by the time it took to travel that distance. If you look at a spacetime diagram at a particle moving in one dimension then you will see a curve whose tangent is related to its speed. If the speed is constant then the speed of the object is defined as the run over the rise, that is to say that the speed is defined as the change in x divided by the change in t. Therefore for a straight line you select a point on the worldline of the particle. If the velocity is positive then you move to the right by an arbitrary amount dx. At the point where you moved to the right ended you now move straight up until you meet the curve. Let dt be the amount measured. Now divide dx by dt to get the speed of the particle, i.e. v = dx/dt. That value can only be c if the particle is moving at the speed of light.
 

Offline AndroidNeox

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Re: How would you age at the speed of light
« Reply #17 on: 15/01/2013 21:00:23 »
c is a constant. That's not a property of light, that's a property of spacetime. It's a matter of geometry... the equal angle between space and time corresponds to c. You can think of it as a tangent a/b, distance/time. The angle always appears the same, to every observer. It's probably an inevitable artifact of observation... something about the way observation is structured, maybe. But, it's not something subject to variation. We do know enough about spacetime to understand that.

That's the whole magnificently cool thing about Relativity is that c is constant. That's why Einstein didn't like the name, "relativity", because the amazing thing he found out was that c is constant. That was the whole thing. Space and time have to adjust themselves to accommodate the fact but it's a fact for all observers at all times and has fascinating implications.

And, personally I would like to get the definition of "c" corrected to not be "the speed of light in a vacuum" but "the maximum speed at which information and energy can pass through space and equal to the constant velocity of all matter and energy through spacetime". Because, everything is always going through spacetime at c. The inertial observer's frame of reference moves along his/her time axis (world line) at the speed, c.

For inertial observers, the observer's time axis and world line are always coincident. For accelerating observers, their world line tips off-axis and they experience acceleration.

In 4-dimensional spacetime, everything always goes at c. Every particle with or without mass is moving at c along some trajectory in spacetime. That's why objects, like photons, moving at c though space cannot experience time... their total velocity is through space and the velocity component along the time axis is zero. The amount that time is slowed by velocity or acceleration are a matter of geometry... measured from the perspective of the observer. There is no universal or godlike perspective. Everything is relative to the observer's frame of reference. The amount of time slowing one inertial observer would see in a passing clock tower would be proportional to the cosine between the observer's world-line and the clock tower's time axis.
 

Offline Pmb

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Re: How would you age at the speed of light
« Reply #18 on: 15/01/2013 21:13:09 »
Quote from: AndroidNeox
c is a constant. That's not a property of light, that's a property of spacetime. It's a matter of geometry... the equal angle between space and time corresponds to c.
I don’t know what angles you’re speaking of so I’ll assume that you’re talking about the angle a worldline of a particle moving at constant speed makes with the spatial or temporal axis. The only way for the angle between the worldline and the x axis to be equal to the worldline and the t axis is if either (1) you’re using units in which c = 1 or (2) you’ve scaled your time axis so that it doesn’t read t by ct. In that case if there is a worldline of a particle which passes through the origin and that worldline makes a 45 degree angle with respect to both axes them that particle is moving at the speed of light

Quote from: AndroidNeox
You can think of it as a tangent a/b, distance/time. The angle always appears the same, to every observer.
That is true only for null worldliness, i.e. for particles moving at the speed of light.

The point is that only particles that move at the speed of light have speed c. The other person was talking about the speed of objects in spacetime where I was speaking about the speed of objects in space. The term “speed of an object in spacetime” is meaningless. There are a few people here and there who like to say that all objects move at the speed of light in spacetime but no relativist would ever make such a statement. In fact when they hear that they sigh and say that its wrong.
 

Offline Pmb

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Re: How would you age at the speed of light
« Reply #19 on: 15/01/2013 21:34:37 »
c is a constant. That's not a property of light, that's a property of spacetime.
I disagree. The properties of spacetime were selected so as to make the speed of light invariant.

By the way, the correct term is “invariant” not “constant”.
 

Offline Airthumbs

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Re: How would you age at the speed of light
« Reply #20 on: 17/01/2013 02:39:04 »
PMB, I believe I owe you a coffee :)
 

Offline Pmb

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Re: How would you age at the speed of light
« Reply #21 on: 17/01/2013 06:07:10 »
PMB, I believe I owe you a coffee :)
Nice! I'll have a chocolate raspberry flavor, cream, sweet. The doughnuts are on me. :)
 

Offline AndroidNeox

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Re: How would you age at the speed of light
« Reply #22 on: 23/01/2013 21:44:17 »
c is a constant. That's not a property of light, that's a property of spacetime.
I disagree. The properties of spacetime were selected so as to make the speed of light invariant.

You're saying that someone chose what the properties of spacetime would be to ensure c is the same for all observers?
 

Offline Pmb

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Re: How would you age at the speed of light
« Reply #23 on: 25/01/2013 04:07:09 »
c is a constant. That's not a property of light, that's a property of spacetime.
I disagree. The properties of spacetime were selected so as to make the speed of light invariant.

You're saying that someone chose what the properties of spacetime would be to ensure c is the same for all observers?
In a manner of speaking, yes. The Lorentz transformation relationships transform events in S to events in S'. These transformations were designed so that c = invariant.
 

Offline yor_on

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Re: How would you age at the speed of light
« Reply #24 on: 25/01/2013 17:06:28 »
But it is also a matter of practical experiments proving the theory Android :)
Otherwise I could argue that 'c' is 'c' 'all the way down', no proof presented..

A theory is a framework describing experiments correctly, as far as one knows at the time of the theory.

(insert turtles as needed)
 

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Re: How would you age at the speed of light
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