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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

Nothing is impossible just highly improbable....

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

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........

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.

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.

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.

c is a constant. That's not a property of light, that's a property of spacetime.

PMB, I believe I owe you a coffee

Quote from: AndroidNeox on 15/01/2013 21:00:23c 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.

Quote from: Pmb on 15/01/2013 21:34:37Quote from: AndroidNeox on 15/01/2013 21:00:23c 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?

don't agree Bill. there is no frame of reference in where you can be at rest with light. and if that doesn't exist then there is no way to 'know' what a photon experience. what Einstein meant is not that there is no 'c'. Only that for you and me there would be no frame of reference in where we would find light being at rest with us. he's not tricky there, he's rather clear.=If you find a frame of reference in where you don't get a reflection from that mirror, aka being 'at rest' with light, I will be sorely interested reading you.

...if that doesn't exist then there is no way to 'know' what a photon experience

If you find a frame of reference in where you don't get a reflection from that mirror, aka being 'at rest' with light, I will be sorely interested reading you.

You stir some interesting thoughts, there, Bill. I need to clarify one thing, though:What is the difference between existing for zero time, and not existing?

The problem is that photons travel through space. To be able to travel through space, time must pass, in order for a particle to have velocity. The photon also has a wavelength. Its energy varies when moving through a gravitational field. These changes cannot happen in zero time. If we consider the passage of time in an impossible reference frame then we are missing the point entirely.

In order to be slowed down by gravity time must pass for the photon. It accelerates in a gravitational field. This is also a non inertial frame.

The impossibility of the passage of time in the frame of the photon has to be a function of rest mass. A photon doesn't have rest mass.

If you consider a classical object moving at 1ft/sec, at one particular instant, for zero time, it will be exactly 2ft from its origin. If you observe only at this instant, you can't measure the object's speed.

A photon could (maybe) be regarded as a configuration or particle which only exists for zero time as part of a continuing process.

Quote from: Bill_ on 11/02/2017 12:36:19 If you consider a classical object moving at 1ft/sec, at one particular instant, for zero time, it will be exactly 2ft from its origin. If you observe only at this instant, you can't measure the object's speed. Even in principle, you can’t make am observation in zero time; so, like trying to work with the idea of a massive object travelling at c (apart from Einstein) this is a no-go situation. In principle, you could make an observation that lasted for Planck’s time, and argue that that was not divisible, but that’s not the same as zero time.

What is the difference between existing for zero time, and not existing?

Quote from: Bill_ on 11/02/2017 12:36:19 A photon could (maybe) be regarded as a configuration or particle which only exists for zero time as part of a continuing process. This may be a mathematical “truth”, but in reality nothing can happen in zero time, and zero cannot ba a part of anything. To be part of something, it must be something.

In special relativity, the time a photon exists can be arbitrarily varied by selecting a suitable inertial frame. This is consistent with saying a photon exists for zero time but from an inertial frame the time it exists is dilated by the factor 0 * 1/gamma i.e. 0/0 which is any arbitrary number. This singularity doesn't seem to bother physicists very much.

'There is no known way to measure the object's speed but the object exists whether or not you observe or measure it.'

As the (classical) object moves, at all times its exact distance is mappable to some point, at which it remains for zero time.

I can't extract your intended meaning from that response.

Quote from: Bill 'There is no known way to measure the object's speed but the object exists whether or not you observe or measure it.'I’m happy to accept that objects exist when they are not being observed/measured.

Classically I could say 'There is no known way to measure the object's speed but the object exists whether or not you observe or measure it.'

Quote As the (classical) object moves, at all times its exact distance is mappable to some point, at which it remains for zero time. To make that claim, you would first have to establish that “zero time” exists as a physical entity.

Quote I can't extract your intended meaning from that response. John Barrow says this about mathematical existence:“Gradually mathematicians lighted upon a new concept of existence. Mathematical ‘existence’ meant only logical self-consistency and this neither required nor needed physical existence to complete it. If a mathematician could write down a set of non-contradictory axioms and rules for deducing true statements from them, then those statements would be said to ‘exist’.” If there can be a profound difference between physical and mathematical “existence” then it seems reasonable to identify a similar difference between physical and mathematical “truth”. When Barrow talks of “deducing true statements” from “non-contradictory axioms”, one has to wonder if the truth of these statements can always be maintained in the real world, or if they are just mathematically true. In many cases, especially those involving “nothing” or “infinity”, the latter seems, often, to be the case.

Quote from: Bill_ on 11/02/2017 12:36:19A photon could (maybe) be regarded as a configuration or particle which only exists for zero time as part of a continuing process. This may be a mathematical “truth”, but in reality nothing can happen in zero time....

Quote from: ultimatebeast on 07/01/2013 22:55:43I 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"If" doesn't require that it's a real possibility, just a speculation, or fantasy.At light speed, the light clock stops working. All processes that depend on mediation via photons, chemistry, biology, etc. would cease. A state equivalent to death! No aging, no perception, nothing. Be careful what you wish for!

Acceleration applies to both direction and speed. For particles with rest mass the acceleration can be positive or negative. The question is does this apply in the same way for light in any choice of coordinates?