An idea about speed of light

[Stickhorse]

I have an idea about the speed of light that – as I’m mainly a complete outsider in the field of physics – maybe has nothing relevant or new at all or is just a complete disaster, but it bothers me a lot.

As we know, speed is the magnitude of the objects velocity, thus it is basically a distance travelled by an object in a certain unit/duration of time. What if traveling faster than light or faster-than-light speed is simply uninterpretable on the grounds of our physical system, because our interpretation and perception of time and space – which are basically define speed or velocity itself – are highly, probably inseparably interdependent with the characteristics of light and our perception of it?

[mathematic]

The speed of light is measured within the reference frame of the instruments, using distance over time.

[Strange]

I have an idea about the speed of light that – as I’m mainly a complete outsider in the field of physics – maybe has nothing relevant or new at all or is just a complete disaster, but it bothers me a lot.

 

As we know, speed is the magnitude of the objects velocity, thus it is basically a distance travelled by an object in a certain unit/duration of time. What if traveling faster than light or faster-than-light speed is simply uninterpretable on the grounds of our physical system, because our interpretation and perception of time and space – which are basically define speed or velocity itself – are highly, probably inseparably interdependent with the characteristics of light and our perception of it?

 

It is not entirely clear what you mean, but it is worth noting that the fact that the speed of light is the same for all observers does result in time and space being observer dependent, which might be what you are saying.

[pavelcherepan]

I have an idea about the speed of light that – as I’m mainly a complete outsider in the field of physics – maybe has nothing relevant or new at all or is just a complete disaster, but it bothers me a lot.

 

As we know, speed is the magnitude of the objects velocity, thus it is basically a distance travelled by an object in a certain unit/duration of time. What if traveling faster than light or faster-than-light speed is simply uninterpretable on the grounds of our physical system, because our interpretation and perception of time and space – which are basically define speed or velocity itself – are highly, probably inseparably interdependent with the characteristics of light and our perception of it?

 

It's true that SR is based on the premise that speed of light in vacuum is constant in all inertial reference frames and is the highest speed information can travel in Universe. On the other hand, while this has indeed been postulated, there has been a large number of experiments that confirmed that our current understanding of the speed of light is correct.

 

Obviously, it's very much possible that our understanding of physics is very wrong and FTL speeds are possible, but currently there are no reliable theories and no observed phenomena of such kind.

[ajb]

As we know, speed is the magnitude of the objects velocity, thus it is basically a distance travelled by an object in a certain unit/duration of time. What if traveling faster than light or faster-than-light speed is simply uninterpretable on the grounds of our physical system, because our interpretation and perception of time and space – which are basically define speed or velocity itself – are highly, probably inseparably interdependent with the characteristics of light and our perception of it?

I think I see what you are saying. It is true that the speed of light has a privileged role in our understanding of the causal structure of space-time. However, this role has been verified many times now, the speed 'c' is a universal constant that allows us to mix space and time giving the causal structure.

 

Special relativity tells us that no observer will measure a relative velocity of a massive body to be equal to or greater than c. One can define separation speed and similar that are greater than c, but these are not what one means by relative velocity. So, in relativity it is impossible to measure (local) speeds greater than c.

[Delbert]

Special relativity tells us that no observer will measure a relative velocity of a massive body to be equal to or greater than c. One can define separation speed and similar that are greater than c, but these are not what one means by relative velocity. So, in relativity it is impossible to measure (local) speeds greater than c.

Not quite sure what you're saying.

The speed of light is based on physics as defined by James Clark Maxwell and is not defined as an absolute speed that would be measured different depending local speed -- that is one could never catch up and travel alongside a light beam. In the universe there's no such thing as absolute speed only relative speed. In other words what ever speed you think you are doing, the speed of light will be the same.

 

But if one takes the view that there is such a thing as absolute speed, just ask yourself: what speed am I (i.e. the Earth) doing right now? Looking at the universe I think you will come up with anything from zero to close to, or even at, the speed of light. In other words the very question as to what speed are we doing is invalid, such that there's no such thing as absolute speed, only relative speed.

 

I understand that the speed of light is a slight misnomer, as more correctly I believe it is the physics of the propagation speed of a massless particle. And as light, I further understand, is deemed to be massless it is referred to as the speed of light.

 

I think Brian Cox explains it perfectly in the book: Why does e = mc² ?

[Delta1212]

Not quite sure what you're saying.

The speed of light is based on physics as defined by James Clark Maxwell and is not defined as an absolute speed that would be measured different depending local speed -- that is one could never catch up and travel alongside a light beam. In the universe there's no such thing as absolute speed only relative speed. In other words what ever speed you think you are doing, the speed of light will be the same.

 

But if one takes the view that there is such a thing as absolute speed, just ask yourself: what speed am I (i.e. the Earth) doing right now? Looking at the universe I think you will come up with anything from zero to close to, or even at, the speed of light. In other words the very question as to what speed are we doing is invalid, such that there's no such thing as absolute speed, only relative speed.

 

I understand that the speed of light is a slight misnomer, as more correctly I believe it is the physics of the propagation speed of a massless particle. And as light, I further understand, is deemed to be massless it is referred to as the speed of light.

 

I think Brian Cox explains it perfectly in the book: Why does e = mc² ?

I think you are misinterpreting ajb's comment.

 

It is possible to observe an object moving away from you at 0.9c, and another object moving away from you in the opposite direction at 0.9c.

 

You would therefore measure a separation velocity between the two of 1.8c. However, the speed of each object as measured in the other's frame is still less than c. That's what ajb means by local measurements of speed.

[ajb]

The speed of light is based on physics as defined by James Clark Maxwell...

This is where the speed of light comes from, as such. It was noticed that Maxwell's equations do not share the same symmetries as Newtonian mechanics and that this made something special about the speed of light. Maxwell invented special relativity, he just did not realise it!

 

...and is not defined as an absolute speed that would be measured different depending local speed

The speed of light in any inertial frame can be considered as an absolute speed in the sense any inertial observer will measure the same speed. But this is not usually what one means by an absolute speed.

 

In the universe there's no such thing as absolute speed only relative speed.

Absolutely true.

 

 

In other words what ever speed you think you are doing, the speed of light will be the same.

Right, as long as you are an inertial observer, i.e. not accelerating this is true. And it is an important part of relativity.

 

But if one takes the view that there is such a thing as absolute speed, just ask yourself: what speed am I (i.e. the Earth) doing right now? Looking at the universe I think you will come up with anything from zero to close to, or even at, the speed of light. In other words the very question as to what speed are we doing is invalid, such that there's no such thing as absolute speed, only relative speed.

We all agree on this. Absolute speeds or velocities are unnatural in special and general relativity.

 

I understand that the speed of light is a slight misnomer, as more correctly I believe it is the physics of the propagation speed of a massless particle. And as light, I further understand, is deemed to be massless it is referred to as the speed of light.

The speed of light c really refers the (local) relative speed as measured by any inertial observer of any massless particle. At the time that special relativity was first developed I don't think there were any other candidates for massless particles. Pauli in 1930 proposed the neutrino, which was thought to be massless for a while. Gluons are again much later and not thought to be free, at low energy anyway. So, without any other candidates at the time only the photon was thought to be massless.

 

 

I think Brian Cox explains it perfectly in the book: Why does e = mc² ?

Can't say, I have never read the book.

You would therefore measure a separation velocity between the two of 1.8c. However, the speed of each object as measured in the other's frame is still less than c. That's what ajb means by local measurements of speed.

Exactly. You can define separation speed and things like that no problem. However, they won't correspond to what one usually means by relative speed (or velocity).

[michel123456]

The speed of light in any inertial frame can be considered as an absolute speed in the sense any inertial observer will measure the same speed. But this is not usually what one means by an absolute speed.

(...)

 

We all agree on this. Absolute speeds or velocities are unnatural in special and general relativity.

Yes, I agree

 

Thus one can state that the Speed Of Light is not absolute. It is a constant though.

IOW the SOL is a relative constant.

Edited May 5, 2015 by michel123456

[Delbert]

It is possible to observe an object moving away from you at 0.9c, and another object moving away from you in the opposite direction at 0.9c.

 

You would therefore measure a separation velocity between the two of 1.8c. However, the speed of each object as measured in the other's frame is still less than c. That's what ajb means by local measurements of speed.

I suppose that's one way to look at it. I did locate the argument for this some time ago, but I can't quite recall it!

 

Other than to say that the other two observers will view the situation different to us. Such that they will see us at a different time, that is age, than they see other object that's suggested to be moving away from them at 1.8c. Whereas we see the other two objects at the same time - that is age. Which will probably mean the 1.8c will turn out to be <1c. I'm sure I've got some diagrams describing it all somewhere, but I can't find them! So I'll have to leave it there.

[ajb]

Other than to say that the other two observers will view the situation different to us. Such that they will see us at a different time, that is age, than they see other object that's suggested to be moving away from them at 1.8c. Whereas we see the other two objects at the same time - that is age. Which will probably mean the 1.8c will turn out to be <1c. I'm sure I've got some diagrams describing it all somewhere, but I can't find them! So I'll have to leave it there.

Indeed, neither one of the two that are separating will measure there relative speed with respect to the other to be c or above.