Massless Energy & Nothing.

[Tormod]

Light at rest does not have a mass because light is a constant c. How can something that never stops have a rest mass?

 

What do you mean? When does light never stop?

 

My understanding is that when light infinitely redshifts it no longer exists as light.

 

Are you talking about optical light here or any part of the EM spectrum? When light shifts it simply moves higher or lower in the EM spectrum. It does not disappear unless the energy it carries is converted into some other form, ie the light is absorbed in a chemical reaction or caught up in a black hole, for example.

 

I don't really understand vacuum fluctuations

 

I don't think anyone really does, either. It is a difficult topic.

[Damo2600]

Hi Tormod,

 

I don't understand what the problem with my post is. When do you ever see light stationary? Excluding the light experiments that Clay posted because this is a different principle all together. But in your general observations of the physical universe when do you ever *SEE* light as being stationary?

 

It doesn't. So I don't see your problem with the question:

 

How can something that never stops have a rest mass?

 

Within the Event Horizon light infinitely redshifts and the energy is converted to (Blank Blank- Perhaps you can fill in the blank for me because I'm not sure)

 

Either way the energy no longer exists as light energy. So you cannot state this as being stationary light because it is not light. Right?

 

I'm hoping Maddog can explain the statement 'something from nothing' at least. Oh and Maddog in case you don't realise the post directly after your post was supposed to be addressed to you, I apologise.

 

Damien

[Tormod]

But in your general observations of the physical universe when do you ever *SEE* light as being stationary?

 

It doesn't. So I don't see your problem with the question:

 

How can something that never stops have a rest mass?

 

Light *can* be frozen in it's tracks:

http://science.nasa.gov/headlines/y2002/27mar_stoplight.htm

 

But I think maybe this explanation is better than anything I can provide:

Does light have mass?

http://math.ucr.edu/home/baez/physics/Relativity/SR/light_mass.html

 

[edit]Pay particular attention to the part about relativistic mass.

 

Within the Event Horizon light infinitely redshifts and the energy is converted to (Blank Blank- Perhaps you can fill in the blank for me because I'm not sure)

 

...energy...

 

Either way the energy no longer exists as light energy. So you cannot state this as being stationary light because it is not light. Right?

 

What you call "Light energy" is simply electromagnetic waves which consist of photons, which are the smallest quantum of electromagnetic force. All electromagnetic forces move around in the form of photons. Energy cannot be created, nor disappear. It can only change shape and type.

 

Thus we can use energy to do work - for example, we need chemical energy generated in a battery to create the light beam in a flashlight. When a light beam is sucked into a black hole, it adds up to the total amount of energy in the black hole.

[Damo2600]

Hi Tormod,

 

The photon has relative mass but according to this theory it has an invariant mass of zero. The way this is explained is by the equation

 

m = sqrt{E^2/c^4 - p^2/c^2}.

 

E = pc

 

So in this equation m = 0

 

I cannot argue with this. It appears to be word jugglery to me. I don't understand though the expression:

 

E = pc

 

I would have assumed that p = c

 

That would mean that

 

E = c^2

 

Which just cuts the m out of Einstien's equation.

 

So with reference to a photon you can use either equation where

 

E = mc^2 where reletavistic mass has a value.

 

or

 

E = c^2 where invariable mass equals zero.

 

Forgive me but I'm scratching my head here at the moment. If you capture a photon in a box, with mirrors on the inside, the mass of the box increases. This I understand the whole geodesics stuff I don't get.

 

I'm sure this is beyond me but I'm having trouble accepting this. It sounds to me as if someones trying to feed me baloney.

 

Damien

[Tormod]

But that was just one of the explanations, right? There are several.

 

If it feels like baloney, read books or talk to someone...You're starting to sound a bit paranoid here. ;)

 

We're not feeding you - you are asking!

[OmegaX7]

Damo; I mentioned earlier that god must not be interjected here. This is science.

Like Tormod stated, the original quiry was if anyone thought energy could exist without mass. I'm not even smart enough to know when I'm getting laughed at here but I am enjoying the exchanges- - so far.

[Damo2600]

Perhaps Tormod,

I just have difficulty accepting two opposing statements. This does seem to me to be the explanation that is being accepted by the posters on this thread. But i'm in over my head in this thread as well. So I'll pull out.

 

Omega X

 

I'm sorry I must have misunderstood what was being implied by your post. Enjoy the rest of your convo. ;)

 

Damien

[Tormod]

Perhaps Tormod,

I just have difficulty accepting two opposing statements. This does seem to me to be the explanation that is being accepted by the posters on this thread. But i'm in over my head in this thread as well. So I'll pull out.

 

Pull out??? Hm.

 

Well...do you mind explaining what the two opposing statements are?

[Damo2600]

O.k. since noone else wants to comment on this I will buy into it. But I'm not happy about it.

 

The light experiments you posted whereby light freezes can not be included. This is because the natural state of light has been altered in order to do this. For e.g. the photon is absorbed within an atom. However light photons by themselves do not freeze. I hope we can all agree on this.

 

The photon in it's natural state always travels at c. In the medium of water the wavelengths of light shorten. The speed is still c however it takes the photon longer to travel from A to B. I hope I am making myself clear enough.

 

So if the shortest distance between two points is a straight line then an extremely short wave length would be the longest distance. So besides infinte red shifting and the experiments you had mentioned: light ALWAYS travels at a constant. So the speed of light therefore is invariant ALWAYS. There is no relativistic speed of light.

 

p always = c

 

However if light has a relativistic mass it must also have a relativistic energy. I'm not the greatest mathematician but here we go:

 

E = mc^2

 

and

 

E = c^2

 

If you take the value of m out of this equation the value of E would also have to change. So relativistic E would have a greater value than invariable E. We can seperate the relativistic mass and relativistic energy.

 

Ei * Er = m * c^2

 

Where

 

Er = m and Ei = c^2 Ei > Er

 

Here Er = relativistic energy and Ei = invariable energy. So the relativistic mass seems to be a separate entity here with it's own Energy. I hope mathematically I have worked this problem out correctly. The other way I thought to sort it out however was:

 

Er = mc^2 Ei = c^2 Ei < Er

 

Of course I am coming at the problem from a different direction than the website linked. However I can't seem to balance Ei and Er.

 

We can measure the mass of a photon. However the photon has no mass. Can you see where I am having difficulty?

 

Damien

[Damo2600]

Sorry there was a formating problem

 

Er = m

Ei = c^2

Ei > Er

 

Er = mc^2

Ei = c^2

Ei < Er

 

Damien

[Damo2600]

Patence is a virtue

 

;)

[paultrr]

The photon in it's natural state always travels at c. In the medium of water the wavelengths of light shorten. The speed is still c however it takes the photon longer to travel from A to B. I hope I am making myself clear enough.

 

 

In air C is not 186300 MPS, nor is it that in water. The only medium C equals that in is the vacuum. Its not just the wavelength that changes with a medium change. Its the actual velocity that changes also. The speed of light in a vacuum is exactly equal to 299,792,458 metres per second. The speed of light through a medium that is, not in vacuum is less than c defined by the refractive index of the medium in question. Yes, its still called C. But the velocity of the photons is different in different mediums. An example of how other particles can move in different mediums faster is found with the Cherenkov effect in the water around a nuclear reactor. The effect is due to electrons moving faster than the speed at which light moves in water. In that case electrons have a a higher velocity in that medium than does light. The velocity of light is only invarient if the medium remains the same.

[Damo2600]

Hi Paul,

 

Two balls bouncing at a constant speed down a tunnel. Both balls bounce and hit the ceiling then the floor. If the angle of bounce is different for both balls then they will travel through the tunnel at different speeds even though they are both travelling at the same speed.

 

When light is travelling through water it is still called *c* because the photon is still travelling at the same speed. A shorter wave length would mean that the photon is travelling up and down more peaks and troughs. The more peaks and troughs mean that, although the photon is still travelling at the same speed, it is an obserbvably slower *c* for us. We can't see the wave lengths so it appears light is slower.

 

Light ALWAYS travels at a constant.

 

Damien

[Tormod]

The photon in it's natural state always travels at c. In the medium of water the wavelengths of light shorten. The speed is still c however it takes the photon longer to travel from A to B. I hope I am making myself clear enough.

 

This is not correct, Damien. The definition of c is the speed of light in *vacuum*. In water, light will travel at less than c.

 

So when the light wave passes through water, c remains the same so the photon travels at less than c, and spends longer getting from A to B.

 

You cannot dismiss the "frozen light" experiments - it does not matter what state the photon is in. The photon is the carrier of light, therefore the speed of the photon is the speed of light in whichever medium it travels.

 

The speed of light in a medium, ie not emtpy space, is less than c. This makes for some interesting examples where other things can move at speeds faster than light - but they cannot travel faster than c.

 

Wikipedia: Speed of light

http://en.wikipedia.org/wiki/Speed_of_light

[Damo2600]

I'll state it a little more clearly the wave speed is EXACTLY the same.

The time it takes to travel from A to B is different.

How can this be that light has slowed down?

 

(Frozen light is NOT the same principle.)

 

Can I be more obvious?

 

Damien

[Tormod]

I'll state it a little more clearly the wave speed is EXACTLY the same.

The time it takes to travel from A to B is different.

How can this be that light has slowed down?

 

(Frozen light is NOT the same principle.)

 

Can I be more obvious?

 

Damien

 

This is not obvious at all. I don't understand what you are claiming here. What is "wave speed"? Light slows down in a medium - what else is there to say?

[Damo2600]

Tormod,

 

Simpler still: if I draw a straight line at a constant speed (v) from point A to point B. This is the fastest method by which I can do this at this velocity. Now if I draw the line at the same velocity but in a wave motion from the same point A to the same point B it will take me longer to do this. Right

If I draw a line from the same point A to the same point B at the same velocity but tighten up the wave frequency so there are hundreds of peaks and valleys it will take me a much longer time. Now I am drawing the line at the exact same velocity only it takes me much longer to get from point A to point B.

 

Does that make sense? So this remains true to the fact that light is a constant speed within a vacuum as it does in a denser medium (such as water).

I understood this the first time I heard it and I understand very little about physics.

 

Damien