Time Slower In Orbit?

[Arising_uk]

thanks blags but i aready know the easy stuff the same as most others its the trcky stuff i am interested in.

Sorry but which bit do you find easy? As my mind boggles at the thought that two things moving towards each other can become non-additative with respect to velocity at some point!?

[Blaggard]

thanks blags but i aready know the easy stuff the same as most others its the trcky stuff i am interested in.

Sorry but which bit do you find easy? As my mind boggles at the thought that two things moving towards each other can become non-additative with respect to velocity at some point!?

Yeah it's not easy to undo common sense but since that is the way it works you must. He probably just finds it easy to ignore the common rules of motion at far less than c, and I think we all can if the law says so. I suppose you have to or just dismiss the laws of nature out of hand.

[uwot]

thanks blags but i aready know the easy stuff the same as most others its the trcky stuff i am interested in.

Sorry but which bit do you find easy? As my mind boggles at the thought that two things moving towards each other can become non-additative with respect to velocity at some point!?

Like I said, you can draw your own conclusions, but in the LHC protons travelling at just under c. collide with the energy of just under 2c.
It's the veil of appearance, Arising, as any philosopher knows, what you see, isn't what you get. The point about special relativity is that you can only measure things as they appear; absolute measurement would depend on absolute time and absolute space, and since they are meaningless, so is absolute measurement. In your inertial frame, that piece of space you are travelling in, the light travels at the speed of light for that medium*, that is true even of empty space. The most distant galaxy sighted is over 30 billion light years away. Given that the universe is only reckoned to be 13.7 billion years old, you might wonder how we can see something the light from which ought to take another 16 billion years to get here. The point is that space is stretching, so although light from that galaxy has been travelling at 186 000 miles a second, those miles are growing. If you can imagine that the Big Bang stopped after a couple of nano seconds (before inflation) and the entire universe was only the size of a football in absolute terms, it would still take light several billion years to travel from the point corresponding to that galaxy and wherever we are, even though in absolute terms, it's only a few inches away.
It's not that relativity says that things can or cannot travel at speeds greater than c, relative to each other and in absolute terms, only that it is impossible to measure anything travelling at more than c in any inertial frame and absolute terms have absolutely no meaning. The limiting factor is the fact that photons travel through any given media, including space, at a fixed speed, regardless of how that media/space is stretched or warped by mass or velocity. It doesn't really make sense to talk about things colliding at more than c. as V=d/t and both distance and time are relative, but 14Tev is the equivalent of nearly 2c. That's good enough for me.

*This is where people usually howl, 'But the speed of light is constant!' Yes, in a vacuum. Anyone who doubts that the speed of light varies according to the medium, should look up refractive index, you should be able to discover the speed of light in all sorts of media. Some bright spark has slowed it down to 30mph, I understand.

[Blaggard]

QFT

A very well explained piece of prose uwot. :hatsoff:

Couldn't of put it better myself if I was Einstein.


Slowed is of course a term that makes no sense to light, but you are right someone has inhibited light from moving at c in a medium in very particular circumstances. It was actually a Bose-Einsten condensate of lithium, as to why its speed was 30mph, well there in lies the rub, light always propagates at c in a vacuum, refractive indexes in matter however do slow light but it is of course because of the lattice structure of matter that light can be indeed refracted and naively at least slowed, when light is propogating it travels at c, when light is travelling through any medium be it solid or whatever it can be slowed but it's average speed whilst propagating is still c, and that is an important consideration.

http://www.physicsforums.com/showthread.php?t=511177

This explains it:

Do Photons Move Slower in a Solid Medium?

Contributed by ZapperZ. Edited and corrected by Gokul43201 and inha

This question appears often because it has been shown that in a normal, dispersive solid such as glass, the speed of light is slower than it is in vacuum. This FAQ will strictly deal with that scenario only and will not address light transport in anomolous medium, atomic vapor, metals, etc., and will only consider light within the visible range.

The process of describing light transport via the quantum mechanical description isn't trivial. The use of photons to explain such process involves the understanding of not just the properties of photons, but also the quantum mechanical properties of the material itself (something one learns in Solid State Physics). So this explanation will attempt to only provide a very general and rough idea of the process.

A common explanation that has been provided is that a photon moving through the material still moves at the speed of c, but when it encounters the atom of the material, it is absorbed by the atom via an atomic transition. After a very slight delay, a photon is then re-emitted. This explanation is incorrect and inconsistent with empirical observations. If this is what actually occurs, then the absorption spectrum will be discrete because atoms have only discrete energy states. Yet, in glass for example, we see almost the whole visible spectrum being transmitted with no discrete disruption in the measured speed. In fact, the index of refraction (which reflects the speed of light through that medium) varies continuously, rather than abruptly, with the frequency of light.

Secondly, if that assertion is true, then the index of refraction would ONLY depend on the type of atom in the material, and nothing else, since the atom is responsible for the absorption of the photon. Again, if this is true, then we see a problem when we apply this to carbon, let's say. The index of refraction of graphite and diamond are different from each other. Yet, both are made up of carbon atoms. In fact, if we look at graphite alone, the index of refraction is different along different crystal directions. Obviously, materials with identical atoms can have different index of refraction. So it points to the evidence that it may have nothing to do with an "atomic transition".

When atoms and molecules form a solid, they start to lose most of their individual identity and form a "collective behavior" with other atoms. It is as the result of this collective behavior that one obtains a metal, insulator, semiconductor, etc. Almost all of the properties of solids that we are familiar with are the results of the collective properties of the solid as a whole, not the properties of the individual atoms. The same applies to how a photon moves through a solid.

A solid has a network of ions and electrons fixed in a "lattice". Think of this as a network of balls connected to each other by springs. Because of this, they have what is known as "collective vibrational modes", often called phonons. These are quanta of lattice vibrations, similar to photons being the quanta of EM radiation. It is these vibrational modes that can absorb a photon. So when a photon encounters a solid, and it can interact with an available phonon mode (i.e. something similar to a resonance condition), this photon can be absorbed by the solid and then converted to heat (it is the energy of these vibrations or phonons that we commonly refer to as heat). The solid is then opaque to this particular photon (i.e. at that frequency). Now, unlike the atomic orbitals, the phonon spectrum can be broad and continuous over a large frequency range. That is why all materials have a "bandwidth" of transmission or absorption. The width here depends on how wide the phonon spectrum is.

On the other hand, if a photon has an energy beyond the phonon spectrum, then while it can still cause a disturbance of the lattice ions, the solid cannot sustain this vibration, because the phonon mode isn't available. This is similar to trying to oscillate something at a different frequency than the resonance frequency. So the lattice does not absorb this photon and it is re-emitted but with a very slight delay. This, naively, is the origin of the apparent slowdown of the light speed in the material. The emitted photon may encounter other lattice ions as it makes its way through the material and this accumulate the delay.

Moral of the story: the properties of a solid that we are familiar with have more to do with the "collective" behavior of a large number of atoms interacting with each other. In most cases, these do not reflect the properties of the individual, isolated atoms.

2 photons hitting each other have 2c/mv energy, they do not however travel towards each other at 2 times the speed of light as that is impossible: no non mass object such as the photon which we believe to be massless, can travel at less than c when propagating relatively or not, no mass object can travel at c no comoving objects can move at >c either relatively or in conjunction by comoving towards each other.

[uwot]

(QFT? Wassat?)

I think all the article says is that rather than bounce from atom to atom, as is commonly assumed, photons bounce from lattice to lattice, and in between travel at c.; at least in solids. I have no reason to doubt it.

2 photons hitting each other have 2c/mv energy, they do not however travel towards each other at 2 times the speed of light as that is impossible:

If you say so. Where does the energy come from if it isn't kinetic?

[Blaggard]

(QFT? Wassat?)

I think all the article says is that rather than bounce from atom to atom, as is commonly assumed, photons bounce from lattice to lattice, and in between travel at c.; at least in solids. I have no reason to doubt it.

2 photons hitting each other have 2c/mv energy, they do not however travel towards each other at 2 times the speed of light as that is impossible:

If you say so. Where does the energy come from if it isn't kinetic?

QFT = Quoted For truth. The energy comes from the Lorentz transforms at exactly that value and not more.

[uwot]

QFT = Quoted For truth.
The energy comes from the Lorentz transforms at exactly that value and not more.

Fair enough. So what actually happens in the Lorentz transforms?

[James Markham]

I think the point is understandable if we think of the same situation regarding cars. If two cars are both traveling at 60mph, and they collide head on, it's only equivalent to a car crashing into an immovable object at 60mph, in the case of the head on collision, each car acts in place of an immovable object, so that each car experiences a 60mph crash. If we make the mistake of assuming they crash together and each suffer the equivalent of a crash at a speed of 120mph, then each car would suffer one half of a 240mph collision.

I think the point is that they each converge on a given position, and relative to that position they are each only traveling at c.

[uwot]

I'm afraid that isn't true, James. Even a Volvo isn't an immovable object, but you will be worse off if the car you collide with is one of those, rather than a Mini.
As I understand it, Special Relativity doesn't make any claims about what happens in objective or absolute terms, it is essentially about what you can see. If two cars were approaching each other at the speeds reached in the LHC, the photons from the other car would be so blue shifted as to be invisible and so energetic as to be deadly themselves, but not as deadly as the imminent crash, which would cause an explosion that vapourised the entire planet.
I'm no mathematician, all I can work out is that in the LHC, 7Tev+7Tev=14Tev. Since E=mc², 7Tev=mc². Perhaps if you add them together, one c is cancelled out. Dunno. Howsit work?

[jackles]

ok if c is absolute to both closing photons is the observation then in an omni present frame of referance as regard to c.by omni present i mean unmoving.if this is so then the situation regards c is semi sizeless to the sizeless and there for unmoving observation of c.so is light as a wave semi nonlocal or put the other way around are light waves semi local.

[uwot]

ok if c is absolute to both closing photons is the observation in an omni present frame of referance as regard to c.by omni present i mean unmoving.

It looks as if the universe is made of some stuff that can be stretched and warped. Warp it enough and you make matter. Give it a kick and you send waves through it. The idea of something unmoving doesn't apply to any portion of this stuff; it is all moving.
Photons in effect are waves, they travel through the same amount of stuff in a given time, regardless of how the stuff is warped or stretched. So for instance, empty space is very stretched out stuff, a Black Hole is very condensed stuff. From an 'omni present frame of reference' light seems to travel very fast in empty space and very slow in a Black Hole. To a photon, it is always covering the same amount of stuff.
The particles in the LHC are protons, rather than photons, they collide with an energy that is equal to 2 protons travelling at <c. It looks like they are colliding with an impact velocity of almost 2c. The most plausible explanation is that, from an unmoving frame of reference, that is what they are doing.

[jackles]

uwot i think you are thinking in the right terms.but light is semi locality it cannot reach rest state in local terms and its not nonlocal (instantaineouse) so it can only be descibed as semi local to the observer who autmaticaly takes a fully nonlocal status as the looker.which means the looker cannot be local to the event as the observer.so the consciousness of the observer is at some point nothing viewing something.

[HexHammer]

I think the point is understandable if we think of the same situation regarding cars. If two cars are both traveling at 60mph, and they collide head on, it's only equivalent to a car crashing into an immovable object at 60mph, in the case of the head on collision, each car acts in place of an immovable object, so that each car experiences a 60mph crash. If we make the mistake of assuming they crash together and each suffer the equivalent of a crash at a speed of 120mph, then each car would suffer one half of a 240mph collision.

I think the point is that they each converge on a given position, and relative to that position they are each only traveling at c.

You are extremely unclear and it seems you are very wrong in beginning to talk about 240mph.

If 2 cars each drive with 60mph, they only due to relativity crash with a force of 60mph, not 120.

[James Markham]

Hex, yea that's what I meant.

[Blaggard]

QFT = Quoted For truth.
The energy comes from the Lorentz transforms at exactly that value and not more.

Fair enough. So what actually happens in the Lorentz transforms?

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

Plug some numbers in, Einstein shamelessly ripped the maths off, but he was right about the relativity issue so it's ok.

Special relativity

The crucial insight of Einstein's clock-setting method is the idea that time is relative. In essence, each observer's frame of reference is associated with a unique set of clocks, the result being that time as measured for a location passes at different rates for different observers.[18] This was a direct result of the Lorentz transformations and is called time dilation. We can also clearly see from the Lorentz "local time" transformation that the concept of the relativity of simultaneity and of the relativity of length contraction are also consequences of that clock-setting hypothesis.[19]
Transformation of the electromagnetic field
For the transformation rules, see classical electromagnetism and special relativity.

Lorentz transformations can also be used to prove that magnetic and electric fields are simply different aspects of the same force — the electromagnetic force, as a consequence of relative motion between electric charges and observers.[20] The fact that the electromagnetic field shows relativistic effects becomes clear by carrying out a simple thought experiment:[21]

Consider an observer measuring a charge at rest in a reference frame F. The observer will detect a static electric field. As the charge is stationary in this frame, there is no electric current, so the observer will not observe any magnetic field.
Consider another observer in frame F′ moving at relative velocity v (relative to F and the charge). This observer will see a different electric field because the charge is moving at velocity −v in their rest frame. Further, in frame F′ the moving charge constitutes an electric current, and thus the observer in frame F′ will also see a magnetic field.

This shows that the Lorentz transformation also applies to electromagnetic field quantities when changing the frame of reference, given below in vector form.

And:



The momentarily co-moving inertial frames along the world line of a rapidly accelerating observer (center). The vertical direction indicates time, while the horizontal indicates distance, the dashed line is the spacetime trajectory ("world line") of the observer. The small dots are specific events in spacetime. If one imagines these events to be the flashing of a light, then the events that pass the two diagonal lines in the bottom half of the image (the past light cone of the observer in the origin) are the events visible to the observer. The slope of the world line (deviation from being vertical) gives the relative velocity to the observer. Note how the momentarily co-moving inertial frame changes when the observer accelerates.