how fast does light think light travels?(physics question)

[NUKE]

Originally posted by AKIron
I think Einstein was saying that gravity is curved space, so the shortest distance between point a and b wasn't a straight line hence light appeared to curve.

with the star visible from behind the sun during an eclipse, he proved that gravity could bend the light around the sun.

edit: which doesn't make sense, gravity "pushed" the star's light around the sun instead of "pulling" it into the sun or otherwise dispersing it?

edit again: I can see how it could be so after thinking a few seconds Light was like an airstream flowing around a ball in an air tunnel.

[AKIron]

Here's something I just found that may help to visualize.

"Space-Time Continuum
It may seem like a gimmick, but the picture illustrates one of the most profound elements in Einstein’s theory. Einstein saw time and space as a fabric, sort of like the taut surface of a trampoline.
     If you put a bowling ball on a trampoline, it will distort the surface. And then if you roll a golf ball past the bowling ball, its course will be curved because of the indentation in the surface of the trampoline.
     Similarly, the pathway followed by light from a distant object is distorted by the presence of mass, such as a galaxy of billions of stars. The light will curve because the “fabric” through which it travels is warped by the mass."


Look at this way. From the perspective of the golf ball it is just moving on it's merry way being neither pushed nor pulled along. When it encounters the curve it doesn't perceive an additional force but continues in what it perceived to be a straight line.

[mietla]

Originally posted by NUKE
Think again about what? That I don't buy all the space/time theory stuff? When Einstein proved that a star's light could be visible from behind an eclipse, it proved that light was effected by gravity I thought.

Really, read Einstein and Feynman. After you are done, you'll have an "epiphany",

"Wow, this is so obvious and common sensical, how was it that I could ever think any other way."

[AKIron]

Brian Greene's "The Elegant Universe" is an excellent book for the layman imo and gave me a much better understanding of some of these difficult concepts.

[mietla]

Originally posted by AKIron
I think Einstein was saying that gravity is curved space, so the shortest distance between point a and b wasn't a straight line hence light appeared to curve.

Correct, light is following the straight line in its frame of reference which may appear curved in other observer's frame of reference.

Remember, there is no such thing as an object trajectory. For a kid boucing the ball of off the floor of the moving train the ball moves in a straight line up and down.

For the observer on the ground, the ball moves in a series of parabolas.

Both of them can PROVE that each one of them is right, and both of them will be right (in their frames of reference of course)

So, what is the REAL trajectory of the ball, huh?

SRT is really simple, you just have to forget V = V1 + V2 and accept a Lorentz transformation instead. A simple addition is an extremely good approximation (that's why no man have noticed any  discrepancy for thousands of years of civilisation), but if you get to really high velocities, it shows very clearly.

[Holden McGroin]

Originally posted by lasersailor184
Holden, so far you've only said that a photon doesn't experience time.

You haven't said why or how...

Experiments in the late 19th century were looking for the great initial reference frame to which ether was connected.

They measured the speed of light from a fixed star whose light track was tangent to our solar orbit, and compared the speed to a measurement taken six months earlier.  The speed of our orbit known and the speed of our movement through the ether could have been detected by the difference in the two light speeds.

Strange to the observers, the speed was identical regardless of the orbital velocity of the Earth.  The speed of light was constant.

If the speed of light is constant and not additive to the speed of the observer, then something strange must be happening.  The two componants of the ratio making up our concept of speed must be changing in relation to the speed of the obsrever, and so time and distance paralell to the velocity need to change in order to keep the speed ratio the apparent constant that it is.

H.A. Lorentz figured a way to quantify the apparent slowing of time inside a speeding ship: (apparent to the outside observer anyway)
                                                           
This equation, experimentally quantified, shows that as v=c, the time dilation reaches infinity.  

That means that the entire lifetime of a photon is experienced simultaneously.  Time does not pass on a photon.

Length also changes by the formula:

That's the how, as for the why as a theologian.

[WldThing]

This is the most entertaining debate that i have read in the O Club so far this month.

[mietla]

Originally posted by AKIron
Here's something I just found that may help to visualize.

"Space-Time Continuum
It may seem like a gimmick, but the picture illustrates one of the most profound elements in Einstein’s theory. Einstein saw time and space as a fabric, sort of like the taut surface of a trampoline.
     If you put a bowling ball on a trampoline, it will distort the surface. And then if you roll a golf ball past the bowling ball, its course will be curved because of the indentation in the surface of the trampoline.
     Similarly, the pathway followed by light from a distant object is distorted by the presence of mass, such as a galaxy of billions of stars. The light will curve because the “fabric” through which it travels is warped by the mass."


Look at this way. From the perspective of the golf ball it is just moving on it's merry way being neither pushed nor pulled along. When it encounters the curve it doesn't perceive an additional force but continues in what it perceived to be a straight line.

Bingo, what you've just described is a 2 dimensional space (the initially flat trampoline which being horizontal, does not "know" up-down dimension) curved into a third dimension, up-down.

The ants living on a trampoline and confined to its surface, will not be able to perceive the up-down dimension. All they will see is a large bowling ball "magically" causing the golf ball to go round and round in orbit.

Unless the ants make a mental jump and realise, ...wait a minute... maybe we are really on a flat 2 dimensional surface curved in a 3-rd  dimension (which we never saw or experienced), they will alway see this phenomenon as a strange attraction between a bowling ball and a golf ball. They can measure it and create a law that the force between the balls is proportional to both masses and inversely proportional to the distance between them, but they will never have a clue why.


Which is exactly where we are, We know F = G* m * M / R^2, but we have no clue why (except of the antropomorphic principle which is a philosophical cop out anyway).

[AKIron]

Originally posted by mietla
Which is exactly where we are, We know F = G* m * M / R^2, but we have no clue why (except of the antropomorphic principle which is a philosophical cop out anyway).

And here we are back at "free will" and philosophy. Is it the mass that warps space or the warps in space that collect mass. I would think that since I can act upon an object of mass and still observe it's inherent gravitational force that the gravitational force is inherent in the mass. But what if I am mistaken about actually enacting a change in the mass? What if the movement of my hand was caused by the fluctuation in space/time and I only perceived it to be my will? Hehe, I'd probably understand this better with a bit of scotch.

[mietla]

Originally posted by AKIron
I'd probably understand this better with a bit of scotch.

I'm an inch of Scotch in front of you

[Holden McGroin]

Discussion of existentialism is two threads over.

[moot]

There'll be a gravity probe launched on the 19th.
http://einstein.stanford.edu/index.html

[bozon]

what a lot of people here are confusing are two different theories with bad names for them:
1. Special relativity
2. General relativity

The names are bad because the 1st one is not a special case of the 2nd.

"Special relativity" is a later name given to Einstein's theory from 1905 which explained Maxwell's equations (electro-magnetism). I think the paper was called "on the electrodynamics of moving bodies" or something like that. It was known that they were invariant to Lorentz transformation, but only einstein understood what it ment.
This theory explained the magnetic field (or actually the magnetic force on a moving charge) as a deformed electric field due to the fact that the fields expands in a finit speed - SOL.
You can get maxwell's equations from only the electric field and assuming that light( the field) expands in a finit and constant speed in every frame of reference.

"General relativity" was published about 10 years later (1916?) and deals with explaining gravity. It actually doesn't use a "gravity force" but warp space-time instead. this is the same space-time from the 1st theory and the confusion comes from here.
This is a MUCH more complicated theory with difficult equations. Even Einstein needed the help of some top mathematicians to work it out.
The famous Eclips experiment was to test this theory (if the space is curved around a mass, even massless photon will bend around the mass, regardless of "gravity")

Bozon

[Griego]

Originally posted by lasersailor184
Remember, just because we haven't found anything that goes faster then the speed of light, doesn't mean it doesn't exist.


  Neutrino's have been observed to travel faster than the speed of light.


  And to hitech, There are as many reality's as there are observers.

[bozon]

Originally posted by Griego

Originally posted by lasersailor184

  Neutrino's have been observed to travel faster than the speed of light.

  And to hitech, There are as many reality's as there are observers.

The neutrinos travel faster then the light - not faster then the speed of light. It's the light that was slowed down due to interaction with matter.

There is only one reality. your perception of reality might be different from another's, but it's the same reality (when you close your eyes, does the world disappear?)

Bozon