# Light, matter and reference frames

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#### BoJangles2

##### Guest
Light and matter behave in different ways.

The Michelson-Morley Experiment proved light is measured at the same speed in all directions, how about matter?

If the LHC is speeding matter up to within a small percentage of the speed of light, shouldn’t there be slowing and speeding up somewhere in the circuit it takes on the way to the detectors ,due to the fact the earth is spinning, moving around the sun and the sun around the galaxy at some ungodly speed( we ought not to be exceeding the speed of light), or am I confusing things a little here.

I thought my understanding of matter is that, you could never have matter travelling faster than c in any reference frame (i.e. moving or not).

I think I’m probably getting confused with reference frames or something

Or how about this one, if 2 people fired balls at each other at .999c (and they missed each other) an ant on one of the balls would see the other ball fly past at +c. For which he then scratches his head and wonders why something passed him at +c

Basically all I’m thinking is that is rounded down to the following, if you’re firing matter around the LHC, it must slowdown as it takes the corner in the direction of our absolute motion through space (if there is such a thing)
If matter can travel at the speed of light in any reference frame, then 2c is possible in some references, if not, only half c is possible in some references. Or is it the case there is an absolute reference frame, Man I’m confused

Can someone please put me out of my misery and address a couple of these issues, thanks

Oh an hi SDC, it’s been ages since I’ve posted

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#### Shpaget

##### Guest
Well, do the parts of the spinning wheel on a car slow down and speed up as it rolls around?
Yes, when you take the ground as the point of reference, but if you take the axle as reference point the wheel doesn't really care how the Earth moves underneath it, nor how the solar system moves in the galaxy.

All it cares about and all the forces it experiences come from the motion relative to the axle.

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#### BoJangles2

##### Guest

Shpaget":2bfmqa5k said:
Well, do the parts of the spinning wheel on a car slow down and speed up as it rolls around?
Yes, when you take the ground as the point of reference, but if you take the axle as reference point the wheel doesn't really care how the Earth moves underneath it, nor how the solar system moves in the galaxy.

All it cares about and all the forces it experiences come from the motion relative to the axle.
So I guess what your saying is that, if you’re on a train travelling at .9c, you should be able to throw a ball at .9c away from you in the direction of the train, and a person on the side of the tracks would measure the speed of the ball travelling at +c speeds. *scratches head*

I actually thought in this scenario, the person on the train trying to throw the ball, would need infinite energy to speed the ball (up to c) as far as the observer (on the side of the track) was concerned. Which lead me to think; that in the case of the LHC and due to the relative motion of earth through space, somewhere along the LHC circuit the matter they fire must be slowing down, and not travelling at close-to-c due to the intrinsic speed at which mater can travel.

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#### csmyth3025

##### Guest
BoJangles2":1g4lteyv said:

Shpaget":1g4lteyv said:
Well, do the parts of the spinning wheel on a car slow down and speed up as it rolls around?
Yes, when you take the ground as the point of reference, but if you take the axle as reference point the wheel doesn't really care how the Earth moves underneath it, nor how the solar system moves in the galaxy.

All it cares about and all the forces it experiences come from the motion relative to the axle.
So I guess what your saying is that, if you’re on a train travelling at .9c, you should be able to throw a ball at .9c away from you in the direction of the train, and a person on the side of the tracks would measure the speed of the ball travelling at +c speeds. *scratches head*
One of the consequences of Special Relativity is that no material thing can be accelerated to the speed of light as seen by an observer. The Wikipedia article on Special Relativity can be found here: http://en.wikipedia.org/wiki/Special_relativity#Causality_and_prohibition_of_motion_faster_than_light

The usual example given is that of a train (call it system K) travelling due east with a velocity v with respect to the tracks (system K'). A child inside the train throws a baseball due east with a velocity u with respect to the train. In classical physics, an observer at rest on the tracks will measure the velocity of the baseball as v + u.

In special relativity, this is no longer true. Instead, an observer on the tracks will measure the velocity of the baseball as (v+u)/(1+(v*u/c[super]2[/super])) . If u and v are small compared to c, then the above expression approaches the classical sum v + u.
In your example, the above formula would yield: (.9c+.9c)/(1+(.9c*.9c/c[super]2[/super])). Since we're using one as the value of c, this gives us 1.8c/1.81 = ~.994c. This is the speed that the observer on the tracks would see.

Chris

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#### BoJangles2

##### Guest
Once again thanks for the reply,

so even when k,v and c are .9c (for instance) it will still equall less than c to any observer?

So what’s going in on relativity that is causing v+u equalling less than c, even when v and u are approaching c. I can see the maths, but in laymen’s terms why is it the case?

Is time dilation, length contract or simultaneity raising its head?

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#### csmyth3025

##### Guest
BoJangles2":2b4giyml said:
Once again thanks for the reply,

so even when k,v and c are .9c (for instance) it will still equall less than c to any observer?

So what’s going in on relativity that is causing v+u equalling less than c, even when v and u are approaching c. I can see the maths, but in laymen’s terms why is it the case?

Is time dilation, length contract or simultaneity raising its head?
You might say that it's all three. It has to do with making a "transformation" from one frame of reference to another. If you want to understand it you might try the Wikipedia "Introduction to Special Relativity" here:
http://en.wikipedia.org/wiki/Introduction_to_special_relativity

Chris

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