# Do the Large Hadron Collider take earth's rotational speed?

1. May 24, 2013

so according to wiki: protons have a Lorentz factor of about 7,500 and move at about 0.999999991 c, or about 3 metres per second slower than the speed of light (c)

If we consider speed of earth's rotation or speed at which two galaxies approach each other (collision or otherwise)?

2. May 24, 2013

### wotanub

Could you rephrase? I don't understand what you are asking.

3. May 24, 2013

### DrChinese

We really have no way to determine either the Earth's absolute velocity or absolute direction of travel, net of all of the gravitational effects of celestial bodies. We could be traveling a few percent of the speed of light, for all we know. So you might deduce from those statements that such does not matter.

In fact, according to relativity, the laws of physics are independent of any absolute reference frame. So the Earth's movement, per se, is not a factor in calculating the results. (As far as anyone knows, there is no absolute reference frame anyway.)

So when we say it is moving at 99.9999% of c, we mean relative to the observer.

4. May 24, 2013

### phinds

As DrChinese implied, all motion is relative. You, as you are reading this, are both absolutely motionless from a frame of reference of the chair you are sitting in AND moving at 0.999999991 c from a frame of reference of that particle you mentioned.

Also, you may not be aware, speed "addition" in relativity is not simple arithmetic, it is algebraic and the sum NEVER exceeds c.

5. May 28, 2013

I don't have a background in physics. So excuse my ignorance.

So far that I know about velocity of a particle is it's a measure of distance per unit time. If a particle is at a position at one time, and another position at another time, we take the difference of the position and the time, thus we have the speed.

Now, the particle on the LHC is moving at a certain speed, assuming that at one point, it is moving parallel to that of the earth's rotation. Wouldn't you agree that the position has changed, not only by the velocity at which it travels, but also at the velocity of the earth's rotation? As in, the earth has carried it a certain distance, as well as it's own velocity.

6. May 28, 2013

### phinds

Yes, the movement of the Earth does change the resultant velocity vector but

(1) the amount the Earth moves while a particle moves in the LHC is utterly trivial
(2) relativistic velocities do NOT add as "v1+v2" (Google relativistic velocity addition if you want to know more)

7. May 28, 2013

### Staff: Mentor

Not if the LHC is the reference frame.

The problem here is lack of definition of reference frame: the LHC is the reference frame so the particle speed is measured relative to it.

8. May 28, 2013

### phinds

Good point.

I was unthinkingly creating a reference frame which was neither the Earth nor the LHC to talk about relativistic velocity addition.

9. May 28, 2013

### krash661

i once came across this,

Last edited by a moderator: Sep 25, 2014
10. May 28, 2013

### phinds

An amusing presentation, although flawed.

1) He keeps adding vectors as thought they were scalers, but I understand why he doesn't want to add that complication just because it would make his presentation factual instead of wrong. he is not orders of magnitude wrong.

2) He mentions a "fixed point in the universe" which is also seriously wrong, but it is somewhat understandable what he means and he does point out that this has a difficulty, though the doesn't say what it is.

3) He keeps adding "directions of motion" as though they don't combine and ends up having movement be in "7 different directions" which is going to be a bit tough in a 3-spacial-dimension universe, although again it's pretty understandable what he means (which is something like "COMPLICATED 3D motion which I choose to call 7-directional motion")

Last edited by a moderator: Sep 25, 2014
11. May 28, 2013

### krash661

ok.
i'm interested in this at times,
so do you have any resources of such ?

edit-
or at lease have your own calculation ?

Last edited: May 28, 2013
12. May 28, 2013

### phinds

I can only suggest that you study basic cosmology.

13. May 28, 2013

### krash661

can you show the correct calculation from your prospective?
at lease ?

edit-
i also came across this,
" Scalar (mathematics), a quantity that can multiply vectors in the context of vector spaces
Scalar (physics), a quantity which is independent of specific classes of coordinate systems
Vectors are quantities that are fully described by both a magnitude and a direction."

and also, clarify which type of vector you are referring to

14. May 28, 2013

### krash661

Hmm.

15. May 28, 2013

### Staff: Mentor

Vectors are elements of vector spaces. There are no different types of vectors, just different types of vector spaces. I assume Phinds means a Minkowski space, as this is the framework of special relativity.
Somehow I doubt that this helped, but it is a precise answer to your last question.
All calculations can be done in this space and with Lorentz transformations.

16. May 28, 2013

### krash661

ok, so all these vectors below are all " vector spaces "?

http://en.wikipedia.org/wiki/Vector_(mathematics_and_physics [Broken])

Last edited by a moderator: May 6, 2017
17. May 28, 2013

### phinds

No, the calculations would be incredibly complicated and a HUGE waste of time. You should focus on the concepts.

18. May 28, 2013

### Staff: Mentor

(I fixed the link in the quote)

19. May 28, 2013

### Staff: Mentor

As phinds mentioned, velocity doesn't add that way. If you work out the math you find that a Lorentz factor of 7500 is c-2.664822 m/s. That is the speed of the particles in the frame where CERN is at rest. In the frame where the center of the earth is at rest CERN is moving at 465 m/s (or it would if CERN were located at the equator). In that frame the forward moving particles are moving at c-2.66481 m/s and the backward moving particles are moving at -c+2.66483 m/s.

20. May 29, 2013