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CERN Acceleration

  1. Oct 22, 2003 #1
    I remenber reading something about how CERN accelerate particle to near the speed of light. 90% or even like 95% if I recall right but I do have trouble beleive this since wouldn't a object so close of the speed of light start to get infinity heavy and crush the small tubes in which the particle accelerate in?
  2. jcsd
  3. Oct 22, 2003 #2


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    The particals in those accelerators do indeed gain thousands of times their rest mass before colliding. The instruments used to detect collissions have to be callibrated for this. However, even a proton with its mass multiplied two thousand times is only as massive as two thousand protons. Still to slite to do any real damage.
  4. Oct 23, 2003 #3
    Ideally the accelerator is design so that the accelerated particles would not collide with the accelerator tube. Electromagnetic forces are applied to prevent it.
  5. Oct 23, 2003 #4


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    I'm sure someone has an exact number, but they are much faster than that: 99.999% or so. Fast enough that using %C starts to lose meaning and they just talk about energy.
  6. Oct 23, 2003 #5
    faster than a speeding... ahhh bullet doen't work.
  7. Oct 25, 2003 #6
    I'm not sure what the correct formula is to know how every the particle but if at 100% of C it reach a infinite mass, I would of tough by 99.99% it would have enough power to have some "implosion" like effect on the accelerator tube. And also you need infinity energy applyed for it to reach C, so I would of toutgh maknig it go at 99.99% would of required more then CERN could possibility get. But I guess I'm just wrong, odd are against the fact of me finding a flaw in eastein theory :P
  8. Oct 25, 2003 #7
    Yep. I see no reason for an "implosion effect" as you see. Because it's going 99.999% the speed of light, it's still under c. And even at those speeds, the increase in mass is pretty "small". It's would be different if I were accelerating a 1977 Gremblin. But protons and electrons are light in the overall view of things. The same with energy. Of course you need more energy to accelerate the prontons or electrons but due to it's relative mass/energy being so small already it can be done, given the right resources (CERN).
  9. Oct 26, 2003 #8


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    As russ_watters mentioned, the "number of nines" in the percentage is not too useful in accelerators.

    A better measure is the energy of the particles in the lab frame. The energy of a particle moving at 99.5% of c is about 10 times its rest mass. At 99.99875% of c, the energy is 200 times its rest mass.

    Fermilab accelerates protons (rest mass ~ 1 GeV) up to an energy of about a thousand times their rest mass, which corresponds to 99.99995% of the speed of light... i.e., just some 330 miles per hour short of c.
  10. Oct 26, 2003 #9


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    Most posters on this thread seem to think that particles travelling near the speed of light are more gravitationally massive than the same particles at rest. That's not the case, and is an example of how the concept of "relativistic mass" leads one astray.
  11. Oct 26, 2003 #10


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    By being heavy I assume that you mean that the particle is sitting on something and its weight can't be supported. Not true for a particle accelerator. They're in the tubes for such a short time span that the amount that they fall under the acceleration of the Earth's gravitational field is negligible so they never hit the side of the tube. And there are focusing mechanisms anyway and they keep the particles on track.

    As far as the increase in the intensity of the gravitational field - While that is true, i.e. the field strength increases with speed, the gravitational field even for those energies are so small as to be undetectable. Simply find the mass equivelence of the particle energy in those accelerators and you'll see that the mass is still so small as to be of no gravitational importance.

  12. Oct 26, 2003 #11


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    This is incorrect. Your notion that 'relativistic mass' leads one astray has led you to the incorrect notion that the gravitational mass of a particle does not increase with speed. That is wrong. It does increase with speed.

    The source of gravity is not rest mass. The source of gravity is relativistic mass. aka the source of gravity is mass-energy (which is just another phrase for relativistic mass).

    If you'd like to read more about this then there is an article in the Americam Journal of Physics on this topic. See

    Measuring the active gravitational mass of a moving object, D. W. Olson and R. C. Guarino, Am. J. Phys. 53, 661 (1985)
    Relativistic mass is not confusing once it is properly understood.

    For more on relativistic mass as the source of gravity see
    Cosmological Principles, John A. Peacock, Cambridge Univ. Press, (1999). See section 1 pages 17-18

    Section 1 is online at
  13. Oct 26, 2003 #12


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    If the rest mass of a particle is m_o and the mass is m and the speed of the particle relative to the lab is

    m = m_o/sqrt[1-(v/c)^2]

    This assumes the definition of mass whereby the quantity mv is a conserved quantity. Once the mass is defined in this way then one can define momentum as the product mv as momentum. I.e. mass is defined such that momentum is conserved. The 'm' defined as such is sometimes refered to as relativistic mass. The increase in mass is a result of time dilation. I.e. time dilation and mass increase are one in the same phenomena.

    For details and proof see --

  14. Oct 27, 2003 #13


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    Re: Re: CERN Acceleration

    I don't think so (Chazz, please correct me if I'm wrong about this). I think he's talking about the effect increased mass would have on momentum. Those accelerator tubes aren't straight, and a more massive partical would be more difficult to keep going "round the bend"; it would want to go straight and hit the wall of the tube. Of course, the crucial point in all this is that a proton accelerated to a couple thousand times its original mass is still lighter than a speck of dust.

    PMB, regarding the relationship between relativistic mass and gravitational pull, were you one of the contributors to my "Relativistic Black Holes?" thread in the old PF? I must admit, this is an aspect of relativity I don't yet fathom.
  15. Oct 29, 2003 #14


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    Re: Re: Re: CERN Acceleration

    Yes. That was me. I enjoy discussing the topic of mass. Its my area of research.

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