Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Does velocity dammage e=mc^2?

  1. Dec 27, 2006 #1
    Does velocity "dammage" e=mc^2??

    hi there, this is my first post in this forum, so i can begin to introduce myself:
    i'm 17 years old and i really enjoy logic, as physics has matematics(that is logic) and make me think(use the brains, you know) i love it more than any other subject:tongue2: , i'm from Portugal.

    So my question is about some concepts that i'm problaby getting confuse: already asked to several teachers about it but no1 could actually solve it defenetly...(and problaby is a stupid question), as I still haven't learnt in school relativity...:rolleyes:

    so we know that by general relativity that E=mc^2 (sorry, don't know how to post equations)
    and we know too that "m" of a body is influenced by the relative speed of that body. m'=m/sqrt[1-(v^2)/(c^2)] or someting like that, at this time, i prefer to understand the concept, not the expression...

    knowing that, i made an example to explain what's my point/question:

    we have 2 persons "A" and "B", "A" is in a spaceship at 0.8c relative to referencial, "B" is "stoped" in relativity to the referencial. In the spaceship, there is a determinated quantity of Hidrogen. Imagine we can transform that all hidrogen in energy(total consuming of hidrogen trought E=mc^2)
    At a determinated time, we decide to "transform" all that hidrogen in energy, creating a huge explosion.

    My question is: what man, "A" or "B", receive more energy from the explosion?:confused:
    considerating that the mass of the hidrogen is bigger in "B" than in "A" by the second premiss annouced above...

    because this is really annoying me(in the good sense of course) is it actually possible more energy be recieved to another person only because he is moving in relation to something?? in that case, in a nuclear explosion, is better to stay stopped than trying to run away..:rofl: :biggrin:

    thanks in advance, and hope don't take much time to you...

    hope too to learn alot trought this forum...:P

    regards, Littlepig
    Last edited: Dec 27, 2006
  2. jcsd
  3. Dec 27, 2006 #2
    The problem you will continue to have with ones like this, is thinking of mass as actually changing with speed. That is a very old idea to think of the mass “as if it increases” with speed. Which works ok in a limited way, such as getting to E=mc^2. But modern science accepts the idea is incorrect in application and mass should be understood as intrinsic and unchanging with speed. Only momentum “p” or ‘mv’ is factored to increase with speed, and not mass.

    Search here, wiki, and, google; you will find a lot addressing this point, as well as many cases where unfortunately the idea of mass increasing with speed continues to be taught as if it were real, it is not.
  4. Dec 27, 2006 #3
    ahhhhh, now makes more sense, I mean, i don't get why don't it influenced mass, but then i get a bigger question: if the mass don't is influenced by speed, why corps tend to get bigger and bigger as long as they get speed??
    it's usual to say that, a corp with mass is impossibilitated of reaching to c as his mass tends to inf as the velocity tends to c, but does't actually in CERN the particles get bigger??

    In how you explain, then isn't actually the mass that inscreases, is the momentum, and then, the limit of speed of light is c because momentum can't be diferent from 0 to a body reaches to c...in other words, c isn't the limit of speed, is the limit that a body with mass 0 can reache?? so the bigger the mass, the less is the value of limit of v that a body can take?!? is my logic right??

    meanwhile, going to search stuff. Thank you for your help...:shy:
  5. Dec 27, 2006 #4
    As no one is thinking of not using c as THE max speed limit.
    Thus any mass (including 0 mass) has a max speed limit of c.
    The 0 mass light photon actual moves at c; and in fact can move at no other speed no matter who looks at it, from no matter what speed the observer is moviing, light still moves at speed c (basic 'SR' Special Relativity).
    But for any real mass, while it remains the same at mo; as the speed increases it must create a momentum "mv" that if factored by relativistic "gamma" to a larger number than expected by classical thinking.
    Thus momentum as v approaches c would approach infinity and creating it would require an impossible amount of energy to reach it. Therefore no one expects to see anything, other than light, to reach “c”.
    Closest thing to it would be neutrinos, in fact when the figured out they did have mass is when they knew they couldn’t be moving at c as they once thought.
    Last edited: Dec 27, 2006
  6. Dec 27, 2006 #5


    User Avatar
    Science Advisor

    If mass were to move at c, it would have infinite mass if you use the relativistic factor. The closer you get to the speed of light the higher the mass gets, but the harder it will be to accelerate it. Infinite mass requires infinite force to accelerate it further, so using basic logic it will never get to that point.
  7. Dec 27, 2006 #6
    As already stated - current science does not use the relativistic factor on mass as if it would increase to an "Infinite mass". Use the relativistic factor to the momentum, that identifies the energy required as approaching infinite.

    Personally I like to think of it as applying the relativistic factor to the speed meaning a relativistic speed approaching infinity for the still same unchanged intrinsic mass of m0; Still giving the same “p” approaching infinity. Although it makes more sense than mass increasing to infinity, that is just my thinking, and a relativistic increase to the speed used to figure momentum is no more the current science view than is relativistic mass.
    Last edited: Dec 27, 2006
  8. Dec 28, 2006 #7

    please have a critical look at

    arXiv.org > physics > physics/0505025

    Relativistic velocity transformation as a genitor of transformation equations (relativistic dynamics)

    The fundamental equations of relativistic dynamics are derived from a thought experiment and from the transformation of relativistic velocity avoiding collisions and conservation laws of momentum and energy.
    Full-text: PDF only
  9. Dec 28, 2006 #8
    Did you read the OP?
    This is a 17 year old working on developing an understanding of relativity (hopefully a modern one) to establish his own view. Why would you expect that he could critic one of your papers – or did you just want to show off being published on the arXiv.

    As to a critical look at your paper:

    The heart of it simply assumes the old fashion view of relativistic mass increase as being real, it is not an approach to confirm such a view. And even as a thought experiment, for this purpose it is not realistic to expect such a balance scale to be effective at relativistic speeds, the interactions forces traversing the solid beams to confirm balance would be nuts to calculate and confirm in all reference frames.

    IMO to naive to be useful.
    Last edited: Dec 28, 2006
  10. Dec 28, 2006 #9
    bernhard.rothenstein, i really would like to read it...:cry: if i could understand a thing of it: as i said, I still haven't learnt Relativity in school, all i know is from asking things extra school, like i'm doing now...but i start reading something in here...and :bugeye: nop...I'm only understanding now the philosopy of relativic teory...

    well, another thing i've learnt(and hope someday deny somehow): mass don't change with speed...^_^ only momentum: (obvius: p=mv)

    but then another question comes: you said that as velocity tends to c, more and more energy is required to make the body moves faster and faster, if the body don't get bigger mass, for where goes that energy spent?? then, we can asume that: or energy conservation isn't aplied in this case, or the energy needed to make variations of speed, varies from their current velocity: you need less energy to put a car from 10m/s to 20m/s than from 40m/s to 50m/s where c is the limit speed(and limit energy(that is inf)).
    (and considerating "of course" that classical physics are "all" "wrong"):approve:

    ty for your patience and time spent...
    regards, Littlepig
  11. Dec 28, 2006 #10
    Spend some time learning about “Gamma” aka ‘Lorentz gamma factor’ aka ‘Lorentz factor’ aka ‘Lorentz term’. You need to understand Relativity first, so take your time to think them through and you will see you already have the answers to most of your questions.

    Example you ask:
    You already said it yourself – it goes into creating a larger and larger relativistic MOMENTUM “p” (nearing infinite as the speed goes to c).
    No conservation laws of anything are violated, you’re jumping to assumptions without thinking them through when you do that.

    If you want to be in step with current science think of it as “p” the momentum that is increased by gamma.
    NOT an increasing m, (that would imply mass was not conserved).
    Or even increasing v instead of mass as I do.
    Just apply gamma to p.

    Take your time – - focus on just SR for a good while before you even start on GR, that really is a much bigger issue than most folks like to think.
    I know you will want to jump into that soon, so do your self a favor and wait awhile on that one.
    Work through and really understand some of the SR paradoxes and really understanding SR first.

    I'll leave you to it for awhile -- have fun.
  12. Dec 28, 2006 #11

Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?

Similar Discussions: Does velocity dammage e=mc^2?
  1. Does E = mc^2? (Replies: 11)

  2. What does E=mc^2 mean? (Replies: 20)

  3. How does E=mc^2 ? (Replies: 21)

  4. Why does E=mc^2 (Replies: 9)