Why does matter gain mass as speed increases?

7 Answers
OK, these days I'm on a kick about mass, relativity, speed of light, and other things I know very little about...but am trying to learn about. I read that particles gain mass as they go faster, but I'm afraid I don't quite understand how that happens. Why or how does a mere particle (which, I 'assume', has some 'fixed' parameters such as atomic weight, etc.) transform itself into something more 'massive' when it travels faster and faster? What do YOU think?

All objects have a rest mass. That is the mass which would be measured for an object not moving (in your reference frame). If we start moving this object relative to ourselves we have to accelerate it. As it is accelerated it takes more and more force to make a change in velocity (or momentum). From relativity, the mass "acts" as if it had a mass mo/[(1-(v/c)^2]^1/2, where mo is the rest mass, v is the velocity and c is the speed of light. As v gets close to the speed of light, the mass gets bigger and bigger. It is harder to accelerate. This means it is impossible to get the object to reach the speed of light.

This Relativistic effect has nothing to do with the Forces found in nature; i.e., the weak and strong nuclear forces, the force of gravity, the electromagnetic force. It has nothing to do with the Higgs Boson. However, the Higgs Boson and the Standard Model of particle physics does start to explain why there is such a thing as mass in the first place.



I think I can help you with your question. Einstein?s famous E=mc2 tells us just as you said, that matter gains as speed is increased. Your question is why does this happen?

We'll to simply answer with, it happens because E=mc2 is not really telling you why it happens, it's still just telling you that it happens.

We know this happens because E=mc2, it doesn't tell us why.

But I can tell you why E=mc2, and that is due to the constants that govern the nature of our universe. There are 4 universal constants in our world. They govern all the physics in our universe, that is, speed of light, gravity and so on.

The 4 constants are.
The weak nuclear force,
The strong nuclear force
The electromagnetic force
and Gravity.

This is why E=mc2. Now you may ask then, why do we have these four constants? That is the question many scientists are trying to ask with several hypotheses. One of the reasons why we are trying to, and have found the higgs boson (AKA God Particle)

However, this doesn't settle it yet, because it's still a constant that just seems to have been "put in there".


It has to do with the equivalence principle being discussed above and also the fact that all moving objects have kinetic energy with respect to a static reference frame. The relationship that we are familiar with E = 1/2 mv^2 is a mere approximation for sub-luminal speeds that works well for everyday speeds and objects but truly, the relationship breaks down when you approach speeds near the speed of light. The speed of light is a natural barrier that cannot be broken and as such it requires ever more energy to bring a particle closer to that limit, so much so that it becomes asymptotic at c itself. This has been verified experimentally using the Lorrentz equations, also listed above. As long as mass and energy of opposite sides of the same coin and are interchangeable commodities, you can see why adding velocity (and energy) to an object will increase its mass.


The famous equation E = m * c^2, does not really explain in any way why matter would seemingly "gain" mass when their velocity increases. It is instead relating the mass quantity with the energy quantity which of course is useful in itself but does not provide any answer of the reasons. The reason why matter will become heavier for very high velocities has to do with the properties of the relativity theory, and in particular how the space-time are entangled. However, it is beyond my expertize and I will await someone else to elaborate upon this further. The question is very interesting though, and it is indeed puzzling why added kinetic energy all of a sudden would turn into mass and why this is the most prominent when we have a speed that is comparable to the speed of light.


Hey, all.
Thanks for your intelligent Mybestanswer for this question. I don't know if I can say I completely understand it yet, but some of the discussion here has helped put it into better perspective, anyway.

It's well above my level of mathematics, physics, (etc.), but it intrigues me in a different way, I think. It's more like solving a riddle, for me, I guess.because the math would surely give me a headache, y'know? I'm just sayin'.
Thx, again.and I'll try to select a "Best Answer" soon (thought it'll be tough.they're all pretty darn good!).


Royalg23 is correct. One of the implications of relativistic theory is that, as you apply more and more energy to an object (to accelerate it) you inevitably increase its relativistic mass (Einstein's famous equation hints at this, but it is really intended to apply only to the "rest" mass of an object, with no consideration of kinetic energy).


E = M x c^2

As speed increases the energy of particle increases...

This means that the mass of the particle increases, too...

It is because of its energy of motion...