# I Mass increase with velocity

#### Chemong

Summary
I read mass increase is proven everyday in accelerators
In an accelerator when you're pushing/pulling a charged particle with a field that travels at the speed of light why should we expect to the particle to exceed the speed of light.

Related Special and General Relativity News on Phys.org

#### Dale

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The speed that the field travels at is actually irrelevant. You can put the field in place before the particle gets there, or time it so that it arrives at every point just as the particle does. You can even accelerate a particle with a DC field that doesn’t propagate at all.

But the idea of relativistic mass is nearly a century out of date.

#### Chemong

Dale, thanks, I do understand what you said. But I still wonder if speed has any effect because I wonder if particles and fields interact instantaneously. Is it possible the because of the speed the interaction of the particle and field becomes less effective. As I understand it we really don't know for example what an electron is. We know a lot about how it behaves but don't know what it really is. Or can say an electron and a field interact in zero time or are there some limits.

#### Dale

Mentor
We know a lot about how it behaves but don't know what it really is.
I completely disagree with this statement.

Suppose I could correctly predict what you would do in every possible scenario. How you would behave in every relationship and in every possible circumstance. Even when you did things randomly I could correctly predict the frequency of every decision.

Would you say I don’t know who you really are? I wouldn’t. I think that with that level of knowledge I would know exactly who you really are. In my opinion any sense in which someone could claim I didn’t know who you are would be contrived and rather unimportant.

Such is our knowledge of electromagnetism.

#### Chemong

We have wonderful equations. But they are I think approximations. I remember einstein even said we don't truly understand the electron. I'm curious of the reality behind the equations.

#### Dale

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I remember einstein even said we don't truly understand the electron.
We didn’t in his day. Our current theory, QED, was developed later and is a complete description of all known EM phenomena. It has also correctly predicted many phenomena that were not observed until after the theory was developed.

I'm curious of the reality behind the equations.
In science that is the purpose of performing experiments. We test our theories against experimental observations in order to make sure that the equations do in fact correctly represent reality. As far as I know there is no known EM experimental observation which indicates that reality is inconsistent with QED.

#### Chemong

Thanks Dale. I never finished my Dr degree in physics 50 years ago. I know QED makes wonderful predictions but my gut feeling is we still don't understand what the electron is while we do understand how it behaves. I guess my real gripe is the speed of light being the speed limit. That's why I originally brought up the question of trying to break the speed barrier with electrons in an accelerator. The why of the speed limit being the speed of light in the universe bothers me. When someone tells me something is, I ask why.

#### PeterDonis

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break the speed barrier with electrons in an accelerator
An accelerator can't accelerate electrons to exceed the speed of light. In fact it can't accelerate them to reach the speed of light. The SR equations governing this have been confirmed thousands of times in accelerators.

#### Chemong

Thanks Peter. I do know this. I just wonder if we've gotten it wrong in saying that it's because the mass of the particle becomes infinite. I don't believe it really becomes infinite but rather that it's apparent mass becomes infinite. There is a difference between the these two interpretations.

#### Dale

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my gut feeling is we still don't understand what the electron is while we do understand how it behaves
See post 4. I don’t think there is any meaning to this claim. If I could accurately predict your behavior in every circumstance and interaction would you also claim I don’t know who you are?

Don’t ignore this question this time, please answer it. What additional knowledge is required before claiming that we know what something is? That is, beyond a complete understanding of all its behaviors and interactions.

The why of the speed limit being the speed of light in the universe bothers me. When someone tells me something is, I ask why.
If the principle of relativity is correct then there are only two possibilities locally: Galilean relativity and special relativity. It is a simple matter to determine which is the case. Even if you use a DC field, so there is no issue of propagation, we find that the acceleration of an electron follows the prediction of special relativity and not Galilean relativity.

I just wonder if we've gotten it wrong in saying that it's because the mass of the particle becomes infinite
I feel like I am repeating myself a lot here (post 2). This idea is about a century out of date. Saying it nowadays is kind of a gaffe.

#### Orodruin

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but my gut feeling is we still don't understand what the electron is while we do understand how it behaves
In physics, understanding how something behaves is to understand it. There is no distinction between the two. Nature also does not care about what your gut feeling is.

I just wonder if we've gotten it wrong in saying that it's because the mass of the particle becomes infinite.
Again, this description is a century out of date.

#### PeterDonis

Mentor
I just wonder if we've gotten it wrong in saying that it's because the mass of the particle becomes infinite.
As @Dale has already noted, the concept of "relativistic mass" is long out of date. So this claim is not so much wrong as irrelevant; nobody views things that way any more, so you don't need to worry about whether it's right or wrong.

The energy of the particle, however, certainly does increase without bound as its speed approaches $c$, according to the SR equations. That, again, is confirmed every time we run an accelerator experiment.

I don't believe it really becomes infinite but rather that it's apparent mass becomes infinite.
"Apparent mass" is just vague ordinary language; it doesn't mean anything. The physics is what it is regardless of what ordinary language words you want to use to describe it.

Also, please review the PF rules on personal speculations. All of the things we are discussing here are well understood and, as has already been noted several times, have extensive experimental verification. Rather than trying to make up your own interpretation, you should just be learning what the actual physics says.

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my gut feeling is
So long as you hold "gut feeling" over evidence, you will not understand. Some will even say you're not doing science.

#### haushofer

I remember einstein even said we don't truly understand the electron.
What is "truly understanding"?

We always use a description to describe the world, whether it be math or language or something else. But even physics does not have a one-to-one description to many phenomena. We often have different ways to understand the same phenomena.

Don't forget: Einstein was quite a mystic in his philosophy and believed, guided by the enormous successes of his intuition, he could reason himself to "the ultimate theory of reality."

#### Chemong

Peter, I have a degree in physics, I know what it says. I am speculating, is that not allowed on this website. I am speculating that maybe we interpret the meaning of the equations wrongly. As for the electron I don't think we understand what charge is. I'm trying to look beneath the equations.

#### Ibix

I am speculating, is that not allowed on this website.

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#### Mister T

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. I guess my real gripe is the speed of light being the speed limit.
Imagine chasing after a light beam trying to catch it. No matter how fast you travel, it recedes from you at speed $c$. Thus you can never catch it. That is, you can never reach a speed of $c$.

You can derive the equations of special relativity using this idea as a basis. You can then, as you say, try to look beneath the equations, but when you do that all you can ever see is the ideas used to derive those equations.

For example, the total energy of a free electron is $E=\gamma mc^2$ where $\gamma=\frac{1}{\sqrt{1-(v/c)^2}}$. You can see that as the speed $v$ of the electron approaches $c$ the energy increases beyond all bounds. Thus you can see that $v$ will never equal $c$. This idea is "beneath" the equation because the idea was used to derive the equation.

#### PeterDonis

Mentor
I am speculating, is that not allowed on this website.

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