Relativistic Mass ?

L

Lakon

Valued Senior Member
In another thread ..

http://www.sciforums.com/showthread...f-a-Pendulum&p=3032168&viewfull=1#post3032168

Prof Layman said ..

All frames would say that an object had increased in mass, but then all of frames cannot be correct if they all say that it has a different amount of mass that would prevent it from accelerating differently. The relativistic mass increase could only be felt by the other object that was traveling with a relative velocity. So then say if you had two object traveling close to the speed of light, they could say they are at rest and slowly gravitate to each other and at the same time both objects would just gravitate to the body that was at rest more.

I find this fascinating, and somewhat bewildering, and don't understand it. But to make the question it brings to my mind even simpler, can I put it as follows;

An solid object is moving at near c, in an area of space so far away from any other object, as for any influence by any other object to be zero. Questions ..

1) How does it know it's moving at near light speed for it's mass to increase towards infinity ?
2) Is it a real mass increase? Ie, does it gain more matter, protons, etc ? If so, where do they come from ? If not, how does it's mass increase ?

I didn't want to crowd the 'pendulum' thread with this, so I started this one. Any (simple) help would be appreciated.
 
Prof.Layman said:
All frames would say that an object had increased in mass, but then all of frames cannot be correct if they all say that it has a different amount of mass that would prevent it from accelerating differently. The relativistic mass increase could only be felt by the other object that was traveling with a relative velocity. So then say if you had two object traveling close to the speed of light, they could say they are at rest and slowly gravitate to each other and at the same time both objects would just gravitate to the body that was at rest more.
Click to expand...

Basically I was saying that relativistic mass increase should be applied in the same way as time dialation. Two objects traveling together at the same rate of speed would measure their clocks to be the same, so then they would also measure their mass to be the same. But, an outside observer traveling at another constant speed would not measure their clocks to be the same as the outside observer. So then the outside observer would measure their mass to increase, but only measure their mass to increase relative to the outside oberserver and not each other.

The different time variables that result in time dialation come from assuming there are two different coordinate systems that measure time differently. These variables are what determine that there should be a relativistic mass increase. So then the relativistic mass would be observer dependent in the same way time dialation is.
 
Lakon said:
An solid object is moving at near c, in an area of space so far away from any other object, as for any influence by any other object to be zero. Questions ..

1) How does it know it's moving at near light speed for it's mass to increase towards infinity ?
2) Is it a real mass increase? Ie, does it gain more matter, protons, etc ? If so, where do they come from ? If not, how does it's mass increase ?
Click to expand...
The first question here is a problem I was trying to address, before MotorDaddy stole my thunder by claiming that we don't even know what velocity is. I think the answer to this question lies in Galilean Relativity, and is a concept known as Galilean Invariance. It states that the laws of motion are the same in all inertial frames. So then no matter what speed you travel the laws of motion are the same. Also you cannot know your true velocity because there is no absolute frame of reference. So then there is no way to know if you are actually traveling close to the speed of light, and in fact you never will because no matter how much you speed up or slow down you will always measure light to be the same speed faster than you. The speed of light is invariant, it does not depend on your speed.

So then one observer cannot claim that his speed is more valid than everyone elses and then say that your frame has a mass increase that would be the only value that everything else would measure in all frames. I think the relativistic mass increase would only be felt by the other observer that detected a difference in his clock. So the extra gravitational pull would only be felt by the relativistic observer, so then Galilean Relativity and Galilean Invariance could then remain true. Otherwise, if an increase in mass was felt by an object traveling at a relative speed due to an outside observer than his frame would no longer be Galilean Invariant.

To answer the secound question, no i don't think it is real mass increase and it does not gain more matter or protons, etc. I think the increase in mass would only be felt by the other observer, and it would be due to two observers traveling at relativistic speeds relative to each other, and the extra pull of gravity would only be between these two objects. I think this is the only way relativity could stay Galilean Invariant.
 
Lakon said:
1) How does it know it's moving at near light speed for it's mass to increase towards infinity ?
Click to expand...

It does not. From its own perspective it weighs the same as it always did.

2) Is it a real mass increase? Ie, does it gain more matter, protons, etc ? If so, where do they come from ? If not, how does it's mass increase ?
Click to expand...

It is a mass increase, but this is not due to the addition of any additional matter - so there are no new protons etc. The additional mass comes from the total energy of the system relative to another system. Remember E=MC^2? At non-relativistic speeds the additional mass from the energy is negligible, but as you approach the speed of light it becomes more significant.
 
billvon said:
It does not. From its own perspective it weighs the same as it always did.



It is a mass increase, but this is not due to the addition of any additional matter - so there are no new protons etc. The additional mass comes from the total energy of the system relative to another system. Remember E=MC^2? At non-relativistic speeds the additional mass from the energy is negligible, but as you approach the speed of light it becomes more significant.
Click to expand...

Correct. And to state the simplified version of the formula so that it more clearly fits the answer to the question: M=E/c^2. So for every incremental increase in energy there is a slight increase in the mass.
 
billvon said:
It does not. From its own perspective it weighs the same as it always did.



It is a mass increase, but this is not due to the addition of any additional matter - so there are no new protons etc. The additional mass comes from the total energy of the system relative to another system. Remember E=MC^2? At non-relativistic speeds the additional mass from the energy is negligible, but as you approach the speed of light it becomes more significant.
Click to expand...
If I am not mistaken, the truth of what you say is generally accepted science, buy the how of what you say is perhaps the question. Do you have the generally accepted explanation for how and why there is a mass increase that cannot be detected in the inertial frame, but that would be observed from the rest frame?
 
quantum_wave said:
If I am not mistaken, the truth of what you say is generally accepted science, buy the how of what you say is perhaps the question. Do you have the generally accepted explanation for how and why there is a mass increase that cannot be detected in the inertial frame, but that would be observed from the rest frame?
Click to expand...

Well, if we agree that E=MC^2 (or in a more pertinent form M=E/C^2) then adding energy to an object by accelerating it will eventually add to its mass. Since the energy of momentum is not absolute, but instead depends on what reference frame you choose, then you would see a different mass when looking at the same system from different frames.
 
billvon said:
Well, if we agree that E=MC^2 (or in a more pertinent form M=E/C^2) then adding energy to an object by accelerating it will eventually add to its mass. Since the energy of momentum is not absolute, but instead depends on what reference frame you choose, then you would see a different mass when looking at the same system from different frames.
Click to expand...
Agreed, and again you are speaking the truth as it is generally accepted. Is the evidence strictly mathematical?
 
billvon said:
Well, if we agree that E=MC^2 (or in a more pertinent form M=E/C^2) then adding energy to an object by accelerating it will eventually add to its mass. Since the energy of momentum is not absolute, but instead depends on what reference frame you choose, then you would see a different mass when looking at the same system from different frames.
Click to expand...

How do you know the acceleration is an increase in velocity and not a decrease in velocity?
 
billvon said:
Well, if we agree that E=MC^2 (or in a more pertinent form M=E/C^2) then adding energy to an object by accelerating it will eventually add to its mass. Since the energy of momentum is not absolute, but instead depends on what reference frame you choose, then you would see a different mass when looking at the same system from different frames.
Click to expand...

That's a good reason why mass is an invariant. Momentum is added during the acceleration. Not mass. Momentum is frame dependent just as energy is.

In geometric units it's

E=M

c^2 is needed to make the conventional units Joule = Joule. That's it. Trying to use c^2 to manipulate the physics is nonsense.
 
Motor Daddy said:
How do you know the acceleration is an increase in velocity and not a decrease in velocity?
Click to expand...

You've got to be kidding. Acceleration results in the increase in instantaneous velocity. Deceleration results in the decrease in instantaneous velocity. Go experiment with your 'Short' Motor Daddy. When you step on the gas the car accelerates and when you let up on the gas the car decelerates. Make sure you keep an eye on your 'Motor Daddy's Short' speedometer so you know what is happening.
 
brucep said:
You've got to be kidding. Acceleration results in the increase in instantaneous velocity. Deceleration results in the decrease in instantaneous velocity. Go experiment with your 'Short' Motor Daddy. When you step on the gas the car accelerates and when you let up on the gas the car decelerates. Make sure you keep an eye on you speedometer so you know what is happening.
Click to expand...

You have no clue of which you speak! That's some funny stuff right there! Bwahahahahaahahahaa
 
brucep said:
That's a good reason why mass is an invariant. Momentum is added during the acceleration. Not mass. Momentum is frame dependent just as energy is.

In geometric units it's

E=M

c^2 is needed to make the conventional units Joule = Joule. That's it. Trying to use c^2 to manipulate the physics is nonsense.
Click to expand...
That sounds very enlightened, and would let me think that the acceleration added kinetic energy but not mass.
 
Motor Daddy said:
That is the real world, how do you know whether the velocity is increasing or decreasing when you are accelerating?
Click to expand...
Don't you get pushed back in your seat when you are accelerating and pushed forward when you are decelerating?
 
quantum_wave said:
Don't you get pushed back in your seat when you are accelerating and pushed forward when you are decelerating?
Click to expand...

Of course not. Since his head is nothing but a balloon filled with hot air, it lurches forward with acceleration - just like a helium birthday balloon. ;)
 
Read-Only said:
Of course not. Since his head is nothing but a balloon filled with hot air, it lurches forward with acceleration - just like a helium birthday balloon. ;)
Click to expand...
It is not in my nature to agree with that visual image of my friend and our favorite entertainer. I do wish he would defend himself with some scintillating justification that answered the obvious differences between generally accepted science and his views, but I'm sure he is saving that part for the clincher, someday, maybe.
 
quantum_wave said:
Don't you get pushed back in your seat when you are accelerating and pushed forward when you are decelerating?
Click to expand...

In order to be "pushed back in the seat" the vehicle had to change velocity first. You are blind to the road. You have no idea if you are traveling, as you have no way of measuring your own velocity. All of a sudden the seat slams into your back! or was it your back slamming into the seat?
 
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