How to make money with relativity

[Jacques]

Let have 10kg of gold and take a train.

Because of the velocity, relativity tell me that I now have a little bit more gold ! Now I throw it at the same velocity as the train toward the back, to my friend who is beside the track. Again because of the velocity relative to me the mass is increased again...

If I do that many times I will endup with a lot of gold

 

Isn't that illogic ?

[Severian]

Isn't that illogic ?

 

Yes it is.

 

First of all, unless your friend who is not on the train plans on running around with the gold at light-like speeds then it's 'mass' (as you quaintly call it) will revert to the mass it had before getting on the train, since the important quantity is its velocity with respect to the observer. Alternatively, if you ask your banker onto the train, he will weigh the gold and find that it is exactly the same weight as normal, because his velocity with respect to the gold is zero.

 

Secondly, rest mass (which is the correct quantity here) doesn't change. In relativity the relation between velocity and momentum is non-linear. It is the desire to keep it linear which has lead some books to 'redefine' mass as momentum divided by the velocity. This is a silly redefinition, and certainly has no equivalence with gravitational mass (which is used to price gold).

[Jacques]

So it is not right to say that mass increase with velocity ?

[Severian]

No.

 

(It depends on your definition of 'mass' of course, but with the definition that physicists use, no.)

[Jacques]

So the particule in accelerator does't increase mass ?

Why is it harder and harder to accelerate ?

 

The definition of mass I am used to is a quantity of matter.

[Severian]

So the particule in accelerator does't increase mass ?

Why is it harder and harder to accelerate ?

 

It is harder to accelerate because momentum (which is linked to energy) increases non-linearly with velocity.

 

[math]p = \frac{mv}{\sqrt{1-v^2/c^2}}[/math]

 

Even if you put in really huge amounts of momentum (p) you will never get velocity (v) to equal c.

 

The definition of mass I am used to is a quantity of matter.

 

But how do you measure that 'quantity'? Is it the volume it contains, the downward force it exerts on a set of scales, or what?

[Tommio]

The way i understand the original question is

 

if i am travelling faster the mass increses. altermatly will this give me more gold?

 

no - more gold assumes more atoms. as speed increses as does mass, but the number of fundamental parts does not. as soon as the speed decreases the observed mass would return to normal.

[Jacques]

Number of atoms time the atomic mass of the element.

The downward force is not a mesure of mass. It's a mesure of force. The same mass on the moon will exert a different force on a scale.

[[Tycho?]]

Number of particles will not change.

[swansont]

Number of atoms time the atomic mass of the element.

The downward force is not a mesure of mass. It's a mesure of force. The same mass on the moon will exert a different force on a scale.

 

Whch is why you use a two-pan balance, which measures mass. You have a set of reference masses, and you are comparing the amount of your sample to that. As long as you have some reasonable gravitatonal field, you will get the same answer.