Question about Relatavistic mass

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In summary, when discussing objects moving at relativistic speeds, it is often mentioned that as an object approaches the speed of light, it gains mass. However, the idea of mass in relativity is not the same as in classical mechanics. It is a measure of energy and inertia, and the source of gravity in GR is the stress-energy-tensor. Whether an object with the mass of a star would have the same gravitational pull as a star depends on the circumstances. The increase in mass is simply a way to discuss the amount of kinetic energy the object contains.
  • #1
DHF
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I am trying to get my head abound something and I am hoping you guys can shed some light on this for me.

When discussing objects moving an relativistic speeds, its often mentioned that as an object approaches the speed of light, it gains mass.
My question is: is this mass real? If you somehow managed to impart enough energy on a probe to move it fast enough that it has the mass of a star, would that probe have the same gravitational pull of a star? Or is the increase in mass simply something we use to discuss how much kinetic energy the object contains?
 
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  • #2
DHF said:
My question is: is this mass real?

That depends on the definition of "real". It is as real as any other measurable quantity.

DHF said:
If you somehow managed to impart enough energy on a probe to move it fast enough that it has the mass of a star, would that probe have the same gravitational pull of a star?

There is no reasonable answer because the source of gravity in GR is not mass (no matter which kind of mass) but the stress-energy-tensor. Depending on the circumstances the probe can have the gravity of a stars or not.

DHF said:
Or is the increase in mass simply something we use to discuss how much kinetic energy the object contains?

In relativity it is in fact a measure of the energy. In it's original meaning it is a measure of the inertia.
 
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Thank you very much for the clarification.
 
  • #5
Thank you, reading it now.
 

1. What is relativistic mass?

Relativistic mass refers to the mass of an object as it approaches the speed of light. It takes into account the effects of special relativity, where the mass of an object increases as its velocity increases.

2. How is relativistic mass different from rest mass?

Rest mass is the mass of an object when it is at rest, while relativistic mass takes into account the increase in mass as an object's velocity increases. This means that relativistic mass will always be greater than or equal to an object's rest mass.

3. What is the equation for calculating relativistic mass?

The equation for calculating relativistic mass is m = m0/√(1-v2/c2), where m0 is the rest mass, v is the velocity, and c is the speed of light.

4. Why is relativistic mass important in physics?

Relativistic mass is important because it helps to explain the behavior of objects at high speeds. It also plays a role in concepts such as momentum and energy, as they are dependent on an object's mass.

5. Does relativistic mass have any practical applications?

Yes, relativistic mass has practical applications in fields such as particle physics, astrophysics, and engineering. It is also important in the development of technologies such as particle accelerators and space propulsion systems.

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