Object's mass does not increase as it approaches the speed of light?

In summary, the conversation discusses the concept of mass being invariant and its relation to an object's speed and energy. The term "relativistic mass" is considered old-fashioned and the source of gravity is not just limited to mass or energy, but also includes other factors such as pressure and stress.
  • #1
Gear300
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I read in a book that mass is invariant. Does this mean that an object's mass does not increase as it approaches the speed of light?
 
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  • #2


Gear300 said:
I read in a book that mass is invariant. Does this mean that an object's mass does not increase as it approaches the speed of light?

If an object starts moving relative to you then its mass would be larger compared to when it was at rest relative to you. What is invariant is rest mass i,e the mass of any object when it is at rest relative to you.
 
  • #3


Gear300 said:
I read in a book that mass is invariant. Does this mean that an object's mass does not increase as it approaches the speed of light?

In most modern treatments, that's the case. What increases is the object's energy. In the past this was called "relativistic mass", but since we already have a perfectly good word to describe it, this terminology has fallen out of favor.
 
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Is there any advantage of considering mass as not being a scalar, but making the distinction between rest massa and relativistic mass? Or is the notion of "relativistic mass" just old-fashioned?
 
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Just old-fashioned.
 
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So then when we consider gravity, do we consider it as a consequence of the total energy or the rest mass (I had viewed time dilation and length contraction as a result of the curvature of space-time due to the heavier mass of an object approaching light-speed)?
 
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In GR the space-time (Riemann) tensor is related to the energy-momentum tensor.
 
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To second what Meir said, in GR the source of gravity is not just mass or energy, but the entire stress-energy tensor. There are terms including energy, momentum, pressure, stress, etc. So it is not correct to either say that the invariant mass or the relativistic mass is the source of gravity.
 

FAQ: Object's mass does not increase as it approaches the speed of light?

1. Does an object's mass increase as it approaches the speed of light?

No, according to Einstein's theory of relativity, an object's mass does not increase as it approaches the speed of light. Instead, its mass appears to increase from the perspective of an observer who is at rest relative to the object.

2. Why does an object's mass not increase as it approaches the speed of light?

This is due to the fact that as an object's speed increases, its energy also increases. This increase in energy results in an increase in the object's apparent mass, but not its actual mass.

3. Is there a limit to how fast an object can travel before its mass becomes infinite?

Yes, according to Einstein's theory of relativity, an object's mass would approach infinity as it approaches the speed of light. However, this is not physically possible as it would require an infinite amount of energy to accelerate an object to the speed of light.

4. How does the concept of mass-energy equivalence relate to an object's mass at high speeds?

The concept of mass-energy equivalence, as described by Einstein's famous equation E=mc^2, shows that an object's mass is equivalent to its energy content. As an object's speed increases, its energy also increases, resulting in an apparent increase in mass.

5. What are the implications of an object's mass not increasing as it approaches the speed of light?

This has significant implications for our understanding of the universe and the laws of physics. It allows for the possibility of objects traveling at extremely high speeds without violating the laws of conservation of mass and energy. Additionally, it supports the idea of time dilation and explains why objects with high speeds experience time differently than objects at rest.

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