# Speed of light, mass equation

#### ThoughtProces

I was wondering if there is and what is the equations that show that as an object accelerates towards the speed of light its mass increase to infinite.

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#### jtbell

Mentor
You're probably thinking of this equation:

$$m = \frac {m_0} {\sqrt{1 - v^2 / c^2}}$$

#### ThoughtProces

i do believe this is the equation do you have a derivation of where it comes from or could you point me to a site for which it has the derivation.

thanks

Mentor

#### ThoughtProces

thanks for the link, it should prove to be a good read

#### ThoughtProces

I guess another question is how do we measure the initial mass of an object if we are all traveling at a changing velocity due to the constant acceleration of an expanding universe. Or is the initial mass relative to the expanding universe in its own frame of reference?

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