# Does the density of a stick change according to special theory of relativity? Provided the stick is moving at nearly the speed of light? [closed]

## closed as unclear what you're asking by Aaron Stevens, ZeroTheHero, John Rennie, Buzz, Jon CusterFeb 8 at 15:52

Please clarify your specific problem or add additional details to highlight exactly what you need. As it's currently written, it’s hard to tell exactly what you're asking. See the How to Ask page for help clarifying this question. If this question can be reworded to fit the rules in the help center, please edit the question.

• It would be helpful if you could actually write a question rather than just posting an equation. – ZeroTheHero Feb 7 at 22:56

Sure it does. If the stick has a linear density $$\lambda=m/x$$ where x is the length, then if it's moving at velocity $$v$$ away from you, the length would appear to be:

$$x'=\frac{x}{\gamma}$$

where:

$$\gamma=\frac{1}{\sqrt{1-(v/c)^2}}$$

the, the density measured by the observer would be:

$$\lambda'=\lambda\gamma$$

And because $$\gamma>1$$, it would appear to be more dense.