# Can you travel faster than the speed of light?

## Light

Light has a peculiar property. It always travels at the same speed, no matter what.

In 1905, Albert Einstein, while discovering the Theory of Relativity, showed that light travelled at only a constant speed. The speed of light is around 300,000 kilometers per second.

Now, Einstein did not prove this or anything, he just postulated it (which means he took it as an reasonably made assumption). Using this postulate, he discovered the theory of relativity: a milestone in physics.

The theory of relativity (which we won’t talk about here much) has been experimentally proven several times. Experiments including high speed muons, light itself, and high energy quarks have shown the theory to be true. …

# Why do astronauts float?

## And how is it related to falling elevators?

We all know that astronauts who visit space do not feel gravity. How else do you get all the neat spacewalks and the floating globules of water? But, the reason for why this happens is actually a little-known fact.

## The Common Explanation

We are told that astronauts float in space because there is no gravity at such high altitudes. This also makes sense.

The International Space Station is approximately 408 kilometers above the atmosphere. …

# Where does mass come from, really?

## And why the whole universe does not travel at light speed.

Objects are heavy. This may be one of the oldest facts that humans have ever known. A apple, and cartwheel, and big bag of chocolate muffins, they are heavy. But what does ‘heavy’ mean? Let’s look at what physics has to say.

## Mass

The earliest ‘definition’ of mass can be easily attributed to Isaac Newton.

According to Newton, things are heavy because of an internal property all objects possess. He called it ‘inertia’. Inertia is a tendency for objects to not move.

To move an object you have to put an force on it. But, the object still resists. If you try and push a beachball it seems to move quite easily, but actually it does resist the push a bit. That is the beachball’s inertia. An ant on the other hand can conform for you that the beachball is hard to move. The puny force that the ant applies cannot overcome the beachball’s resistance. For the ant, the experience is somewhat similar to you pushing on a three story building. …