July 25th, 2014
Waning Crescent Moon
moon
Seth Jarvis

Cosmic Quiz: Weightless Astronauts?

This week’s Cosmic Quiz question comes from Daniel Wallace: Why are astronauts aboard the International Space Station weightless while they are still so close to the Earth? Great question!

Seth Jarvis

Why are planets spherical?

Anthony Garcia wrote in to ask, “Why are planets perfect spheres, or at least appear to be perfect?” Nature loves spheres. It can’t get enough of them.

eric

What is dark matter?

The short answer is no one really knows. Dark matter is a name given to something that, so far, has only been detected by the gravitational force that it exerts on visible matter and light. In fact, that gravitational force…

eric

What is gravity?

A common answer to a child’s question of “Why do things fall?” is, “Because of gravity.” But knowing the name of something does not mean that we understand it. Originally, “gravity” was simply the built-in tendency of most objects to…