What does it mean when space is a vacuum?

To start with see this question We see that a gravitational force is directly proportional to the product of masses of the two bodies. $F_G prop M_1.M_2$ It...

In stars under very high temperature and pressure hydrogen atoms fuse into helium atoms and release energy as Gama rays. 4 hydrogen atoms make one helium atoms and 0.7% of...

The gravity between two planets is way too weak. The vicinity of a strongly gravitating object that produces a great deal of space-time curvature, such as a black hole, is...

Using Kepler's third law we can relate the period $T$ to the semi-major axis distance $a$. $T^2=a^3$ Given that $T=1,000,000$ then: $a^3=1,000,000,000,000$ Taking the cube root gives: $a=10,000AU$ What is...

Usually, when taking photos of anything in space, the object of your photo is lighted OR produces light directly. Against an almost totally black background, in order to capture said...

This can be a difficult concept for some, but most of space contains no matter whatsoever–it's just emptiness. Dark Matter, a little understood thing that seems to have gravity but...

An explosion is a rapid expansion in volume along with a rapid release of energy. There are several types of explosion. A container which has its contents at a higher...

Infrared waves are a form of electro-magnetic radiation and can travel in vacuum at the speed of light. These infrared waves are resultant from the Sun. When these light come...

WE get heat from Sun by radiation in the form of electro magnetic radiation infra red and visible light.

Space is never a pure vacuum. Interstellar space contains hydrogen, helium and other lighter elements. They are quite disperse but it isn't a true vacuum. Also, due to quantum effects...