Space Is Less Empty Than Vacuums

Added: 2026-05-17

[00:00:00]beyond.

[00:00:01]Interstellar space is home to the interstellar medium, a cocktail of gas, dust, and cosmic rays.

[00:00:07]This vast expanse of space between the stars is far from empty. Instead, it's filled with this intriguing mixture that paints a picture of our cosmos far more fascinating than a simple void. Let's start with the gas. Predominantly formed of hydrogen, helium, and a sprinkling of heavier elements, this gas accounts for about 99% of the interstellar medium's mass. But, don't be fooled by its significant presence. This gas is incredibly sparse, with an average of just one atom per cubic centimeter.

[00:00:37]That's less dense than the best vacuum we can create here on Earth.