In the 1930s, Swiss-American scientist Fritz Zwicky first put forward the idea of dark matter. He had noticed that some galaxies in space spin around too quickly for the gravity of all their visible matter to hold them together. Observations in the 1970s confirmed he was right. So if gravity wasn’t keeping the galaxies together, what was then?
So..what do we know?
Less than four percent of the matter in the universe is the ordinary stuff we know about—the atoms and molecules that make up the mountains, seas, stars, planets, animals, and even ourselves. So, what makes up all the rest?
The remaining 96 percent of the universe is made up of invisible matter so mysterious that there is no way to detect it directly. The only reason we know it exists is because of its effect on everything else. It seems there may be two types of hidden matter—dark matter that makes up 23 percent, and dark energy that accounts for a whopping 73 percent.
It is now known that all the stars glittering in each galaxy are really embedded in huge “haloes” of dark matter stretching far beyond the visible edge of the galaxy. The stars are like a scattering of salt in the center of a very big bun of dark matter that cannot be seen. It is the mass of this dark matter that provides the gravity necessary to hold the spinning galaxies together.
The more you know
Dark matter is like an incredibly thin gas that doesn’t move. The stars and planets whizz through dark matter as if through a fog. The solar system is flying through this dark matter fog at more than 136 miles per second (220 km/s). What’s most amazing is that dark matter particles are so tiny they simply pass straight through us as Earth carries us around. In fact, a billion dark matter particles pass through you every single second!