NOT TO BE CONFUSED WITH EXOTIC ATOMS!!!
By Oleksandr Koliakin
Edited by Luke
Exotic matter is hypothetical matter that has negative mass (what we mean by hypothetical is that it hasn't been proven to exist.) Exotic matter is NOT antimatter and is something quite different from 'normal' matter we humans experience.
Exotic matter has unique properties. If we substitute negative mass into equations used to calculate the curvature of spacetime (see our spacetime article about that) we will notice that it bends spacetime in a completely different way than matter with positive mass. If we look at how a planet with positive mass bends spacetime, we see that it creates a sort of valley. A planet made from exotic matter (it would have with negative mass) would instead curve spacetime to shape it more like a hill or a mountain. If we are close enough to a large object such as a black hole, time runs slower for us. We might spend an hour near a black hole and then come back to Earth and realize that on Earth many years have passed since you left. Exotic matter would create the opposite effect, meaning that you could spend a few years near an object with enough negative mass but when you ask a person far away from the object how much time has passed, he would say that only a few hours had passed.
We also get an interesting result if we substitute objects with negative mass into Newton's equation of gravity. If the mass of the first object is positive and the mass of the second object is negative (so we basically take one object made from normal matter and a different object made from exotic matter), we will see that we get a negative result meaning that the object with negative mass (the one made from exotic matter) is actually pushing an object away instead of attracting it. However, if we substitute two objects with negative mass into Newton's equation, we get a positive result. This suggests that objects with positive mass attracts only objects with positive mass (normal matter attracts normal matter) and objects with negative mass only attract object with negative mass (exotic matter attracts exotic matter).
Some scientists think that particles with negative mass might be able to travel faster than the speed of light. These hypothetical particles are called tachyons or tachyonic particles and have so far not been observed.
Exotic matter would have its uses for us as a species. If we were ever to discover a wormhole and then find out how to build one we would need exotic matter. Gravity would always be trying to compress our wormholes to make the, collapse into a black hole. We would need something to hold the wormhole open. This is where exotic matter comes in. As said before, exotic matter has negative mass, meaning that it is repulsive. We could use this to counter the force of gravity.
"Wormholes" video by the Kurzgesagt YouTube channel.