Negative mass

Negative mass is a strange kind of mass that behaves differently than regular mass. It was just an idea in science fiction until recently. Scientists now think negative mass could exist in the universe.

When you push a regular mass like a ball, it moves away from you because of something called "Newton's third law." This law says that when one object pushes another, the second object pushes back in the opposite direction with an equal force.

But with negative mass, it's different. If you push it, it moves towards you instead of away. It's like pushing a balloon filled with a heavy liquid, because the balloon moves closer when you push it. This means negative mass has a negative force, instead of a positive one like regular mass.