10 Mind-Blowing Facts About the Universe

7. Negative Mass Is Theoretically Possible

All normal matter has positive mass.

But equations in physics allow for something strange: negative mass.

A negative-mass object would behave in the opposite way—
push it, and it moves toward you.
Drop it, and it would fall upward.

So far, no negative-mass particle has been observed, but mathematically, it’s possible.