Arguments Against Time Travel: Exotic Matter

There are two main issues that make us think these theories and their equations may be unrealistic.

The first issue is a practical one: Building a time machine seems to require exotic matter, which is matter with negative energy. All the matter we see in our daily lives has positive energy-matter with negative energy is not something you can just find lying around.

From quantum mechanics, we know that such matter can theoretically be created, but in too small quantities and for too short times.