# What's the exact point about time travel?

Benjamin_harsh
TL;DR Summary
What's the exact point that stopping our scientists to create time machine in reality?
It shows theory of time machine proved, what's the exact point that stopping our scientists to create time machine in reality?

## Answers and Replies

Mentor
It shows theory of time machine proved

What "theory of time machine" are you talking about?

Benjamin_harsh
What "theory of time machine" are you talking about?
I mean theory part of time machine.

Mentor
I mean theory part of time machine.

I have no idea what you are talking about. Please give a reference.

Mentor
There is no indication that you could travel to the past.
There is no indication that you could travel to the future with realistic effort. Relativistic spacecraft make it possible in principle but not with any effort we can imagine.

Mentor
Basically, we do not have a theory of time travel.

We have some notions of time travel into the future as described in the theory of Special and General Relativity as illustrated in the Twin Paradox. We have experimental results confirming the passage of time is different for different observers with GPS clocks and other tests.

We have even more vague notions of time travel to the past within the limits of closed time-like curves but nothing more.

For engineers to build a working time travel machine, they would need a definitive theory and a physical experiment that accomplished it. To say something is possible but with no means to show it then the engineers have nothing to work with.

https://en.wikipedia.org/wiki/Time_travel

As an example, consider the invention of the laser. It started with a paper describing the possibility of a coherent beam of light and then further papers about the excitation of atoms. The experimental scientists and engineers then discover what kinds of materials work best for lasing and finally, products are produced.

Without the theory and the physical experiments showing it's feasibility and a means to achieve it, real working products could not be produced.

https://en.wikipedia.org/wiki/Laser

Mentor
Summary:: What's the exact point that stopping our scientists to create time machine in reality?

It shows theory of time machine proved, what's the exact point that stopping our scientists to create time machine in reality?
For SR-based time travel it is insufficient energy. For GR-based time travel it is the complete lack of any evidence that exotic matter actually exists.

Demystifier and jedishrfu