What's the difference between three dimensions and four dimensions?

The fourth dimension has an extra time axis than the third dimension, through which you can travel in time and space.

4-degree space-available for time machine:

After acknowledging the existence of aliens, Stephen Hawking, a famous British physicist, made an amazing remark: It is theoretically feasible to claim that flying humans into the future time machine, and the required conditions include wormholes in space or spacecraft with a speed close to the speed of light.

As for the key point of the time machine, Hawking emphasized the so-called "four-dimensional space". The "four-dimensional space" is close to human beings, but it is too small to be seen by the naked eye. They exist between space and time.

Hawking pointed out that in theory, just visiting or "wormholes" can't take people to other planets. If the two ends of wormholes are in the same position and separated by time instead of distance, then spacecraft can fly in and out, still close to the earth, and just enter the so-called "distant past".

Hawking said that if scientists can build a spacecraft with a speed close to the speed of light, the time of the spacecraft in the cabin will inevitably slow down, because it cannot violate the law that the speed of light is the maximum speed limit. Then flying for a week is equivalent to being on the ground 100 years, which is equivalent to flying into the future.

Einstein put forward it in his theory of relative space. The first dimension is a straight line, the second dimension is a plane, the third dimension is a solid, and the fourth dimension is time. In the creation of literary and film works, the constant fourth dimension refers to the fantasy world outside reality.