Daniel Robbins

The multiverse is a theory that suggests our universe is not the only one, and that many universes exist parallel to each other. These distinct universes within the multiverse theory are called parallel universes. A variety of different theories lend themselves to a multiverse viewpoint.Not all physicists really believe that these universes exist.

General relativity was Einstein’s theory of gravity, published in 1915, which extended special relativity to take into account non-inertial frames of reference — areas that are accelerating with respect to each other.General relativity takes the form of field equations, describing the curvature of space-time and the distribution of matter throughout space-time.

General relativity was Einstein’s theory of gravity, published in 1915, which extended special relativity to take into account non-inertial frames of reference — areas that are accelerating with respect to each other. General relativity takes the form of field equations, describing the curvature of space-time and the distribution of matter throughout space-time.

Many physicists feel that string theory will ultimately be successful at resolving the hierarchy problem of the Standard Model of particle physics. Although it is an astounding success, the Standard Model hasn’t answered every question that physics hands to it. One of the major questions that remains is the hierarchy problem, which seeks an explanation for the diverse values that the Standard Model lets physicists work with.

For most interpretations, superstring theory requires a large number of extra space dimensions to be mathematically consistent: M-theory requires ten space dimensions. With the introduction of branes as multidimensional objects in string theory, it becomes possible to construct and imagine wildly creative geometries for space that correspond to different possible particles and forces.

String theory is a type of high-energy theoretical physics, practiced largely by particle physicists. It’s a quantum field theory that describes the particles and forces in our universe based on the way that special extra dimensions within the theory are wrapped up into a very small size (a process called compactification).

Talking about time travel and string theory without mentioning science fiction would be an obvious omision. Here are some key science fiction novels and films related to the time travel concepts discussed in this chapter, although the list is by no means complete. Spoiler alert: Some plot details are revealed in the descriptions below.

In physics, time travel is closely linked to Einstein’s theory of relativity, which allows motion in space to actually alter the flow of time. This effect is known as time dilation and was one of the earliest predictions of relativity. This sort of time travel is completely allowed by the known laws of physics, but it allows only travel into the future, not into the past.

Waves (as we usually think of them) move through some sort of medium. If you flick the end of a jump-rope or string, a wave moves along the rope or string. Waves move through the water, or sound waves through the air, with those materials acting as the medium for the wave motion. In classical physics, waves transport energy, but not matter, from one region to another.