Physics
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In physics, time is considered to be a fourth dimension. Physicists argue that space-time can be understood as a sort of stretchy fabric that can bend due to forces such as gravity. In classical physics the future is just a half of the timeline, which is the same for all observers. In special relativity the flow of time is relative to the observer's frame of reference. The faster an observer is traveling away from a reference object, the slower that object seems to move through time. Hence, future is not an objective notion anymore. A more significant notion is absolute future or the future light cone. While a person can move backwards or forwards in the three spatial dimensions, many physicists argue you are only able to move forward in time.
One of the outcomes of Special Relativity Theory is that a person can travel into the future (but never come back) by traveling at very high speeds. While this effect is negligible under ordinary conditions, space travel at very high speeds can change the flow of time considerably. As depicted in many science fiction stories and movies (e.g. Déjà Vu), a person traveling for a short time at near light speed will return to an Earth that is many of years in the future.
Some physicists claim that by using a wormhole to connect two regions of space-time a person could theoretically travel in time. Physicist Michio Kaku points out that to power this hypothetical time machine and "punch a hole into the fabric of space-time", it would require the energy of a star. Another theory is that a person could travel in time with cosmic strings.
While a person cannot go back in time, information can. The bell inequality in quantum physics allows for information to be sent back in time, but only as long as no one has tried to retrieve it in the past.
Read more about this topic: Futurity
Famous quotes containing the word physics:
“The pace of science forces the pace of technique. Theoretical physics forces atomic energy on us; the successful production of the fission bomb forces upon us the manufacture of the hydrogen bomb. We do not choose our problems, we do not choose our products; we are pushed, we are forced—by what? By a system which has no purpose and goal transcending it, and which makes man its appendix.”
—Erich Fromm (1900–1980)
“Mathematics should be mixed not only with physics but with ethics.”
—Henry David Thoreau (1817–1862)
“Now the twitching stops. Now you are still. We are through with physiology and theology, physics begins.”
—Alfred Döblin (1878–1957)