If we think about it, the ‘’future’’ is really is an eventuality brought about by the passage of time. So it comes as no surprise that time has been a much discussed topic in the field of relative physics ( that branch that deals with time travel).
Back to the Basics
What really is time? The origins of scientific study of time can be traced back to the 16th century within the works of Galileo Galilei. However, it was Newton’s theories of absolute time and space that dominated the study throughout the Scientific Revolution of the 18th and 19th century.
According to Newton, time was an independent entity that passed uniformly for everyone across space. It advanced at a consistent pace and could only be measured mathematically. David Kaiser compares Newton’s conception of absolute time to Shakespeare’s famous quote, ‘’All the world's a stage.” To Newton all the action took place on this unrelentingly rigid stage called space-time.
Basically, Newton’s view of time is the layman’s understanding of time rooted in the belief that time is universal and impartial to everyone. Because his notion of time was so very close to what people experienced on a daily basis, it was believed to be the accurate understanding for centuries. Even so, Newtonian time is still hailed as a very good theorization of what time really is and how it behaves in our world.
In 1905, Albert Einstein with his theory of relativity revolutionized the established notions of space and time. Einstein explained that time is rather a relative than a constant and that it slows down or speeds up depending on how fast one moves in relation to something else. For instance, a person inside a spaceship, travelling at nearly the speed of light would age much slower that his daughter at home. (And might see her at deathbed in a space station named after her. Murph?)
He further described space-time as a four-dimensional fabric. When anything that has mass like the Sun or the earth rests on this fabric, it causes a dimple or a bending of this fabric. This bending triggers objects to move along a curved path. This curvature in ‘space-time’ results in gravity. Essentially, gravity is what arises when matter bends space and time.
Thus, in Einstein’s version, space-time, too, is an ‘actor’ on the stage impacted by other big actors like the Sun. Einstein famously wrote in his memoirs, “Newton, forgive me.”
Come Josephine in my time machine,just not yet
Much of the research on time travel is based on bending the ‘‘space-time’’ fabric to the extent that time lines turn back on themselves to form a loop. This loop is termed ‘closed time-like curve’. To go back in time a traveller would have to have to circle inside the loop, with each lap taking the traveller further back in time. Like everything else in life, this theory too has its shortcomings. With great gravity, comes great responsibility. The creation of such a time curve would require exceptionally strong gravitational fields with impossibly precise maneuvering. If not handled correctly, the consequences could be disastrous. For real this time.
There are other alternative theories of time travel (keyword: theories), but the conception of the ‘closed time-like curve’ is the closest we’ve gotten to inventing a time-machine. So yes, in theory it is possible to go back in time but not in the cutesy way Hermione did in Harry Potter. The heart-wrenching way that Cooper did in Interstellar is more like it.