Humans have always been fascinated by time travel. Physicists have been trying to prove time travel possible for years, if only theoretically. Now, physicist Ben Tippett of the University of British Columbia, Canada, and astrophysicist David Tsang of the University of Maryland have come up with a model for a time machine that Tippett says is “mathematically possible.” They’ve nicknamed the model a Traversable Acausal Retrograde Domain in Space-time, or TARDIS, as a nod to the time-traveling sci-fi hero, Dr. Who. The results are published in Classical and Quantum Gravity.
In order to understand how such a machine would work, here’s a brief refresher on Einstein’s Theory of General Relativity. Einstein posited that the three spatial dimensions we are most familiar with—left-right, up-down and forward-backward—cannot be separated from the fourth dimension of time. In essence, they comprise a four-dimensional surface, “across which the stars and planets and all the rest of the matter in the universe tumble,” write Tippet and Tsang in a paper titled “The Blue Box White Paper,” when they first started contemplating their time machine. In addition, another key law of physics, known as Classical Energy Conditions requires two conditions: matter must be gravitationally attractive, and can never move faster than the speed of light. Any matter that defies either of those criteria is considered “exotic” or “unphysical.” So far, no such exotic matter has ever been discovered, but more on that later. In our understanding of the universe through Einstein’s theory, the planets and stars might appear to move through space in straight lines; however, when they come close to each other, space-time curves, bending the trajectories of these nearby planets and stars into ellipses.
Taking a picture of a black hole focuses less on its core than its edges, and the light and debris surrounding it. Scientists have long believed that black holes are large, extremely strong gravitational bodies that prevent even light from escaping. A series of special telescopes were placed across the globe to capture giant amounts of data about a black hole in our own galaxy. Researchers now begin to process this information, hoping to create the first photograph of a black hole by 2018.
It has been one hundred years since Albert Einstein came up with his crowning intellectual achievement--the theory of relativity. That theory, published in 1915, posited that space and time are part of a single, interwoven continuum called spacetime. More importantly, spacetime itself is malleable and “warps” under the influence of matter. What we know as gravity is actually the bending of spacetime by objects with mass.