Science 53

Time Travel

Time travel is the concept of movement between certain points in time, analogous to movement between different points in space by an object or a person, typically with the use of a hypothetical device known as a time machine. Time travel is possible based on the laws of physics, according to new calculations from researchers at the University of Queensland. But time-travelers wouldn't be able to alter the past in a measurable way, they say the future would stay the same. Ali Razeqi says his time machine uses "complex algorithms" to see the future. It's not quite Back to the Future, but a young Iranian inventor claims to have built a time machine that can predict a person's future with startling accuracy. The bending of space-time causes objects to move on a curved path and that curvature of space is what we know as gravity. Mathematically one can go backwards or forwards in the three spatial dimensions. But time doesn't share this multi-directional freedom. According to theoretical physicist Carlo Rovelli, time is an illusion: our naive perception of its flow doesn't correspond to physical reality. Indeed, as Rovelli argues in The Order of Time, much more is illusory, including Isaac Newton's picture of a universally ticking clock. More than 100 years ago, a famous scientist named Albert Einstein came up with an idea about how time works. He called it relativity. This theory says that time and space are linked together. Einstein also said our universe has a speed limit: nothing can travel faster than the speed of light (186,000 miles per second). In fact, according to Albert Einstein's famous equation, E = mc² , time travel is possible, at least in one direction. Going the other way back to the past presents a trickier challenge. His idea was that, theoretically, the closer we come to traveling at the speed of light (186,000 miles per second), the more time would appear to slow down for us from the perspective of someone who, in relation to us, was not moving. He called the slowing of time due to motion time dilation. In the Special Theory of Relativity, Einstein determined that time is relative in other words, the rate at which time passes depends on your frame of reference. Time slows down as you travel faster because momentum bends the fabric of spacetime causing time to pass slower. It is possible to stop time, but you need to travel at light speed." The practice is, admittedly, a bit more difficult. Addressing this issue requires a more thorough exposition on Special Relativity, the first of Einstein's two Relativity Theories. To create a time machine would require negative energy, and quantum mechanics appears to allow only extremely small regions of negative energy. And the forces needed to create an ordinary-sized region with time loops appear to be extremely large. Special relativity states that nothing can go faster than the speed of light. If something were to exceed this limit, it would move backward in time, according to the theory.

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