Have you ever wished you could travel through time? Well, this is more possible than you might think. Although you cannot go back into the past and change life as Marty McFly does in the Back to the Future movies, scientists believe that time travel is theoretically feasible. Technically speaking, everyone travels in time; we all travel forward at approximately one second per second. However, Einstein’s general and specific theories of relativity explain how time travel on a greater scale could exist.
Einstein’s theory states that time and space are not absolute but linked, and gravity depends on the curving and warping of space and time. He theorized that the faster a person or object travels, the slower time passes. If an object appears stationary relative to people on Earth, its motion is only traveling through the dimension of time. If the same object starts to move, however, some of this motion is diverted through space, meaning less motion can be used to travel through time. Special relativity predicts a smaller amount of time will pass for a quickly moving object in space compared to the time passing on Earth.
Think about two clocks. Scientists have run several experiments in which the two clocks are set to the same time, but one stays ‘stationary’ on Earth and the other moves. In 2010, scientists at the National Institute of Standards and Technology used extremely precise clocks to prove that clocks tick slower than usual at speeds as slow as 25 miles per hour or height differences as small as one foot (NASA Space Place, 2020). The faster the clock goes, the slower time passes. This supports the idea of time dilation; time moves relative to the observer and time moves slower as gravity increases.
Did you know that your head is actually older than your feet? As a person is standing, their head is further from Earth’s gravitational field than their feet. Due to the stronger gravitational time dilation, this slight age difference occurs. Changes like this are minimal and go unnoticed. Situations like this lead scientists to wonder what will happen if this occurs on a larger scale. There is a lot left to discover and understand when it comes to time travel.
Scientists continue to explore complex scenarios, like the grandfather paradox. In this theory, a time traveler goes back in time and kills their grandfather. However, if this happens, the time traveler would have never been born, and thus they would be unable to travel through time to kill their grandfather.
Also, scientists are currently exploring quantum mechanics, the study of matter and lights on a subatomic level, in hopes of answering more questions. In quantum physics, it has been supported that a particle can be in multiple places at once. Because of this, scientists wonder if people can access parallel universes. Some scientists believe the theory of quantum gravity (the theoretical framework that describes how gravity works for subatomic particles) will change the world’s view on whether or not time travel is possible.
There is much to learn about traveling into the past. This idea of time travel is based on mathematical speculations not supported by known physics. If people could travel into the past, scientists believe it would be impossible to change the past and alter the future. They think the universe’s timeline would correct itself before any permanent changes were made. So Marty McFly has nothing to worry about – even if he goes back in time, he cannot stop his parents from falling in love.
