Ever since H.G Wells´ The Time Machine, time travel has become a staple in science fiction media. From educational stories like The Magic Treehouse to thrilling action movies like The Terminator and The Avengers, the fantasy of being able to see into the past with one's own eyes or see what the future holds for humanity has always been a fascinating concept to explore within fiction. But how much of it is truly fiction?
Albert Einstein created what might be considered the most important theory in modern physics, the theory of relativity. He posited that time is not an objective concept but rather is relative to the observer. Two different observers will experience the same amount of objective time differently. This effect is called time dilation. While this effect is too small to be observed on Earth, we have measured it in space. Astronauts on the International Space Station have noticed that despite their clocks being fully functional, they seemed to be slightly behind clocks on Earth when measured over very long periods. This case of time dilation was due to their high speed orbiting the Earth and the decreased gravity they experienced in the upper orbit. This means that the astronauts on the International Space Station age ever so slightly slower than the rest of us on Earth. This effect could, hypothetically, be used to cause someone to only experience a few minutes while everyone else not under the effects of time dilation experiences hundreds or even thousands of years.
So we now know that ¨time traveling ¨ into what is relatively the future is possible, but what about traveling into the past? Another important aspect of the theory of relativity is that time is proportional and relative to space. This is where we get the term ¨spacetime¨. The reason gravity causes time dilation is that it pulls and stretches space and, by extension, time. That leaves the question of how ¨time traveling ¨ backward through time would work. We currently don't have any theories or methods, but we do have some interesting possibilities. The closest thing anyone has theorized to a true time machine would be the tipler time machine, also known as the tipler tube. This is a hypothetical machine made of an infinitely large cylinder rotating in space. This machine relies on spacetime phenomenons called closed time-like curves. If you think of time like a roller coaster only going in one direction, a closed time-like curve is a loop-de-loop that puts you back at the point you got in on. Unfortunately, making a stable closed time-like curve is impossible on Earth without either having an infinite amount of space or some form of negative energy. While many scientists are exploring various vectors to make this possible, you won't be taking a trip to the Roman Empire or Jurassic Period any time soon.
About the Author
Jacob is a Junior at Northwood High School who enjoys playing the saxophone and learning new things. He hopes to study to become a particle physicist after graduation.
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