Einstein’s Special Relativity says that when
an object moves at a speed close to the speed of light, time goes slower for
that object. For example, if you are traveling close to the speed of the light
in the universe and come back earth, the people born in the same year as you
will be grandpas but you will be very young. And here is how time traveling based on
general relativity works: Einstein’s General Relativity proposes that time goes
more slowly in the region with lower gravitational potential. And this is why
there are space and time distortions near black holes. And scientists use
distortions in spacetime, such as black holes, to come up with how time
machines could work. And some scientists came up with a design of a time
machine that uses the theory of general relativity. Developed by Willem Jacob
van Stockum, Kipler cylinder, a solution to the equations of general relativity,
suggests that if there is a cylinder infinitely long and spins fast enough,
then a spaceship flying around the cylinder on a spiral path could travel back
or forward in time. However, it does
not exist in reality because the size and
speed required are so big, it cannot be built with current technology.
Image explaining Tipler Cylinder
Imagined image of Tipler Cylinder
Despite such efforts made by numerous
scientists, the future of time traveling based on general relativity
looks
grim. Stephen Hawking objected to time traveling based on general relativity by
saying that time machine based on general relativity cannot be built in a region
that contains no matter with negative energy
density.
Bibliography
Is time travel possible? NASA
Time Travel. Wikipedia
I really enjoyed reading this blog because I am fascinated by the idea/concept of time traveling. My roommate (who is also taking this course with me) and I were having a discussion one night about the possibility of time traveling and how it would be possible if we could travel at the speed of light. I guess my question is, how fast can we "spin" this machine as of now? I am also wondering why do we need matter with negative energy density to make time travel somewhat possible?
ReplyDeleteI also enjoyed reading this post. I read about the Tipler cylinder when I was in highschool and heard about it at a lecture of theoretical physicist Dr. Michio Kaku about five years ago. To expand on this post, and perhaps to make it even more relative to our discuss on the nature of space-time, Dr. Kaku described the fabric of space-time "wrapping" around the rotating cylinder, similar to rolling up a rug. Two or more layers of space-time wrapped around the cylinder implies that two different locations/times are now in close proximity to each other, and a wormhole could theoretically be used to form a bridge to another location/time. Dr. Kaku went on to describe the obvious limitations of this theory, not the least of which are our limited grasp of the physics/existence of wormholes, lack of time/space accuracy, and obviously the sheer amount of energy that the theory necessitates. Nonetheless, quite an interesting theory that your post reminded me of.
ReplyDeleteI really liked your post on time travel. It's interesting to think that you could travel the speed of light and come back you would be much younger than everyone here on earth. I think the idea for traveling by Willem Jacob van Stockum was extremely interesting, even though it is not feasibly possible. It's interesting that Willem Jacob Van Stockum came to America to study under Albert Einstein, and actually enlisted in the Royal Canadian Air force.
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