Time travel is always a fun and exciting plot device, one
that can allow a character to be anywhere and any when they need be in the
story. Thus the question was presented to me, ‘Bobby, I am writing a sci-fi
story that includes time travel. The problem I have is I really don’t
understand time travel and I don’t know what to believe when I research it on
the internet. Can you give me a Cliff notes version that I can actually
understand?’
Whew. That is a doozy. How can I explain the concept of time
travel when my own knowledge is from reading and researching the concept for my
own Multiversal stories and tales. Not
one to refuse a challenge, I decided to try.
Hence, gentle readers we begin. Time at its most basic
level, is the rate of change in the universe and we are constantly undergoing
change. All life ages, the planets move around the sun, and things wither and crumble.
Humans measure the passage of time in seconds, minutes,
hours and years, but this doesn't mean time flows at a constant rate. The same
as water in a river rushes or slows depending on the size of the channel, time
flows at different rates in different places. In other words, as Einstein
proved, time is relative.
An important concept to remember is time can't exist without
space, and space can't exist without time. The two exist as one: the space-time
continuum. Therefore, any event that occurs in the universe has to involve both
space and time.
According to Einstein's theory of general relativity,
gravity is a curve in space-time and astronomers observe this phenomenon when
they study light moving near any sufficiently massive object. Large stars, for
instance, can cause a straight beam of light to curve in what we call the
gravitational lensing effect. What does this have to do with time? Any event
that occurs in the universe involves both space and time. Therefore, gravity does
not just pull on space; it also pulls on time.
Another aspect of Einstein’s theory involves speed and the
rate at which we experience time. Time paradoxically seems to pass more slowly
the closer you approach the speed of light. So the faster you go, the slower
the rate at which time passes, so if you left Earth and flew at 99.99% the
speed of light, you’d age one-year on your ship while everyone you knew on Earth
would have died, having aged 233 years for your one-year.
According to Einstein's theory, there is nothing that
precludes time travel into the past, but the very idea of pushing a button and
going back to yesterday violates the law of causality, or cause and effect.
Every event happens in our universe leads to yet another in an endless one-way
string of events. In every instance, the cause occurs before the effect. Try to
imagine a reality, where a murder victim dies of the gunshot wound before
actually being shot. It violates reality, as we understand it; therefore, many
scientists dismiss time travel into the past as impossibility.
Of course, this does not mean you cannot send your
protagonists backward in time. There is some discussion on the idea of using
faster-than-light travel to journey back in time. After all, if time slows as
an object approaches the speed of light, then the theory speculates exceeding
that speed can cause time to flow backwards.
Then we have the science-fiction writer’s standby, the
Wormhole. However, what does wormhole actually mean? Einstein's general theory
of relativity allows for the existence of wormholes since it states that any
mass curves space-time. To understand this concept and curvature, think about
two people holding a sheet up and stretching it taut. If you then place an
orange on the sheet, the weight of the orange will roll to the middle of the
sheet and cause the sheet to curve at that point. Now, if a marble is placed on
the edge of the sheet it will travel toward the orange because of the curve.
Now if we fold this sheet over, and leaving a space between
the top and bottom. We then place an orange on the top side will cause a curvature
to form. If an equal mass, another orange, is placed on bottom part of the
sheet at a point that corresponds with the location of the orange on the top,
the second mass will eventually meet with the orange. This is similar to how
wormholes could develop.
Therefore, where the sheets meet a tunnel would, in theory,
join and allow passage between the orange on top of the sheet and the orange on
the underside of the sheet.
While there is a great deal more to time travel and if you
are seriously thinking about using the concepts of time travel in your story,
you should research it in detail. Nevertheless, as this is a quick explanation,
I hope it helps. I got back an email telling me that it helped, he is going to
proceed with the time travel aspect but with a better understanding than before
and that is all I ask for.
