Time seems to flow like a river; it goes in one course. Imagine we are fishes in the water. At a regular pace, we swim with the smooth current of the river. But can the movement through time be manipulated? Can we actually travel through time—the fish going against the water or the fish jumping forward to advance faster? Can we open a portal to the past or find a shortcut to the future? Time travel is the movement between two different points in time similar to a movement between two different places. With time travel, people are enabled to move either back into the past or forward into the future. Travelling through time has been the subject of many great science fiction novels and movies. Even though time travel only came from the unbounded imagination of man, many people still ponder if travelling through time would be ever possible in reality.
One question continues to baffle
literally everyone: is time travel really possible? Many people such as the
presentist philosophers, who only believes that only the present exists, would
disagree to the concept of time travel. They would say that time travel is
nothing but a figment of human imagination. On the other hand, there are
debates going on in the scientific world that focuses on the possibility of time
travelling. But because of the theory of relativity of Albert Einstein in the
20th century, modern scientists, particularly the theoretical scientists, see
time travel possible in the real world.
As
our eyes perceive, the physical world has 3 dimensions—the length, width, and
depth—called the spatial dimensions. A table would have these 3 spatial
dimensions. Even a sheet of paper is 3D (three-dimensional). Most people would
say that they live in a 3 dimensional world, but according to Albert Einstein’s
theory of relativity, the universe comprises the 3 spatial dimensions and a 4th
dimension—the time dimension, thus creating spacetime. This denotes that space
and time are intertwined with each other.
THEORY OF
RELATIVITY
In
one of the facts asserted by Albert Einstein in his theory of relativity, he
claims that the speed of light is the same for all observers, regardless of
their motion. This means that a man riding a high-speed rocket and a man at
rest on Earth would both observe a beam of light travelling at the same speed.
In the relativity (the theory of
relativity), one consequence of the space-time principle is time dilation. What
would be the difference for these two observers then? As a result, the man on
the rocket would experience time to slow down. In his case, time dilates. That
implies that if that particular man is travelling near the speed of light for 1
earth-year, after coming back to Earth, he would have only aged for 1
earth-month. Thus, time dilation simply states that as an object approaches the
speed of light, that object would experience time slowdown.
Through time dilation, time
travel, particularly to the future is in fact possible. Michio Kaku, the Henry
Semat Professor of Theoretical Physics in the City College of New York and a
communicator of science, explains in his book Physics of the Impossible that
when an observer on Earth were to peer into the rocket with a telescope, he
would see clocks inside the rocket running slowly. Consequently, the man in the
rocket would see the clocks on Earth tick faster. So, when the speed of the
rocket is closer to the speed of light, the more the man experience time travel
to the future because of time dilation.
However, time dilation is not
significant to normal situations like cars travelling on a highway or even jet
planes going faster than the speed of sound.With the speed of light in vacuum
of about 300,000 km/s, light can go around the earth seven and a half times in
one second. In comparison, Usain Bolt’s recorded top speed of 12.27 m/s is only
four hundred-millionths of the speed of light. The fastest manned vehicle in
history, reaching 11 km/s, was Apollo
10. But according to Stephen Hawking, to travel in time we will have to go more
than 2,000 times faster than Apollo’s. Therefore, the changes are only
significant to objects travelling near the speed of light.
Aside from objects travelling
near the speed of light, can objects travel greater than or equal to light
speed? Unfortunately, relativity says that objects cannot travel at the speed
greater than or equal to that of light. Particles with mass can attain speeds
that approach light speed, but never actually reach it. Albert Einstein had
said that the speed of light is the “Cosmic Speed Limit” for everything with
mass in the universe. An object having mass needs an infinite amount of energy
to break the “Cosmic Speed Limit” which is impossible.
Charles Liu, an astrophysicist
of the City University of New York, explains that, mathematically, you can go
backward or forward in the three spatial dimensions length, width and height.
But the time dimension is only restricted to a single direction. In the
four-dimensional universe, an object is able to move only forward in time (as
cited in Goudarzi, 2007).
For now, the only definitive
part of time travel is that we’re stepping further into the future with each
passing moment. Time travel like tunneling into the past or jumping to the
future is but away from the full grasp of modern science. However, scientists
had proposed an alternative way to time travel, which is the use of wormholes.
WORMHOLES
Imagine two points on a sheet of
paper, several feet apart. We learned from grade school that a straight line is
the shortest possible way between the two points. But, this is not necessarily
true. You could curl the sheet of paper until the two points touch each other.
By curling the paper, you are making a 'wormhole' in the paper. Then we would
see that the shortest distance between two points is actually a wormhole.
A wormhole, also known as
Einstein-Rosen Bridge, is a theoretical 'tunnel' or shortcut connecting at
least two points of space-time. The regions bridged could be two parts of one
universe—the curled sheet of paper with two points touching each other—or two
completely different universes—a sheet of paper with a point touching another
sheet of paper on one point. In theory, after a wormhole is established, matter
may travel through one mouth of the wormhole to reach the destination on the
other side. This kind of wormhole that allows matter to travel through it is a
traversable wormhole.
In the famous tale of Lewis
Caroll’s Through the Looking-Glass, Alice steps through the
"looking-glass" and is whisked away to a strange land. The character
was instantaneously transported from one place to another through “the looking-glass”, a wormhole linking a
room in her house from the strange land. But what if instead of that
“looking-glass” leading to the strange place, it would take you to the same
room but in a different time? Can wormholes behave like a time machine?
Since wormholes connect two
regions of spacetime, does that mean that it can connect two different points
of time? Brian Greene, a professor of physics and mathematics at Columbia
University and a specialist in quantum
field theory, explains that “if you fiddle with the wormhole openings, you can
make it not only a shortcut from a point in space to another point in space,
but a shortcut from one moment in time to another moment in time”. Thus,
wormholes can act both as a bridge between two spatial regions (i.e. a
teleportation device) and a link between two different points in time (i.e. a
time machine). So that means you can travel to the future and end up in another
place in the universe with the use of a wormhole.
Time travel was once considered
a scientific heresy. Discussing it in a scientific conference was taboo for it
may label the speaker a crank. But now, it seems that time travel is not just a
mere fabrication of the human imagination. Time travel got the attention of not
only the sci-fi genre but also the scientific world today. Through the theory
of relativity of the great Albert Einstein, gave us a sudden realization: man
may actually be able to time travel.
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