introduction
Time
Travel
Time
travel is the concept of moving between different points in time in a manner
analogous to moving between different points in space. Time travel could
hypothetically involve moving backward in time to a moment earlier than the starting
point, or forward to the future of that point without the need for the traveler
to experience the intervening period .Any technological device whether fictional, hypothetical or actual that would be used to achieve time travel is
commonly known as a time machine.
Understanding
time
What
is time? While most people think of time as a constant, physicist Albert
Einstein showed that time is an illusion; it is relative it can vary for
different observers depending on your speed through space. To Einstein, time is
the fourth dimension. Space is
described as a three dimensional arena, which provides a traveler with coordinates
such as length, width and height showing location. Time provides another coordinate
direction although conventionally, it only moves forward.
Einstein's
theory of special relativity says that time slows down or speeds up depending
on how fast you move relative to something else. Approaching the speed of
light, a person inside a spaceship would age much slower than his twin at home.
Also, under Einstein's theory of general relativity, gravity can bend
time.Picture a four-dimensional fabric called space-time. When anything that
has mass sits on that piece of fabric, it causes a dimple or a bending of
space-time. The bending of space-time causes objects to move on a curved path
and that curvature of space is what we know as gravity.Both the general and
special relativity theories have been proven with GPS satellite technology that
has very accurate timepieces on board. The effects of gravity, as well as the
satellites' increased speed above the Earth relative to observers on the
ground, make the unadjusted clocks gain 38 microseconds a day. In a sense, this
effect, called time dilation, means
astronauts are time travelers, as they return to Earth very, very slightly
younger than their identical twins that remain on the planet.
Forward time travel
There
is no widespread agreement as to which written work should be recognized as the
earliest example of a time travel story, since a number of early works feature
elements ambiguously suggestive of time travel. Ancient folk tales and myths
sometimes involved something akin to travelling forward in time for example, in Hindu mythology, the
Mahabharata mentions the story of the King Revaita, who travels to heaven to
meet the creator Brahma and is shocked to learn that many ages have passed when
he returns to Earth.
Another
one of the earliest known stories to involve traveling forward in time to a
distant future was the Japanese tale of UrashimaTarō, first described in the Nihongi
. It was about a young fisherman named Urashima Taro who visits an undersea
palace and stays there for three days. After returning home to his village, he
finds himself 300 years in the future, when he is long forgotten, his house in
ruins, and his family long dead. Another very old example of this type of story
can be found in the Talmud with the story of HoniHaM'agel who went to sleep for
70 years and woke up to a world where his grandchildren were grandparents and
where all his friends and family were dead.
More
recently, Washington Irving's 1819 story "Rip Van Winkle" tells of a man named Rip Van Winkle who takes
a nap on a mountain and wakes up 20 years in the future, when he has been
forgotten, his wife dead, and his daughter grown up. Sleep was also used for
time travel in FaddeyBulgarin's story "PravdopodobnieNebylitsi" in
which the protagonist wakes up in the 29th century. Another more recent story
involving travel to the future is Louis-Sébastien Mercier's L'An 2440, rêves'il
en fûtjamais, a utopian novel in which the main character is transported to the
year 2440. An extremely popular work, it describes the adventures of an unnamed
man who, after engaging in a heated discussion with a philosopher friend about
the injustices of Paris, falls asleep and finds himself in a Paris of the
future.
Backward time travel
Backwards
time travel seems to be a more modern idea, but its origin is also somewhat
ambiguous. One early story with hints of backwards time travel is Memoirs of
the Twentieth Century by Samuel Madden, which is mainly a series of letters
from British ambassadors in various countries to the British Lord High
Treasurer, along with a few replies from the British Foreign Office, all
purportedly written in 1997 and 1998 and describing the conditions of that era.
However,
the framing story is that these letters were actual documents given to the
narrator by his guardian angel one night in 1728 for this reason, Paul Alkon suggests in his
book Origins of Futuristic Fiction that the first time-traveler in English
literature is a guardian angel who returns with state documents from 1998 to
the year 1728, although the book does not explicitly show how the angel
obtained these documents. Alkon later qualifies this by writing, It would be
stretching our generosity to praise Madden for being the first to show a traveler
arriving from the future, but also says that Madden deserves recognition as the
first to toy with the rich idea of time-travel in the form of an artifact sent
backwards from the future to be discovered in the present.
A
more clear example of backwards time travel is found in the popular 1861 book
Paris avant les hommes by the French botanist and geologist Pierre Boitard,
published posthumously. In this story the main character is transported into
the prehistoric past by the magic of a lame demon, where he encounters such
extinct animals as a Plesiosaur, as well as Boitard's imagined version of an
apelike human ancestor, and is able to actively interact with some of them.
Another
early example of backwards time travel in fiction is the short story The Clock
That Went Backward by Edward Page
Mitchell, which appeared in the New York Sun in 1881.Mark Twain's A Connecticut
Yankee in King Arthur's Court (1889), in which the protagonist finds himself in
the time of King Arthur after a fight in which he is hit with a sledge hammer,
was another early time travel story which helped bring the concept to a wide
audience, and was also one of the first stories to show history being changed
by the time traveler's actionsThe first time travel story to feature time
travel by means of a time machine was Enrique Gaspar y Rimbau's 1887 book El
AnacronópeteThis idea gained popularity with the H. G. Wells story The Time
Machine, published in 1895 which also featured a time machine and which is
often seen as an inspiration for all later science fiction stories featuring
time travel using a vehicle that allows an operator to travel purposefully and
selectively. The term time machine,
coined by Wells, is now universally used to refer to such a vehicle. Since that
time, both science and fiction have expanded on the concept of time travel.
Through the
wormhole
General
relativity also provides scenarios that could allow travelers to go back in
time, according to NASA. The equations, however, might be difficult to
physically achieve.One possibility could be to go faster than light, which travels
at 186,282 miles per second (299,792 kilometers per second) in a
vacuum.Einstein's equations, though, show that an object at the speed of light
would have both infinite mass and a length of 0.
This
appears to be physically impossible, although some scientists have extended his
equations and said it might be done.A linked possibility, NASA stated, would be
to create wormholes between points
in space-time. While Einstein's equations provide for them, they would collapse
very quickly and would only be suitable for very small particles. Also,
scientists haven't actually observed these wormholes yet. Also, the technology
needed to create a wormhole is far beyond anything we have today.
Alternate
time travel theories
While
Einstein's theories appear to make time travel difficult, some groups have
proposed alternate solutions to jump back and forth in time.
Infinite cylinder
Astronomer
Frank Tipler proposed a mechanism where one would take matter that is 10 times
the sun's mass, then roll it into very long but very dense cylinder.After
spinning this up a few billion revolutions per minute, a spaceship nearby following a very precise spiral around this
cylinder could get itself on a closed,
time-like curve according to the
Anderson Institute. There are limitations with this method, however, including
the fact that the cylinder needs to be infinitely long for this to work.
Black holes
Another
possibility would be to move a ship rapidly around a black hole, or to
artificially create that condition with a huge, rotating structure.Around and
around they had to go, experiencing just half the time of everyone far away
from the black hole. The ship and its crew would be traveling through time
physicist Stephen Hawking wrote in the Daily main 2010.
.
Imagine they circled the black hole for five of
their years. Ten years would pass elsewhere. When they got home, everyone on
Earth would have aged five years more than they had.
However,
he added, the crew would need to travel around the speed of light for this to
work. Physicist Amos Iron at the TechnionIsrael Institute of Technology in
Haifa, Israel pointed out another limitation if one used a machine it might fall apart before being able to
rotate that quickly.
Cosmic strings
Another
theory for potential time travelers involves something called cosmic strings narrow tubes of energy stretched across the
entire length of the ever expanding universe. These thin regions, left over
from the early cosmos, are predicted to contain huge amounts of mass and
therefore could warp the space time around them. Cosmic strings are either
infinite or they are in loops, with no ends, scientists say. The approach of
two such strings parallel to each other would bend space time so vigorously and
in such a particular configuration that might make time travel possible, in
theory.
Grandfather paradox
Besides
the physics problems, time travel may also come with some unique situations. A
classic example is the grandfather paradox, in which a time traveler goes back
and kills his parents or his grandfather the major plot line in the Terminator movies or otherwise interferes in their relationship think Back to the Future so that he is never born or his life is
forever altered.
If
that were to happen, some physicists say, you would be not be born in one
parallel universe but still born in another. Others say that the photons that
make up light prefer self consistency in timelines, which would interfere with
your evil, suicidal plan.Some scientists disagree with the options mentioned
above and say time travel is impossible no matter what your method. The faster
than light one in particular drew derision from American Museum of Natural
History astrophysicist Charles Lu.Also, humans may not be able to withstand
time travel at all. Traveling nearly the speed of light would only take a
centrifuge, but that would be lethal, said Jeff Tollaksen, a professor of
physics at Chapman University, in 2012.Using gravity would also be deadly. To
experience time dilation, one could stand on a neutron star, but the forces a
person would experience would rip you apart first.
EFFECTS OF TIME TRAVEL
If
you could travel back through time and meet your younger self several different
things could happen. You could, as we have said, try to warn yourself against
this or that choice, perhaps steering yourself toward a different career of
course, likely changing the present-you in the process. And, again, you could
ask your younger self to help someone you learned later needed help. If you
thought your finances needed a boost, meanwhile, where's the harm in giving
your younger self some handy stock tips? You might, for example, tell the
younger you about this nascent search company called Google.
In
any case, it's safe to assume that if you used your time well with your younger
self, you might return to the present to find a much more prosperous,
presumably happier you. Hollywood, not surprisingly, has taken aim at this
theme numerous times. The time travel movie Back to the Future (1985) explored
changing the past to affect the present.
And,
in a scene from J.K. Rowling's Harry Potter and the Prisoner of Azkaban, Harry
uses a Time Turner to go back in time to save his friends. In the process of doing
so, he also actually saves himself from a nasty fate. A meeting with your
younger self might not be quite this dramatic, but imagine how strange it would
be to converse with yourself as you were, say, 10 years earlier. It seems safe
to imagine that seeing your former self might have a significant impact on your
future development. Even stranger to consider, you could actually collect
copies of yourself at various times by making what physicist Paul Davies refers
to as successive hops back in time. You could end up with a strange array of
selves from various stages of your life. Clearly, there could be some serious
upside to traveling back in time to meet your younger self. Now where is that
time machine?
Time machines
It
is generally understood that traveling forward or back in time would require a device
a time machine to take you there. Time machine research often involves bending
space-time so far that time lines turn back on themselves to form a loop,
technically known as a closed time-like
curve.
To
accomplish this, time machines often are thought to need an exotic form of
matter with so called negative energy
density. Such exotic matter has
bizarre properties, including moving in the opposite direction of normal matter
when pushed. Such matter could theoretically exist, but if it did, it might be
present only in quantities too small for the construction of a time machine. However, time travel research suggests time
machines are possible without exotic matter. The work begins with a
doughnut-shaped hole enveloped within a sphere of normal matter. Inside this
doughnut-shaped vacuum, spacetime could get bent upon itself using focused
gravitational fields to form a closed time-like curve. To go back in time, a
traveler would race around inside the doughnut, going further back into the
past with each lap. This theory has a number of obstacles, however. The
gravitational fields required to make such a closed time-like curve would have to be
very strong, and manipulating them would have to be very precise.
Thinking
about time travel requires seeing it as a fourth dimension, or it's hard to
wrap your head around the idea, other than to plan your itinerary. And the
possibilities with time travel are limitless you get to decide not just where you want to
go, but when If you look online, you can
find books and other instructions on how to build your own time machine.Yet
even if it were theoretically possible to build a carousel spinning at the
speed of light the speed you need to
travel to traverse time there are
practical obstacles to this ride becoming a reality. The huge amount of
centrifugal force generated by a carousel turning at light speed is an example
of the practical limitations to the theory of time travel. Specifically, the
flywheel is the fastest spinning object that currently exists. It is able to
reach a speed of up to 200,000 revolutions per minute. Yet rotor disintegration
is a problem that cannot be overcome with today's technology. The speed of
200,000 revolutions per minute, as fast as that is, doesn't come close to the
speed of light 186,000 miles (300,000 kilometers) per second.
If
you are both brilliant and positive, like physicist and cosmologist Stephen
Hawking, you believe it's possible one day to travel through time at least to
travel forward. Hawking sees the fourth dimension of time in the same physical
terms as you see the objects around you while you read these words. He also
joins other physicists who believe that there may be tunnels in time that fit
well within the laws of nature. There are tiny cracks and openings in time
within quantum foam called wormholes. The holes are too small for humans to
enter, so the next challenge is how to enlarge them so that people and some
sort of spaceship or other machine fast enough to travel through the hole at
nearly the speed of light, can sneak through.It also might help to have a
physicist such as Hawking around to consult with as you build your time
machine.
As
for travel to the past so you can make up for mistakes or erase ugly childhood
memories you probably should use your
time and energy on apologies or counseling instead. According to Hawking,
traveling to the past will likely never happen because of paradoxes, or the
fundamental rules of cause and effect. You can't go back and change the past;
this would create chaos. Quantum mechanics may make it possible using closed
timelike curves It's complex and involves quantum computations, so it's unlikely
that a DIY kit for a back in time machine will appear online in the next few
years. If you could only find a way to travel to the future to find out if
quantum physicists have solved past time travel challenges. But then if you do,
how do you know you will be able to get back to the past?
This form of travel into the future is theoretically
allowed using the following methods:[24]
Using
velocity-based time dilation under the theory of special relativity, for
instance:
Traveling
at almost the speed of light to a distant star, then slowing down, turning
around, and traveling at almost the speed of light back to Earth, Using
gravitational time dilation under the theory of general relativity, for
instanceResiding inside of a hollow, high mass objectResiding just outside of
the event horizon of a black hole, or sufficiently near an object whose mass or
density causes the gravitational time dilation near it to be larger than the
time dilation factor on Earth.Additionally, it might be possible to see the
distant future of the Earth using methods which do not involve relativity at
all, although it is even more debatable whether these should be deemed a form
of time travel
So is time travel possible?
One
possibility, although it would not necessarily lead to time travel, is solving
the mystery of how certain particles can communicate instantaneously with each
other faster than the speed of light.But can there really be such a
unified theory? Or are we perhaps just chasing a mirage? There seem to bethree
possibilities:
1. There
really is a complete unified theory which we will somedaydiscover if we are
smart enough.
2. There is
no ultimate theory of the universe, just an infinite sequence of theories that
describe the universemore and more accurately.
3. There is no
theory of the universe events cannot be predicted beyond a certain extent but
occur in a random and arbitrary manner.
CONCLUSION
While
time travel does not appear possible at least, possible in the sense that the
humans would survive it with the physics that we use today, the field is
constantly changing. Advances in quantum
theories could perhaps provide some understanding of how to overcome time
travel paradoxes.The possible existence of time
machines remains an open question. None of the papers criticizing the two
proposals are willing to categorically rule out the possibility.
Nevertheless, the notion of time machines seems to carry with it a serious set
of problems.so on the conclusion Time
travel may be theoretically possible, but it is beyond our current
technological capabilities.
REFERENCEs
·
Hawking, Stephen. (1988). A Brief History of Time, 9, 72-81.
·
Brier, B. (1973). Magicians,
Alarm Clocks, and Backward Causation, Southern Journal of Philosophy, 11, 359-364.
·
Wells, H. (1985). The Time Machine.
·
Crichton,Micheal
(2003). Timeline, 2, 27-63.
·
http://www.dailymail.co.uk/home/moslive/article-1269288/STEPHEN-HAWKING-How-build-time-machine.html
www.google.com
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