Why Going Faster than Light Leads to Time Paradoxes
Intro Space travel is something that fascinates
us all, scientists and civilians, alike.
So, there is little doubt that there are multiple theories that attempt to decode this problem
and make it much more efficient and achievable.
However, this comes with a set of challenges that scientists must attempt to explain before
any progress can be made.
One such challenge that is of particular interest is traveling faster than the speed of light
and all the side effects it may have.
Time paradoxes are one of the main problems that plague scientific theory when such a
discussion takes place.
Let's take a look at why going faster than light may lead to time paradoxes.
The Speed of Light The speed of light traveling through a vacuum
is exactly 983,571,056 feet per second.
That's about 186,282 miles per second — a universal constant known in equations as "c,"
or light speed.
According to physicist Albert Einstein's theory of special relativity, on which much of modern
physics is based, nothing in the universe can travel faster than light.
The theory states that as matter approaches the speed of light, the matter's mass becomes
infinite.
That means the speed of light functions as a speed limit on the whole universe.
The speed of light is so immutable that, according to the U.S. National Institute of Standards
and Technology, it is used to define international standard measurements like the meter, and
by extension, the mile, the foot, and the inch.
But despite the speed of light's reputation as a universal constant, scientists and science
fiction writers alike spend time contemplating faster-than-light travel.
So far no one's been able to demonstrate a real warp drive, but that hasn't slowed our
collective hurtle toward new stories, new inventions, and new realms of physics.
A light-year is a distance that light can travel in one year — about 6 trillion miles.
It's one way that astronomers and physicists measure immense distances across our universe.
Light travels from the moon to our eyes in about 1 second, which means the moon is about
1 light-second away.
Sunlight takes about 8 minutes to reach our eyes, so the sun is about 8 light minutes
away.
Stars and other objects beyond our solar system lie anywhere from a few light-years to a few
billion light-years away.
And everything astronomers "see" in the distant universe is history.
When astronomers study objects that are far away, they are seeing light that shows the
objects as they existed at the time that light left them.
This principle allows astronomers to see the universe as it looked after the Big Bang,
which took place about 13.8 billion years ago.
Objects that are 10 billion light-years away from us appear to astronomers as they looked
10 billion years ago — relatively soon after the beginning of the universe — rather than
how they appear today.
As early as the 5th century, Greek philosophers like Empedocles and Aristotle disagreed on
the nature of light speed.
Empedocles proposed that light, whatever it was made of, must travel and therefore, must
have a rate of travel.
Aristotle wrote a rebuttal of Empedocles' view in his treatise, On Sense and the Sensible,
arguing that light, unlike sound and smell, must be instantaneous.
Aristotle was wrong, of course, but it would take hundreds of years for anyone to prove
it.
It wasn't until Albert Einstein came along that we truly understood the nature of light.
Special Relativity Einstein's theory of special relativity unified
energy, matter, and the speed of light in a famous equation: E = mc^2.
The equation describes the relationship between mass and energy — small amounts of mass
(m) contain, or are made up of, an inherently enormous amount of energy (E).
Because energy is equal to mass times the speed of light squared, the speed of light
serves as a conversion factor, explaining exactly how much energy must be within matter.
And because the speed of light is such a huge number, even small amounts of mass must equate
to vast quantities of energy.
To accurately describe the universe, Einstein's elegant equation requires the speed of light
to be an immutable constant.
Einstein asserted that light moved through a vacuum, not any kind of luminiferous Aether,
and in such a way that it moved at the same speed no matter the speed of the observer.
Think of it like this: Observers sitting on a train could look at a train moving along
a parallel track and think of its relative movement to themselves as zero.
But observers moving nearly the speed of light would still perceive light as moving away
from them at more than 670 million mph.
That's because moving extremely fast is one of the only confirmed methods of time travel
— time slows down for those observers, who will age slower and perceive fewer moments
than an observer moving slowly.
In other words, Einstein proposed that the speed of light doesn't vary with the time
or place that you measure it, or how fast you are moving.
Therefore, objects with mass cannot ever reach the speed of light.
If an object ever did reach the speed of light, its mass would become infinite.
And as a result, the energy required to move the object would also become infinite, something
that is impossible.
That means if we base our understanding of physics on special relativity, which most
modern physicists do, the speed of light is the immutable speed limit of our universe
and is the fastest that anything can travel.
Time Paradoxes Science fiction loves the idea of "warp speed."
Faster-than-light travel makes countless sci-fi franchises possible, condensing the vast expanses
of space and letting characters pop back and forth between star systems with ease.
But while faster-than-light travel isn't guaranteed impossible, we'd need to harness some pretty
exotic physics to make it work.
Luckily for sci-fi enthusiasts and theoretical physicists alike, there are lots of avenues
to explore.
All we have to do is figure out how to not move — since special relativity would ensure
we'd be long destroyed before we reached high enough speed — but instead, move the space
around us.
One proposed idea involves a spaceship that could fold a space-time bubble around itself.
Sounds great, both in theory and in fiction.
Scientists have theorized that even if we can find a way to travel faster than the speed
of light, it may lead to some strange time paradoxes that are worth looking into.
One of these is the grandfather paradox.
It is a potential logical problem that would arise if a person were to travel to a past
time.
The name comes from the idea that if a person travels to a time before their grandfather
had children, and kills him, it would make their own birth impossible.
So, if time travel is possible, it must somehow avoid such a contradiction.
The logical inconsistency of time travel is a common theme in time-warping fiction, but
it's also of interest to philosophers.
In early versions of the grandfather paradox, some tried to argue that time travel was impossible
on logical grounds.
But contradictions such as the grandfather paradox don't mean that time travel is impossible.
The logical consistency of time travel largely depends on the concept of time, and physicists
have many different ways of conceptualizing time.
For example, if some laws of physics are considered probabilistic, rather than precisely determined,
it opens the possibility of multiple outcomes from a trip back in time, some of which may
not be contradictory.
Another thing to consider is an inconsistent causal loop.
While equally thought-provoking, this theoretical model of time travel is paradox free.
According to physicists, such a loop might play out like this: A math professor travels
into the future and steals a groundbreaking math theorem.
The professor then gives the theorem to a promising student.
Then, that promising student grows up to be the very person from whom the professor stole
the theorem, to begin with.
Then there's the post-selected model of time travel, which involves distorted probability
close to any paradoxical situation.
What does this mean?
In simple terms, this time travel model would make the grandfather virtually death proof
and some quantum fluctuation will occur to prevent a paradoxical situation from taking
place.
But then there's another possibility: The quantum theory that the future or past you
travel into might just be a parallel universe.
Think of it as a separate sandbox: You can build or destroy all the castles you want
in it, but it doesn't affect your home sandbox in the slightest.
In this instance, a person could travel back in time, kill their grandfather and face no
consequence in their original universe.
Outro These are just some of the theoretical problems
that may arise with the ability to travel faster than light.
However, such technology is still far from our reach, if it is even possible in the first
place.
If you liked this video, please also consider taking a look at this one which talks about
the strangest planet discovered in the universe by NASA.
Do you think time travel is possible?
Please share your thoughts in the comments section below.