Is time travel possible?

I hate to break it to you but no. AT LEAST of right now though! With not all scientists believing that time travel is possible, it is still considered a hypothesis based on quantum physics, also known as quantum mechanics.

I've literally never heard of quantum physics? What is it?

It's the branch of physics on the scale of atoms and electrons - the very small things in science. This fundamental theory helps to draw conclusions, based on how subatomic particles behave, about the physical world. It is based on three principles - quantized properties, particles of light, and waves of matter.

Quantum physics developed from classical physics, also known as classical mechanics after some measurements could not be understood. This is because classical physics only describe how things move at everyday sizes and speeds; therefore, couldn't describe very small particles as they travel extremely fast.

According to Live Science, "In classical mechanics, objects exist in a specific place at a specific time. However, in quantum mechanics, objects instead exist in a haze of probability; they have a certain chance of being at point A, another chance of being at point B and so on."

Okay, but how does this have anything to do with time travel?

Because any theory regarding time travel is based on quantum mechanics. Many thought experiments, experiments that take place only in the mind, have tested the limits of the quantum theory. Such groundbreaking experiments have resulted in new scientific theories being developed.

What groundbreaking experiments?

One such thought experiment is Schrödinger's Cat. In the experiment, a cat, poison, a Geiger counter, radioactive material, and a hammer are inside a sealed container. When the radioactive substance decays, the Geiger detects it, causing the hammer to smash the poison, thus killing the cat. However, radioactive decay is a random process so it's impossible to predict when the poison will be released.

Until someone opens the box; therefore, observes the system, it's impossible to predict if the cat is alive or dead. Thus, until the system collapses into one configuration, the cat will, as Schrödinger put it, be "living and dead ... in equal parts" until it is observed. As a result, one can only assume all possible states the cat can be, rather than making a specific prediction of the status of the cat. However, once someone opens the box and sees the cat, that person would know if the cat is alive or dead. With the knowledge that "the cat is alive," or "the cat is dead," the cat could no longer exist in both states.

This experiment proved that the Many Worlds interpretation, a theory that holds that there are many worlds which exist in parallel at the same space and time as our own, is feasible.

This is relevant because…?

According to National Geographic, "In any physical system, without observation, you cannot say what something is doing," says Martell. "You have to say it can be any of these things it can be doing—even if the probability is small." Therefore, anything is possible. For example, it is possible that I am a sophomore in college, as I never broke my foot; therefore, never took a gap year. Nothing is certain until you physically see it, thus interfering with the system of endless possibilities.

I'm still confused. Enlighten me.

Another thought experiment is quantum suicide. In the experiment, a man has a gun pointed at his head.

The gun is rigged to a machine that measures the spin of a quantum particle (quark). Each time the trigger is pulled, the spin of the quark is measured. If the quark is measured as spinning clockwise, the gun will fire. If the quark is measured as spinning counterclockwise, the gun won't fire.

The man pulls the trigger, but nothing happens. He pulls the trigger again and again, but the gun won't fire. Although it's functioning properly and loaded with bullets, the gun will never fire, making the man become immortal.

Rewinding to the beginning of the experiment, the man pulls the trigger the first time. The quark measures as spinning clockwise, and as a result, the gun fires, thus killing the man.

But how could the man be dead? The gun never fired when he pulled the trigger in scenario 1? The man is both alive and dead. Each time the trigger is pulled, the universe is split in two, continuing to split each time he pulls the trigger.

If an action has more than one possible outcome, then the universe splits when that action is taken. This holds true for actions not taken as well. Therefore, if one ever found him or herself in a situation where they could have died, then in a parallel universe, that person would be dead. However, a person cannot be aware of their other selves in parallel universes.

This experiment also proved that the Many Worlds interpretation is theoretically possible.

And this relevant because…?

According to HowStuffWorks, highly respected physicist Niels Bohr said, "When we observe a quantum object, we affect its behavior. Observation breaks an object's superposition and essentially forces the object to choose one state from its wave function, the sum total of possible states of a quantum object."

Okay so based off these theories, time travel could be possible. How?

There are two widely known hypothesizes within the scientific community that would permit time travel. Such hypothesizes are accepted as they are based on Albert Einstein's theory of gravity and theory of relativity, which have been proven right.

Einstein's theory of gravity allows for the possibility of wormholes – a bridge connecting one location to another, allowing something to travel from any location in the universe to another.

If one put the openings of a wormhole near a black hole, then the time of the two openings will not take off at the same rate, causing whatever passes through the bridge to travel from one moment in time to another.

The catch is that it would only work in traveling forward as it would be impossible to go back further in time than the point at which the wormhole was created.

So, we could only travel to the future?

Not necessarily. Einstein's theory of relativity shows that time passes at different rates for people who are moving relative to one another. However, the effect only becomes large when traveling very, very fast.

Let's say there are two twins. One stays on Earth. The other leaves Earth in a spacecraft that travels at lightspeed. When that twin returns to Earth, (s)he would be younger than her/his twin that remained on Earth. This is because time would pass differently on the spacecraft, due to it traveling so fast than on Earth. If only a few years passed onboard, many years would have passed on Earth. This scenario is known as the twin paradox.

This concept of elapsed time measured by two observes is called time dilation.

A modern example of time dilation at work involves GPS satellites. The GPS chip in smartphones works due to the 24 satellites that orbit Earth. They're able to triangulate one's location from figuring out how long it takes time-stamped data to transmit to and from the smartphone.

However, when building this system, scientists realized that the clocks on GPS satellites ran 8 microseconds a day faster than clocks on Earth due to how fast they're traveling - 9,000 miles per hour. Despite it being such a small difference, it's a big enough difference to disrupt location data, making scientists adjust GPS technology to run on slightly slower clocks to account for the time difference.

Therefore, this theory has been proven to work in traveling to the future. However, it wouldn't work for an object – or person – to travel a significant amount of time in the past or future as it would require them to travel faster than light.

The existing laws of nature don't prevent something from being able to travel faster than light, however, that doesn't mean it is possible. BUT maybe it is possible, and just no one has a clue on how. Maybe, it doesn't follow the rules of our existing theories. After all, it's hard to understand traveling faster than light when considering our existing theories.

That sounds cool and all, but why would someone want to time travel?

Because of how many rewards it could present. What if a time traveler saw the effects that automobiles would eventually have on our planet? What if someone was able to witness the specific effects of pollution and global warming would have on the environment? How might that change people's minds on what forms of transportation they use? How might that change people's minds on living an eco-friendlier lifestyle?

A journey into the future could obtain medical advancements, including new medicines, treatments, and surgical techniques, allowing people to live longer, healthier lives. In addition, time travelers could acquire knowledge of the future of the world in general, enabling him or her to warn the time (s)he came from of natural disasters, geopolitical conflicts, epidemics and other events of worldwide importance. Additionally, a time traveler could resolve historical debates and/or confirm whether certain events happened in the past. For example, did Lee Harvey Oswald act alone in killing John F. Kennedy? Time travel could answer this question. Also, a time traveler could prove or disprove religious beliefs. Likewise, a time traveler could have in face-to-face encounters with influential, preeminent individuals such as Jesus, Buddha, Napoleon or Cleopatra. This could easily change the world's perceptive on various topics. The world itself could easily physically change with time travelers bringing back objects from the past, such as extinct special or dead languages.

With that said, why wouldn't we want to time travel?

It could have dire consequences. What if the wrong people got ahold of such technology? What if individuals exploited it for personal gain? For example, a person could travel to the future just to see the winning numbers of a jackpot lottery to become wealthy. What if terrorists used time travel to plan out future attacks? How might that change the economic and political stability of every country?

Anything a traveler altered in the past would have to remain consistent with the future from which (s)he journeyed. Changing the past would change the future, creating a casual loop. This is known as the paradox effect. Such loops though would only pose problems if changes in the past brought unwanted changes in the future that the traveler came from.

The pros sure seem to outweigh the cons. How much could time travel really affect life as we know it?

It could cause people to cease to exist. How? Let's say there's a woman named Kelly. Kelly's first husband dies in a car accident. His name was James. She had two kids with him. She soon meets a man name Leo at some bar and they hit it off. They get married and have two kids together. Somehow time travel is deemed possible and easily accessible, so she decides to go back in time to save James. The idea sounds great. Two lovers reunited.

But…?

When she returns to the present, Leo and the two kids she had with him are gone. Where did they go? Well, Leo could be married to some other woman as he never met Kelly, and the kids could no longer exist as saving James could result in her never meeting Leo; therefore, never having two kids with him. BUT the kids she had with James before he died do still exist as nothing with that changed.

Wait, what?

For example, in NBC's hit series Timeless, the main female protagonist, Lucy Preston, loses her sister as traveling back in time causes her to cease to exist. Resiliently having to save all the passengers aboard the Hindenburg, Irene Doehner, a survived passenger's granddaughter marries Henry Wallace, Amy Preston, Lucy's step-sister's father. Furthermore, since this marriage prevents Wallace from ever meeting Carolyn Preston, Lucy and Amy's mom, Amy Preston is never born.

Okay, so what additional effects could it have?

It could cause history to dramatically change; therefore, change the present. How? Let's say someone is extremely racist and wants to make African Americans slaves again because they believe whites are supreme. To accomplish this, that person travels back in time to make sure the Confederacy was victorious in The Battle of Gettysburg and Vicksburg, allowing the South to be victorious in the American Civil War.

Which could result in…?

The United States could become a series of smaller countries rather than one whole one, with the North thriving much more than the South in years to come as they were on the path for more intensive industrial and urban development. Slavery could not end in 1863; therefore, other nations, such as Brazil, could not emancipate their slaves, as they did, after witnessing the bloody confrontation of the American Civil War. Overall, slavery could continue to be a vital part of the social and political structures of large countries in the Western hemisphere.

Example??

One show that portrays this idea of the past dramatically being changed; therefore, dramatically affecting the future is Amazon's original series The Man in the High Castle. In it, Franklin D. Roosevelt is assassinated in February 1933 when Giuseppe Zangara opened fire during Roosevelt's speech in Miami, Florida. In reality, Zangara shot five people and killed the mayor of Chicago. But in this timeline, since Roosevelt was dead, there was no New Deal, Manhattan Project, and Lend-Lease Agreement; therefore, England is defeated, and America becomes even weaker and isolated with the attack on Pearl Harbor. Lastly, with the Nazis never getting defeated in 1945, they drop a hydrogen bomb on Washington, D.C., causing the government to surrender soon after. This causes the United States to be ruled over Japan and Germany as the Axis powers win World War II.

Other consequences?

Yes! Because, sometimes when people solve a problem, a new problem can arise.

I'm lost. What does that even mean?

Let's say someone's loved one died in World War II, causing them to travel back in time to an Upper Austrian town at the turn of the century to kill Hitler as a baby. Without Hitler, World War II could never happen.

But…?

If World War II never happens, women could still be stereotypical housewives who have no say in society. Feminism could be much less prominent as it is today since the second wave feminism started after World War II ended. This is because the war changed women's roles by altering their place in society. The war gave women more freedom in their lives since it forced men to leave behind many of their responsibilities. With their wives being obligated to take care of these

responsibilities, many unique opportunities became available to them, including the option to work.

Is that it?

No! Sometimes when someone tries to prevent something, that person causes that "something" to happen.

That makes no sense. Please explain.

One show that portrays this idea is Syfy's popular series 12 Monkeys. Cole, a man from the post-apocalyptic future, time travels to locate and rid the world of the source of the plague that will eventually annihilate humanity. However, in doing so he becomes the reason why humanity is on the brink of extinction. The plague came a corpse from the future that had been time traveled to the Himalayas in the late 9th century. To save the world, he must remove himself from all of the time so that time travel was never invented; therefore, the corpse never existed.

Bottom line?

Changing the past or witnessing the future can result in unexpected consequences. Such ramifications could change the entire world without anyone knowing it. Physicist Paul Davies describes unrestricted time travel that "form[s] a complete loop to both the past and future -- would ultimately lead to total mayhem."

Hence, why time travel is so compelling in fiction.

Because of how mysterious it is?

In one perspective, yes. The ability to travel through time is many people's favorite storyline in fiction as it is wrapped in so much mystery. There's so much that humans don't know, forcing people who fear what they don't understand and inspiring people who are passionate about exploring and learning new things to uncover the unknown.

Fiction based on time travel is often filled with clues and twists. Anything is possible when time travel is involved, making it that much harder for people to solve the mysteries of such a piece of fiction. However, this is what makes time travel fiction so fascinating as it's never predictable; therefore, never boring.

The key to making any piece of fiction entertaining and engaging are good twists and/or unpredictable plot points to screw with your mind, leaving your mind blown.

Is that the only reason?

Such pieces of fiction often pack an emotional punch as they are full of emotion, life and death circumstances, and real-world implications.

They make you think about what you would do if you were put in the characters' shoes. Would you do anything if you knew you could not exist in a blink of an eye? Would you travel back in time to save humanity if it meant you, or someone you love, would never be born? Would you intentionally change history to solely benefit yourself, even if it meant others getting hurt in the process?

Any other compelling arguments?

Everyone has regrets; therefore, everyone has wished at least once that they could travel back in time to fix some type of issue or mistake, they made. This makes such pieces of fiction much more appealing as they draw on people's deepest desires and wishes. After all, a "what if" scenario always intrigues people.

Has science fiction influenced modern day society?

Absolutely. Multiple fields have improved because of the ideas presented in the science fiction genre. It has influenced the creation of innovative technology and inspired future innovators to think "out of the box."

The "communicator" in the hit television seriesStar Trek allowed Captain Kirk to wirelessly contact other starships throughout the galaxy. Sound like something you might have in your pocket? A cellphone does the same thing as the "communicator," except for that it only works wirelessly on Earth, not throughout the galaxy.

Large screens on the walls and interactive games amused people in Ray Bradbury's Fahrenheit 451. Sound like something you have might have in your living room? A big flat screen TV does the exact same thing – provides entertainment.

Space travel has been in all forms of science fiction. But one example includes a group of astronomers who travel to the Moon in a spacecraft in A Trip to the Moon directed by George Melies. Sound like something you learned in school or possibly watched happen? The Moon Landing via Apollo 11 was the first spacecraft that allowed two people to travel to our Moon.

Electric cars were present on the planets in the well-known Star Wars saga. Sound like something you might have? The vehicles coming out in the automobile market today are powered by solar energy and electric currents.

Conclusion?

Science fiction has allowed people to come together, as their longing for knowing more about the universe unites them, to predict and create the future. As works of science fiction often paint a picture of what the future could look like, many people then become inspired to help make that future come true. With that said, science fiction is becoming less and less a fantasy, and more and more reality.