Let, travel through time!

We all travel in time! For example, we travel one year in time between birthdays. And we are all traveling in time at approximately the same speed: 1 second per second. However, when we think of the phrase "time travel," we are usually thinking of traveling faster than 1 second per second. That kind of time travel sounds like something you'd only see in movies or science fiction books. Could it be real? Science says yes! Time travel is the concept of moving between different points in time. Time travel could involve moving backward in time to a moment earlier than the starting point or forward to the future of that point. Time travel has been a popular topic for science fiction for decades. The reality, however, is more muddled. To understand time travel we must understand what is time?

What exactly 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 that is direction although conventionally, it only moves forward. (Conversely, a new theory asserts that time is "real").

How do we know that time travel is maybe possible?

More than 100 years ago, a famous scientist named Albert Einstein came up with an idea about how time works. He called it relativity. Einstein's Theory of Special & General Relativity says that time and space are linked together. Einstein also said our universe has a speed limit: nothing can travel faster than the speed of light (186,000 miles per second). What does this mean for time travel? Well, according to this theory the speed of time depends on how fast you are moving relative to something else. The faster you travel, the slower you experience time. For example, if someone in a spaceship flies around the earth at the speed of light, that person would age much slower than a person back on earth.

Two types of time travel: Forward and backward time travel

Going forward in time is (relatively) easy. Going back is much harder. But Einstein’s theory of general relativity seems to allow it. Forward time travel: my time goes slower than yours (like aging slower than everyone else). Backward time travel: my time goes faster than yours (like aging faster than everyone else).

Different ways to travel through time

1. Speed: This is the easiest and most practical way to get to the far future – go really fast. According to Einstein’s theory of special relativity, when you travel at speeds approaching the speed of light, time slows down for you relative to the outside world.

2. Wormholes: General relativity also allows for the possibility for shortcuts through space-time, known as wormholes, which might be able to bridge distances of a billion light-years or more, in theory, different points in time. But wormholes collapse fairly quickly & would only work for tiny particles.  Technology to even create a wormhole goes beyond anything we have today.

3. Gravity: The next method is also inspired by Einstein. According to his theory of general relativity, the stronger the gravity you feel, the slower time moves. As you get closer to the center of the Earth, for example, the strength of gravity increases. Time runs slower for your feet than your head. To travel to the far future, all we need is a region of extremely strong gravity, such as a black hole. The closer you get to the event horizon, the slower time moves – but it’s risky business, cross the boundary and you can never escape.

4. Suspended animation: Another way to travel to the future may be to slow your perception of time by slowing down, or stopping your bodily processes and then restarting them later. Bacterial spores can live for millions of years in a state of suspended animation until the right conditions of temperature, moisture, food kick start their metabolisms again. 

5. Using light: Another idea put forward by the American physicist Ron Mallet, is to use a rotating cylinder of light to twist space-time. Anything dropped inside the swirling cylinder could theoretically be dragged around in space and in time, in a similar way to how a bubble runs around on top of your coffee after you swirl it with a spoon.

6. Using Time machines: A machine in which people or objects can be transported into the past or the future. 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. Though, at present, it only exists in science fiction stories & movies. If the true time machine would ever invent, it can only travel forward not backward. Because if it is capable to travel back in the past, it may create some inconsistent loop (paradox). Which physics doesn’t allow.

So if you wanted to create a fictional world involving travel through time, here are some rules by which you should try to play.

Is it possible for a human being to travel through time?

If we take an example of popular web series “Dark” then we get that throughout the series Dark explores the existential implications of time and its effects upon human nature. Also, it is showing hidden connections among four estranged families as they slowly unravel a sinister time travel conspiracy which spans several generations. So, yes, time travel is indeed a real thing. But it's not quite what you've probably seen in the movies. We can't use a time machine to travel hundreds of years into the past or future. That kind of time travel only happens in books and movies. But the math of time travel does affect the things we use every day. Under certain conditions, it is possible to experience time passing at a different rate than 1 second per second. Advances in quantum theories could perhaps provide some understanding of how to overcome time travel paradoxes. And there are important reasons why we need to understand this real-world form of time travel.