# WHAT EXACTLY IS TIME TRAVEL AND SOME THEORIES

Time travel, moving between different points in time, has been a hot topic in science fiction for decades. In the franchise from Doctor Who to Star Trek and Back to the Future, people got into some kind of car. They reach the past or the future and prepare for new adventures. They all have their own time travel theory.

However, the reality is more confusing. Not everyone has the same opinion, so, some scientists believe that this idea of time travel is impossible. Some people even say that time travel is possible. For anyone who decides to do so, this attempt is fatal.

## WHAT EXACTLY IS TIME?

Although most people think time is a constant, the physicist Albert Einstein showed that time is an illusion; it is relative—depending on their speed in space, different observers may have the difference.

For Einstein, time is the “fourth dimension”. The space is described as 3D sand, which provides travelers with coordinates indicating the location, such as longitude, latitude, and altitude. Time provides another coordinate, one direction, although usually it only moves forward (in contrast, the new theory claims that time is “real”).

Einstein’s special theory of relativity states that time slows down or speeds up depending on the speed of your movement relative to other objects. As the speed of light approaches, the people on the spacecraft are much older than their twins. Even according to Einstein’s general theory of relativity, gravity can change time. Imagine a four-dimensional structure called space-time.

When something of quality falls on this piece of fabric, it will dent or twist in space and time. Moving objects on a curved path, this kind of space curvature is called gravity. Both general relativity and special relativity have been tested using GPS satellite technology, which has a very accurate clock.

The speed of satellites on Earth relative to observers on Earth causes the uncorrected clock to increase by 38 microseconds per day. (Engineers calibrate to explain the difference. In a way, this effect called time dilation means that time travelers returning to Earth are very, very young than their identical twins on Earth.

## ALTERNATIVE THEORIES ON TIME

Although Einstein’s theory seems to make time travel difficult, some groups have proposed alternative solutions for jumping back and forth in time.

### INFINITE CYLINDER

The infinite cylinder astronomer Frank Tipler proposed a mechanism (sometimes called a Tipler cylinder) in which matter 10 times the mass of the sun must be picked up and then rolled into a very long but very dense cylinder.

### BLACK HOLE

Another possibility is to allow the spacecraft to move quickly around the black hole, or to artificially create this state with the help of a huge rotating structure.

## Time machines

It is typically understood that traveling forward or back in time would need a tool — a machine — to require you there. machine analysis usually involves bending frame of reference up to now that point lines flip back on themselves to make a loop, technically referred to as a “closed time-like curve.”

To accomplish this, time machines usually are thought to wish an exotic kind of matter with supposed “negative energy density.” Such exotic matter has eccentric properties, as well as getting the other direction of traditional matter once pushed.

Such matter may on paper exist, however, if it did, it would be a gift solely in quantities too little for the development of a machine.

However, time-travel analysis suggests time machines are potential while not exotic matter. The work begins with a ring-shaped hole engulfed among a sphere of traditional matter. within this ring-shaped vacuum, the frame of reference may get bent upon itself victimization targeted attractive force fields to make a closed time-like curve to travel back in time, an individual would race around within the doughnut, going more into the past with every lap. This theory includes a variety of obstacles, however.

The attractive force fields needed to form such a closed time-like curve would need to be terribly robust, and manipulating them would need to be terribly precise.