Is time still "gold"?

Humans are humans. We make mistakes and learn from it. However, if you were given the chance, will you want to go back in time? In my view, time -travelling is one of the most fascinating concept in science so I decided to comprehend if it is conceivable.

According to physicist Albert Einstein, time is relative. As opposed to what most of us know, time is not constant because it can vary for different observers depending on your speed through space. Time is the “fourth dimension” on earth, together with a three-dimensional arena called space which offers coordinates — such as length, width and height —showing location. Time provides another coordinate — direction — although conventionally, it only moves forward. We are living in a four-dimensional fabric called space-time. Since it’s a fabric, it curves and bends depending on forces that acts upon it. In our case, a certain magnet or core attracts the fabric that causes a dimple or a bending of space-time and this force is called the gravity. (more technical terms coming up) Now, I hope you guys are familiar with the theories of relativity. These 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.  This resulted to a phenomenon called time dilation that enabled astronauts to travel in time. Yes! Astronauts are time travelers because as they travel in space they are very, very slightly younger than their own self if they have stayed on Earth.

However, aging and time-travelling are not the same. Some scientist say that you can only go back in time if you move faster than the speed of light which is impossible for a normal breathing person because you would have both infinite mass and a length of 0. While Einstein's theories appear to make time travel difficult, some groups have proposed alternate solutions to jump back and forth in time. First was the infinite cylinder or the Tipler cylinder by U.S. astronomer Frank Tipler. He has a simple recipe for a time machine: First take a piece of material 10 time the mass of the Sun, squeeze it together and roll it into a long, thin, super-dense cylinder – a bit like a black hole that has passed through a spaghetti factory. Then spin the cylinder up to a few billion revolutions per minute and see what happens. Tipler predicts that a ship following a carefully plotted spiral course around the cylinder would immediately find itself on a "closed, time-like curve." It would emerge thousands, even billions, of years from its starting point and possibly several galaxies away. There are problems, though. For the mathematics to work properly, Tipler’s cylinder has to be infinitely long. Also, odd things happen near the ends and you need to steer well clear of them in your timeship. However, if you make the device as long as you can, and stick to paths close to the middle of the cylinder, you should survive the trip! The second was balck holes. A black hole is a region of space from which nothing, including light, can escape. One said that when you come closer to it the time slows down. Physicist Stephen Hawking wrote in the Daily Mail in 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." But one needs to travel as fast as the speed light which is still impossible.  Next was called cosmic strings which makes time-travelling possible in theory because it is a narrow tube that 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. The last one was time machines that according to experts will only be possible with exotic matter that will make a double-shaped hole envelope that will affect the space-time fabric more than the gravity.

So is time-travelling possible? As of now the answer is impossible but hey, we once believed that the Earth was flat and the center of the universe right? However, let us just hope for the future where everything is possible.

Reference: http://www.space.com/21675-time-travel.html