Reality and Imagination:- Time Machines
This article is a part of a series on articles on Time Machines and Teleporters. This is article 2/2.
The last time we ventured into the world of science fiction, we explained teleportation. Now lets head towards another aspect of fiction that has captured millions of minds, and find out how, Time Travel is very different, and paradoxical to teleportation than you think.
Is Time Travel Possible?
The answer given by theoretical physicists is yes! But, there is a catch. We cant hop on into a delorean or a TARDIS like Marty McFly or Doctor Who and go where ever we want in time. Infact, the only possible way that time travel can be obtained, without much fuss (and I really mean it. You may think it is impossible by the time we reach the end of this paragraph and I say that in sarcasm) is by using special relativity. Remember that in special relativity, the faster you move to the speed of light the slower time will elapse for you and for you only. This, as we discussed, is due to something called the Lorentz Dialation or Lorentz Contraction. This is where it comes in clutch. Imagine that you are selected by the United Nations Space Command (the UNSC) to accompany and assist Master Chief and his team of Spartans to take over and disarm the Intergalactic Nuclear Halo Ring. You use the UNSC ship Pillar of Autumn’s Slipstream to go the Alpha Halo, defeat the covenant and the Flood fleets there and disarm it’s internal mechanism. But, all hell breaks loose when Cortana, in order to carry out her evil plan, awakens the Arbiters and also escapes through a ship she originally hid there, and also destroys your Slipstream. You run for your life, and manage to set the ship to on course to Earth at the speed of about 99.9999999999995% the speed of Light. You manage to reach Earth, and are releived to see that it is safe from Cortana, who has been finally defeated, but the one thing you notice is that the news channel broadcasting the news shows a date about 6 million years into the future. You have become a time traveller, just by accelerating yourself near to the speed of Light. This insight, was also mentioned in Einstein’s theory of general relativity, but it is understandable how something this big was not the talk of the town back then, as with General Relativity(more on that in the next series), Einstein had once again changed our premonition of space and time. Of course, it would be impossible for us to reach a speed that fast, but this is the only way to time travel without creating much of a fuss.
What about Time Travel to the Past?
As you can see, special relativity allows time travel to the future, but what about the past? Well that is pretty paradoxical, but, there is a way. Building up on General Relativity, Einstein realised that when an object, such as the sun, rotates, it drags space time with it. And as Gravity is woven into the fabric of space itself, it basically is responsible for the drag we experience. So, in 1949, Kurt GÕdel, one of Einstein’s collegues, imagined an infinitely long cylender, one that has a defined radius, but an infinite lenght, and rotated it. He calculated that from the drag, the spacetime around the cylender would, in theory, arranged in such a way that if you would start a journey at 11 AM, you would make a full circle and see yourself starting the journey at 11 AM, because you have just gone into something, upon further pondering by physicits, has been named the “wormhole”. You may remember that wormholes are used extensively for travel through space, like in the movie Interstellar, but they can be used for travel to the past too, surprisingly, by using special relativity.
Imagine that it’s Master Chief’s Birthday, and since your reputation as a capable and smart spartan/technician has earned you a promotion, you have your own small spaceship, and decide to get chief his favorite Andreomedan Fish Chips. Your sister, a snappy one, wants to see the Andreomeda, and insists that you take the wormhole with you. Imagine that the wormhole is a meter long. So you blast away in your spaceship, your sister talking to you as you zoom off into intergalactic space at 99.99999995% the speed of light. When you do reach the Andreomeda, your sister is taking in the view, and when you do get your Andreomedan Finger Chips, you zoom back to earth. Keep in mind that the lenght of the wormhole never changes, its still a meter. Now, you land in DC, but once again, you see a date of 4 million years into the future. Your sister explains using her newfound appreciation of time dialation what had happened, and then you hop into the wormhole, and go back to your sister, 4 million years into the past. As you can see we have travellled into the past, but there are several challenges, which we will tackle next, and ask the natural question- Can we make a Wormhole time machine?
A Few Caveats
There are a few problems with the wormhole time machine, which directly are obstacles to the invention of the wormhole time machine. The first one is the wormhole itself. Although theory predicts that there is atleast one of them, they havent been detected. The larger part of the community believes that they can be formed in Particle Smashers or Particle Accelerators as the result of high speed collisions. But their observational evidence remains a null. Another problem is that even if they can be produced by smashing fundamental particles together, they would be too small for us to walk and hop on through. Another thing is that since a worm hole hasnt been discovered, we dont know what’s inside of it. Again, theoretical predictions suggest that there must some anti-matter in them, such as positrons, and it will be very unstable, collapsing in about a milisecond. However, many physists, such as Stephen Hawking, have suggested that there mush some amout of dark matter present in them too, so that the collapse is countered by the negative/repulsive gravity and make the wormhole somewhat more stable. But the biggest problem of them all is that there is a limit to where we can go into the past. The limit is set at the exact time that the wormhole was created. As from the Fish and chips example, the mouth of the wormhole remains fixed at your house, and you are moving relative to it. Thus, if you created it at 11 AM, you cant go back 4 Million years and an hours, or to 10 AM of the date you left for Andreomeda. This is the biggest challenge we are facing in the making of time machine.