Through out my life I have heard many people say, “If I knew then what I know now” or  “If I could do it all over again”. I suppose many people have pondered at one point or another, what it would be like to travel in time. As a kid I wondered what it would be like. I never thought very much about the science behind it, or whether or not it was even possible, I just knew I wanted to build a time machine.

By Scott Lenig
2009-08-08

I recall several times digging around in my parent’s garage, looking for tools and knick-knacks that look like they might belong on a time machine. However, despite my scientific initiative, my parents always thwarted my efforts before I was able to get the engine off of our lawn mower. I was left to simply contemplate what time travel is all about.

I wondered, is time travel really possible? Is there a science behind it all? I guess if you think about it, we are all time traveling right now. Only it is just no fun moving through time at the simple pace of one second per second.  Let’s face it, when we fantasize about time travel we dream of going hundreds, maybe even thousands of years into the future or past.

Well, Time travel is possible. Scientists have even known the formula for over a century now. If one mention’s the word “Scientist,” Albert Einstein is often the first name that comes to mind, and for good reason too.

In 1905 when Einstein was just 25 years old he published his special theory of relativity. In his theory the central idea is that time is elastic. Essentially time can stretch and shrink. I can sense the readers out there thinking to them selves “How exactly can time stretch and shrink?” Well, the answer is relatively simple. All you have to do is move really fast.

You see according to the special theory of relativity, the exact amount of time it takes you to get from one spot to another depends on how the observer is moving. In other words, the faster you move the faster you get there.

But just how fast can one move? Science shows that we cannot move at the speed of light (186,000 miles per second). We cannot because the faster an object moves, the more massive it becomes and the more massive it becomes the more energy is required for it to build speed. Simply put, collecting enough energy to go the speed of light is just out of the question.

Light is an interesting subject to think about. The nearest star to our planet is about 4 light years away from us. Traveling at 186,000 miles per second it takes that light 4 years just to reach earth. This means that at night when you go outside and look at the stars you are actually looking into the past. The light that you are seeing from those stars actually first shone years and years ago.

Our own galaxy is somewhere around 100,000 light years across. So using conventional travel methods it would take a whopping 100,000 years to go from one side of the Milky Way to the other, That is of course, if we were able to go the speed of light.

At least that is how long it would seem to take if we were watching from here on earth. To the Astronaut it would seem to have taken a much shorter amount of time. Why? Because time is stretched by speed, the faster you move the more time slows down, or as I said before, the faster you go the faster you get there!

To quote the book How To Build Time machines by Paul Davies “ In a spaceship traveling at 99 percent the speed of light, a trip across the galaxy would take just 14,000 years. At 99.99 percent of the speed of light, the gain is even more spectacular: The trip lasts a mere 1,400 years. If you could reach 99.999999 percent of the speed of light, the trip could be completed in a human lifetime.”

To further explain in more understandable terms picture this; here we are in 2009 and you and your friend have acquired a space ship that can go 99 percent of the speed of light. Your friend gets in the ship and takes off at near the speed of light. They travel 10 light years then turn right around and comes right back at the same speed. When their trip is over, only three years have gone by for them. But here on earth it is now the year 2029. It took your friend ten earth years to get there and ten earth years to get back but because she was the one in motion only 3 years have gone by for her.

In a way your friend has just time traveled 20 years into the future and it only took 3 years. Now let’s just hope your friend does not change their mind and decide they want to go back in time so things can be the way the used to be. If that is the case it may seem that your friend is out of luck. For high speed motion is a one-way ticket to the future.

But is there a way to get back? The short answer is yes. But what is that way? In 1937 a man named W.J van Stockum published a paper in the Scottish scientific journal. Van Stockum used Einstein’s work to figure out what would happen if an object went into orbit around a rotating cylinder. What he learned was that if this cylinder spun fast enough the object could return to the time before it even left. What this means is that a closed loop in space is also a closed loop in time.

When I first heard about this I wondered why no one really knew much about it. It seems like such a revolutionary discovery. Then I realized the flaw in Van Stockums logic. In order for his idea to work, this cylinder would have to be infinitely long.

About 10 years later however, another person found a much more realistic way of traveling into the past. An Austrian logician named Kurt Godel. Godel learned that if the entire universe were rotating, it should be possible to find orbits in space that actually spiral back into the past.

All though his work in this area was meant more as a simple curiosity than a serious look into the matter, his work slowly led scientists to look into something that was coined “Einstein-Rosen Bridges”, better known today as wormholes.

Worm holes open up the possibility of traveling anywhere (or when) in the universe by shortening the distance between point A and point B rather than shortening the amount of time it takes to get there. This works because to open a wormhole is to fold the universe in on itself.

Think of it this way. Imagine the universe as a piece of paper. On one end of the paper is a dot. That dot is earth. On the other end is a planet that we are interested in exploring. Well this planet is millions of light years away so by conventional means going there is out of the question. Fold that piece of paper in half so that one planet is right above or below the other and you have just shortened the distance between the two by a great amount and therefore have made it possible to go there.

Opening a wormhole loops the universe on itself there by shortening the distance between two objects and just as Van Stockum wrote, a loop in space is also a loop in time. To loop time is to be able to go to any time you wish.

What this all means is that with the help of rapid movement and high speed your friend can travel into the future, and with the help of a wormhole your friend can also go into the past.

As you see, scientists have known how to travel through time for many years. The only thing that has kept us from doing so is a lack of technology. The question is will we ever gain this technology and if so how will it affect the universe and our daily lives? Only time will tell.


[edit on 8-8-2009 by gimme_some_truth]

s&f
amazing post, the bit about 99.999999% the speed of light was mind-blowing
and the bit about the travel 20 years into the future.

my favourite thread for quite a while

An excellent summation on time travel possibilities. It helped me to understand the concepts behind the theories quite a bit more than I already did.

S & F

Very cool thread. I always had a hard time understanding some of those concepts in physics and you made them very clear and comprehensible. Right on!

So, if we, the laymen, can already understand the true possibilities of time travel, I wonder if people in the "know" aren't already trying or testing the possibilities out. Maybe they are already messing up with the timeline. Of course something like that would be abovetopsecret. Imagine the reactions from the masses! Imagine our reaction!

I'm very interested in the philosophical issues that spring from time traveling.
If one person in the present travels to the past how would that affect the present? Would there be two different presents? If so, it seems like the traveling would be kind of pointless except for the traveler. What are your thoughts?

Originally posted by Geladinhu


I'm very interested in the philosophical issues that spring from time traveling.
If one person in the present travels to the past how would that affect the present? Would there be two different presents? If so, it seems like the traveling would be kind of pointless except for the traveler. What are your thoughts?

Ah, all very good questions. While I can ultimately only speculate I will gladly share with you my thoughts.

I imagine that it would be possible to alter the present or future by going into the past and changing things. Your mere presence in the past would change the future I would imagine.

There would be a big ethics issue as well. I can see people being tempted to go back in time trying to change certain things. Imagine if you could go back in time and kill Hitler before he ever had a chance to wreak havoc on the world. At the same time, imagine if a person went back in time, knowing what they know now with the intent of changing the past so that Hitler won... Yikes.

I do believe there are multiple "presents" ( Realities) happening at once. String theory suggests a total of 11 demensions. Perhaps there is a reality that has only one demension and another with two and as you know, ours has 3. String theory suggests the exsistence of an infinite number of paralel universe all existing at the same time and in a way, in the same spot.

I do not know much about string theory but I am certain you can find the answers to your question within that theory.

Hmm,perhaps I will learn about string theory and write about that...

Originally posted by Raider of Truth


hope we as a whole can manage this one day

Now that would be truly amazing. It may be a long way off, but I bet we as a species will manage this one day.

Originally posted by james420
s&f
amazing post, the bit about 99.999999% the speed of light was mind-blowing
and the bit about the travel 20 years into the future.

my favourite thread for quite a while

completely agree. I dont post on here often but have been reading for over a year and i have to say...wow. way to explain it in simple terms. How cool would it be to be able to explore some far off planet for a few years and when you got back to earth it was 100 years in the future!? Its like 2 dreams coming true at once. S&f sir

Ive always wondered about the danger of going BACK into time. Would the "craft" or materials utilised to get there still theoretically be in existance as they havent yet been invented yet. It'd be the same as a undiscovered Metal from 1000 years just suddenly appearing on Earth this very second, even though its not been found yet.

I also wonder about the dangers of ones "soul" so to speak, would we leave the person we was behind if we travel back in time and yet havent even been born yet. We'd effectively become a vegetable and 100% likely drop dead the second we emerge from the wormhole. The same can be said for teleportation, unless we can find ways of storing entire thoughts/memories/body controls then humans are unlikely to go back in time unless we develop A.I. beings to do our work for us.

i realise that you dont want or need know-it-alls in this thread, but i found your "friend in a spaceship" example unsatisfying. i offer the following:
_____

you see, einstein is describing a specific relationship of space and time.

for example: moving at the speed of light requires you to occupy all of space at all of time. (kinda like the star trek enterprise going into warp speed.)

moving at 0 speed requires you to occupy 0 space at 0 time . (as in a black hole.)

take a closer look at the black hole. near infinite density and a near absolute stop of the passage of time RELATIVE to us. if we were to witness a person crossing the event horizon of a black hole, we would watch over the course of our entire lifetime, as only a moment of their life passes.

on the other hand, for the person whom is moving into the black hole, their own timeframe seems to go on as normal. but they will watch the entire universe and everything in it pass away in a flash.

______