A Brief History of Time 3

Well, here it goes. Time travel. Time travel is probably the most disputed and most popular topic about the laws of our universe and the effects of time. People have long wondered if you could go back in time and change things that you did wrong. People have also wanted to go into the future to see what's in store for the rest of their lives. In my opinion, time travel is physically impossible, at least for living creatures! However, many attempts have been made at creating a possibility to travel time.

One of the theories among common people is that traveling faster than the speed of light will allow you to go back in time. I believe that not only is it physically impossible for anything to travel faster than the speed of light, but I argue that even if we could, it would not be going back in time! Take a look again at Dr. Hawking's fabulous light cones diagram.
As we look at the light cone, over time, light travels farther and farther. An object slower than light can only travel inside the boundaries of the light cone. However, something faster than light can go outside the light cone. Here's the problem. Even though you are going outside the light cone, you are still going forward in time. No matter how fast you get, you cannot go so fast that you go back in time. In fact, the only way to move downwards on the time axis is to travel at a negative speed! That means you would have to travel a negative distance over time (which is impossible) or that you would have to travel a distance in negative time (which is the item being disputed). Nothing can go anywhere in a negative amount of time though.

Something that is also missing in this example is that if you were going backwards in time, what makes you think you can go forward again? So now there is this idea that you can switch between negative and positive speeds at any time, traveling negative or positive distances at will! I highly doubt this is possible, and I would like to hear someone tell me how to travel at a negative speed!

I think that theory is pretty much destroyed in my mind. However, there are many more interesting theories out there. One such theory is that of a wormhole, and wormholes are becoming a more popular theory. Wormholes connect two areas in space time in a shorter distance than three dimensions allow. Space time is said to be curved, and wormholes supposedly could connect two portions of spacetime as shown in this diagram.
The wormhole can take you to somewhere before many events have happened there! Here's the problem. A wormhole also moves you somewhere else in space. So, congratulations! You went back in time! But now you are stuck somewhere else in an earlier time period. Since light shows us what happens somewhere else, you may be going back i time, but you cannot change the past. You are actually still affecting the future of your previous location from your current location! Here's an attempt at a better explanation. Say I am on Earth right now on April 22, 2010. I am sucked through a wormhole and end up on the sun on April 14, 2010. If it takes light 8 days to get to the Earth, I am still technically only able to affect the "present" or the "future". I am not greatly familiar with wormholes, but what if this was the case? What if wormholes were still only able to take you back relatively, but not in actuality? This scenario I doubt has ever been examined. If wormholes can take you back in time, is it back far enough? Further research is required to answer that question.

Where are these wormholes? There are supposed to be microscopic wormholes that allow small particles of matter and antimatter to enter and leave our existence. This involves quantum mechanics, which is a very uncertain science. Experiments have shown particles to appear and disappear in a vacuum tube (that means no matter was inside, and no matter could get in or out through physical means!). Where do these particles come from? Scientists believe wormholes may be the answer, allowing particles to jump in and out of space and time. One key question. How come we do not do the same? Why don't wormholes appear in a person's brain and cause his memory cells to be whisked away to some other time period, resulting in the man forgetting where he left his house key? I suppose wormholes can only occur under certain conditions. One condition is thought to be in a black hole.

A black hole is a very complex system. Black holes will be covered more in depth in a later post, but for now, you only need to know the basics of a black hole. Black holes form when a star of a very large mass collapses on itself, creating a ton of gravitational force, forces so great, that even light cannot escape. This massive amount of gravity bends space time so much that it is said to create a singularity, or a point in which the laws of general relativity cannot mathematically explain the result. This is because according to relativity, the space time curvature would be infinite. Scientists believe this radical conclusion can be solved by entering wormholes. The problem with that is that the gravity would crush matter drastically, and you would have to travel faster than the speed of light to get through the wormhole.

Allow me to further explain why you cannot go faster than the speed of light. According to our current laws of physics (which I believe are very much correct) energy and mass are proportional. If you have two masses, one of 10 grams and one of 5 grams, the 10 gram mass will have more energy. Speed and mass are also related. The faster an object is traveling, the greater amount of mass an object has. Finally, speed and energy are related, because to move an object of any mass requires energy. As explained by Dr. Hawking, as an object picks up speed, it acquires more mass. As it picks up mass, the object needs more energy to increase its speed. As you get closer to the speed of light, the object needs more and more energy to speed it up because it is accumulating more and more mass. An object of any mass cannot reach the speed of light because an object would acquire an infinite amount of mass in the process, requiring an infinite amount of energy to make the object go faster. The only thing that can travel as fast as light is something with no mass, such as a particle of light (amazing!).

That, however, does provide evidence as to why wormholes only affect small particles! Because only a small particle of no mass can travel fast enough to go through a wormhole! However, this also shows that humans cannot physically travel time through a wormhole (sad face). Humans have mass, so that ends that! Also, a human would be absolutely destroyed in a black hole! The intense amount of gravity would rip a human being to shreds! Say goodbye to wormhole time travel (for humans, anyway).

A few final thoughts. If we could travel time, then how come we haven't seen any beings appear? Or, even more intriguing, are history professors of the future among us, learning what they can about us to tell their students in the future? Are they the aliens that we supposedly see? Are they what we interpret as ghosts? How come we aren't all destroyed? Most likely if we could travel time, someone would ruin it for everyone and destroy the world with nukes before humans even existed! Dr. Hawking makes a point that there could be multiple histories, and if you go back in time, you are creating another history. However, that would mean you live more than once, or if time travel occurred in the new histories, you would live infinitely many times! I find that ridiculous! Therefore, I believe time travel is impossible for certain for a human being, and even if microscopic particles could travel time, it would have very little effect on humans. That is my current stand. If you have any other time travel theories or protest my reasoning for any of the above mentioned theories, comment and I may or may not respond.

A Brief History of Time 2

Very few people know and understand space time in its entirety, but you could probably ask any common person on the street if they have heard of the equation E=Mc squared and find that they have heard of it. Many people can tell you what the equation stands for, that energy is equal to mass multiplied by the speed of light squared. Some people also know that this equation comes from Einstein's theory of relativity. However, few actually understand what general and special relativity entail. In A Brief History of Time, Stephen Hawking helps us to understand what relativity is all about, and where even this well known theory has its weaknesses.

Einstein's Theory of Relativity is broken up into two parts: Special Relativity, and General Relativity. Special Relativity has to do with the light cones discussed in A Brief History Of Time 1. Those cones in special relativity are always the same anywhere in the universe in this theory. Any event can only effect other events that occur in the future light cone. So if the sun were to burn out, I will still wake up to the sunlight the next morning, and I will still go about my day as normal. That event cannot be effected by the sun, because it is too far away in space to be in the future light cone. However, eight days later, I will not wake up to the sun because that event is in the future light cone of the sun's burning out. Over time, the area in space that the light cone covers increases, and more events can be affected by the event of the sun burning out. However, Einstein did not take into account the force of gravity. When gravity is included, the theory of General Relativity is referred to.

It used to be thought that space time was smooth and continuous (space time being the four dimensional realm in which we live in). However, it has been shown by observing an eclipse that light is bent by gravity. If light is bent by gravity, then the light cones must also be bent, and so the general theory of relativity is created! If the light cones are bent, then space time supposedly must also be curved. It is said that the Earth orbits the sun elliptically because gravity causes the Earth to move along a curved space time track. Earth in space time is actually going straight, but we see it as curved. Because of this curvature, general relativity predicts that time should run slower near larger planets.

The idea that time can be slowed by the curvature of space time is a key point to general relativity, because in this theory, all things are relative to the observer. Distance, size, and even time depend on the observer's view of reality. The most intriguing relativity in my opinion is that of time, that depending on the observing, time may appear to run slower or faster. I think that the key word in this case is appear. A small insect may only live a day, but to that insect, that one day is a lifetime. Many scientists use this a reason to believe that we can go backwards in time, but I find that a relatively poor reason (haha, puns...). In a later chapter, Stephen Hawking puts forth the idea of real and imaginary time. The idea that imaginary time will continue at a steady rate while real time is curved and reversed and other interesting ideas. I think he has it backwards. The fact that all things are relative should imply that we believe in imaginary time! The real time is the one that continues at a steady rate. Let's face it, even though the small insect thinks one day is extremely long, we still see it die at our own rate. Just because the insect thinks it is a lifetime, does not mean it is right. I think that there is one absolute time that is the real time, and the way we experience this time is our imaginary time. Therefore, going back in time is not going to happen! Time marches on, and we can't change that, no matter how long our interpretation of reality thinks time is.

Next week we will discuss time travel in greater detail, and I will do my absolute best to trump any time travel theory that I can find! Send me your theories on time travel and I will do my best to provide evidence as to why they are false, or if they are possibly true, for what reasons it is possible using evidence from either A Brief History of Time or from other sources if necessary (but considering how much information is in this book, I should not need many other sources). Stephen Hawking discusses one time travel theory in great depth: wormholes. So many great time travel theories, so little time!

A Brief History of Time 1

The vast universe which we live in is full of questions. How did our universe begin, or did it even have a beginning. If it has a beginning does it have an end? What are the boundaries of our universe if any? And what about time? Does time have a beginning or end? What does time have to do with the whole scheme of things? Is time its own dimension, is it relative, or is it absolute? Can we alter time, or travel back to the past? Can we go into the future? So many questions that we may never be able to answer, but nevertheless we try to approach these questions with the best of our knowledge. One of the greatest minds in our world is that of Stephen Hawking, a very intellectual scientist and doctor who tries to answer these questions, or at least get us closer to the answers, in his book A Brief History of Time.

One of the many concepts pondered by many is the idea of time as a fourth dimension. For most of mankind's existence, we have only recognized three dimensions: length, width, and height. We can plot a point in a coordinate space using these three dimensions as shown below:

The three dimensions of length, width, and height are represented as x, y, and z axis respectively. But have you ever considered that when plotting an event in our universe, a point in space is not enough information. Consider this example. If you are walking down the sidewalk, then the event of you being in a certain position occurs in a specific space of three dimensions. However, you are no longer in that same position five seconds later. You are now farther down the sidewalk at a different location. To plot an event, the time is extremely important. We cannot plot an event in three dimensions because events often times only occur in certain positions at a certain time. Therefore, a fourth dimension, time, must be added. Dr. Hawking believes we cannot imagine a fourth dimensional object. However, I think we in our lives imagine things in fourth dimensional terms all the time. For example, recall that person walking down the sidewalk. If you think about it, it is in four dimensions, because time is allowing it to move. I think scientists are thinking too hard, coming up with objects like tesseracts that are supposed to represent four dimensional objects in three dimensions. Perhaps it is not so difficult as we make it seem.

Another way of thinking of time in three dimensions besides a tesseract, which i prefer, is shown here from Stephen Hawking's A Brief History of Time:

In this diagram, Space is represented on a two dimensional plane, while time extends upward through space, almost like a three dimensional space. You may be wondering what the cones are in this diagram. The cones represent light cones that are emitted from an event. For example, if the sun burnt out, we would not know it for another eight days. Why? Because light travels in a cone over time, and since we are so far away from the sun, it takes eight days for the "light cone" to reach us. All this cone really represents is that it takes time for an event to be seen in different parts of the world. As time goes on, the event affects more and more of space. This is the way I see it relate to our view of the universe. In our realm of 3 dimensional space, this light cone appears to be a sphere. Imagine looking at this diagram from above. It would appear to be a circle. Over time the circle would get bigger and bigger until it covered the entire space. Because space is represented in two dimensions on this diagram, it appears to be a circle, but in 3 dimensions, it is a sphere! Light from the sun goes out in all directions, acting as a sphere, so if it were to burn out, the following darkness would also be spherical.

One might ask what purpose this all has, and maybe there will be nothing gained other than a greater understanding of our universe. Nevertheless, over the course of this independent reading, I will attempt to explain what Stephen Hawking has to say about our universe and add input wherever possible. Often times, I will have to enter my own interpretations in order to make more sense of what Dr. Hawking is trying to tell us. I think that this kind of knowledge of how our universe works is very fascinating, and could show great importance to us in the future. If we know more about the universe, perhaps we can predict our future, and know more about our past. But with knowledge comes responsibility, and I have a bad feeling that the knowledge we may gain will in the end destroy us all. In attempt to predict the end of the world, we may cause it! A Brief History of Time is full of great questions, and many attempts at answering them, and I hope that as I proceed in reading it, I will be able to answer some of the many questions I have about time and the universe in general.

Independent Reading Day 7

I completed Pebble in the Sky by Isaac Asimov this week. Pebble in the Sky was an excellent book. It encompassed many areas of not just the future, but modern life. The book showed the greed and corruption of governments very well. It also introduced galactic life without ever leaving the Earth. I thought that this book was very clever.

The plot that is brought together in Pebble in the Sky is that the government on Earth uses Dr. Shekt's synapsifier on the biologists of the government. They used the biologists to develop biological warfare weapons against the rest of the world. Because Earth had been exposed to diseases such as the flu virus for so long, they became immune, but the Outsiders of the Galaxy do not have this immunity, so Earth has that advantage, and exploits it. The weapons are filled with disease, and the Galaxy will not be able to stop it.

The plot is ingenious. I was surprised that Earth would be able to have a weapon to take on the entire Galactic Empire! However, the Earth government was extremely greedy in this case. They would annhilate the entire Galaxy so that they could reign supreme over what? Just Earth anyways! Eventually, the galaxy would be recolonized, and Earth would once again be shoved off as a poor planet. Yet the government did not care, so long as they had power. I hope that Iran will not make that kind of decision with its nuclear weapons, just for power.