Time travel is a popular science fiction staple, from Back to the Future, to Dr. Who its use has captured the attention of many audiences. Although for now, time travel only exists in a fictional realm, there are many reasons why it could work. General relativity proposes that everything around us, space-time, is one set of dimensions. This suggests that as we can move through space by walking around or any other movement, there should be a way to move through time by moving along its dimension. This is obviously more complicated than it sounds, but theoretically there should be a way to do it.
Now, as is true in many cases, when general relativity seems to provide an answer, quantum mechanics is there to provide a problem. The first of these problems that I can see comes from quantum uncertainty. What I mean by this is, suppose you went back in time 65 million years ago, to the time of the dinosaurs. Currently we think we have a pretty good understanding of what this era would have looked like, based on fossils and carbon dating among other things. But right now this is just a probability of what things would have looked like at that time, and this probability eventually gave rise to our world today. However, since no one was there 65 million years ago, it is still just a probability. Probabilities are what quantum mechanics operate in. What this means is everything has a probability of being a certain way until it is observed as being one way or another, at which time it locks into a certain state of being. In the dinosaur case, the idea we have for that time is just a probability of what it may have looked like, but as soon as someone were to go back and observe how the world really was then, one probability will take form which may or may not be the one we imagined. In any case, there are going to be differences and these could have terrible consequences for today's world.
Another risk comes from the many worlds approach to quantum mechanics, in which every probability that exists does happen in some universe. For example if you flip a coin, quantum mechanics says that the 2 probabilities of heads or tails both happen, in their own universe one of which you happen to observe. So for time travel, when there is a probability of what a certain time looked like or will look like, if you were to travel to a certain time you may observe what you expected, but you may be in a completely different universe. This could make returning difficult because you would have to travel to one specific universe among and infinite possibility. So, even if you did travel to a different time you would be stuck there.
Obviously if anyone would like to reenact Marty McFly, we still have some work to do.
Monday, August 25, 2014
Saturday, August 23, 2014
Quantum Computing
Computers have been changing the way our world works since they were invented. They have advanced us and helped us become the global society we are today. They have also been advancing themselves from huge computers with basically no power, to computers we have today which can run simulations of galaxies. The next step in this computational evolution is quantum computing.
Basic computing we know today, such as the laptop you're reading this on, works by using a series of 0's and 1's to relay commands. What this means is everything your computer does is controlled by either a 0 or a 1 and whichever digit is selected controls a different response. This is using classical mechanics, because the digit being used is either a 0 or a 1, but can never be both (keep in mind a computer is doing thousands of things at a time, so its not just one digit, its thousands). As a result, large calculations and computations can be very time consuming. Quantum computing utilizes the uncertainty principle associated with quantum mechanics. What I mean by this is instead of all commands being done by either a 0 or a 1, every command uses both 0 and 1 at the same time.
Using this property of quantum mechanics, the computer can make each entry both 0 and 1 at the same time because the digit is like Schrödinger's Cat, the famous thought experiment. For this thought experiment, imagine a cat is placed in a closed box with no windows or anything to observe the box's contents. Placed in the box with the cat is a vile of poison set to open randomly at any moment once the box is closed. When the box is shut, there is no way to know if the cat is dead or alive without opening the box and observing its contents, so until the box is opened the cat can be thought of as both dead and alive. This applies to computing because the computer can operate using both 0 and 1 at the same time because the digit is always 0 and never zero, and it is always 1 and never 1 all at the same time.
This isn't the easiest concept to come to grips with, knowing one things can be 2 different things at the same time, but using it could make computers exponentially faster. Instead of taking time to sift through every command that comes to a computer and doing it all in order, a quantum computer would be able to do thousands of commands and calculations in a split second, almost infinitely fast. And because everything is taking place at the same time, the more calculations you add do not add more time to the process. It would also greatly reduce the size of computers, or at least the computational piece of a computer. Instead of needing a processing chip like we have now, a quantum computer would only need a few atoms to complete the quantum process.
The unprecedented speed and size of quantum computers certainly makes them a prize of the future, and has astounding possibilities of what they could create. For example, since a quantum computer makes every calculation at once, this means it has the possibility of making every calculation imaginable at once, without even being told to. Such as if we had a quantum computer make a random passage of words, it would simultaneously make every passage of words that would every or has ever or could every be written, because they are all possibilities.
The sheer power of quantum computing is intriguing, and at the uWaterloo, I will be experiencing its development first hand. On campus, the newly built QNC, or Quantum Nano Centre seen here, is focusing primarily on the development of quantum computers. In association with the Perimeter Institute for Theoretical Physics, some ground breaking work is being done in the field and you and I may be reading this blog on a quantum computer sooner than you think.
Basic computing we know today, such as the laptop you're reading this on, works by using a series of 0's and 1's to relay commands. What this means is everything your computer does is controlled by either a 0 or a 1 and whichever digit is selected controls a different response. This is using classical mechanics, because the digit being used is either a 0 or a 1, but can never be both (keep in mind a computer is doing thousands of things at a time, so its not just one digit, its thousands). As a result, large calculations and computations can be very time consuming. Quantum computing utilizes the uncertainty principle associated with quantum mechanics. What I mean by this is instead of all commands being done by either a 0 or a 1, every command uses both 0 and 1 at the same time.
Using this property of quantum mechanics, the computer can make each entry both 0 and 1 at the same time because the digit is like Schrödinger's Cat, the famous thought experiment. For this thought experiment, imagine a cat is placed in a closed box with no windows or anything to observe the box's contents. Placed in the box with the cat is a vile of poison set to open randomly at any moment once the box is closed. When the box is shut, there is no way to know if the cat is dead or alive without opening the box and observing its contents, so until the box is opened the cat can be thought of as both dead and alive. This applies to computing because the computer can operate using both 0 and 1 at the same time because the digit is always 0 and never zero, and it is always 1 and never 1 all at the same time.
This isn't the easiest concept to come to grips with, knowing one things can be 2 different things at the same time, but using it could make computers exponentially faster. Instead of taking time to sift through every command that comes to a computer and doing it all in order, a quantum computer would be able to do thousands of commands and calculations in a split second, almost infinitely fast. And because everything is taking place at the same time, the more calculations you add do not add more time to the process. It would also greatly reduce the size of computers, or at least the computational piece of a computer. Instead of needing a processing chip like we have now, a quantum computer would only need a few atoms to complete the quantum process.
The unprecedented speed and size of quantum computers certainly makes them a prize of the future, and has astounding possibilities of what they could create. For example, since a quantum computer makes every calculation at once, this means it has the possibility of making every calculation imaginable at once, without even being told to. Such as if we had a quantum computer make a random passage of words, it would simultaneously make every passage of words that would every or has ever or could every be written, because they are all possibilities.
The sheer power of quantum computing is intriguing, and at the uWaterloo, I will be experiencing its development first hand. On campus, the newly built QNC, or Quantum Nano Centre seen here, is focusing primarily on the development of quantum computers. In association with the Perimeter Institute for Theoretical Physics, some ground breaking work is being done in the field and you and I may be reading this blog on a quantum computer sooner than you think.
Thursday, August 21, 2014
Dark Matter and Dark Energy - Part 2
Dark matter and energy make up about 95% of the universe's total mass, as we discussed previously. We also have no idea where this mass comes from or what these so called dark substances really are. For an overview of dark matter and energy, refer to my previous post. In this post I will be discussing my personal theory of where these mysterious masses come from.
Dark matter and energy can both only be observed through they're effect on regular matter that we can see, mostly its gravitational influence. But we cannot actually see it, electromagnetic radiation does not interact with dark matter other than being bent through gravity as in the picture to the right, and no other forces seem to either besides gravity. According to string theory, gravity is the only force that can operate between different spacial reference frames, or universes for lack of a better term. In the future I will elaborate on the workings of string theory but for now this is all you need to know. What this means for dark matter is that it could be the matter of a completely different universe, but its gravity is still felt between the spatial gap. In my mind this shows where dark matter and energy come from. Since gravity is the only force that can be transferred between braneworlds (a set of spatial dimensions like ours, or a universe) and gravity is the only influence felt by dark matter in our universe, this shows me dark matter was not something that was created in our universe but something present in its own universe.
At the big bang, all known matter and energy began to expand outward from an infinitesimal single point of infinite mass and infinite density, along with space and time. From this moment, observed from WMAP's mapping of the cosmic background radiation, we have seen that matter and energy had small differences in density across the universe's horizon. Intuitively, you would think that because the big bang was the beginning of everything, all matter and energy should be distributed evenly across the cosmos. Luckily for us, the subtle differences in density of matter and energy is what gave rise to all particles and matter as we know it; without these small variations us and everything around us wouldn't exist.
You're probably asking yourself where these variations come from. The main reason is quantum fluctuations, which are small uncertainties arising from the quantum properties of matter. After these fluctuations, matter started to snowball into larger and larger constituents. These then began to be drawn together by gravity into things such as planets, galaxies and clusters.
This is where dark matter comes in. Dark matter has provided a type of scaffolding for the entire universe. With its exceptional gravitational force, dark matter drew all of the normal matter into these large formations after the quantum fluctuations made atoms and matter as we know it possible. Dark matter does not appear to have come from the big bang, as normal matter has, but instead from a different origin. Because matter, energy, as well as space-time were created at the big bang and expanded into empty nothingness, dark matter and energy must have come from somewhere outside of our space-time continuum.
Dark matter and energy can both only be observed through they're effect on regular matter that we can see, mostly its gravitational influence. But we cannot actually see it, electromagnetic radiation does not interact with dark matter other than being bent through gravity as in the picture to the right, and no other forces seem to either besides gravity. According to string theory, gravity is the only force that can operate between different spacial reference frames, or universes for lack of a better term. In the future I will elaborate on the workings of string theory but for now this is all you need to know. What this means for dark matter is that it could be the matter of a completely different universe, but its gravity is still felt between the spatial gap. In my mind this shows where dark matter and energy come from. Since gravity is the only force that can be transferred between braneworlds (a set of spatial dimensions like ours, or a universe) and gravity is the only influence felt by dark matter in our universe, this shows me dark matter was not something that was created in our universe but something present in its own universe.
You may have noticed that I've mostly only talked about dark matter and not dark energy. Dark matter and energy have similar characteristics, and both are only observed through their gravitational influence. Dark matter provides the attractive force for galaxies to be drawn together, while dark energy provides the repulsive force, or negative gravity which is also allowed through string theory, which drives the universe's outward expansion. Both of these forms of gravity likely come from matter and energy of other universe's.
There is no way to test this theory right now, but it is where I believe dark matter and energy originate from.
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