When it comes to modern cosmology not many physicists are more unique and popular than Stephen Hawking. Besides being a great scientists, Hawking has also become a world wide celebrity - he's often featured in science documentaries, radio shows and even science fiction. But what made Hawking so popular?
Perhaps Stephen Hawking became so popular due to his most controversial discovery of the so called black hole information paradox. Long story short, Hawking discovered that black possibly destroy the information of what fell into them. This great Horizon documentary tells the story of this great discovery. In addition it has some interesting biographical facts about Stephen Hawking plus all the cool stuff that usual comes with Horizon documentaries like cool visuals and great narration.
What is really great about this documentary is that it also features the famous theoretical physicist from Stanford - Leonard Susskind. Susskind, as many of the physicists of the time, did not believe that black holes might swallow the information, so he, for many years, tried to created a theory, which would resolve the information paradox. This gave rise to a very interesting professional competition between these two great scientists.
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Recently I had an amazing opportunity to attend a lecture by the Sir Roger Penrose himself. Roger Penrose is a great mathematician and mathematical physicist working in a variety of fields of physics and mathematics. He is also a very famous author of books such as The Road to Reality, and The Cycles of Time.
His lecture was about trying to answer the question "Can We See Through The Big Bang to Another Universe?". In other words, the lecture was about one of the theories of Roger Penrose, regarding the history and the fate of the universe, the so called cyclic model of aeons.
In conclusion, it was a great lecture. I have to be honest I didn't understand some of the parts, however some really unique and fascinating ideas were presented, which I really liked. And it is needless to say that the feeling of attending a lecture with the top notch physicists and mathematicians was really amazing.
But these aren't the only good news. I happen to found another recording on Sir Roger Penrose lecture about the same topic. I listen through it and it's the same lecture. So here it is and I hope you enjoy it.
Hey, I found this great BBC documentary called "What is Reality?". It's about the various theories and experiments of physics which could help to answer this question. It involves a lot of great stuff about quantum mechanics (for example the famous double-slit experiment), particle physics and some cosmology.
I really like that it illustrated the whole bizarre side of quantum mechanics and the way it changes our understanding of reality. So check this out here or on YouTube. Thanks for reading!
PS. do any of you guys know how to write eqautions in Blogger? I would appreciate if you'd share this knowledge ;]
Cosmology is one of the most important branches of physics, however it also has many unanswered questions and mysteries. This article lists the top 10 mysteries of cosmology.
10) When were the first stars formed. What were they like and how they looked? Today we know quite a lot about the history of the universe. According to the big bang theory, the universe started about 13.7 billion years ago. About 3 seconds after the Big Bang, nucleosynthesis set in with protons and neutrons beginning to form the nuclei of simple elements, however it took about 100 000 years for the atoms to form the ordinary matter, which can be found in our universe these days. Later, due to gravitation, various stars formed. We know a lot about star evolution today, however it’s still not clear when were the first stars formed. Hopefully new telescopes will be invented and we will find out even more.
8 ) Why is there an almost empty area of space next to the centre of our galaxy?Scientists believe that in the centre of the Milky Way Galaxy there is a massive black hole. All the stars in our galaxy seem to be orbiting this super massive black hole. However, there also seems to be an empty area of space close to the centre of our galaxy, which according to current scientific knowledge is very strange. According to theory, the black hole at the centre of the universe should eventually attract many stars closer to the centre of milky way. However, observations show that it is not the case. Hopefully new telescopes will shed some light on the problem.
7) Do Black Holes really exist? Everybody knows what a Black Hole is, however, scientists have never observed one directly. It is possible to guess that every galaxy has a Black Hole in the centre of it by various gravitational effects, however it is much more harder to detect a Black Hole directly, because it doesn’t radiate light. Let’s hope in the near future scientists will observe the so called Hawking’s radiation (according to Hawking Black Holes do radiate energy, although very slowly) and he will win his Nobel price.
6) Is it possible to create a quantum gravity theory. The two great theories of the 20th century do a great job when it comes to describing the world of the big (universe, galaxies and so on) and the world of the small (subatomic particles). I am of course talking about the general theory of relativity and the quantum mechanics. According to astrophysicists the first moment of the universe – the big bang started from a singularity. To find out how exactly the universe started it is necessary to join these to big theories, because at the star of the universe all the matter was formed in a microscopic singularity, which had extraordinary strong gravitational properties.
5) How exactly gravity works? Many of the great minds throughout the history tried to answer this question. Newton formulated the law of gravitation, which easily enables to calculate the movement of heavinly bodies to a great degree of accuracy. However, Newton had no idea how that magnificentinvisible force worked. Einstein came up with the famous general theory of relativity, which explained that gravity was the result of the deformation of time and space. Still, there are many questions, like is the space time physically detectable, are gravitons real, do gravitational waves really exist and so on. Many modern experiments are being carried out, which aim to solve some of these problems, however it may take many more years or even another great mind like Newton and Einstein to totally conquer the mystery of gravity.
4) Why is there an arrow of time? Is it possible to turn it around? Most of the laws of physics work great independent of the direction of time, time seems to be running from the past to the future. But why exactly does time only go to one direction? Why is the future different from the past? Also, is it possible to travel back in time?
3) What is Dark Matter? By observing the movement of the galaxies and planets it is possible to find out how much mass is in the various galaxies. Interestingly, the observation show that there’s actually less visible matter in observed galaxies than the theory suggest. This invisible matter is called the Dark Matter.
2) What is Dark Energy? Almost everyone knows that the universe is expanding, even more interesting is that the universe is not only expanding, but also it’s expansion is accelerating. Thus scientists believe that there is some kind of an invisible energy, which is spread throughout all the universe. This energy, which is called Dark Energy, is the cause of the acceleration of the expansion of the universe. However, no one has an idea what exactly it is.
1) What happened before the big bang? Some believe that it was god, who caused the beginning of the universe, others believe in quantum fluctuations, others think our universe was a part of another universe in a multiverse and so on… To be honest, nobody knows what exactly happened before the big bang. It is the ultimate secret of both cosmology and physics. Will we ever find out the answer to this question? Only time will tell.
Ever since the beginning of human kind, humans were fascinated by the concept of time.
It’s probably mostly due to the fact, that time was always a very important thing. Even prehistoric people had their system of measuring time, which was basically watching the stars, the sun and the moon. Later civilizations discovered various clocks, starting with simple sand or sun clocks, ending with complex water clocks. In Middle Ages mechanical clocks were discovered.
As we can see, civilizations throughout the history believed in two different time models. The first one and possibly the earliest was cyclic time model. Most of the ancient civilizations measured time by observing the sun, the moon and the change of the seasons, which naturally led them to think that time runs in cycles. For example in ancient India years were named and once the 60 names are finished, the next year starts with the first name again. Ancient Aztecs also had special calendars divided in cycles. After every cycle, they believed, a new similar cycle starts once again. It’s interesting to notice that the famous Mayan calendar also measured time in cycles. So it’s not true that it ends in 2012, actually only one of the cycles will end at 2012 and then a new cycle will begin.
Another way of thinking about the run of time was linear time model. It’s the most familiar model to us. Perhaps, the best comparison about time was given by Einstein, who said that time is like a river. This river, by the way, can fork, have whirlpools and run in very interesting ways.
The biggest question, when talking about time, is, of course, what exactly time is. What is that magical river, which brings us to the future? It seems that this question is harder to answer than you might think. Let’s see how people throughout various periods of history answered this question.
Many ancient civilizations believed that time, like all the nature, is controlled by the gods. The Vedas, the earliest texts on Indian philosophy and Hindu philosophy dating back to the late 2nd millennium BC, describe ancient Hindu cosmology, in which the universe goes through repeated cycles of creation, destruction and rebirth, with each cycle lasting 4,320,000 years. Ancient Greeks believed that that time, as well as their destiny was controlled by divine deities for the Mount of Olympus. However, ancient Greek philosophers had more sophisticated ideas. Some of them believed that time is infinite – the universe, as well as time had no begging, nor will it have an end. However, there were philosophers, like Zeno, who didn’t believe in any kind of change. Zeno, in his famous paradox (Zeno’s paradox) argued that any kind of change or movement is impossible. This lead to the conclusion, that time is only an illusion.
Philosopher and theologians argued that both universe and time had a beginning, and will have an end. They believed, that time started at the beginning of the universe.
Immanuel Kant, a famous Prussian philosopher, had his own ideas. He believed that time was only an idea like numbers, or dimensions. Kant thought of time as a fundamental part of an abstract conceptual framework, together with space and number, within which we sequence events, quantify their duration, and compare the motions of objects.
Immanuel Kant
Isaac Newton shared similar ideas. He believed that time is like an arrow, which always goes only one way. He believed that time was universal – it was running at the same rate for all observers.
All of these ideas caused two distinct viewpoints of time among philosophers and scientists. One view is that time is a fundamental part of the structure of the universe. It’s like another dimension, in which events occur like in normal special dimensions. Other point of view is that time is not a part of the structure of the universe. Time, according to this point of view, is not an event, nor a dimension or a thing.
Isacc Newton
The big breakthrough in understanding the nature of time came in the beginning of the XX century. Einstein, with his famous theories (Special and General Theories of relativity) showed that time is not universal. The rate of the clock depends how fast you are moving. Simply speaking, time flow depends on various conditions, which include the velocity of the body. Later in his General Relativity Theory Einstein showed that time also slows down in a gravitational field. These two very important conclusions lead scientists to believing that time actually is a part of the fundamental structure of the universe. Also when Einstein showed that time travel (at least to the future is possible) it became clear that the old view of time as nor a dimension or a thing was wrong.
Now, a century later, we know many wonderful things about time. We know that time is highly connected with the form of Space Time continuum. For instance, if you would spend some time orbiting a huge star, the gravitational field of which is very strong, you would age slower than let us say your twin brother who is spending his days on Earth. We also know that the speed of time flow is connected to the velocity of the body. Another great discovery is the so called arrow of time. It’s clear that time goes from the pas to the future. This makes time a unique dimension. We can freely movie in any of the three special dimensions, but when it comes to time we are prisoners. Scientists believe that the entropy of the universe is the so called arrow of time. In this case entropy can be viewed as a measure of disorder. According to thermodynamics, the entropy of a closed system tends to increase. And since universe is a closed system, entropy in the universe increases steadily. Thus, for instance, a broken cup of coffee, newer comes back to the table and fixes itself as it was traveling back in time.
Albert Einstein
Only one thing is really certain – time is connected to the geometrical properties of the space-time continuum. The newest discoveries of astrophysics gave us many mysteries. Mysterious Dark Matter and Dark Energy are great examples, that we still don’t know many secrets of the Universe and time itself. For instance some scientists believe that time is highly connected to the accelerating expansion of the Universe, which is supposed to be caused by the Dark Energy. This Dark Energy, according to scientists, is constantly changing the form of the Space-time continuum. This means that in order to understand more about the Space-time continuum, the Universe and the time itself we need to understand what Dark Energy is. Even at this moment, due to the Dark Energy, the time itself can be speeding up. All in all, the mysteries of the Dark Energy and Dark Matter hold many secrets of time.
Our generation is a really lucky generation, because we know more about Universe and time than any other generation throughout the history. So let’s hope we will find out the secrets of the universe sooner or later. After all, who wouldn’t like to find out what exactly is the magical river of time.
4:51 PM
silentbob14
