Modern Physics: Quantum Theory, Relativity, String Theory, and Beyond....

[fritzd]

Modern Physics: Quantum THeory, Relativity, String Theory, and Beyond....

Hi Guys!

I was trying to find a thread where I can post this but I could find any. I would like to share my recent experience. I'm sure some of you Quantum Physics, String Theory, etc.. enthusiasts will find this interesting. Maybe we can also discuss our thoughts on these topics and other related stuff in this thread.

Anyway, as some of you might have not known, few weeks ago, there was a big conference in Vienna, Austria, where I am currently. It was a very big celebration to commorate Erwin Schrödinger's great achievements. He is Austrian, by the way. It has been 50 years since his death in 1961. There were several notable physicists and even still living close friends of Schrödinger who came and shared their experience with Schrödinger.

Official flyer of the event.
http://physik.univie.ac.at/uploads/m...osium_2011.pdf
Webpage:
SingleView[tt_news]=1391&tx_ttnews[backPid]=293&cHash=538f7d91380

It's nice for us science enthusiasts to remember or learn about Schrödinger's achievements and all the people involved in it.

Unfortunately, due to my PhD work I was not able to attend all talks. I was, however, able to join Walter Thirring's talk. He knew Schrödinger personally. In fact, he studied under him. He said that after Schrödinger had already forumalted Quantum Mechanics, Schrödinger had taught courses about it and as well as General Relativity (I never knew this!). Anyway, Schrödinger did so many calculated hinting on everything future physicists' have discovered such as the works of Feynman, the Higgs mechanics for mass (main reason for the LHC) but he just never published it.
Walter Thirring - Wikipedia, the free encyclopedia

Recently(yesterday), I was also in by A.J. Kox. http://elearning.mat.univie.ac.at/ev...11/esi-kox.pdf
A.J. Kox - Homepage

It was called, "The Debate between Erwin Schrodinger and Hendrik Lorentz on the Principles of Quantum Theory." I would say it was one of the most memorable experiences I've ever had. I learned so many things about Henrdik Lorentz and Erwin Schrödinger and as well as Einstein. Lorentz had a meaningful life. He became a full professor at 24!!!!!!!!!! While I'm just starting my PhD at 25! He was a very good friend of Einstein. He also helped Einstein a lot in his Relativity. (Actually in Special relativity, Einstein uses the Lorentz transformations.) They were very good friends to the point that Lorentz actually asked Einstein to succeed him in his position.

Anyway, the main heart of Kox's talk was about how Schrödinger corresponded with Lorentz before finalizing Quantum Theory. Lorentz was known to be a very precise guy and was very very knowledgable about any topic in physics. In those times, when somebody had an idea and need an opinion about, Lorentz was the best guy to get it from. Schrödinger sent Lorentz a letter explaining all his ideas including calculations. Lorentz was very much impressed with Schrödinger's idea but was a bit skeptical. Without going through the details of their correspondence, the bottom line in the end was that, Lorentz was responsible for making Schrödinger realize that Quantum Theory was a non-Classical theory and would change how we view the world. This was the final ingredient that Schrödinger needed to formulate the Quantum Theory we know now. Heisenberg also formulated his own version of the theory which also deserves equal recognition. But interstingly, it was Schrödinger who showed that both his theory and Heisenberg's are both equivalent.

I am amazed on Hendrik Lorentz indirect contributions to Modern Physics. You might also consider reading on his life and contributions. Hendrik Lorentz - Wikipedia, the free encyclopedia

For those who don't know Schrödinger, he is one of if not the most important persons of Quantum Physics. We all enjoy our modern technology today mostly because of Quantum Mechanics.
Erwin Schrödinger - Wikipedia, the free encyclopedia

There are many other scientists or physicists who we do not know about but we are actually reaping the benefits of their work. Learning about the history of physics and how it developed is quite fun. You don't really need to know about the inner workings about the theory itself.

Another fun fact: James D. Watson, one of the disoverers of the DNA structure (NObel Prize in PHysiology 1962), was inspired by Schrödinger's book, "What is life?" I haven't read the book but I never knew that he wrote such book.
James D. Watson - Wikipedia, the free encyclopedia
What Is Life? - Wikipedia, the free encyclopedia

[rodsky]

You must have had an interesting time during the conference Fritz what a great opportunity. Even greater is your enthusiasm for sharing your experiences with us. Carry on the torch of enlightenment!

And who can forget Schrödinger's Cat?

http://www.youtube.com/watch?v=HCOE__N6v4o

-RODION

[pusang_iring]

As a lay person, the only time I was hearing of the name Erwin Schrodinger was when Schrodinger's cat was referenced in pop culture. And when Schrodinger's cat was explained, it didn't make any sense to me from a logical point of view. Cat both dead and alive? That's not possible! Until now, I don't know the real meaning of Schrodinger's cat and why it is important to QM.

[fritzd]

You must have had an interesting time during the conference Fritz what a great opportunity. Even greater is your enthusiasm for sharing your experiences with us. Carry on the torch of enlightenment!

And who can forget Schrödinger's Cat?

YouTube - Schrodingers Cat

-RODION

salamat sir Rods. Yes, it was really a great experience and I wish everyone could witness it. It's quite overwhelming to be around great physicist who Schrödinger personally. And yes, ironically, I never mentioned Schrödinger's famous cat. hehe.

As a lay person, the only time I was hearing of the name Erwin Schrodinger was when Schrodinger's cat was referenced in pop culture. And when Schrodinger's cat was explained, it didn't make any sense to me from a logical point of view. Cat both dead and alive? That's not possible! Until now, I don't know the real meaning of Schrodinger's cat and why it is important to QM.

I will try to explain it as simple as possible and to the best of my knowledge. Anyway, it means that the very very small world or the quantum world doesn't work like our real macroscopic world. It is not deterministic meaning you can not predict the exact outcome of an event. In strict sense, the quantum world behaves probabilistically or statistically. Let's take for example an example of a simple coin flip. When you flip a coin, you know that there is a 50% chance that it will land either heads or tails. Since we have an equal probability, the result is very much random.

When early pre-modern physicists wanted to describe the very very small or the world of atoms, they wanted to know how electrons behaved, where the are exactly located, how they orbited around the nucleus,etc.... They restricted their calculations to their deterministic world of Classical physics as laid down by Isaac Newton. We all know or maybe some of us that this failed miserably. Going back to Schrödinger, he radically changed the way we view the atom or matter all iin general. Instead of knowing exactly, where the electron is, what we see is actually the statisticcs or probability of where the electron in an atom will most likely be (which is mostly everywhere). It is really confusing for people new to QM. It took me 2 eyars to completely grasp the idea.

Ok, going back to the coin flip, Schrödinger's cat is exactly like the coin flip. Schrödinger just really picked a random example as well. He couldn't have picked a more interesting situation. haha You have probably heard the story again and again. A cat in a box. Is it dead or alive? According to QM, it can be alive, dead or both until you open the box. It may seem like it doesn't make sense but that's how it is. And it has extremely meaningful and amazing consequences to modern physics and our universe. Our universe is not deterministic. We can only know the statistics/probability. We can never know how an event(experiment,etc..) would end up but we can, however, calculated the different possible outcomes and its corresponding probabilities.

Take for example, this die! http://averweij.web.cern.ch/averweij/nepal/nepal_09.JPG It's not equiprobabilistic like the regular die which has 1/6 probability for each number. Now, it seems like 4 sides are more favored that the other two. (With lots of geometry and trigonometry, you can calculated this exactly.) If you take data from throwing this die several times, you will find that your result is simple statistics. In a nutshell, this is what quantum physics is all about. Not knowing what the exact outcome but knowing what to expect most of the time. Anyway, that's it. That's what I know. hehe Sorry for the long explanation. I hope I've shed some light into this topic. hehe

[cromagnon]

^this is refered to the , strings behavior within an atom right . wherein they behave statisticaly and probility... i think so , hehe

[pusang_iring]

I will try to explain it as simple as possible and to the best of my knowledge. Anyway, it means that the very very small world or the quantum world doesn't work like our real macroscopic world. It is not deterministic meaning you can not predict the exact outcome of an event. In strict sense, the quantum world behaves probabilistically or statistically. Let's take for example an example of a simple coin flip. When you flip a coin, you know that there is a 50% chance that it will land either heads or tails. Since we have an equal probability, the result is very much random.

When early pre-modern physicists wanted to describe the very very small or the world of atoms, they wanted to know how electrons behaved, where the are exactly located, how they orbited around the nucleus,etc.... They restricted their calculations to their deterministic world of Classical physics as laid down by Isaac Newton. We all know or maybe some of us that this failed miserably. Going back to Schrödinger, he radically changed the way we view the atom or matter all iin general. Instead of knowing exactly, where the electron is, what we see is actually the statisticcs or probability of where the electron in an atom will most likely be (which is mostly everywhere). It is really confusing for people new to QM. It took me 2 eyars to completely grasp the idea.

Ok, going back to the coin flip, Schrödinger's cat is exactly like the coin flip. Schrödinger just really picked a random example as well. He couldn't have picked a more interesting situation. haha You have probably heard the story again and again. A cat in a box. Is it dead or alive? According to QM, it can be alive, dead or both until you open the box. It may seem like it doesn't make sense but that's how it is. And it has extremely meaningful and amazing consequences to modern physics and our universe. Our universe is not deterministic. We can only know the statistics/probability. We can never know how an event(experiment,etc..) would end up but we can, however, calculated the different possible outcomes and its corresponding probabilities.

Take for example, this die! http://averweij.web.cern.ch/averweij/nepal/nepal_09.JPG It's not equiprobabilistic like the regular die which has 1/6 probability for each number. Now, it seems like 4 sides are more favored that the other two. (With lots of geometry and trigonometry, you can calculated this exactly.) If you take data from throwing this die several times, you will find that your result is simple statistics. In a nutshell, this is what quantum physics is all about. Not knowing what the exact outcome but knowing what to expect most of the time. Anyway, that's it. That's what I know. hehe Sorry for the long explanation. I hope I've shed some light into this topic. hehe

Thank you for your answer fritz. Your answer have inspired me to read this further on wikipedia and I've learned a lot. But I still have some questions.

I now know the reason why I haven't grasped Schrodinger's cat the first time. It was because I assumed all along that the universe was deterministic; therefore, any information that contradicts that I just rejected. I thought Schrodinger's cat was impossible. I thought uncertainty principle is wrong. I thought they are just the result of errors from the experimenter and inaccuracies from the equipment. Your coin example is a good illustration of this. I don't think coin flipping is an example of indeterminism. If I knew all the forces acting on the coin, then I would predict 100% whether it comes tails or heads. But since we don't have that kind of detail in our measurement, then we just postulate a 50/50 chance.

But when wiki told me uncertainty is fundamental in nature, I couldn't believe. I still think they are wrong (especially superposition). But not as certain anymore thanks to that double-slit experiment. What logic tells me is hard to shrugg off.

My questions are, why the Schrodinger's cat or any superposition seems to vanish when it is observed? It's like when people tell there's a God, but will not show himself. Or a ghost, but will not reveal. That makes me skeptical.

What do u think of many-worlds interpretation? I like it because it tells me that the other 'states' in the superposition happened in a different universe, and would not violate the law of noncontradiction in Logic. That's the way I understood it.

If matter is both particle and wave and is inseparable like in the double-slit experiment. Why don't macroscopic objects feel like a wave but only a particle? What are the properties of a particle and a wave? And are those mutually exclusive? I don't even know whats a particle and a wave. My idea of a particle is synonymous with matter. So every big object (big particles) and little objects like proton, electron is a particle. But now I've learned the photon is also a particle, but they don't have mass...how can that be? And I can't imagine a wave.

Thanks.

[fritzd]

Thank you for your answer fritz. Your answer have inspired me to read this further on wikipedia and I've learned a lot. But I still have some questions.

I now know the reason why I haven't grasped Schrodinger's cat the first time. It was because I assumed all along that the universe was deterministic; therefore, any information that contradicts that I just rejected. I thought Schrodinger's cat was impossible. I thought uncertainty principle is wrong. I thought they are just the result of errors from the experimenter and inaccuracies from the equipment. Your coin example is a good illustration of this. I don't think coin flipping is an example of indeterminism. If I knew all the forces acting on the coin, then I would predict 100% whether it comes tails or heads. But since we don't have that kind of detail in our measurement, then we just postulate a 50/50 chance.

But when wiki told me uncertainty is fundamental in nature, I couldn't believe. I still think they are wrong (especially superposition). But not as certain anymore thanks to that double-slit experiment. What logic tells me is hard to shrugg off.

My questions are, why the Schrodinger's cat or any superposition seems to vanish when it is observed? It's like when people tell there's a God, but will not show himself. Or a ghost, but will not reveal. That makes me skeptical.

What do u think of many-worlds interpretation? I like it because it tells me that the other 'states' in the superposition happened in a different universe, and would not violate the law of noncontradiction in Logic. That's the way I understood it.

If matter is both particle and wave and is inseparable like in the double-slit experiment. Why don't macroscopic objects feel like a wave but only a particle? What are the properties of a particle and a wave? And are those mutually exclusive? I don't even know whats a particle and a wave. My idea of a particle is synonymous with matter. So every big object (big particles) and little objects like proton, electron is a particle. But now I've learned the photon is also a particle, but they don't have mass...how can that be? And I can't imagine a wave.

Thanks.

Cool! You are absolutely right about about why it is hard to comprehend QM at first. People tend to think deterministically. Actually, it is possible to see matter's wave nature at a macroscale. It can easily be understood using the de Broglie wavelength, the apparent wavelength of any particle. The equation goes like this,

de Broglie wavelength = Planck's constant / momentum.

So to observe the wave nature of matter, we need to have a de Broglie wavelenth in the order of our observe world probably in centimeters, meters, or higher. Going back to the equation, we need the particle or matter to move extremely fast!!! This can be done easily with electrons! You can do double slit interference measurements with electrons. You can also do it with live cows, but you have to calculated the velocity you need to obtain the right momentum according to to mass of the cow. And that is incredibly large! Cows' would instantly die. hehe Anyway, in principle, it is possible.
Matter wave - Wikipedia, the free encyclopedia

Another method of observing quantum effects at a macroscale is with ultracold atoms or molecules. This is what I'm specializing. I made a thread about it here. https://www.istorya.net/forums/scienc...d-physics.html
The heart of it is the Bose-Einstein Condensate which was predicted by Einstein and Bose a long long time ago. It was created in the lab around 20 years ago. It's a very interesting field.
Bose-Einstein condensate - Wikipedia, the free encyclopedia
YouTube - Bose-Einstein Condensate

[pusang_iring]

Cool! You are absolutely right about about why it is hard to comprehend QM at first. People tend to think deterministically. Actually, it is possible to see matter's wave nature at a macroscale. It can easily be understood using the de Broglie wavelength, the apparent wavelength of any particle. The equation goes like this,

de Broglie wavelength = Planck's constant / momentum.

So to observe the wave nature of matter, we need to have a de Broglie wavelenth in the order of our observe world probably in centimeters, meters, or higher. Going back to the equation, we need the particle or matter to move extremely fast!!! This can be done easily with electrons! You can do double slit interference measurements with electrons. You can also do it with live cows, but you have to calculated the velocity you need to obtain the right momentum according to to mass of the cow. And that is incredibly large! Cows' would instantly die. hehe Anyway, in principle, it is possible.
Matter wave - Wikipedia, the free encyclopedia

Another method of observing quantum effects at a macroscale is with ultracold atoms or molecules. This is what I'm specializing. I made a thread about it here. https://www.istorya.net/forums/scienc...d-physics.html
The heart of it is the Bose-Einstein Condensate which was predicted by Einstein and Bose a long long time ago. It was created in the lab around 20 years ago. It's a very interesting field.
Bose-Einstein condensate - Wikipedia, the free encyclopedia
YouTube - Bose-Einstein Condensate

Got it. But what is the purpose of cooling in Bose-Einstein condensates? Is it to lower the moment um according to de Broglie formula? And how would macroscopic objects behave if they now have quantum properties? How different would they be compared to normal objects? I'll read your links when I have the time.

Tell me if this is valid. I imagined a Schrodinger's cat scenario in which we can prove if the cat superposition is true or false. Suppose we can now make a cat with quantum properties and its alive. Then we'll just make Schrodinger's original thought experiment; but in addition of a poison releasing at a random time, we'll add FOOD that would be released along with the poison. Then we'll just proceed with the rest of Schrodinger's experiment. So half of the time the cat is found dead when we open the box, and half of the time the cat is found alive when we open the box. But if the cat was really 'dead and alive' before we open the box, then these scenarios are possible:

Corollary 1: The cat is found alive when box was opened
Corollary 2: Cat is found dead when box was opened along with the released vial of poison and food
Corollary 3: Cat is found dead with the released poison BUT THE FOOD EATEN

We only need to observe scenario 3 to prove that the cat was both dead and alive because the only way to explain scenario 3 is when the cat was dying but the cat was also eating. Let's just assume this cat is really really hungry.

[reggielovescake]

Layu.a na gud ani? Abi nakog ang point ni Schrodinger kay simple ra kaayo about sa solution? na you need to make a better equation to predict at a molecular level na prediction..

[fritzd]

Layu.a na gud ani? Abi nakog ang point ni Schrodinger kay simple ra kaayo about sa solution? na you need to make a better equation to predict at a molecular level na prediction..

No sorry. That wasn't his point. He just wanted to give a very simple straight example to describe something very complex. But the solution to the complixity is really just to treat matter as waves as simple as that. Although really solving it could become a nightmare, but I think that was his main point.

Got it. But what is the purpose of cooling in Bose-Einstein condensates? Is it to lower the moment um according to de Broglie formula? And how would macroscopic objects behave if they now have quantum properties? How different would they be compared to normal objects? I'll read your links when I have the time.

Tell me if this is valid. I imagined a Schrodinger's cat scenario in which we can prove if the cat superposition is true or false. Suppose we can now make a cat with quantum properties and its alive. Then we'll just make Schrodinger's original thought experiment; but in addition of a poison releasing at a random time, we'll add FOOD that would be released along with the poison. Then we'll just proceed with the rest of Schrodinger's experiment. So half of the time the cat is found dead when we open the box, and half of the time the cat is found alive when we open the box. But if the cat was really 'dead and alive' before we open the box, then these scenarios are possible:

Corollary 1: The cat is found alive when box was opened
Corollary 2: Cat is found dead when box was opened along with the released vial of poison and food
Corollary 3: Cat is found dead with the released poison BUT THE FOOD EATEN

We only need to observe scenario 3 to prove that the cat was both dead and alive because the only way to explain scenario 3 is when the cat was dying but the cat was also eating. Let's just assume this cat is really really hungry.

I think you just made the example more complicated as reggielovescake pointed out. hehe Anyway, the system you are describing is not the traditional Schrödinger cat state. I would say there will be now 5 possbilities, the 4th being the cat found dead but the food wasn't eaten, and mayb ethe cat found alive but the food was eaten. But if you do the math, the 3rd possibility you pointed out will mostly be more probable. I could be wrong though. Schrödinger's cat state has defined as a two dimensional state space sometimes called a cat state. A good example of this is the polarization of light or electron spin.

Going to your first question about matter-waves, check out the youtube video I posted, though short it briefly explains in good detail how temperatures affect the de Broglie wavelength. In a nutshell, as you decrease the temperature of matter, their de Broglie wavelength also increase independent of the de Broglie equation which I pointed out earlier. THis is a really peculiar thermodynaic and statistical effect which hints to quantum mechanics. At low temperatures, each of the wave extend or each atom overlap with each other and they all form into one big quantum state or like a one big entity. How would matter waves behave? They will behave like waves. Anything we can do with waves whether it be sound or light, we can also do now with matter. BUt, of course, you have to get matter into the state where it will display its wave properties, which is not easy.