We are living in a world full of technology in almost every part of our lives. From agriculture to medicine, from telescopes to computers, we are benefiting the advances in these fields. But these technologies have some sort of development and history behind. Even though we aren't using these advantages for good reasons sometimes, we still have to acknowledge the process behind these innovations and inventions that makes our lives easier and better. I have recently found a 12 hour video lecture about modern physics, which involves the discoveries within the last century or so, with basic level mathematical explanations. Yes i have watched all of it :) So in this post, i will briefly explain what's going on in the video.
These days, we have lots of resources to be able to start learning stuff. I am writing this blog post to give you a starting point to learn modern physics and the math behind it. Because we need to appreciate the effort and the story of these advances. The video is down below. I will briefly explain the sections in the video. Then you can go ahead and watch the whole video. In the end, you will feel your perspective is changed and you will be able to show off in your social groups :)
Now you are thinking, why would anyone watch 12 hours of modern physics course? Can't you just start reading about the atoms and quantum mechanics and wave-particle duality? No, you can't. Because these concepts have centuries long effort and deduction and motivation and determination. But what mostly fascinates me is the change in perspective that some of the scientists had. Those new perspectives and out of the box thinkings gives rise to revolutions. Sometimes in order to solve a puzzle, you need to break it apart. Sometimes you need to step out of the ordinary. Sometimes you need to forget and disregard the presumptions. Let me point out the important takeaways i had from the video.
The basics
This introductory part is about the basics of physics and mathematics. The rest of the course uses all these terms and calculations. These discoveries are before 20th century. There are concepts like gravity, vectors, light, electricity, mass ...etc. It talks about human perception and misconception of the scales and events. We humans usually can think about a thousand year or a millimeter at most. But our scales are insignificant compared to real measures in the nature and the universe.
The basics of special relativity
This is the first transition to modern physics. This part introduces the concept of relativity with Einstein. You learn to define every event with relative information to observer. Therefore, there must be a universal medium in the universe where everyone can agree on. It is called a frame of reference. There is another important discovery here. Light travels at the same speed even if you are moving. So it is a universal constant. That brings simultaneity problem. Your observations take time because it takes time for the light to travel to your eyes. To come around this problem, we need a transformation. At this stage we are beginning new sort of physics and understandings.
The Lorentz transformation
There is a Galilean transformation that describes motion with equations but it doesn't take relativity into account. So Lorentz improves these equations and describes motion with referential transformation. It's like saying "my speed is 5 mph according to you". Lorentz math introduces a term called gamma factor, which will be used a lot later. It describes relative motion while taking the speed of light into account.
The Muon as test of special relativity
This is where you appreciate the creativity. Back in those days, people didn't have particle accelerators. Therefore they have taken advantage of the natures particle accelerator, the sun. Muons are particles which comes from the sun and they decay. They lose mass by radiating their nucleus. They test these particles and prove that fast moving muons live longer. They lose less weight while moving fast. This is a revolution that implies time dilation is real. If you go fast, you age slower.
The doppler effect
Towards making our way into general relativity, they talk about the doppler effect. It is basically the sound effect of a moving ambulance. Its sound is high pitched towards you and low pitched while moving away. We know that stars emit light. Some stars emit the same kind of light, meaning the same frequencies. They realize the sun and a distant star has the same output with a slight shift. It proves that the universe is expanding and it causes light to stretch somehow.
Momentum and mass in special relativity
In this part, they incorporate special relativity and gamma factor into conservation of momentum. If two objects collide, the total momentum will be conserved. But there is a difference between rest mass and mass in motion. Therefore the concept of intrinsic mass, the mass you just have without any motion, emerges here. They build this on top of kinetic energy from the classical physics. It results in e = mc^2.
The general theory of relativity
Her we come to the real discovery. Einstein realizes that gravity and acceleration is related or almost the same in nature. This new look at the reality is unique. This was a prediction of Einstein and it is later proved. People saw light coming from the stars located at the back of the sun while a solar eclipse is going on. This means that the space is bent and light travelled a curved path. Einstein formulates this within 10 years.
Heat and Matter
This part is about heat energy. We are moving towards waves, energy and quantum mechanics. Heat energy is invisible but quantifiable. The heat also results in the pressure of gases as we know, PV = NRT. This will be related to the blackbody radiation. It is all connected.
The blackbody spectrum and photoelectric effect
Because of the experiments before, scientists concluded that heated objects should emit ultra high frequency energy, known as ultraviolet light. It was called ultraviolet catastrophe. But it is not what the nature is doing. So Max Planck comes in and suggests that energy (like heat) can also be quantified. It yields to "h", planck's constant. The formula we arrive is E = hf. It also helps to explain the photoelectric effect, which brings Einstein a nobel prize.
X-rays and compton effects
These two gives the hints for the basis of particle wave duality of the nature. This section explains how x-rays are discovered. They weren't just imprinted in scientists' brains you know. Then Compton explains the electrons trajectory when they are scattered from a matter. These discoveries will lead to first atom models. People realize the existence of the small particles by observing waves and their motions. This is another revolution.
Matter as waves
This part includes scientists like John Dalton, JJ Thomson, Marie Curie, Ernest Rutherford. This part is all based on electrons scattering from a nickel atom. They discover that light behaves differently at different wavelengths. And the first atom models are born. Then Louis de Broglie comes in and asks this profound question unlike others: Why does matter have to behave like a particle?
The Schrodinger wave equation
This dude is smart. This part produces a probabilistic (due to wave nature) equation for matter by using the knowledge from blackbody radiation, photoelectric effect, atomic models and classical physics. Weirdly it includes square root of -1, which is "i" and establishes a consistent relation between matter and wave based on time invariance. In other words, time i relative but this equation doesn't care. Matter is not just particles but this equation doesn't care. Weird dude :D His equation gives rise to standard model of particles today.
The bohr model of the atom
This is yet another revolution. Neils Bohr proves that electrons (negative charged particles) can only have certain levels of energy. We know heat and energy are quantifiable. He proposes that electrons states are also quantifiable. This also creates 3D atom model. It should be included in schrodinger equation to make it fully space-time compatible.
Free particle model
This final part explains that based on the matter wave equations above, you can't exactly know the velocity and the position of the particle at the same time. Heisenberg proves this and formulates it as uncertainty principle.
There you have it. As you can realize, all these advances are somewhat related. Most of them are built on top of the existing knowledge while bringing a new set of ideas. This is a good place to actually start learning about the math behind all your daily life, the story behind your daily used items. As i mentioned before, the turning points are the most fascinating ones. If you want to continue this journey, this course takes away from the schrodinger equations to the quantum mechanics in another 12 hour lecture video. Well, i will probably watch that too one day. See you at the next post :)
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