April 6, 2014
The other day Alexey emailed me, wondering why physics textbooks never explain why the laws of physics are the way they are. They give us these mathematical expressions but why those as opposed to something else? It all seems so arbitrary.
In computer simulations, the code is written by a programmer who determines the rules for how things behave. The universe works differently. Its code is embedded and runs within the fabric of space-time. The properties of this fabric determines the “code” and rules for how things behave in that that universe.
Space-time seems to be a fabric composed of tiny vibrating pieces of energy “strings” which extend into multiple dimensions. Depending on how this fabric is curled and scrunched up, energy will “pulse” through it differently, giving rise to different forces, types of particles, and all the laws which run that universe. This fabric is very pliable and it is capable of producing nearly an infinite number of different universes.
Stanford professor Dr. Leonard Susskind compares this fabric and how it’s curled up to DNA. In biology, different DNA sequences give rise to different types of organisms. Within each cell of a living organism’s body, you can find a copy of their DNA code. In the same way, if you examine the properties of super tiny patches of this space-time fabric, its bending and folding is a sort of DNA sequence for that universe.
This fabric contains a lot more than just our universe. It contains many other universes as well. They’re all tied together in this common fabric, just like bubbles are in a champagne bottle. Unfortunately the scale of these bubbles is so massive, there’s no way we could travel between them.
So Alexey’s question gets more complex. If this fabric can bend and fold in all these different ways, why is each area of space-time within our universe so uniform in every direction? If the bending and scrunching was different throughout our universe, you’d have different laws of physics within different areas of space and time. Time would flow differently, different types of particles with different masses would exist in different areas of space, some areas would have stars and galaxies, other areas would not, etc. The “laws” could also change over time as well. How come this doesn’t happen?
It turns out that our entire universe originates from a very tiny patch of this space-time fabric which was blown into a huge bubble. Since it all originates from a small uniform patch, our universe is pretty uniform overall. If you look at all the stars and galaxies from a “birds-eye” perspective, they’re spread throughout space very evenly. The fabric is bent, curled, and scrunched in pretty much the same way throughout our universe, hence the “laws” of physics are the same everywhere.
There’s a lot more to say about this sort of thing, but I better stop now before I get way over my head. I still have a lot to learn about this stuff myself.
April 1, 2014
Dr. Susskind of Stanford has been continuing work on his course series ‘The Theoretical Minimum’. He’s even set up a full website for it which you can find here:
You’ll find courses on Classical Mechanics, Quantum Mechanics, Special Relativity and Electrodynamics, General Relativity, Cosmology, Statistical Mechanics, Quantum Entanglement, Particle Physics (3 courses), and String Theory.
He describes the aim for the courses on the front page,
“A number of years ago I became aware of the large number of physics enthusiasts out there who have no venue to learn modern physics and cosmology. Fat advanced textbooks are not suitable to people who have no teacher to ask questions of, and the popular literature does not go deeply enough to satisfy these curious people. So I started a series of courses on modern physics at Stanford University where I am a professor of physics. The courses are specifically aimed at people who know, or once knew, a bit of algebra and calculus, but are more or less beginners.”
If you’re interested in learning some deep physics, you should check it out!
March 29, 2014
Last night I was watching videos of slow motion and found a video of people jumping up and down on a trampoline at thousands of frames per second. You could see every detail and movement as they performed backflips and bounced off the trampoline. About a year ago I was jumping up and down on a trampoline and that got me thinking about time.
We barely perceive any of the time happening around us. Human consciousness is very choppy. Our awareness of the world happens when information is processed by our brains. This takes time and we perceive a “frame” of time every ten to fifteen milliseconds. That’s about seventy frames per second. That’s why when we’re watching a movie it can be running thirty frames per second yet still appear like smooth motion to us. If you recorded the playback of a film with a high speed camera, say 30,000 frames per second, you’d see each frame of the movie and the motions would be choppy.
All of this got me thinking about how we’re so often associated with our bodies. The atoms of my body persist throughout all of these frames of time, but consciously I do not. My conscious existence phases in and out, in and out, in and out. When I’m watching a movie, a frame is displayed on the screen and I perceive it, and then I’m phased out. A long gap of time exists where I’m not there, and then I’m phased back in roughly when the next frame appears on the screen. It appears continuous and fluid to me, but it is not in reality. How many frames existed where I wasn’t around? Let’s just say that if you could perceive events trillions of time faster, when the frame on your computer screen changed, you’d watch the light travel across your desk and would perceive subtle changes in the shadows from objects on your desk. You’d also be staring at the same frame on the screen for a long time.
Some people ask what is the frame rate of life? Human consciousness is dependent on the rate of information processing in our brains, which as I said is about seventy frames per second. As for the world, it’s much stranger. In short, there is no absolute frame rate. The question is misguided and is based on bad assumptions about how reality works.
Is it possible to always build faster and faster video cameras, capturing more and more detail? The answer is no. If you could perceive events fast enough, you’d see the light coming into your eyes pixel by pixel, colored dot by colored dot, and the images would come in slowly and at random times, trickling in over time. If you perceived even faster than that, you’d have long periods of time where you’d just see black and then you’d see a photon hit your eyes. Then you’d wait a long time and a photon would once again hit your eyes. You’d have to assemble the “pieces” in memory, like a person putting together a puzzle before you could perceive anything going on around you.
Events from different times would get all jumbled up. You’d be seeing photons from many different periods of time. It’s a similar problem to when you look out into space and see images of stars from millions of years in the past. Each star, depending on its distance away from us, is from a different era of time. The light took a long time to get here. The same thing would be happening for you in your backyard. Photons from different areas of a blade of grass would come to you at different times and since they’re emitted at random times, you’d have to be pretty clever to put all of this together into a proper scene.
The atoms making up our world and our bodies, when not being directly observed, lose their definite assignments of location and speed (also, both can’t be known at the same time exactly), and they’re not moving through an absolute space. Relativity theory tells us that space and time are one and the same thing, and I don’t know how to easily explain all of that. The amount of mass and energy within the area of space dictates the flow-rate of time and they’re related by Einstein’s equations of general relativity. Different observers moving through space-time in different directions and speeds perceive things differently and will disagree on how much time took place between events. I doubt that helps much, but what I’m saying is that there’s no absolute frame rate of reality. It varies from observer to observer because the amount of time between events depends on how you’re moving through space-time. This Youtube video talks about the problem and offers a good visualization.
I really wish this video would have shown what happens at really high speeds. If the train would’ve been moving at speeds near that of the speed of light, the man from the ground would see the train compressed and extremely shortened in length. The woman inside the train would also see the world outside the train scrunched up, shortened in the direction of motion. The same weird “time dilation” effects with the lightning bolts and people perceiving events differently would still take place.
It’s weird and counter-intuitive. Also, perceiving the world at this level of detail, the world would spontaneously pop in and out of existence as photons fired off. All of our world is grounded on a statistical fuzz. The world is bubbling in and out of existence. If you experienced things with this much detail, you’d experience the randomness directly. Now you’re starting to get into the world of physics at the cutting edge, the very fabric of space-time and its quantum nature. At this level of reality, you have to rethink what space and time are. It’s an eternal world. Electrons are going both forward and backward through “time”. Up, down, left, and right do not exist. There’s little super-tiny wormholes. Everything is like a bubbly froth, phasing in and out like the surface of turbulent water. It’s commonly dubbed the space-time foam.
I’m completely fascinated with this foam.
We don’t perceive the world in this way. It appears continuous, time seems to flow properly in one direction, and objects seem to be solid and persist. Reality at its deepest levels is far more interesting. Our brains are so slow, they just sort of average over huge numbers of signals from the external world, such as all the photons coming into our eyes, and then build this fictitious model of the world around us. Our conceptions of space, time, and the objects within them are all wrong.
We barely perceive anything, whether it be all the detail of the world around us, or all the moments in time. Our consciousness is just skipping through this reality, like a small rock skipping across the surface of a pond. We don’t experience the full depth of this world. Science makes us aware that this deeper reality exists, but it’s all so counter-intuitive, I oftentimes wonder what it means to “understand” it.
March 29, 2014
IBM scientists animated a boy and his toy ball using individual atoms.
March 26, 2014
A plant on the verge of death receives a little water and is placed in the sunlight.