ThreeAmmo


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Prehistoric Masking

#art #history

I finished rereading Scott McCloud’s great book Understanding Comics recently. Like a good conversation with an intelligent friend, it keeps giving even after it’s over. It got me thinking about a few things. One such thoughts was about prehistoric cave art.

In chapter 2, the book argues (comics style) that simplified or iconic pictorial representations of things are more relatable, more accepting of us projecting ourselves onto them. We make a face out of a circle with two dots and a line inside of it, then let our imagination fill in the blanks. Since iconic representations are abstract, they are universal. This simple cup can stand in for the one on your desk, that rectangle can be your computer monitor and the stick figure is you, at least for a moment. The reason this is possible, according to the book, is that we do not see ourselves. My face is a mask that is visible to others, but not to me, so my mental image of my own face is very abstract. Now imagine if you are presented with a photo-realistic picture of someone, it would be much harder to identify with that picture. We might not see our own face much, but we see everyone else’s. A realistic picture is specific, not universal, and it makes you aware of its specificity just like you are aware of the details in the appearances of others. We “mask” ourselves in iconic images, and perceive otherness in realistic ones.

Now consider stone age cave paintings. Some of these paintings contain realistic depictions of animals, but whenever human figures are present they are pretty much stick figures (check out the pictures in this Wikipedia article on cave painting). Here’s a quote from Ian Tattersall’s Becoming Human:

[W]hile human images are commoner in Ice Age art than generally thought, they are almost invariably significantly less realistic than those of other animals—especially on the cave walls.

Well, you see, that gives me ideas. Is this very early art reflecting the same dichotomy McCloud talked about? In an image of iconic hunters pursuing realistic animals, can we assume that the artists instinctively represent themselves with simple lines while the animal—the other—is detailed and natural-looking? I’d like to know more about that.


Take 2

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Alright, let’s try this again. Had a busy couple of months and it took the wind out of my sails. As simple as this website was planned to be, it should be simpler. Maybe more sections will be added over time when there is actual content for them, and maybe better Home and About pages.


Godot Body2D node

#godot

In real life, we walk around. We bump into each other, we bump into footballs and we bump into light posts then fall and bump into the ground under the force of gravity. Typical human experience. We like to relive this experience in video games.

The physics of these situations are then described by two things:

  • Physical contact (collisions),
  • Action at a distance (forces, spooky or otherwise).

Collisions happen when objects come into contact. Forces act on objects depending on their position, regardless of proximity. We also encounter ghosts, these are objects that we cannot collide with, we usually pass through great-grand-auntie with no detectable effect, and they do not obey the force laws of the world.

Objects that interact with the world according to the two ways mentioned above are described in Godot as PhysicsBody2D nodes. Anything (node) that ends with Body2D is going to inherit all the properties of the PhysicsBody2D node.

When we hit a light post, or a wall, or a building, these objects don’t react to us colliding with them. They also don’t respond to gravity or other forces. These are StaticBody2D nodes. They remain, well, static. But we can’t pass through them, we still collide with them. We get affected by them, but we cannot affect them.

We kick a football and it moves. That’s an object that moves (more precisely, changes its state of motion) only when acted upon by an external force, it cannot move on its own. In game, this force is provided by the collision between the player and the ball. Objects that can be moved through application of in-game physics are RigidBody2D nodes in Godot. The in-game physics are defined by the developer, something analogous to \(F=ma\) and collisions.

When we decide to walk around, this motion is not caused by external, visible forces from the outside world. Same with cars, they really move because of the engine inside but that is internal to the car, it’s not an outside force. In Godot, these objects (people walking and cars moving) can then be thought of as agents having free will, their motion is not described by the dynamical law \(F=ma\). When an agent decides to move, this free-will motion is not dynamical in that sense, it’s kinematical. We can only describe it in terms of change in position, but not the causes of this change. This is the KinematicBody2D node in the Godot engine. The free will (internal forces) are provided by the player’s press on the control buttons or a behaviour code. These objects can be made to obey physics but this has to be coded, they do not obey general world physics like RigidBody2D nodes.

I’m talking about 2D nodes only because I didn’t even touch the 3D engine, but I imagine the ideas would be similar.


The End of Physics

#physics

A perfect start for a physics blog.

A few days ago, I came across this article by the director of the IAS, Robbert Dijkgraaf, in which he argues that fundamental physics is not only alive and well, but that it’s prospering. Throughout the article, I couldn’t help but feel that he made the case for exactly the opposite.

Exaggerated or not, one hears the reports of late 19th century physicists declaring the completion of the fundamental laws of physics and that all that is left is to refine measurements to more decimal places (check this discussion on Stack Exchange). This is often used as a cautionary tale against any claim that physics is over, after all, the 20th century started with two great revolutions of fundamental physics, relativity and quantum mechanics. The moral of the tale is to never think that we have discovered all the laws because, over a century ago, people thought the same and they were wrong. But isn’t the ultimate goal of theoretical physics to find the final laws at some point? Did we catch ‘em all? I certainly hope not, otherwise this website will be pointless.

Dijkgraaf’s argument, that fundamental physics is not dead, is based on three points:

  1. Fundamental physics won some major Nobel prizes in the 21st century. But even he admits that this is irrelevant since these prizes were won for theoretical predictions made way back in the 20th century.
  2. We still have a lot to discover since we don’t know much about 95% of the universe (dark matter and dark energy). This arguments never fails to un-impress me. I will write about it later. Again, even he doesn’t feel like this is such a strong argument, he stopped it at one paragraph, before he launches to the main argument of his article, the third point.
  3. We still have a lot to research in fundamental physics, because fundamental physics is not only fundamental physics. If that sounds weird, that’s because it is.

The truth is, the realm of the smallest particles is not the only place you can find the fundamental laws of physics. They can also “emerge” out of the collective behavior of many constituents.

Read that a couple of times. Think about it.

He is expanding the scope of fundamental physics to include the study of “all manifestations of matter and energy in the universe”, meaning that the study of exotic states of matter is part of fundamental physics. Seeing the state of particle physics nowadays, Dijkgraaf is trying to claim the successes and discoveries of condensed matter physics as ones of fundamental physics. But they’re not.

A fundamental law is one that cannot be derived from other laws. It cannot “emerge”. In fact, ‘fundamental’ and ‘emergent’ are antonyms in physics-speak. To me, this sounds a lot like the alleged 19th century argument for the end of physics. The actual fundamental research is over, we can only do emergent stuff now, and be happy about it. This seems to be (kind of) Peter Woit’s opinion about the article as well.

I like condensed matter physics. I think it has interesting problems to solve, discoveries that keep coming up and exciting possibilities for future technology, and it is certainly where the money is. But it is not fundamental. And it is not the kind of romantic physics that got me into this field in the first place. It would be a sad situation for me to be a physicist when physics is actually over. I missed the golden age, only by a hundred years.

But maybe all is not lost.


First Post

#untagged

I finally made a website. Now what?

Just like the pyramid builders, I am leaving a legacy for the world. Primarily, a documentation of my attempts to learn physics, music, and game development, I have already mastered advanced web design. Most likely I will not resist the urge to ramble on indefinitely about other subjects, this space will double as a blog of sorts.

I have some knowledge of physics, but not nearly enough. Additionally, I want to collect this knowledge into a coherent set of principles. I like semi-axiomatic/foundational approaches to subjects that are traditionally presented as matter-of-fact. An example of that is Landau’s “derivation” of the classical mechanics Lagrangian, I will definitely write a post about that sometime. And since this is theoretical physics, I will ramble on about philosophy as well.

Musically, I only play a little guitar. But what I want is to learn some music theory and some sound design. Music theory is interesting to me mainly because I feel like I can build music pieces with a creative application of rules. Think Bach, with a computer. I will attempt to learn the mathematical side of it and see where it takes me.

As for video games, this will probably be the steepest hill to climb since all I know about programming is 1+1=2. Or was it 1+1==2? We’ll see.

Hopefully this website will push me to do all that, and get past the desire for non-existent perfection.