PHYSICS

HUGE DISCLAIMER to all science nerds who always want everything to be right and true all the time! This post is my way of trying to memorize and learn things and I'm not aiming to state what is true in here. Statements may be simplified and speculative and sometimes even false (probably because of my own misconceptions of things I've recently learned). You should see this post as a peek into how my brain structures things.

KNOWLEDGE

The world, somehow, consists of both the things that exist and the things that don't exist. I say this because we can obviously think and fantasize about ideas that don't exist in our physical world. You can see a car running in 100 km/h, but you can't see the value "100 km/h" or the number 100. We can imagine eternity and do calculations on and get practical use of imaginary numbers that don't exist - math seems to be a part of some other non-existing spiritual world, and it's unclear if the fundamental math formulas we use in physics are what control our world, or if math is just our human way of understanding and explaining what happens the best we can.

We humans have a tendency to want to know about everything, which makes us able to imagine things that don't exist, and this gives us existential anxiety. No one knows what consciousness is or why we feel like we decide our own actions, but we all know it's there. And some things we can never know, like what's outside the universe, what comes after life, what happened before the universe, what existence is, etc. Even if we get answers to these we can always ask "but what's outside of _that_ then?" so by definition we can never find all answers. The reason religion exists is probably to give us inner peace as an antidote to this. Religion isn't about finding the objective truth no matter what, it's to give people inner peace, while science gladly gives you existential dread and headaches if that's what's closest to objective truth.

Science is our best method yet for coming closer to the objective truth of the physical world. And all science is physics, if you dig deep enough - chemistry is physics on a higher level, biology is chemistry on a higher level and for a specific case... But when you get further up than that things starts to get blurry. On a human, geographical, societal and historical level, it becomes harder to see what's true and not true among all the "facts" and "science" about it out there, but that's because we wrongly call it science while it's not really scientific (yes, they use the scientific method... but the results coming out of it aren't too promising). We don't examine human behavior on a subatomic level, which means there's no connection between physical laws and the human sciences at all. And maybe we wouldn't even be able to describe human nature with laws and equations no matter how hard we tried and how incredible equipment we had? What if everything coming out of human nature is driven by something else than clear physical laws? If free will exists, using science to understand what humans do probably won't work (or maybe free will is a part of physical laws we are yet to discover...).

Other types of knowledge may be more practical, and involve ideas like free will and subjective experience and may give the desired results when applied even if the underlying ideas aren't objectively true. Just by living life you learn things that can't be described scientifically but only be felt intuitively. This, combined with the fact that we clearly can create knowledge about things that don't exist (like math and ethics), it's clear that we have lots of knowledge that aren't physics, even if physics is the science of everything that exists.

Physics consists of the things we can see, and the things we can't see.

The things we can see are inside the observable universe's limits, with light in our eye's visible interval (or within our other senses' capacities), don't require a microscope or other tool to access, and are accessible to us in our current time era and our normal much-lower-than-light speed. This type of physics is easy to understand, since it describes normal things we see every day, and that's also why this type of physics came first. This type of physics may even feel like it's more real and more reasonable than more advanced physics, but that's just because of the limitations of our human senses.

To understand, or even come close to understand, the things we can't see - like how atoms and subatomic particles look, what happens in a black hole, what happens at the speed of light, or what happened right after the big bang - we need tools or abstract thinking. With tools we can transform what we can't see to something we can see, like making infrared light look like "normal" red on a screen and then with our abstract mind imagine what infrared light is. It feels like we understand infrared light, but we kind of only understand the transformed version of it.

Abstract thoughts can create ideas that don't seem to exist in reality - like Einstein's thought experiments and equations - but which later get proven to exist by real-life measurements. If we didn't have this ability to imagine things that don't exist we wouldn't know which impossibilities to look for and prove wrong. Science somehow often requires us to get knowledge from the spiritual world of non-existence to find what really exists.

THINGS WE CAN SEE

From what our human senses can grasp about physics, everything is movement in 3 dimensions and time. But there's no single center point that everything else revolves around. This means you can never be still, because there's no way to prove what is still and what is moving when comparing two objects to each other. You can either move in a constant speed, or increase/decrease speed. Increasing/decreasing speed requires a force (while moving in a constant speed happens without doing anything, maybe that's why it feels the same as being still?). A force converts one form of energy to another. The amount of energy in the universe is always the same, and energy can only be converted into different forms, not created or removed.

These simple facts can pretty much explain everything that physically happens in our day-to-day life.

Energy exists in two forms. Either kinetic energy, which is movement, or potential energy, which is energy that is stored and waiting to be used. All the types of energy we see in various unique shapes and appearances in our daily lives are just variations of these two types.

Electrical energy is kinetic energy from electrons moving together from one place to another. Or when they don't move, that energy is stored as potential energy. Different materials lead electrons differently well, and some materials are good enough for electrons to flow through them. This quality is the material's resistance, and the less resistance the more easily electrons flow through. Many electrons flowing through a material is a current of electrons, but it's the difference in electrons between two sides of this material that makes the electrons flow; they want to flow from more electrons to less electrons to even things out (very over-simplified). The difference between these two "poles" is the voltage. The current is equal to the voltage divided by the resistance, so the more voltage and the less resistance gives a bigger current.

Alessandro Volta invented the battery and gave name to the voltage unit Volt, Andre-Marie Ampere discovered how an electric current affected a compass magnet needle and gave name to the unit of current Ampere, and Georg Simon Ohm created the connection between these three and called it "Ohm's law", or I = U / R (current = voltage / resistance). Ohm also gave name to the resistance unit Ohm.

Magnetism is another version of electricity - a moving electric charge creates a magnetic field. That's why the universe has a fundamental "force" called the electromagnetic force. It's the electromagnetic force that converts the potential energy to kinetic energy in the electrons. The electromagnetic force lets an object with negative charge affect an object with positive charge (and vice versa) on infinite distances through out the universe, at least in theory, but its strength weakens with distance.

When electrical energy meets a resistor, it converts to thermal (heat) energy, which is why lightbulbs get hot and which in turn is why they're so wasteful of their energy. Thermal energy is also kinetic energy of particles moving, or potential energy waiting to be used, but the difference from electricity is that electricity is electrons all moving towards the same direction while thermal energy is the average movement of particles in a material. Temperature is a measurement of the kinetic energy (not the potential energy) of a substance, and is measured in Celsius or Kelvin (the science temperature unit which is always 273 degrees higher than Celsius). Or in "Fahrenheit"...

When particles move randomly they create thermal energy, and when these particles together collide with a surface, they create a pressure towards that surface. Pressure is the sum of the individual forces of all individual particles pressing against the surface, divided by the surface's area. It's measured in Pascal, named after Blaise Pascal who discovered that air pressure lowered with elevation (among other things), and the force and area are measured in Newtons and square meters.

When it comes to random particles going in different directions, there are some ways they are more likely to go in than others. This is "entropy", the fact that things tend to go from ordered to disordered states more often than the other way around. It's not a law with a famous equation, but it's obviously very true and also the only "proof" we have that time exists (in the other physical laws you can reverse the equations and make everything go backwards, but entropy is the only one going in only one direction, "proving" that future is something else than past). A pyramid made of sand will spontaneously fall apart to a mess, but a mess of sand won't spontaneously build itself back up to a pyramid shape. Except if humans are there to make things structured and ordered, which means that either entropy is kind of false, or we humans are just a rare special case that statistically shouldn't exist and will eventually fall down into a random mess just like the sand pile...

Entropy is the second law of thermodynamics, and there are four well-known laws of thermodynamics; the first law is basically that energy can't be created or destroyed but only transformed (as we've already mentioned), the second law is entropy, and then there's the third and "zeroth" thermodynamic laws too, but they're less interesting.

Gravity is another fundamental force, that makes objects get drawn to other objects, and it's much weaker than the electromagnetic force. The "bigger" object the stronger the gravitational force, but its strength also weakens with distance just like the electromagnetic force. Mass is what makes an object "bigger" to gravity, and we intuitively understand this concept while it's at the same time hard to define. Gravity is defined as the force coming from mass, and mass is defined as how much gravity something creates... And we experience this all the time on Earth when our bodies (which have a mass) stay on the ground and falls back to the ground again when we try to escape it by jumping. That's gravity (if you didn't know before).

Mass can also be described as how difficult it is to make an object move. Since force is equal to an objects mass times acceleration, you need more force to make a more massive object accelerate its speed. This equation, F = ma, ties together what we said in the beginning about movement in space and time and how there is no center, nothing can be still and the only thing that really takes effort is acceleration.

Other than the electromagnetic force and gravity, there are two more fundamental forces in the universe and both work in the atom's core: the strong nuclear force and the weak nuclear force. The strong nuclear force holds together the protons and neutrons to build the atom's nucleus, and it also holds together the quarks which are even smaller particles that together make up the individual protons and neutrons (and who knows if these are made up of even smaller parts...). This force is much stronger than electromagnetism and gravity, but works on a smaller distance.

These forces are used inside stars like for example the sun, in nuclear power plants and nuclear bombs, to create huge amounts of energy by either breaking an atom's nucleus or by adding more particles to it. Splitting an atom's nucleus is called fission and combining two nucleuses is fusion (which is used in the sun). The energy gets created by the over- or underweight of protons/neutrons you get when you change the nucleus. This is where the formula "E = mc²" - or energy is equal to mass times the speed of light squared - comes from, which means that energy and mass are kind of the same in a way (over-simplified), and that you get extremely high energy from very little mass, which explains the power of the sun and the danger of nuclear bombs.

The weak nuclear force converts quarks to different types of quarks, which in turn can make the proton that is made out of the quarks turn into a neutron, or the other way around. This force is weaker than the strong force and operates on even smaller scales.

We haven't gone into relativity yet, but a consequence of E = mc² is that relativity says that you need more and more energy to accelerate into higher speeds (sounds reasonable), but when you get close to the speed of light the energy needed to continue accelerating starts to go towards infinity, because of some division by zero that almost happens. However, this means that something with mass can't travel at the speed of light, and something traveling at the speed of light can't have mass. Which means that photons, the particles sending light, don't have a mass.

All in all, these are the four fundamental forces that make things happen in the physical world.

So, all forms of energy are either kinetic energy or potential energy. And "work" is when you use a certain amount of energy. When talking about mechanical work, it can be measured as the force used on an object for a certain distance, which uses the unit Newtonmeters (force * distance, or Newtons * meters). Since force is the most basic concept in Isaac Newton's physics (which is also pretty much the basics of the physics of things we can see), the unit of force is named Newton after him. But then, force times distance gives work, which is measured in Joule, which is also what energy is measured in since energy and work are two ways to approach the energy concept ("energy" is more about the raw concept of energy, while work is the energy you actually use).

The unit for both energy and work, Joule, was named after the English physicist James Prescott Joule, who both worked to debunk the "caloric theory" about heat being a substance itself that was said to travel between substances to give them heat. Joule's work later inspired the idea of energy conservation, where energy can't be created or destroyed, only transformed.

When measuring other types of energy and work, an "electron volt" is the energy needed for an electron to move through a current of one Volt, a kilowatt-hour is 3 600 000 Joules (hour = 3600 seconds, times kilo = 1000?), and probably something more too.

Effect is the amount of work done in a certain time, and now we start to reach ideas that I feel exist more to make it easier for you to buy lightbulbs than for understanding physics... Effect is measured in Watts, which is one Joule per second (convenient for us that we can rely on the units using meters and seconds so we don't have to memorize more obscure names of old men from the 1800s than we need), and is named after James Watt, the Scottish inventor who did some cool things to improve the steam engine to make industries better, or something... I thought he was the lightbulb guy, but turns out he's not.

THINGS WE CAN'T SEE

That was the physics of things we can see, which had to involve lots of things we can't see (electrons, subatomic particles, etc) to be understandable. If we go even further outside of our human abilities, and try to travel in the speed of light, what I just said about force, energy and acceleration won't work any longer. So the basic physics of things we can see is in a way more practical than true, and in the best case only true within certain speeds (the much-lower-than-light speed we humans always travel in).

If we moved at the speed of light, the physics of things we can see would fall apart, and this is because of Einstein. And also because of the fact I started everything with, that we move in space and time but have no center point to revolve around. This combined with the fact that speed can't go faster than the speed of light (...duh?), means that...

... Here I put in a breather for me to meditate on the fact that I'll never understand special relativity emotionally, even if I may understand it theoretically ...

I understand special relativity practically by thinking about the speed of light, then thinking about how I usually measure speed: in kilometers per hour. Speed equals distance per time, but if you can't go faster than the speed of light, increasing speed won't increase speed anymore, so you have to change any of the other two - distance, or time - instead. It feels like special relativity is the consequence of how we use light to exchange information about pretty much everything, and if we try to catch up with the light by going almost as fast as it ourselves, our way of experiencing things will get really weird.

If you move relative to another object, that object will look thinner to you than it "actually" is. But the tricky thing here is that there is no "actually" in special relativity because everything is relative to something else, so that's just how I phrase it to understand it. But this only happen at speeds close to the speed of light, and you get the visible length of the other object in your eyes (you being the almost-speed-of-light-travelling person), by multiplying the objects "actual" length with the square root of the following: one, minus your speed (relative to the other object) times itself divided by the speed of light times itself.

Or: Object's length in your eyes = object's "actual" length * sqrt(1 - your_speed² / lightspeed²)

When it comes to time, the calculation is similar. If you move faster than another object, your time will go slower than the time will go for the people who are on that other object. Your clock will tick slower than theirs. Here, the amount of seconds that goes past for you (who travel in speeds near light speed) is one second divided by the square root of the following: one, minus your speed squared divided by the speed of light squared.

Or: Time gone by for you = time gone by for people on the other object / sqrt(1 - your_speed² / lightspeed²)

This is special relativity and it's very hard to understand intuitively, because we're used to always see ourselves as the center point of our measurements. Trying to understand that you never have a center point to revolve around creates a headache and then we go think about something else instead that has practical use. It's also hard to understand special relativity because we rarely travel in speeds near the speed of light. You will never see this stuff happen with your bare eyes, but somehow we know it's true because of Einstein's abstract thoughts. And this is just special relativity, I won't even get started on general relativity in this post...

Even though special relativity is difficult to relate to, it still follows our intuition about cause and effect. It's still a pretty reasonable theory in many ways. If you instead of going fast you go deep down, to an atomic and subatomic level, physics get more and more unreasonable to our human senses. Quantum physics shows that light is a particle, but behaves like a wave, and becomes a particle again as soon as you try to measure the wave... This is the edge of our understanding of the world, and it seems like the world itself is mad that we've understood so much and tries to hide its details when we try to see them.

According to quantum physics the same particle can do many things at the same time, which gives rise to ideas about parallel universes and massively powerful quantum computers (imagine parallel computing like in a GPU, but in a single atom or something like that), and here is where my knowledge ends. But I've read paragraphs about teleportation, particles on different ends of the universe communicating in instant speed, and about how we can't really know anything at all because of the particles' strange way of behaving and the limits of our tools and our senses.

********

You don't need to be a physicist to know physics. If you understand physics you understand the world, and then you have a good starting point for doing pretty much anything.

(... Left out for convenience: Density = mass / volume, the Doppler effect, various ways to approach force like pendulums and springs, force equals change of "momentum" over time, angular momentum, etc, waves and their reflection and/or refraction through or not through lenses, ... and the rest of the world’s knowledge. And... parts of the cover image are AI generated by craiyon.com - they still require me to credit them)

Advertisement (illegal to click the link)

This Is (NOT!) A Car Club - GAME TRAILER (YouTube)