Physics - Feynman Lectures on Physics, Atoms in Motion P1
Hello, in this post I'm going to try to resume what I'm starting to learn in Physics, the material I'm using as base is this: https://www.feynmanlectures.caltech.edu/I_01.html.
Atoms in Motion
Introduction,
If you're going to become a physicist, you need to study a lot of things, principally the last two hundred years, because of the fast evolution of various famous physicists, like Albert Einstein, Isaac Newton, and much more.
Even in a course of 4 years, in the end, you would feel that there's much more to study, and there is!
But, despite the tremendous amount of work that has been done for the past hundreds of years, it's possible to summarize a large extent of this content, and this is what we call laws.
And even with this "simplification" that we call laws, they're still hard to grasp and understand if you don't have a solid foundation, so let's start our studies with understanding the relation of physics with other sciences, the relations of other sciences with each other and the meaning of science.
You might ask why we can't start just showing the basic laws, how they work and how they interact with the world, wouldn't it be simple?
Well, no,
First, because we still don't know all the basic laws that exist and even those we know, we don't fully know them, only an approximation of the truth, and sometimes only what we think that is the real truth, not necessarily the truth.
And second, because to correctly explain what the laws do, it's necessary to know some unfamiliar ideas that needs advanced mathematics concepts to even understand what the words mean.
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Let's start with the principle of science, the definition of it is basically this phrase: "The test of all knowledge is experiment. Experiment is the sole judge of scientific “truth.”".
Ok, but what is this knowledge?, Or from where come the laws that need to be tested?
The answer is experiment, you need to try, try and try again, and this is going to give hints that you can use to produce those laws.
But aside from experiments, its also necessary to have a great imagination, to create and transform those hints into a generalization that we call laws, you need to guess and imagine what those strange patterns are, experiment and check if your guess was right, if it wasn't, imagine again, experiment again, until you can discover their mysteries, or have an approximation of them.
This process can sound simple in the paper, but it's so difficult that exists two types of physicist, the theoretical physicist, who image, guess, and deduce new laws and the experimental physicist, who experiment, imagine, deduce and guess.
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Remember that we said the laws of nature are only an approximation, we first need to find the "wrong" ones, until we find the "right" ones. But how do we know that the experiment is wrong?
First, in a trivial way, it would be if something is wrong with the equipment, but this can be easily solved, you only need to check it, reconfigure or change some pieces, so let's not focus into this type of wrong experiment.
How can the experiment be wrong? Only by being inaccurate. For example, the mass of an object never seems to change: a spinning top has the same weight as a still one. So a law was produced: "Mass is constant, independent of speed".
Nowadays, this law is found to be incorrect, because mass is found to increase with velocity, but an appreciable increase needs velocity near that of the light.
An example of a true law is: "if an object moves with a speed of less than one hundred miles a second the mass is constant to within one part in a million", speaking this form, the law can be considered correct.
In practice, some people would think that this makes no difference, you would never ride a bike at the speed of light, so we can use the mass-constant law right?
Well, yes and no, because for ordinary speeds it's ok to use it this way, but for high speeds, we would be wrong, and the higher the speed, the more wrong it would be, a way to understand it would be with this image:
In this image, you can clearly see that the line isn't truly straight, but the difference is so little that practically don't make difference, because you could still reach point B, but if the distance is greater...
As you can see, that small difference now can lead you to a completely different place.
And this happens with all of our approximate laws, even a small difference can make us look at the world in a different manner. Even a very small effect sometimes requires profound changes in our ideas.
Should we teach the correct but unfamiliar law with its strange and difficult conceptual ideas, for example the theory of relativity, four-dimensional space-time, and so on? Or should we first teach the simple “constant-mass” law, which is only approximate, but does not involve such difficult ideas?
The first is more exciting, more wonderful, and more fun, but the second is easier to get at first, and is the first step to a real understanding of the first idea. This point arises again and again in teaching physics. At different times we shall have to resolve it in different ways, but at each stage, it is worth learning what is now known, how accurate it is, how it fits into everything else, and how it may be changed when we learn more.
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