Explaining Physics Pdf Download
Ailene Goldhirsh
As a CS-Physics double major undergrad entering my senior year, I have begun reading a handful of articles from both fields. Specifically, I have read some articles from programming language-related journals (eg. OOPSLA, ICSE, SIGPL) and physics-related ones (eg. Nature Physics, Physics Review, J. Physique).
From them, I noticed that most PL articles spend a few pages on explaining the preliminaries, especially but not limited to when the research is about a rather specialized topic (such as quantum computing).In contrast, I felt that physics papers often forego this step, especially but not limited to when the research is about a rather specialized topic (such as cavity QED), either trusting the reader to already have the required knowledge or sending them on a footnote trail journey.
It shouldn't be a surprise that papers in programming languages and in physics are quite different. PL is about constructing things, usually based on principles learned from earlier languages. Physics is about discovery of things in the real world. The former is artificial in a real way, so it is natural to explain something about the base conditions to set the stage for what follows. It might not be necessary to do the same for working physicists.
Programming languages create artificial worlds. It isn't "science" in the same way that physics is, though there can be scientific elements, such as user interface (API) design. So, a reader needs some initial guidance about where to start thinking and evaluating what will follow. This would probably only be necessary in physics if a paper were to take a radical approach to an old problem. That might be necessary in a textbook, but not in a professional paper. The fields are different. You wouldn't be surprised to see different structure in a history paper and a CS paper, I'd guess.
Beyond the conventions, which often favor succinct, appropriately-cited introductions (common across physics, chemistry, materials science, biology, etc...), there is also the issue of journal restrictions on number of figures, number of citations, word/character count etc. Often times a lot of stuff which can be considered general background has to be omitted in favor of citing a review (for example), or even a more specific equation derivation which is relevant will at best be relegated to the supporting information.
The physics behind a football's flight is primarily determined by three factors: gravity, air resistance, and spin. As the football is kicked or thrown, it experiences a downward gravitational force, which causes it to follow a parabolic path. The air resistance, or drag, acts in the opposite direction and slows down the ball's motion. Finally, the spin of the ball creates an imbalance in air pressure, causing it to curve in a particular direction.
The shape of a football, specifically its oblong shape, is what allows it to travel long distances and be thrown accurately. The shape creates uneven air pressure, with the nose of the ball having higher pressure and the sides having lower pressure. This imbalance causes the ball to travel further and have a stable flight path.
Football players wear helmets to protect their heads from potential injuries. The helmets are designed to absorb and disperse the force of a collision, reducing the impact on the player's head. They also have a face mask to protect the player's face from contact with other players or the ground.
A football player's weight can affect their performance in various ways. Generally, a heavier player will have more mass, which can make them harder to tackle or push around on the field. However, too much weight can also slow a player down and decrease their agility. It's essential for football players to maintain a healthy weight and body composition to optimize their performance.
Football fields have different types of grass to provide a safe and suitable playing surface. Different types of grass have various characteristics that can affect the ball's movement and players' footing. For example, some types of grass are better at absorbing impact, while others are more resistant to wear and tear. The type of grass used on a football field is chosen based on the climate, location, and desired playing surface for the sport.
I have been interested in philosophy for a while and I was just curious on what you guys thought about this question. On one hand you have a science that is able to (basically) relate all the bodies in this reality in terms of quantity and space with rigorous proofs. On the other you have a science that is trying to describe the universe, but it lacks the rigor that math has.
Physics, and in general science, is all about developing "models" that we hope fit to physical reality as much as possible. Fitting criteria are explanation of current observation (that is not necessarily the pure reality in its essence as the observation might well be restricted by not only the instruments but also the current paradigm and theories of the science branch) with least amount of assumptions and desirably with simpler models, and at least a little bit prediction power broadening our current view of the physical world.
The models central to this endeavor is heavily math oriented/based/expressed-in but they usually are more than this.Beside the strong math involvement in the models, they include certain presuppositions resembling axioms of mathematics (but not being the same) or principles. Contrary to mathematical axioms they are quite open to change or complete disposal and typically extending.
Mathematics can be used to model all possible universes, but it does not tell us which one is the one we inhabit. Physicists can choose one of these models and experimentally determine whether or not it correctly describes the particular universe we inhabit.
Pure math isn't bothered by that, if they are true then it describes the real world, if they aren't then it describes a world different from reality. Whereas physics is highly bothered by that because it's interested in what the real world looks like. So physics makes heavy use of math to build models and run simulations and thought experiments, but crucially relies on experiments and observations in order to verify them, while math doesn't care if they are true.
So unless pure math just happens to be completely based on true assumptions there's a good chance that it will need some updates sooner or later to correct the course and better describe the real world and the process of conceiving these "updates" would be called science.
Pretend that there is a group of bombs that are triggered by a single photon bouncing off a small mirror at the nose of the bomb. If the bomb is not a dud, the bomb explodes when the photon hits its trigger mirror. See illustration below.
What happens now? You can work the math out if you wish. The bottom line is that there is now a 50% chance the photon will hit the rock (as per part 1 above) and a 50% chance that it will hit the full-silvered mirror between points C and E. If it does hit the full-silvered mirror between C and E, then, of course, there is a 50/50 chance it will come out at either point G or point F. So the odds are these then:
But once the photon reaches either of the full-silvered mirrors we, in theory, can know which mirror the photon bounced off of. If the detector between B and D registers a photon, then we know that is the path the photon took. But if the detector does not register the photon, then we can be sure that the photon took the C and E path. Either way, we know (after reviewing the detector data) for sure which path the photon took. The very fact that we know have this data available causes the evolution of the equations to start over.
Because the evolution of the quantum equations starts over, the interference pattern also disappears now. To demonstrate why this is, do the math. Where we left things was that we either had B iD or iC i(iE) but not both.
David Deutsch, on the other hand, would say that we live in a multiverse of many realities and that what actually happened is that in 50% of the alternate realities out there, the bomb did explode. That reality then decohered from ours and could no longer communicate with us and that is why we got the photon at point G. (i.e. that is why the exploding bomb acted more like the rock. It caused that reality and ours to stop communicating.)
The simple truth is that: quantum physics says something about reality that is wholly counter intuitive and simply fantastical. It is either saying something about counterfactuals being (in some sense) physically real or its saying we live in a multiverse of realities. Either way, if you are like me, your mind is probably blown out of your head and lying on the floor behind you. Excuse me while I pick mine up again and shove it back into my head.
Except that if God has free will and evil exists as a real option then there must be some world in which he is evil. I think MWI has lots and lots of problems for Mormon theology. Of course I think it has lots of lots of problems period.
The many worlds interpretation is hands down the most ridiculous physical theory I have ever come across. It has about as much merit as the proposition that Maxwellian anti-demons are causing entropy to increase by robbing the universe of information.
Just for the record, one of the main reasons Penrose wrote about the example in my post was to disprove the idea that the wave function was about probabilities and to prove that it was physically real.
Reality of the wavefunction, of course, does not invalidate MWI. A non-statistical wave function, however, completely invalidates the only argument supplied in favor of MWI, and that is the primary result described in the article I referred to.
Not at all. The article itself points out that the theorem depends on a critical assumption that it is always possible to prepare totally uncorrelated states by multiple methods and then bring them together in a measurement, and that there are interpretations (other than MWI) in which that assumption is just wrong. The paper itself notes that this assumption is NOT true for entangled states, where a measurement on particle X can guarantee what a similar measurement on particle Y will show.
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