# Tag Info

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At the physics 101 level, you pretty much just have to accept this as an experimental fact. At the upper division or early grad school level, you'll be introduced to Noether's Theorem, and we can talk about the invariance of physical law under displacements in time. Really this just replaces one experimental fact (energy is conserved) with another (the ...

14

It works with a lot of body parts. It will work with a piece of wire too. This keys work at about 433 Mhz, a resonant Lamda/4 antenna is about 18 cm. Obviously the whole key is shorter, the antanna is not tuned for maximum power transmission. By bringing the key close to some conductive material, the power transmitted increases. A very recondite answer ...

9

Vectors are probably the most important tool to learn in all of physics and engineering. Some random examples: Classical Mechanics: Block sliding down a ramp: You need to calculate the force of gravity (a vector down), the normal force (a vector perpendicular to the ramp), and a friction force (a vector opposite the direction of motion). E&M: Electric ...

8

1.) Find something that interests you. The secret to learning is to do something you can be passionate about. For one person it may be building metal detectors (cicuits etc.) and another may be more interested in string theory or crystal physics. Explore your local library's physics section. 2.) Become competent in the area that interests you. Thomas ...

8

No, physics is not rigorous in the sense of mathematics. There are standards of rigor for experiments, but that is a different kind of thing entirely. That is not to say that physicists just wave their hands in their arguments [only sometimes ;) ], but rather that it does not come even close to a formal axiomatized foundation like in mathematics. Here's an ...

7

The bodies internal electrical resistance is quite low. Bodily fluids have enough ions (dissolved salts mainly) for the conductance to be high. The thin layer of skin provides almost all of the resistance. Once the skin resistance is overcome (by wetting, or for higher voltages arcing), the low internal resistance dominates. So for instance, how good a ...

7

The proposed partition of physics into Thermodynamics, Classical Mechanics, and Quantum Mechanics is quite arbitrary. To take just one conspicuous example, statistical mechanics does not fit, as it is the discipline that mediates between these three areas of physics. The Physics and Astronomy Classification Scheme (PACS) ...

6

A friend sent this as his explanation and it seems quite satisfactory to me: For a balloon to fly in a straight line, the direction of the jet of expelled air would have to be in line with the balloon’s centre of mass and its centre of drag – the point where the forces resisting the balloon’s forward motion are symmetrical If these two centres don’t ...

6

JETP english archive (73-96), may be found here http://www.jetp.ac.ru/cgi-bin/e/index . Russian archive also starts at 73, so I think earlier versions may be found in libraries only. I found some issues of Proceedings of the RAS here: http://elibrary.ru/issues.asp?id=7781 in Russian only. It seems that they are not translated at all. And normal electronic ...

6

You start by starting the process. It really doesn't matter all that much how you start, only that you start. Go to the library, look through some books, etc. At first, you'll find much of what you read opaque. But, in a short time, you'll start connecting some dots and then more and then more still. You'll revisit material that was initially ...

5

OK, this is for experimental high energy physics as I worked in the field for over 40 years. There are groups in institutions, universities and research ones. There are many such in each country, and there are many countries. The group leaders in the group decide who signs a paper, mainly by the man hours put in the construction and running of the ...

5

Depends on what you mean by "sense" for technology. Condensed matter physics is the obvious answer, but that's partly because there are more condensed matter physicists than any other sort (particle physics gets all the press, but the condensed matter division of the APS is the largest). A great many of those people are employed in industry, so it's an area ...

5

Успехи физических наук 1918-2011 years For example - А.М. Прохоров, Н.Г. Басов Молекулярный генератор и усилитель УФН 57 (11) (1955) English version - Physics-Uspekhi 1958-2011 years

5

The number of SI units is not at all fundamental to nature: the natural Planck units are the fundamental things. But at low energies, large systems, and slow speeds, there are scaling laws that allow you to pick three units arbitrarily. This is why humans think they get to pick three arbitrary scales. This is false, but it seems true from our experience. An ...

5

If you make a cardboard tube, put this into the ballons nozzle and then let go you'll find the balloon goes in a mostly straight line. It probably won't go exactly straight because the balloon probably isn't exactly cylindrically symmetrical, but it will go a lot straighter than without the cardboard tube. I recall doing this in primary school long before ...

4

The lead bird does gain something from the V - it's the same principle as the spoiler on the back of a car. The vortices from the wings of the bird would create a low pressure region immediately behind it, which in simple terms sucks the bird back. The following bird prevents this vortex by splitting the upper and lower air flows with it's wings and so on - ...

4

This doesn't match your stated interests, but the things you talk about are generally well established fields with an enormous history, and it generally takes longer to get to the forefront of research in such areas. If you can code, there is the interesting problem of classical turbulence. It is wide open as mathematics and as physics, and there is a ...

4

I basically agree with Argus, though I take a slightly different perspective. Physicists try to explain the world by constructing mathematical models to approximate it. The phrase mathematical model can sound mysterious, but it just means an equation or equations that predict what's going to happen given some initial conditions. For example Newton's laws of ...

4

The learning time problem affects everybody, physics is intimidating because to learn it, you have to recapitulate the history, there's no underlying aximatic system to deduce from. On t'Hooft's website, you will find a self-study guide put together for this purpose. It should get you started, and I don't think I can improve on t'Hooft. But if you know ...

4

Physics is usually not rigorous. But there is a branch of physics, called mathematical physics, in which physics is treated with full mathematical rigor. There everything begins with formally stated assumptions (axioms) from which everything else is rigorously deduced. In particular, there are fully rigorous treatments of phenomenological thermodynamics ...

3

Even seasoned professionals disagree on this one. Trialogue on the number of fundamental constants by M. J. Duff, L. B. Okun, G. Veneziano, 2002: This paper consists of three separate articles on the number of fundamental dimensionful constants in physics. We started our debate in summer 1992 on the terrace of the famous CERN cafeteria. In the ...

3

I am definitely not a physicist, however I can think of 2 engineering problems off the top of my head. If I'm incorrect about any of these, please let me know. 1)Structural engineering. If forces acting on structure are stronger than structure will support, the structure collapses. 2)Any kind of oscillator/wave propagation, including a/c electrical phase ...

3

I know this is an old question, but for the benefit of people visiting here wondering what the answer was, here it goes: A droplet can stay at rest on an inclined plate because of small heterogeneities on the surface. This can either be a small roughness (of the order of nano/micrometers) or `dirty' spots where the surface chemistry is locally different. ...

3

It's getting to the point where building nanoscale devices is commercially practical, so maybe nanophotonics, nanomaterials, nanofluid dynamics, nanoengineering, nanomechanics (?), etc. This area may be very important for practical quantum computing, but there are many much nearer applications. And some of these are being studied in engineering departments ...

3

A similar foundational cornerstone of physics is the principle of rotational invariance. Suppose that the laboratory finds that neutrinos (or anything else) have different oscillation rates when going in the N-S direction than in the E-W directions, in a vacuum, with no relation to anything else. This would break physics just as badly as faster-than-light ...

3

The answer to your question depends a lot on the what you think what fitting into a framework means. In some aspects condensed matter physics does not fit it any of your categories. While quantum mechanics is used heavily in condensed matter theory there are proponents that it is a different field. So it is not applied QM. P.W. Anderson phrased it ...

3

I don't think it's possible to answer your question in any useful way. For example, I spent 12 years working as a colloid scientist, and I don't recall having to take the age of the earth or indeed the universe when I was trying to calculate the shelf life of a bottle of shampoo. However the interparticle forces in colloids are described using the same ...

3

This answer is very similar to Adam's, though I come to the opposite conclusion i.e. that earth loses mass over time. According to the Scientific American article the earth loses about 3kg of hydrogen per second, and I make that about $10^8$ kg per year. According to this article the Earth gains about $3 \times 10^7$ kg per year from meteors (mostly ...

3

Simple Answer: Nothing is guaranteed 100%. (In life or physics) Now to the physics part of the question. Soft-Answer: Physics uses positivism and observational proof through the scientific process. No observation is 100% accurate there is uncertainty in all measurement but repetition gives less chance for arbitrary results. Every theory and for ...

3

Like you, I want to self-teach myself physics, yet here I am still at around the same stage I was a few years back. Why? Because to learn physics effectively, I need to be immersed in it for days, weeks, months even years at a time. I also need to be coached by good teachers and peers that can steer me in the right direction, and prevent me from being lead ...

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