# Tag Info

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Yes. Two particles at a given position, one moving and the other at rest are having the same kinematic state. But dynamic state takes in the velocity. When you need to specify both position and velocity - it becomes kinetic state. After all kinematics + dynamics = Kinetics.

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For the most part, you are right. Physics is tough, and in many ways high school physics is the hardest because it is the first introduction to a new and difficult way of thinking. Furthermore, teachers are under pressure to complete the curriculum. And there's always the possibility that the teacher him/herself does not have a firm grasp of the subject. ...

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sorry to hear that things are frustrating. I don't think you need the Huygen principle for the double slit experiment. Take a look at the diagram below... The diagram shows two rays from a double slit experiment. The path lengths are slightly different from the two slits. In one case the waves arrive in phase and you get the bright fringe - constructive ...

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Relativists tend to use the proper time, $d\tau$, and the proper distance, $ds$, interchangably. If you're working with proper time you'd expect the equation for it to look like: $$d\tau^2 = dt^2 + \text{other terms}$$ while if you're working with proper distance you expect: $$ds^2 = dx^2 + dy^2 + dz^2 + \text{other terms}$$ The sign problem comes ...

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Could you provide a simple reason for these two conventions? The reason behind the (-,+,+,+) convention (the "mostly plus metric") is that a positive length in 3 dimensional space (e.g., the distance from my head to my toes) should still be a positive length in 4 dimensional space-time. Why should the distance from my head to my toes all of a sudden ...

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One never pluralizes unit abbreviations. Your link goes to the BIPM, the body responsible for maintaining the definitions of the international system of units, and is authoritative. The folks at NIST agree and address most of your questions. I would say The pipe is 0.75 m long. or The pipe is 75 centimeters long. or even The pipe is ...

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cms and kgs are wrong. The SI units are abbreviations which are also used in the plural. You will write 2.6 m/s or 1 m/s, but say "2.6 meters per second" or "1 meter per second" respectively. Keep in mind the SI units are also used in tons of other languages that do not form the plural by attaching an -s. The units look the same in those languages. (e.g. ...

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The first difficulty in making a measurement of this kind is, of course, to build the facility. However once you solve all the engineering issues and put your machines in place, the experiment flow is pretty straightforward: you run and you get the data, in principle without any human intervention. Up to here you just let Nature do its work in a pretty ...

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Most of the reproduction of results in particle physics comes from two sources: Competing experiments running nearly simultaneously. In this case both ATLAS and CMS got comparable results. Now, they are both using the beam from the LHC, so how do we know the beam is properly understood? Because while they were commissioning those machines they reproduced ...

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Do we have any similar experiments where we confirm a theory without being able to reproduce those results? Not today, but once we know how it works we can repeat it on a smaller and cheaper scale. The first electronic calculators required an entire floor, consumed staggering amounts of power and cost a budget-busting amount of money. Today, my phone ...

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The question is "how much scientific confidence can we put into things like the mass of the Higgs". Well, what is the level of certainty? According to CERN it is around 7 sigma. In simple terms at 7 sigma, both the CMS and ATLAS teams are reporting that there’s only a 0.0000000001% chance that they haven’t found a Higgs-like particle.

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A firm understanding of classical physics is essential. This means understanding the qualitative and quantitative aspects of: 1) Newton's three laws of motion (Kinematic and Dynamic perspective) 2) Rotational motion dynamics 3) Electromagnetism 4) Newtonian mechanics (Newtonian gravity) 5) Principle of superposition and waves 6) Classical thermal ...

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There would be a big difference between documenting the advance of truly fundamental physics, and documenting the advance of every investigation, discovery and idea which might count as physics. The fundamental advances are documented in places like encyclopedias, textbooks, and the list of Nobel Prize winners. Perhaps the closest thing to a central, ...

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At present for physics research, a phenomenologist is a theoretical physicist who is well grounded in the current physical theories and at the same time understands the data and can create detailed theoretical models that can predict the behavior of future experiments. In this context, phenomenology is the study of the way current theories fit the data and ...

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Nobody ever tried with LHC, but here is Anatoli Bugorski: http://en.wikipedia.org/wiki/Anatoli_Bugorski Given the damage he received with a beam of 70 GeV protons (intensity ~10^13) you can probably imagine the damage you would receive from 6500 GeV protons (intensity ~10^32). For more info about the "danger" of the LHC beams, I suggest you read about the ...

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The LHC luminosity is $4.6\cdot 10^{32} /cm^2/s$ (reference) - that is an incredibly intense beam, but there is a finite number of protons going around. The thing that really matters though is the number of protons in the beam at one time: there are 2808 bunches in the beam (http://lhc-machine-outreach.web.cern.ch/lhc-machine-outreach/collisions.htm) with a ...

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When they need to empty the beam of particles they are directed into a "beam dump" target Absorption Each beam dump absorber consists of a 7m long segmented carbon cylinder of 700mm diameter, contained in a steel cylinder, comprising the dump core (TDE). This is water cooled, and surrounded by about 750 tonnes of concrete and iron shielding. ...

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I don't have an "official" distinction, but one difference is that statistical mechanics is used for systems with a very large number of particles, and is only concerned with quantities which are averaged over the whole ensemble. Many-body theory deals with smaller systems, and attempts to treat all the particles in the system, within some approximation. ...

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ok, you know that plucking a guitar string makes it vibrate. It vibrates up and down, up and down, again and again in the same pattern until friction stops it. a guitar string can emit different harmonics, but these are just higher or lower notes moving in the same regular pattern Harmonic motion is a term used to describe the same idea, of a process ...

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There isn't an answer to your question because a varying magnetic field doesn't really produce an electric field (and a varying electric field doesn't really produce a magnetic field). Time varying magnetic and electric fields are associated, but it is misleading to imagine that one causes the other. Even physicists tend to instinctively think of electric ...

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You should have a look at Newtons First Law of Motion: "When viewed in an inertial reference frame, an object either remains at rest or continues to move at a constant velocity, unless acted upon by an external force." When the ball is moving up and there is no force at all, then the ball will continue it's motion upwards. But when there is gravity, you ...

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This is a classic misconception that most people share at some point in their lives. For centuries, we struggled to understand this point. For example, the famous Aristotle expresses your misconception that: continuation of motion depends on continued action of a force i.e. you see a ball moving upwards, and think that there must always be a force ...

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Once you release the ball, you are not applying a force to it; it is freely falling (despite its upward motion). The only force acting on it is the gravitational force, pulling it downwards (which is why it slows down and stops momentarily at the apex, before coming back down). See also the related question When a ball is tossed straight up, does it ...

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My take on this is that an experiment requires a manipulation of nature such as to produce a minimum set of conditions necessary to approximate a given phenomenon. Often this means a simplification of the natural case. Experiments may therefore involve a reduction in the complexity of a natural phenomenon in order to render it's workings more evident. The ...

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Ion propulsion rockets are just that, rockets. They're just a different kind of rocket that the typical chemical propulsion rocket. Chemical propulsion uses chemical reactions and thermodynamics to create a high velocity exhaust, and hence thrust. Ion propulsion works by ionizing a gas (typically a gas with a high molecular mass such as xenon), accelerating ...

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Just a start... there are others on this site that know much more about these things (David Hammen, are you reading this?). For any rocket to gain speed, it needs to expel some material - and the faster the material is expelled, the more speed the rocket gains. There is a "rocket equation" that shows the velocity you can reach depends directly on the exit ...

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I think Terran is as good a word as any, as is Geo. Thinking of terms where Solar or Lunar are used. Solar Gravity, Lunar Gravity, Terran Gravity, or Earth's Gravity. Solar Magnetic Field, Lunar Magnetic Field (which, I'm not sure there is one), Earth's Magnetic Field or Geo-Magnetic Field is also used. Earth's, Geo or Terran are the best 3 options I ...

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Technically this question is off topic and would belong in an astronomy SE, but the answers you probably are seeking are terrestrial or terran depending on whether it is a person or an object. Terran has been sorta scooped up by the Starcraft community though so terrestrial is used in almost all cases to my knowledge.

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The relativity of simultaneity is not an axiom, the axiom is that the light velocity is the same in every frame of coordinates. A spot of light travels at the same velocity, c with respect to you, and at the same velocity $c$ with respect to a traveler traveling with respect to you at an arbitrary velocity. So, assume that you send two spots of light to ...

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Waves is one common way in which nature expresses the flow of energy through space and time. A pulse is just a special type of wave - a solitary wave. And solitary waves that dissipate a minor amount of energy into the medium, have low dispersion, and are able to maintain their shape over distance are called 'solitons'. A vortex ring is a good and ...

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It appears that you are looking for the "big picture" of quantum mechanics, not the ability to do extensive calculations. For this, in my opinion, you should start by understanding observables with two possible values (like spin in a particular direction, which is either up or down), rather than observables with infinitely many possible values (like ...

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Yes, you can. Quantum physics is very accessible, and with basic knowledge of calculus you can learn.

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A common misunderstanding of quantum mechanics is the belief that EVERYTHING in the world is quantized, but this is simply not true. For example the position of a free particle is not quantized but may take on any value.

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$$g_{\mu\nu}=\begin{pmatrix}g_{00}&g_{01}&g_{02}\\g_{10}&g_{11}&g_{12}\\g_{20}&g_{21}&g_{22}\end{pmatrix}$$ $\mu,\nu=0,\ldots,N$ are the matrix indices of the metric (and of tensors in general) in $N+1$ dimensions.

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Those Greek letters are indices indexing the components of $g$. Generally if one expresses a rank-2 tensor like $g$ as a matrix, the first index indexes the rows, the second the columns. In your example, we have $g_{rr} \equiv g_{11} = 1$, $g_{\theta\theta} \equiv g_{22} = r^2$, $g_{r\theta} \equiv g_{12} = 0$, etc. As you can see, we sometimes use numbers ...

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Most papers on quantum mechanics don't explain issues like interpretation clearly and non-locality clearly. The most notable exceptions to this are David Deutsch and to a lesser extent David Wallace. "The Fabric of Reality" by David Deutsch is a popular book that explains quantum mechanics, see especially chapter 2. See also "The Beginning of Infinity" by ...

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Lectures on Quantum Theory: Mathematical and Structural Foundations by Chris Isham is a thin, easy to read book. The first 6 or so chapters are a simple introduction to quantum mechanics, but from about chapter 7 or 8 he goes into the Quantum Measurement problem and various interpretations and their associated difficulties. He also discusses Bell's Theorem, ...

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