# Tag Info

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I take it as self-evident that lift can be generated by a wing without any difference whatsoever in the shape of the top or bottom of the wing. After all, balsa wood gliders (or ones that are rubber band powered) fly just fine with completely flat wings. If you look at such a plane, you will see the wing is set at an angle relative to the longitudinal axis ...

0

I assume that the laser is emitting a wavelength that the photodiode is sensitive to. If the laser has too much power, you would burn out the semiconductor. Since a laser is a collimate light source, the power lose is minimal for any distance unless there is fog. What type of photodiode do you have? Some are like transistors with low gain and others are ...

0

Your calculations are correct. The light does indeed take longer to reach the other end of the box when they are moving in the same direction, and vice-versa. How could this help, however, to convince the guy in the moving box that he was the one moving, and not me? When he compares the time that the light takes reaching the end of the box, and the time ...

2

You've completely misunderstood the impact of adding a potential to an entangled state. Atoms a and b should roughly have the same distribution ... because each single measurement of position for each entangled pair in the ensemble should yeild $x_a=x_b$ with respect to their local axes ... because this is what it means to be entangled. (Need a check ...

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You describe a communication protocol exploiting EPR/Bell-type setups. If I understand your protocol correctly, you envisage a 'stream' of entangled ensembles, and preagreed measurements being performed on each block of the stream to yield a 'bit'. There are various ways we could do this: you use harmonic oscillator potential. Fine. We could do the ...

2

There is no reason in principle, that I can think of, for this experiment to be impossible. The entanglement could be achieved by aligning the source and the slits so that the upper slit on one side, the source and the lower slit on the other side are in a line. If the particles are produced in pairs with no total momentum then they will be emitted in ...

2

One: I honestly don't know. I was already hard for me to find this experiment in german - although german is my mother tongue. ^^ I finally succeeded with Ringentladung, which I tried to translate into english but the only thing I could find is this. Maybe a native speaker can help here? Two: The electric discharge - which causes the gas in ...

0

How about a radar gun? It works by measuring the Doppler shift of a radio signal incurred when it bounces off a moving object. The frequency shift of each photon encodes the instantaneous speed of the object when the photon scattered off of it. Difficult to get much more instantaneous than that (especially when you compare to a measurement of position, which ...

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Though I've never done it, I hear Si PIN photodiodes are OK detectors. Here's an early google hit, http://iopscience.iop.org/0022-3735/21/8/014

4

There are many ways to detect X-rays. I will list just a few that are (or have been) used in medical imaging. Essentially there are several strategies, but it always involves stopping the radiation and using the energy released to effect a change - chemical or electrical - that can be detected. Photographic film. Exposure to Xrays has a similar effect to ...

2

There are many devices that can measure rate of a quantity without using approximate derivative and integral. I will give some example here: Pitot tube Pitot tube is a device used to measure velocity of a body with respect to flow. This device uses Bernoulli's equation. For computing the velocity using Pitot tube, the total pressure and static pressure ...

1

Your thought experiment does have a major flaw. According to quantum mechanics in any measurement of two spatially separated atoms a and b what happens to b has absolutely no effect at all on the probabilities of measurement outcomes on b. I'm not going to work out exactly what the flaw is in your proposed experiment, but just indicate why quantum theory ...

2

Years ago, the speedometer in a car moved the needle by spinning a magnet. The physical rotation of the driveshaft turned the cable inside the assembly. The spinning cable is attached to a magnet. The needle is mounted on a disk attached to a spring which provides rotational counter-force. The spinning magnet attempts to spin the disk, but the spring ...

0

The measurement frequency doesn't matter to the Faraday effect at the frequencies you mention (though it might at high RF frequencies). The choice of frequency could matter to the electrical circuit which you are driving the solenoid with though. This is because a solenoid is essentially a large inductor, and circuits with inductors can have resonances. ...

1

Luminosity is necessary in order to turn number of interactions to crossections, because theories provide crossections to compare with experiments. Experiments measure number of interactions. A well known crossection, as is Bhabha scattering, substituted on the right will give the luminosity to be used in the other observed interactions in the experiment. ...

1

You may doubt that energy is conserved, but it is a direct consequence of Noether's theorem together with the assumption of time translation invariance, and this latter assumption is perhaps a bit more palatable/fundamental. That is, it is mathematically true that if the outcome of an experiment doesn't depend on when we perform it, the quantity we call ...

3

Let's assume that an experiment is performed that seems to indicate a violation of the conservation of energy principle. Now, I suppose that it's logically possible that the experiment actually and unambiguously falsifies the principle in which case we must conclude that the principle is approximate and we must seek a deeper principle to guide our ...

4

I will try to give a short introduction into the ideas of scientific truth as I understand them. In mathematics, the world is beautifully simple. We have axioms that the set to be true, and from these we can deduce a plethora of statements to be undoubtedly true - given that the axioms are true. There may be undecidable statements about which we cannot say ...

0

It cannot be demostrated, but it can be checked. This year I've done an experiment which verifies (indirectly) this principle. It is really easy: I take an iron ball, and I shoot it to a pendulum. As a result, the pendulum goes up, and I can measure the deviation angle after the collision. With a sensor, I'm also able to measure the initial speed of the ...

1

I agree with you that the mathematical multiverse theory of Max Tegmark is the triumph of Occam's razor in simplicity (Although I disagree in restricting it only to Godel computable, mathematical structures). Not only it gets rid of explaining the physical universe itself (why there exist a physical universe?) but has many other philosophical advantages that ...

1

Any particular theory of (astro)physics that predicts a multiverse will be disproven the moment experimental results or observations are found to be in conflict with the theory. In physics all theories are falsifiable, so this is not a problem in principle. However, you can then postulate that there may still exist a multiverse and that this idea cannot be ...

0

This is an example of Faraday's Law, one of Maxwell's equations: $$\nabla \times E = - \frac{\partial B}{\partial t}$$ Which relates the curl of an electric field to the time-derivative of a magnetic field. If you consider a static electric field, you can describe the entire system with only Gauss's Law: $$\nabla \cdot E = \frac{\rho}{\epsilon_0}$$ ...

2

Neutrons with the angstrom-scale wavelengths appropriate for diffraction from ordinary crystals have kinetic energies of a few milli-eV. Since neutron detection always involves a nuclear reaction with an energy of a few mega-eV, it's more or less impossible to directly measure small changes in a neutron's energy due to scattering in a crystal. So neutron ...

1

Newton had much precedent. He didn't devise the 1st and 2nd Postulates in a vacuum. Regarding the 1st Postulate: John Philoponus (ca. 490-570) first devised the notion of inertia. …rest is found in all things. For the perpetually moving heavens partake in rest, because the very persistence of perpetual motion is rest.[In De anima, 75, 11]. …the ...

2

The $\chi^2$ statistic is independent of the number of degrees of freedom. But converting that statistic to some type of $p$-value does depend on the degrees of freedom. That is, you calculate $\chi^2$, then with that number and the degrees of freedom you look it up the $p$-value in a $\chi^2$ table. As for the "corrected" version of this test, you may find ...

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The changing acceleration of the electrons explains the created negative electric field of the magnetic induction, the electromagnetic inertia, the changing relativistic mass and the Gravitational Force, giving a Unified Theory of the physical forces. Taking into account the Planck Distribution Law of the electromagnetic oscillators also, we can explain the ...

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The Wikipedia article on angular resolution https://en.wikipedia.org/wiki/Angular_resolution is a source of many useful facts relevant for the question. For example, it was empirically established already by the English 19th century astronomer W.R. Dawes that the angular resolution $\theta$ in arcseconds is about $$\theta = \frac{4.56}{D}$$ where $D$ ...

1

Schrödinger's work is known for two distinct ideas relating to the nature of living systems. The first is what he called "order from disorder," meaning the way in which organisms can maintain a low entropy (or high free energy) state by increasing the entropy of their environment. (I.e. by eating low-entropy food and excreting high-entropy waste). Although ...

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Dimensional analysis allows us to write the solution to any physical system in the form $$f(\Pi_0, \Pi_1, \Pi_2, \dots) = 0$$ where the $\Pi$s are independent dimensionless constants formed from our dimensionful physical parameters. Usually, there is a particular physical parameter we are interested in computing, and so, by rescaling our dimensionless ...

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