Questions tagged [experimental-physics]

for questions about design, process, data, or analysis of experiments and observations.

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16
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1answer
2k views

G4v Gravitational Wave vs General Relativity vs LIGO Observation

CalTech emeritus professor Carver Mead produced an alternative prediction, to General Relativity, for gravitation wave observation which he published last year in anticipation of LIGO observations. ...
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3answers
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Accidental, unplanned breakthroughs in physics [closed]

There is possibly some idiom or saying like this, "If you try too hard for something, you will never get it. If you do not aim for something, it may fall on you accidentally, not as you originally ...
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Does old light contain clues to its age?

Light from celestial objects is old. In the case of galaxies, it's millions of years old. It seems plausible to me that light might show signs of its age. I was surprised that a Google search only ...
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2answers
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How to determine the mass of a quark?

As far as I know quarks are never found in isolation, so how can we determine their rest mass?
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10answers
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How can I determine the rpm of a wheel that's spinning really fast?

Let's say that I have a motor that's spinning really fast. I really want to know the angular speed of the motor. Using a stopclock definitely won't work as no one can time such fast rotations. So how ...
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2answers
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Why do physicists assume that dark matter is weakly interacting?

IceCube, XENON, etc, keep yielding negative results. If dark matter exists, it doesn't interact with baryonic matter at the energy ranges they can detect. The response is to build even bigger ...
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8answers
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Given fluids expand non-linearly, how were physicists able to make a linear temperature scale?

Materials expand with increase in temperature. As far as I know this property for fluids was put in use to make initial thermometers. We know that expansion of fluid is given by the following formula (...
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4answers
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A curious phenomenon with a stick

Recently, I've encountered a really curious thing, namely: Support in the air a straight stick of length, say, 1 meter, using your index fingers in such a way that the left one is e.g. 30cm from the ...
24
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6answers
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How was Avogadro's number first determined?

I read on Wikipedia how the numerical value of Avogadro's number can be found by doing an experiment, provided you have the numerical value of Faraday's constant; but it seems to me that Faraday's ...
10
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1answer
872 views

How to measure Torsion and Non-metricity?

In General Relativity, we most often work with the Levi-Civita connection (metric and torsion-free). What kind of experiment can we make to be sure that our physical space-time indeed is torsion-free ...
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1answer
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Is there any evidence that dark matter interacts with ordinary matter non-gravitationally?

As far as I understand it, dark matter direct detection experiments are based on the idea that dark matter interacts with ordinary matter, it just has a very small cross-section. So far, there's been ...
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4answers
489 views

What is the experimental evidence for the gravitational field having positive energy density?

Recent direct observation of gravitational perturbations attributed to merging black holes and merging neutron stars has reliably confirmed the existence of gravitational waves. The observed fact that ...
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2answers
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Quantum Computing, Qubit Creation/Entanglement

I am currently a high school student researching quantum computing. I was referred to this site by Google and a friend. Currently I am researching the qubit part of quantum computing. My question is ...
28
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1answer
885 views

Best current bounds on nonconservation of momentum?

It's not straightforward to test conservation of momentum experimentally, and many experiments that seem like tests really aren't. For example, in a Newtonian system of identical particles that ...
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3answers
1k views

What is the most compelling evidence of General Relativity in the presence of matter and energy?

The most oft-cited triumphs of GR are things such as the shifting perihelion of Mercury, gravitational redshift experiments, and gravitational lensing. But, as far as I know, these are only ...
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3answers
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Why is there a hiss sound when water falls on a hot surface?

Why is there a hiss sound when water falls on a hot surface? I have searched a lot, asked my teachers but none of them seem to give me the logical answer to it.
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2answers
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In which experiment did protons seem to consist of infinite amount of quarks?

In this video Richard Feynman is telling that in some experiment it seems that the proton should consist of infinite amount of quarks. What is this case he's mentioning? Is it solved now?
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Does mathematical sloppiness in quantum mechanics ever produce incorrect predictions?

Does mathematical sloppiness in standard quantum mechanics ever produce predictions that don't pan out? I'm not talking about things like the WKB approximation, but instead subtle functional analytic ...
10
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1answer
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Experimental data for asymmetric Newton cradle

Using a "successive impact model" (as if each ball were seperated from the other ones), I produced the following animations: You can see any combination of balls with masses of 1 or 2 (left) or 1 and ...
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2answers
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How is angular momentum measured in experiments/in practice? [duplicate]

Possible Duplicate: How does one experimentally determine chirality, helicity and spin? How do you find spin of a particle from experimental data? We read about and study angular momentum in ...
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1answer
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Books on undergraduate experimental physics?

In undergraduate exams, problems sets etc, their are often questions that take the form: Describe an experiment in which you can measure $x$, $y$ and $z$. Does anyone known of any resources, ...
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6answers
1k views

Is there a way to disprove the universe is a simulation? [closed]

Is there a way to disprove the theory which says the universe is a simulation?
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3answers
1k views

How can we 'see'/measure/detect particles during experiments?

I often read (high-level, conceptual) articles and news on the advances of particle physics. In these, statements are made along the lines of 'particle X splits into particles Y and Z which exist for ...
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6answers
3k views

Why should any physicist know, to some degree, experimental physics? [closed]

I've been trying to design a list with reasons why a proper theoretical physicist should understand the methods and the difficulty of doing experimental physics. So far I've only thought of two points:...
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3answers
702 views

Can someone clarify whether the recent experiment closing all remaining loopholes to Bell's Theorem really shut the door on local realism for good?

I saw this recent article on Phys.org that purports to close all remaining loopholes that previous experiments on violations of Bell's inequality left open. My question is, does this really close the ...
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1answer
655 views

The status of the BICEP2 'discovery' after Planck 2014

The tumultous period after the original announcement that the BICEP2 experiment had supposedly detected strong evidence of cosmological inflation in the form of B-mode polarization in the cosmic ...
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3answers
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How hot is the water in the pot?

Question: How hot is the water in the pot? More precisely speaking, how can I get a temperature of the water as a function of time a priori? Background & My attempt: Recently I started spend ...
8
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3answers
528 views

What are the main differences between $p p$ and $p \bar p$ colliders

I know that it is somehow related to the parton distribution functions, allowing specific reactions with gluons instead of quarks and anti-quarks, but I would really appreciate more detailed answers ! ...
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5answers
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Experimentally measure velocity/momentum of a particle in quantum mechanics

In the context of quantum mechanics one cannot measure the velocity of a particle by measuring its position at two quick instants of time and dividing by the time interval. That is, $$ v = \frac{x_2 - ...
7
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1answer
533 views

How to count quarks using Deep Inelastic Scattering?

The Wikipedia article on deep inelastic scattering suggests that the experiment shows baryons have three point of deflections (corresponding to three quarks) and mesons have two points of deflection. ...
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0answers
274 views

Good physics book to discover stuff by yourself [closed]

I am asking for a book/any other online which has the following quality (To be particular: Of classical physics(Newtonian mechanics, sounds, lights etc, stuff upto 1800's)): The book, before ...
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8answers
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Is there any reproducible tested evidence for Ni-H cold fusion? [closed]

The main replications of cold fusion, the ones that are beyond reproach, used Pd/d as the system. But commercial developers have often claim to use Ni-H to achieve similar effects. The claims include ...
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4answers
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What does the $I$-$V$ curve in josephson junction mean?

According to the $I$-$V$ curve for Josephson junction tunneling for S-I-S (superconductor-insulator-superconductor), Do we have any tunneling current for $0< V\leq V_c$? If yes, then why don't we ...
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3answers
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Experiment demonstrating interference patterns of neutrons

The question is about experiments (and references) that demonstrate interference patterns of neutral (chargless) particles (fermions), especially neutrons. Like double-slit experiments for neutrons (...
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3answers
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What is the experiment used to actually observe the position of the electron in the H atom?

Prior to observation, the electron can be found anywhere (from inside the nucleus to the ends of the universe), but once its position is determined the answer is precise (albeit its momentum is not ...
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4answers
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Is the principle of Conservation of Energy empirically verifiable?

Before I am inundated by myriad and vociferous claims that conservation of energy is the single most well-attested and experimentally verified principle in all of science, let me say that I am well ...
2
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1answer
273 views

Why are only some portions of the EM spectrum able to pass through a metal dog bowl?

In this photo you can see part of the bowl, which I turned upside down and placed on top of various electromagnetic sources to determine whether the waves could pass through it. The graph in the ...
2
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2answers
964 views

How many of the Standard Model free parameters are mutually independent: (all of them)?

My knowledge of the standard model is very limited so please let me spell out my assumptions first (and please let me know when I have mangled concepts, terminology or I am plainly just out of my ...
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1answer
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Does my green laser pointer emit three distinct frequencies, or is my measurement flawed?

I was playing around with a cheap diffraction grating and my set of laser pointers, and I noticed that while the red and the blue pointers produce a single point in the spectrum, my green laser ...
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5answers
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Does a magnetically suspended frog feel weightless?

Magnetic levitation has been used to suspend frogs in midair. I was wondering: Does the animal still feel gravitational pull? I mean: Does the frog feel like an astronaut on the ISS, or does he feel ...
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9answers
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What are good mechanics experiments for 10 year olds? [closed]

I'm trying to explain elementary mechanics - without the benefits of calculus or even algebra - and struggling. I'd like to find reasonable ways to demonstrate Newton's laws, minimally, and possibly ...
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1answer
831 views

How the inverse square law in electrodynamics is related to photon mass?

I have read somewhere that one of the tests of the inverse square law is to assume nonzero mass for photon and then, by finding a maximum limit for it , determine a maximum possible error in $\frac{1}...
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3answers
4k views

Can a television detector van REALLY tell if you have the TV switched on? [closed]

In the UK, it was regularly advertised by the BBC, and the Post Office, that they had vans that could check if your TV was on, even if you were in an apartment block full of other people's TVS. TV "...
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2answers
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Mechanical Equivalent of Heat

Recently I have been looking up James Joule's experiment regarding the mechanical equivalent of heat. After viewing some drawings of the apparatus, I assumed that the lines holding the weights would ...
9
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3answers
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Left and Right-handed fermions

Is there a simple intuitive way to understand the difference between left-handed and right-handed fermions (electrons say)? How to experimentally distinguish between them?
9
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1answer
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What are the different ways to measure the spatial curvature of the universe?

Just what the question asks. Assuming the Friedmann-Rovertson-Walker (FRW) metric, what measurements can be performed to determine the spatial curvature of the universe.
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2answers
510 views

How do the LASERs in LIGO realize that space has expanded as a gravitational wave passes by?

I read an article on LIGO, and I heard it mentioned that it is a nontrivial argument to say that the effect can be measured by interferometry. What happens to space as the wave passes? Does the light ...
8
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0answers
317 views

A theoretical model for evaporation occurring when wind is blowing over the surface of water

I've recently done an experiment in which I was studying the variation of the cooling rate of hot water in a draft (wind). The air was blow directly over the surface of the water (kept in a ...
8
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364 views

Has the curvature of spacetime been measured at the human scale?

The curvature of spacetime has been observed many times from the deflection of light around massive astronomical objects. But has it been observed around small objects in a lab? In the Cavendish ...
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1answer
919 views

Can Ohm's law break in metals?

I was rereading Purcell's Electricity and Magnetism as research for another question, and I found this passage: In metals Ohm's law is obeyed exceedingly accurately up to current densities far ...

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