Questions tagged [experimental-physics]
For questions about design, process, data, or analysis of experiments and observations.
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Cooling a cup of coffee with help of a spoon
During breakfast with my colleagues, a question popped into my head:
What is the fastest method to cool a cup of coffee, if your only available instrument is a spoon?
A qualitative answer would be ...
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What experiment would disprove string theory?
I know that there's big controversy between two groups of physicists:
those who support string theory (most of them, I think)
and those who oppose it.
One of the arguments of the second group is ...
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Why is the detection of gravitational waves so significant?
LIGO has announced the detection of gravitational waves on 11 Feb, 2016. I was wondering why the detection of gravitational waves was so significant?
I know it is another confirmation of general ...
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Why is the vibration in my wire acting so oddly?
I was soldering a very thin wire today, and when I had one end firmly soldered, I accidentally bumped the wire diagonally with my tweezers. What I'd expect to happen is that the wire oscillates for a ...
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How exactly do you avoid fooling yourself?
In cargo cult science Feynman writes:
"Millikan measured the
charge on an electron by an experiment with falling oil drops, and
got an answer which we now know not to be quite right. It's a
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What was the major discovery on gravitational waves made March 17th, 2014, in the BICEP2 experiment?
The Harvard-Smithsonian Centre for Astrophysics held a press conference today to announce a major discovery relating to gravitational waves. What was their announcement, and what are the implications?
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What are the next generation physics experiments? [closed]
The LHC and LIGO are two recent examples of hugely ambitious experiments in fundamental physics, both of which took decades to develop.
What are the next major experiments currently being planned and ...
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Status of experimental searches for tachyons?
Now that the dust has settled on the 2011 superluminal neutrino debacle at OPERA, I'm interested in understanding the current status of experimental searches for tachyons. Although the OPERA claim was ...
user4552
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Why do we need large particle accelerators?
The LHC is much larger than its predecessors, and proposed successors much larger still. Today, particle accelerators seem to be the main source of new discoveries about the fundamental nature of the ...
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Why is jumping into water from high altitude fatal?
If I jump from an airplane straight positioned upright into the ocean, why is it the same as jumping straight on the ground?
Water is a liquid as opposed to the ground, so I would expect that by ...
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How did Newton discover his second law?
I've always assumed/been told that Newton's 2nd law is an empirical law — it must be discovered by experiment. If this is the case, what experiments did Newton do to discover this? Is it related to ...
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Home experiments to derive the speed of light?
Are there any experiments I can do to derive the speed of light with only common household tools?
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Why is cold fusion considered bogus?
Cold fusion is being mentioned a lot lately because of some new setup that apparently works. This is an unverified claim.
See for example:
http://hardware.slashdot.org/story/11/01/24/1550205/Italian-...
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What is the upper-limit on intrinsic heating due to dark matter?
Cold dark matter is thought to fill our galactic neighborhood with a density $\rho$ of about 0.3 GeV/cm${}^3$ and with a velocity $v$ of roughly 200 to 300 km/s. (The velocity dispersion is much ...
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2002 research: speed of light slowing down?
Back in 2002 there was some research published hinting that $c$ may have been faster at some distant point. It was based on measurements of the fine-structure constant,
$$
\alpha = \frac1{4\pi\...
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Scattering of light by light: experimental status
Scattering of light by light does not occur in the solutions of Maxwell's equations (since they are linear and EM waves obey superposition), but it is a prediction of QED (the most significant Feynman ...
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Are random errors necessarily Gaussian?
I have seen random errors being defined as those which average to 0 as the number of measurements goes to infinity, and that the error is equally likely to be positive or negative. This only requires ...
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Why does LIGO do blind data injections but not the LHC?
The LIGO group has a team that periodically produces fake data indicating a possible gravitational wave without informing the analysts. A friend of mine who works on LHC data analysis told me that ...
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What is needed to claim the discovery of the Higgs boson?
As I understand the Higgs boson can be discovered by the LHC because the collisions are done at an energy that is high enough to produce it and because the luminosity will be high enough also.
But ...
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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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Why are LIGO's beam tubes so wide?
Gravitational wave detectors and particle accelerators have at least one thing in common -- they require long vacuum tubes through which a narrow beam is fired (a laser in the gravitational wave case, ...
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What technology can result from such expensive experiment as undertaken in CERN?
I wonder what technology can be obtained from such very expensive experiments/institutes as e.g. undertaken in CERN?
I understand that e.g. the discovery of the Higgs Boson confirms our understanding ...
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Physicists adding 3 decimals to the fine structure constant is a big accomplishment. Why?
Yesterday, a team of physicists from France announced a breakthrough in nailing down a "magic number" by adding three decimals to the the fine-structure constant (news article; technical ...
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Cause for spikes in Trinity nuclear bomb test
In Richard Rhodes' book, The Making of the Atomic Bomb, I was reading about the Trinity nuclear test. High speed photos were taken and this one is from <1ms after the detonation. The book mentions ...
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Why do earphone wires always get tangled up in pocket?
What is the reason?
Is it caused by their narrow shape, the soft material, walking vibration or something else?
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Why doesn't increasing the temperature of something like wood or paper set them on fire?
Imagine we have paper book. If we put this into a pan and increase its temperature, this book would not catch on fire. If on the other hand the book interacts with this heat source directly, it does ...
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Has gravity ever been experimentally measured between two atoms?
Has there been any experiments, or are there any references, demonstrating gravity between atoms? If so, what are the key experiments/papers? Or if not, what is the smallest thing that has actually ...
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Is there any physical evidence for motion?
Let's say that we have 2 tennis balls in space, one being in motion (say, pushed by an astronaut), and the other one still.
If we could take a snapshot of both tennis balls, would there be any ...
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What is the proof that the universal constants ($G$, $\hbar$, $\ldots$) are really constant in time and space?
Cavendish measured the gravitation constant $G$, but actually he measured that constant on the Earth. What’s the proof that the value of the gravitation constant if measured on Neptune would remain ...
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Interpretation of "transition rate" in Fermi's golden rule
This is a question I asked myself a couple of years back, and which a student recently reminded me of. My off-the-cuff answer is wrong, and whilst I can make some hand-waving responses I'd like a ...
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Is light actually faster than what our present measurements tell us?
It is well established that the light speed in a perfect vacuum is roughly $3\times 10^8 \:\rm m/s$. But it is also known that outer space is not a perfect vacuum, but a hard vacuum. So, is the speed ...
user182521
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What is the smallest item for which gravity has been recorded or observed?
What is the smallest item for which gravity has been recorded or observed? By this, I mean the smallest object whose gravitational effect upon another object has been detected. (Many thanks to Daniel ...
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Can water falling from a tap follow a spiral path?
The faucet design depicted below is driving me crazy. The water falling from the tap appears to follow a spiral path. No one seems to agree whether it is physically possible for the water to spin in ...
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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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What is the most precise physical measurement ever performed?
Obviously some things, such as the speed of light in a vacuum, are defined to be a precise value. The kilogram was recently defined to have a specific value by fixing Plank's constant to $6.62607015\...
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Did LIGO measurements prove that the speed of gravity equals the speed of light?
This question about the speed of light prompted my own question. In the linked question it is asked if there is experimental proof that the speed of gravity equals the speed of light. I was surprised ...
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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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Why is a leading digit not counted as a significant figure if it is a 1?
Reading the book Schaum's Outline of Engineering Mechanics: Statics I came across something that makes no sense to me considering the subject of significant figures:
I have searched and saw that ...
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How far away are we from probing Planck scale physics directly?
There are three related questions here:
Given the current limits of technology how far away are we from probing Planck scale physics directly?
It's well known, at least in some circles, that atoms ...
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experimental bounds on spacetime torsion
Did Gravity Probe B provide any bounds on Einstein-Cartan torsion? is a non-zero torsion value at odds with the results regarding frame-dragging and geodetic effects?
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Can a mathematical proof replace experimentation?
I know that this is very similar to How important is mathematical proof in physics? as well as Is physics rigorous in the mathematical sense? and The Role of Rigor. However, none of the answers to ...
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How seriously can we take the success of the Standard Model when it has so many input parameters?
The Standard Model of particle physics is immensely successful. However, it has many experimentally fitted input parameters (e.g. the fermion masses, mixing angles, etc). How seriously can we take the ...
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Pouring oil on choppy water to calm it , does it work and if so how?
Near where I live, local fishermen often bring cans of castor oil with them, to calm the water around their boats, if they feel bad weather is due.
They claim this method of sea calming works, (...
user81619
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Are the fast axes on Thorlabs quarter-waveplates mislabeled?
Some members of my lab are performing a polarization-sensitive experiment where they need to use a quarter-waveplate (QWP) with the fast axis in a specific direction. In the process of carefully ...
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What are some dense elements I can use for a demonstration?
I'm musing about how to give students an intuitive feeling about density by letting them lift a same sized volume of different materials, e.g. 1 liter of water, a $10 {\times} 10 {\times} 10 \, \...
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What is the largest number of bosons placed in a BEC?
What is the record for the largest number of bosons placed in a Bose-Einstein condensate?
What are the prospects for how high this might get in the future?
EDIT: These guys reported 20 million atoms ...
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Has the gravitational interaction of antimatter ever been examined experimentally?
I know that the gravitational interaction of antimatter is expected to be the same as normal matter.
But my question is, has it ever been experimentally validated?
I think it would not be a trivial ...
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Understanding which string breaks when one pulls on a hanging block from below
Intro:
In completing Walter Lewin's 6th lecture on Newton's Laws, he presents an experiment (go to 42:44) which leaves me baffled.
Experiment:
(I recommend watching the video; see link above.)
...
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How to determine your position underground?
Crossed my mind after random rant on wikipedia that lead me to articles about chronometers and measuring position.
Let's assume I were trapped in the underground laboratory with lots of equipment ...
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How strong were the gravitational waves that LIGO detected at the source?
Congrats to the LIGO team on the announcement of their discovery of gravitational waves!
The articles I've read say that the distortion we see here is much smaller than a proton. What about at the ...
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