for questions about design, process, data, or analysis of experiments and observations.
169
votes
19answers
58k views
Cooling a cup of coffee with help of a spoon
During the 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 ...
66
votes
13answers
10k views
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 ...
34
votes
2answers
4k views
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?
31
votes
0answers
551 views
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 ...
28
votes
13answers
7k views
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?
28
votes
4answers
2k views
What is needed to claim the discovery of the Higgs boson?
As I understand the Higg's 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 ...
27
votes
13answers
5k views
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:
...
25
votes
10answers
6k views
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 ...
22
votes
3answers
1k views
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 ...
20
votes
2answers
87 views
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?
17
votes
5answers
2k views
Does red shift evidence necessarily imply that the universe started from a singularity?
We are taught that the universe began as a singularity - an infinitely small and infinitely dense point. At the beginning of time there was a 'Big Bang' or, more accurately, 'Inflation'.
The main ...
17
votes
4answers
426 views
How can I determine whether the mass of an object is evenly distributed?
How can I determine whether the mass of an object is evenly distributed without doing any permanent damage? Suppose I got all the typical lab equipment. I guess I can calculate its center of mass and ...
16
votes
1answer
1k views
How did they measure the speed of light observing Jupiter's moons, centuries ago?
I am interested in the pratical method and I like to discover
if it is cheap enough to be done as an experiment in a high school.
Thank you.
16
votes
2answers
360 views
Is there a compound denser than the densest element?
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 10x10x10 cm cube of iron, lead etc. ...
15
votes
5answers
1k views
Home experiments using wireless LAN or mobile phones about electromagnetism?
Are there any nice experiments using wireless LAN access points or routers or mobile phones to demonstrate physical features of electromagnetic fields, especially em-waves?
More precisely I am ...
15
votes
0answers
267 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 ...
13
votes
2answers
1k views
Did the researchers at Fermilab find a fifth force?
Please consider the publication
Invariant Mass Distribution of Jet Pairs Produced in Association with a W boson in $p\bar{p}$ Collisions at $\sqrt{s} = 1.96$ TeV
by the CDF-Collaboration, ...
12
votes
2answers
23 views
Why are binary objects so critical to astronomy?
There are a lot of astronomical objects out there to study but binary objects seem to get more attention. Why is this? What makes binary objects (stars, Kuiper Belt Objects, black holes, galaxies, ...
12
votes
9answers
938 views
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 ...
12
votes
2answers
2k views
Why isn't Higgs coupling considered a fifth fundamental force?
When I first learned about the four fundamental forces of nature, I assumed that they were just the only four kind of interactions there were. But after learning a little field theory, there are many ...
12
votes
1answer
306 views
How are neutrino beams emitted at CERN?
As far I know they come from accelerator collisions, but I have read confusing things like magnetically focused. How could neutrinos be guided magnetically if they aren't affected by
the ...
12
votes
5answers
395 views
What experiments, other than Hubble Expansion, support the Dark Energy theory?
Dark energy is introduced as a constant inside Einstein's equations. Its primary purpose, from what I understand, is to make Einstein's equations compatible with the accelerating expansion of the ...
11
votes
4answers
1k views
How can I measure the mass of the earth at home?
How can I measure the mass of the earth at home?
How was the mass of the earth first measured?
11
votes
4answers
368 views
Do high/low pass lenses exist?
For an experiment I will hopefully be soon conducting at Johns Hopkins I need two different lenses.
The first needs to allow all wavelengths above 500 nm to pass (thus a high pass filter) and cut off ...
11
votes
1answer
375 views
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?
11
votes
1answer
202 views
Cleaning Already Mounted Microspheres on an AFM
I am running an experiment that uses a microsphere (Diameter ~ 50um) mounted onto the end of an AFM cantilever. I run several experiments in a row, but somewhere during a sequence, the microsphere ...
11
votes
2answers
285 views
Is there a way to directly observe the spin texture of the surface states of topological insulators?
Is there a way to directly, here I means in real space, observe the interaction of the surface states of 3D topological insulators with defects (dopings and adatoms)? How to observe the spin texture ...
10
votes
5answers
973 views
The square in the Newton's law of universal gravitation is really a square?
When I was in the university (in the late 90s, circa 1995) I was told there had been research investigating the $2$ (the square of distance) in the Newton's law of universal gravitation.
...
10
votes
2answers
71 views
ATLAS Higgs Interpretation
I came across this abstract, and I am curious as to what the ATLAS Team has actually discovered:
Abstract Motivated by the result of the Higgs boson candidates at LEP with a mass of about ...
10
votes
3answers
519 views
Best way to chill a cup of coffee with cold water and 5 minutes [duplicate]
Initial data
1 x 3/4 full cup of hot coffee / tea / your favorite morning beverage
cold water
5 minutes
Considering that it's starting to get hot outside, and we all want to drink reasonably cold ...
10
votes
4answers
389 views
How do we know that the nucleus isn't a quark-gluon plasma?
The standard picture of the nucleus of atom is that is several distinct nucleons, which themselves are composed of quarks. However, it seems to me like a much simpler picture is that the nucleus is ...
10
votes
2answers
371 views
Reproducing the OPERA result
Are there any other facilities that would be capable of independantly verifying the opera result? In other words, a completely different source/detector for $\nu_{\mu}$ beams?
Alternatively, there ...
10
votes
5answers
3k views
What is the world's biggest Schrodinger cat?
How big is it by a truly quantum measurement?
I am thinking of comparing Science magazines "Breakthrough of the Year" (BYOT) with the Zeilinger buckyball.
The BYOT is a piezoelectric mechanical ...
10
votes
1answer
123 views
Have general relativistic effects of the sun's rotation been measured?
I was wondering if general relativistic effects of the sun's rotation have also been measured, like gravity probes A and B measured GR effects from the earth.
10
votes
1answer
602 views
How to calculate the number of glass sheets that will be broken by a falling object?
In season 1, episode 7 of King of the nerds the contestants are asked to calculate how many sheets of glass will be broken by a falling object. They are shown 1 example case and then asked to ...
9
votes
2answers
562 views
Has quantum entanglement been demonstrated to be able to take place over infinite distances?
In my poor understanding of quantum physics, quantum entanglement means that certain properties of one of two 'entangled' quantum particles can lead to change over infinitely large distances when the ...
9
votes
4answers
755 views
What ways are there to measure the local polarization of a laser beam?
Measuring the polarization of a laser beam is a simple enough task if the polarization is the same everywhere. You can even buy commercial polarimeters.
How do you go about it if the light beam has ...
9
votes
3answers
3k views
How do you determine power flow direction in a transmission line?
Below is a picture of a typical transmission line(about 200 kV). Is there a simple physics experiment which can be performed safely near the line, to determine the power flow direction. Or in other ...
9
votes
1answer
225 views
What dark matter can AMS currently find (or exclude)?
The rumor mill is running again, this time it's about the AMS experiment (Alpha Magnetic Spectrometer) that's going to make a major announcement soon.
I suppose they are looking for peaks in gamma ...
9
votes
4answers
274 views
Can all quantum superpositions be realized experimentally?
When textbooks in QM give example of finite dimensional Hilbert spaces they give examples of photon polarizations or of 2-states systems and sometimes they mention how one can achieve superposition in ...
9
votes
2answers
558 views
ATLAS and CMS calorimeters
I was reading this interesting recent review on arxiv about particle identification:
Particle Identification
In figure 2, there is an interesting comparison between the CMS and ATLAS calorimeter ...
9
votes
3answers
396 views
Can we measure an electromagnetic field?
As far as I can check, the Aharonov-Bohm effect is not -- contrary to what is claimed in the historical paper -- a demonstration that the vector potential $A$ has an intrinsic existence in quantum ...
8
votes
8answers
979 views
What is the name of the principle saying it is meaningless to talk/ask questions that can not be measured/tested?
Watching quantum mechanics lectures and it was mentioned that it is pointless/meaningless to try to talk/question things that can not be tested/measured.
Is this a principle? And if so what is it's ...
8
votes
3answers
535 views
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
votes
5answers
3k views
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 ...
8
votes
6answers
1k views
Experimental evidence of a fourth spatial dimension?
As human beings, we observe the world in which we live in three dimensions. However, it is certainly theoretically possible that more dimensions exist.
Is there any direct or indirect evidence ...
8
votes
2answers
509 views
How are Monte Carlo simulations used in experimental high energy physics?
How are Monte Carlo simulations used in experimental high energy physics? Particularly in studying detectors limitations (efficiencies?) and data analysis.
I will appreciate giving a simple example ...
8
votes
1answer
339 views
Could LEP II have discovered a 125GeV Higgs?
LEP II eliminated the Higgs up to 114.5GeV. If it had been run for longer could it have detected a Higgs at 125GeV?
I Googled for this without any luck, though I did find a comment that LEP II topped ...
8
votes
5answers
209 views
How to communicate institutional knowledge in a big physics collaboration?
I am a graduate student in a large experimental physics collaboration. Newcomers to the collaboration invariably complain about excessive use of jargon and insufficient documentation as barriers to ...
8
votes
1answer
167 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 ...
