for questions about design, process, data, or analysis of experiments and observations.
61
votes
14answers
9k 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 ...
26
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:
...
160
votes
19answers
55k 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 ...
41
votes
33answers
5k views
Great unsolved physics problems [closed]
We all know that some theoretical ideas lack experimental evidence while in other cases there's a lack of a suitable theory for known phenomena and established facts and concepts.
But what problem in ...
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?
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 ...
7
votes
2answers
1k views
How do we know that some radioactive materials have a half life of millions or even billions of years?
If a radioactive material takes a very long time to decay, how is its half life measured or calculated? Do we have to actually observe the radioactive material for a very long time to extrapolate its ...
6
votes
3answers
2k views
Is Dr Quantum's Double Slit Experiment video scientifically accurate?
I'm fascinated by the fundamental questions raised by the Double Slit Experiment at the quantum level. I found this "Dr Quantum" video clip which seems like a great explanation. But is it ...
5
votes
7answers
876 views
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 ...
5
votes
3answers
240 views
Is there a way to decrease the rate of nuclear Beta decay?
In that question and its answers it was mentioned that you could trigger radioactive decay by bombarding atoms with gamma rays of the right energy level (there may be other solutions I do not know ...
1
vote
5answers
503 views
About the Ether Theory acceptance
Why was the Ether Theory refused by Modern Physics? If you please explain me, I just wanted to understand it more.
4
votes
3answers
132 views
How quark electric charge directly have been measured?
How quarks electric charge directly have been measured when quarks never directly observed in isolation? (Due to a phenomenon known as color confinement.)
3
votes
3answers
444 views
Have the Rowan University “hydrino” findings been replicated elsewhere?
In 2009, Rowan University released a paper claiming to replicate Blacklight Power's results on energy generation using hydrino states of the hydrogen atom. The paper appears to describe the procedure ...
11
votes
1answer
368 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?
7
votes
8answers
970 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 ...
4
votes
5answers
1k views
What differs string theory from philosophy or religion? [duplicate]
Possible Duplicate:
What experiment would disprove string theory?
A hypothesis without hard evidence sounds very much like philosophy or religion to me. All of them tries to establish a ...
10
votes
5answers
938 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.
...
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 ...
7
votes
6answers
983 views
What methods can astronomers use to find a black hole?
How can astronomers say, we know there are black holes at the centre of each galaxy?
What methods of indirect detection are there to know where and how big a black hole is?
4
votes
1answer
85 views
Where can I get the most accurate measurements of parton distribution functions?
Where would I look to get the most accurate experimental values of parton distribution functions for the proton? I know these functions aren't measured directly, but I'd basically like to find a fit ...
8
votes
2answers
495 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 ...
12
votes
5answers
391 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 ...
0
votes
2answers
391 views
Does string theory provide quantitative experimental predictions? [duplicate]
Possible Duplicate:
What experiment would disprove string theory?
We carefully observe things, observe patterns and then build theories that predict.
String theory is frequently ...
12
votes
2answers
1k 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 ...
6
votes
4answers
352 views
Matter-Antimatter Asymmetry in Experiments?
As I hope is obvious to everyone reading this, the universe contains more matter than antimatter, presumably because of some slight asymmetry in the amounts of the two generated during the Big Bang. ...
5
votes
5answers
2k views
What is the evidence for Inflation of the early universe?
The theory of Inflation explains the apparent consistency of the universe by proposing that the early universe grew exponentially for a 1E-36 seconds. Isn't a simpler explanation that the universe is ...
4
votes
1answer
224 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.
...
3
votes
2answers
404 views
Is there a different behavior between proton and antiproton beams at the Tevatron?
This question has its origin to the reference on the Aegis experiment at CERN where they aim to produce super cooled antihydrogen and detect whether its reaction to gravity is negative.
It set me ...
1
vote
1answer
144 views
Photometer: measured Irradiance L converted to photon rate
I am conducting an experiment in which the power meter reading of $410\,nm$ narrow bandpass stimulus is noted to be 30 $\frac{\mu W}{cm^2}$ at a distance of 1 inch away from the light source.
I wish ...
1
vote
2answers
181 views
Where to find cross section data for e- + p -> p + e-?
Where to find cross section data for e- + p -> p + e-?
PDG's cross section data listing does not include it.
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, ...
4
votes
2answers
404 views
What experimental proof has been found of Einstein's theory?
As a casual science reader, I've always found the implications of relativity (inconsistent clocks after near-light-speed travel and various space-time paradoxes) to be confusing and magical-sounding. ...
4
votes
4answers
651 views
Measuring the speed of light and defining the metre - absolute or relative?
If the metre is now defined as the distance light travels in vacuum in 1⁄299,792,458th of a second and the speed of light is accepted to be ...
3
votes
2answers
254 views
What is the highest accuracy of measuring time differences achievable today?
I was wondering if it would be possible to shorten the distance between detectors when measuring the speed of neutrinos to, say, 7m rather than the current ~700km? In this way the distance traveled ...
3
votes
2answers
382 views
How Can We Measure The Mass Of Particle?
As we know, the mass of well known particles are below.
$m_{n}\approx0.0000000000000000000000000016749286[kg]$
$m_{p}\approx0.0000000000000000000000000016726231[kg]$
...
2
votes
1answer
107 views
Observable (in principle) signal of a bubble collision in eternal inflation
Assuming a scenario of eternal inflation with a lot of "bubble universes" expanding, Lenny Susskind explains here that a potential signal of a collision of our universe with another bubble could be a ...
2
votes
1answer
156 views
Testing General Relativity
Ever since Einstein published his GR theory in 1916, there have been numerous experimental tests to confirm its correctness--and has passed with flying colors.
NASA and Stanford have just announced ...
1
vote
1answer
2k views
Negative and positive energy and Hawking [closed]
I don't have any physics background (except the material we did in high school-long time ago).
I was watching a documentary with Stephen Hawking about whether God created the Universe and I could not ...
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 ...
19
votes
9answers
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 ...
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.
8
votes
1answer
154 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 ...
8
votes
3answers
527 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 ...
7
votes
2answers
192 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 !
...
4
votes
2answers
297 views
What are the easiest to get/make LN2 superconductors?
I am starting to build multistage Peltier cooler at the moment, and it should be able to reach -100C at least (but if I fail I can always get boring LN2).
Doing some experiments with superconductors ...
12
votes
1answer
303 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 ...
9
votes
4answers
271 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 ...
4
votes
2answers
935 views
Strategies against 50 Hz mains hum on detector signals?
I'm having problems with a strong 50 Hz mains hum on signals created by photodetectors. I assume that they are due to ground loops and I realize that the best option would be to remove those. What are ...
4
votes
2answers
250 views
Accuracy of various optical instruments
I understand that this may not be the type of question allowed here, but I'm not sure. Feel free to close this if you feel that it shouldn't be here
I'm planning on carrying out a certain set of ...
4
votes
1answer
391 views
What is meant by “combinatorial background” in experimental high energy physics
My guess is that they find a certain tracks coming from a certain source by "combintaorially" selecting all track pairs and finding their invariant mass. If this is true, of which I am not sure, how ...
