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1500 questions
44
votes
4 answers
How much information about the scale of a waterfall can be obtained from its sound?
Is it possible to constrain the height, volume flow, or distance of a waterfall from the quantitative analysis of a high-quality recording of its sound?
As an aside, the simulated sounds of fluid splashing or pouring water have been synthesized by…
Mark Rovetta
- 3,905
44
votes
5 answers
Why doesn't the brightness of a bulb change with time?
Household bulbs get alternating current, which means that the voltage of source and current in circuit keep changing with time, which implies that the power supply isn't constant. However, we don't see any changes in brightness of the bulb. Why is…
user181531
44
votes
1 answer
Why doesn't soda go flat immediately after opening?
So, soda is under pressure and has gas dissolved in it. But, when you open it, the gas is still dissolved in it. But, if we wait a few hours, the gas has escaped into the atmosphere.
What factors determine the rate at which gas escapes the soda-gas…
Mohammad Athar
- 681
44
votes
4 answers
What is the quantum mechanical definition of a measurement?
I hear the word "measurement" thrown around a lot in quantum mechanics, and I have yet to hear a scientific definition that makes sense. How do we define it?
mcchucklezz
- 758
44
votes
6 answers
For collision, physical contact is not a necessary condition. Why?
In my textbook, it is written that
"For collision, physical contact is not a necessary condition".
How can collision occur without physical contact? If there is no physical contact, then there would be no contact force between particles to act…
Arishta
- 646
44
votes
9 answers
If a thousand people whisper inaudibly, will the resulting sound be audible?
If a thousand people whisper inaudibly, will the resulting sound be audible? (...assuming they are whispering together.)
I believe the answer is "yes" because the amplitudes would simply add and thus reach an audible threshold. Is this right?
if…
SAH
- 553
44
votes
3 answers
How general is the Lagrangian quantization approach to field theory?
It is an usual practice that any quantum field theory starts with a suitable Lagrangian density. It has been proved enormously successful. I understand, it automatically ensures valuable symmetries of physics to be preserved. But nevertheless the…
user1355
44
votes
3 answers
What is the issue with interactions in QFT?
I've started studying QFT this year and in trying to find a more rigorous approach to the subject I ended up find out lots of people saying that "there is no way known yet to make QFT rigorous when there are interactions".
As for the textbook…
Gold
- 35,872
44
votes
3 answers
What stops us from creating a nuclear fusion reactor as we already have the hydrogen bomb working on the same principle of fusion?
I have been out of physics for some time now since my childhood, so please bear with me if the question below feels too novice.
I grew up with the understanding that the nuclear fusion reaction is still a dream of many people as it's a source of…
Xinus
- 1,251
44
votes
3 answers
Why is the (free) neutron lifetime so long?
A neutron outside the nucleus lives for about 15 minutes and decays mainly through weak decays (beta decay). Many other weakly decaying particles decay with lifetimes between $10^{-10}$ and $10^{-12}$ seconds, which is consistent with $\alpha_W…
Forever_a_Newcomer
- 2,516
44
votes
2 answers
Do gravitons interact with each other?
I always thought the non-linearity of Einsteins field equations implies that there should be direct graviton-graviton interactions. But I stumbled upon Wikipedia which argues:
If gravitons exist, then, like photons and unlike gluons, gravitons do
…
asmaier
- 9,794
44
votes
5 answers
Is there oscillating charge in a hydrogen atom?
In another post, I claimed that there was obviously an oscillating charge in a hydrogen atom when you took the superposition of a 1s and a 2p state. One of the respected members of this community (John Rennie) challenged me on this, saying:
Why do…
Marty Green
- 4,079
- 1
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- 27
44
votes
9 answers
Why ket and bra notation?
So, I've been trying to teach myself about quantum computing, and I found a great YouTube series called Quantum Computing for the Determined. However. Why do we use ket/bra notation? Normal vector notation is much clearer (okay, clearer because I've…
auden
- 7,027
44
votes
6 answers
How to write a paper in physics?
I really like to do research in physics and like to calculate to see what happen. However, I really find it hard to write a paper, to explain the results I obtained and to put them in order. One of the reasons is the lack of my vocabulary.
How do…
Satoshi Nawata
44
votes
6 answers
How to escape the center of a room without gravity?
Imagine you're an astronaut on the International Space Station and your fellow astronauts played a prank on you by taking all your clothes and putting you in the center of a module so that you cannot reach anything with either your hands or your…
Jan Gassen
- 533