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1500 questions
73
votes
7 answers
Why are protons heavier than electrons?
Our teacher told us that protons are nearly 1800 times heavier than electrons. Is there any known reason as to why this is so?
Or is this just an empirical value, one we do not know the reason to?
Shivay Vadhera
- 908
73
votes
12 answers
What is a tensor?
I have a pretty good knowledge of physics, but couldn't deeply understand what a tensor is and why it is so fundamental.
0x90
- 3,316
73
votes
4 answers
Why correlation functions?
While this concept is widely used in physics, it is really puzzling (at least for beginners) that you just have to multiply two functions (or the function by itself) at different values of the parameter and then average over the domain of the…
Kostya
- 19,992
73
votes
11 answers
Could a candle theoretically melt iron?
The title question is rather illustrative. I suppose the real question would be:
Is heat cumulative?
Put back into an example:
If I have a lit candle right beneath an iron bar, assuming the candle will remain lit indefinitely, and that the…
user1869935
- 1,199
73
votes
2 answers
Where are all the slow neutrinos?
The conventional way physicists describe neutrinos is that they have a very small amount of mass which entails they are traveling close to the speed of light. Here's a Wikipedia quote which is also reflected in many textbooks:
It was assumed for a…
Physics Footnotes
- 2,686
73
votes
6 answers
Why don't choir voices destructively interfere so that we can't hear them?
Sound is propagated by waves. Waves can interfere.
Suppose there are two tenors standing next to each other and each singing a continuous middle-C.
Will it be the case that some people in the audience cannot hear them because of interference?…
chasly - supports Monica
- 3,006
73
votes
7 answers
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 other kinds of couplings, even in the standard…
user542
- 1,070
72
votes
7 answers
Does gravity bend gravity?
Let's say that there is a large mass $M$ a light-year or so away from a black hole merger, which causes a very large gravitational wave to be produced. When the gravitational wave reaches $M$, does it bend like light bends when it comes into a…
Tachyon
- 1,866
72
votes
5 answers
Is there a small enough planet or asteroid you can orbit by jumping?
I just had this idea of orbiting a planet just by jumping and then flying upon it on its orbit kind of like superman. So,
Would it be theoretically possible or is there a chance of that small body to be & remain its unity?
Max Abrahamsson
- 963
72
votes
9 answers
Why can't we see images reflected on a piece of paper?
Why can't you see a reflected image on a piece of paper? Say you put a pen in front of the paper, even when light rays are coming from other sources, hitting the pen, reflecting back, and hitting the paper, there is no reflection.
What's wrong with…
katana_0
- 1,195
72
votes
6 answers
Could a computer unblur the image from an out of focus microscope?
Basically I'm wondering what is the nature of an out of focus image. Is it randomized information? Could the blur be undone by some algorithm?
user273872
- 2,613
72
votes
10 answers
Should zero be followed by units?
Today at a teachers' seminar, one of the teachers asked for fun whether zero should be followed by units (e.g. 0 metres/second or 0 metre or 0 moles). This question became a hot topic, and some teachers were saying that, yes, it should be while…
Vidyanshu Mishra
- 1,819
72
votes
3 answers
Why do beams of light (from torches or other directed sources) not extend to infinity?
When I'm in a dark environment, and I turn on a torch, I can see the beam of light from the torch. To the best of my understanding, the main reason why I can see the beam of light is that the light from the torch scatters off dust and other…
QCD_IS_GOOD
- 6,710
72
votes
7 answers
When I boil a kettle, what stops all the water from turning (exploding!) in to steam in one go once it reaches 100°C?
While making a cup of tea in the office kitchen, a colleague asked me this question and neither of us could answer with any certainty. We're guessing it has something to do with the pressure of the column of water, or temperature differences between…
Mark Hatton
- 809
72
votes
2 answers
How to measure the wavelength of a laser pointer?
I'm working on something and I need to know the wavelength of the laser pointer that I'm using.
Can you suggest me a way, using some optics formulae, or anything else to calculate the wavelength?
user82920