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1500 questions
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
- 7,145
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
72
votes
3 answers
How can ants carry items much heavier than themselves?
This morning I saw an ant and suddenly a question came to my mind: how do ants actually carry items much heavier than themselves?
What's the difference (in physics) between us and them?
Paul
- 3,475
71
votes
3 answers
Why does water falling slowly from a tap bend inwards?
This is something anyone could easily verify. When we open a tap slowly, water bends inwards (towards the axis) while maintaining its laminar flow. After a certain height below the opening, the flow becomes turbulent. I've approximately illustrated…
Vishnu
- 5,336
71
votes
2 answers
Does the new finding on "reversing a quantum jump mid-flight" rule out any interpretations of QM?
This new finding by Minev et al. seems to suggest that transitions between atomic states are not instantaneous, but continuous processes wherein a superposition smoothly adjusts from favoring one state to another (if I understand it correctly). The…
WillG
- 3,770
71
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
- 961
71
votes
3 answers
Why does a lot of water vapour come suddenly after the heat source of boiling water is removed?
I have noticed this several times. When I am boiling water, a few seconds before its boiling point, vapours are formed as usual. But if I turn the gas off before boiling, the moment it turns off, I see a lot of vapours being formed all of a sudden…
Abha Vishwakarma
- 741
71
votes
11 answers
What equation describes the wavefunction of a single photon?
The Schrödinger equation describes the quantum mechanics of a single massive non-relativistic particle. The Dirac equation governs a single massive relativistic spin-½ particle. The photon is a massless, relativistic spin-1 particle.
What is the…
nibot
- 9,691
71
votes
3 answers
How big would my telescope have to be if I wanted to see the Mars rover from my backyard?
I imagine that with a big enough telescope, I would be able to zoom in and see the Mars rover in enough detail to make out the details (like the wheels, cameras, etc.). How large would the telescope have to be? (or how can I calculate this value?)
Josh
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71
votes
2 answers
Why is a neutron in free state unstable?
A neutron is a neutral particle which is merely some times more massive than an electron.
What makes it so unstable outside the nucleus that it has a half life only of about 12 min?
kalyani
- 877
71
votes
5 answers
Why do electron and proton have the same but opposite electric charge?
What is the explanation between equality of proton and electron charges (up to a sign)? This is connected to the gauge invariance and renormalization of charge is connected to the renormalization of photon field, but is this explanation enough? Do…
Newman
- 2,626
71
votes
5 answers
Why is the harmonic oscillator so important?
I've been wondering what makes the harmonic oscillator such an important model. What I came up with:
It is a (relatively) simple system, making it a perfect example for physics students to learn principles of classical and quantum mechanics.
The…
Spine Feast
- 2,895
71
votes
9 answers
Does electricity flow on the surface of a wire or in the interior?
I was having a conversation with my father and father-in-law, both of whom are in electric related work, and we came to a point where none of us knew how to proceed. I was under the impression that electricity travels on the surface while they…
N. Owad
- 813
70
votes
8 answers
What is "Induced Atmospheric Vibration"?
The blackout seen today on the Iberian Peninsula has been attributed to a "rare" phenomenon known as "induced atmospheric vibration":
It says that "due to extreme temperature variations in the interior or Spain, there were anomalous oscillations in…
tobalt
- 2,423