Highest scored questions
244,126 questions
826
votes
23
answers
264k
views
Cooling a cup of coffee with help of a spoon
During 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 be ...
- 7,977
543
votes
8
answers
65k
views
Can I compute the mass of a coin based on the sound of its fall?
The other day, I bumped my bookshelf and a coin fell down. This gave me an idea. Is it possible to compute the mass of a coin, based on the sound emitted when it falls?
I think that there should be a ...
- 5,327
522
votes
6
answers
84k
views
How does light bend around my finger tip?
When I close one eye and put the tip of my finger near my open eye, it seems as if the light from the background image bends around my finger slightly, warping the image near the edges of my blurry ...
- 4,979
503
votes
21
answers
57k
views
How does gravity escape a black hole?
My understanding is that light can not escape from within a black hole (within the event horizon). I've also heard that information cannot propagate faster than the speed of light. I assume that the ...
- 5,149
406
votes
8
answers
67k
views
Did the Big Bang happen at a point?
TV documentaries invariably show the Big Bang as an exploding ball of fire expanding outwards. Did the Big Bang really explode outwards from a point like this? If not, what did happen?
374
votes
29
answers
153k
views
Why are mirror images flipped horizontally but not vertically?
Why is it that when you look in the mirror left and right directions appear flipped, but not the up and down?
- 3,935
344
votes
34
answers
59k
views
Do we know why there is a speed limit in our universe?
This question is about why we have a universal speed limit (the speed of light in vacuum). Is there a more fundamental law that tells us why this is?
I'm not asking why the speed limit is equal to $c$ ...
- 7,980
326
votes
11
answers
52k
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 that ...
- 3,847
313
votes
18
answers
87k
views
Why does kinetic energy increase quadratically, not linearly, with speed?
As Wikipedia says:
[...] the kinetic energy of a non-rotating object of mass $m$ traveling at a speed $v$ is $\frac{1}{2}mv^2$.
Why does this not increase linearly with speed? Why does it take so ...
- 3,265
313
votes
2
answers
31k
views
What is Chirped Pulse Amplification, and why is it important enough to warrant a Nobel Prize?
The 2018 Nobel Prize in Physics was awarded recently, with half going to Arthur Ashkin for his work on optical tweezers and half going to Gérard Mourou and Donna Strickland for developing a technique ...
- 137k
306
votes
2
answers
29k
views
Why do ballpoint pens write better on pages that have pages below them?
If I write on the starting page of a notebook, it will write well. But when there are few or no pages below the page where I am writing, the pen will not write well. Why does this happen?
- 2,171
304
votes
10
answers
59k
views
Why don't metals bond when touched together?
It is my understanding that metals are a crystal lattice of ions, held together by delocalized electrons, which move freely through the lattice (and conduct electricity, heat, etc.).
If two pieces ...
- 2,701
304
votes
1
answer
148k
views
Resource recommendations [closed]
Every once in a while, we get a question asking for a book or other educational reference on a particular topic at a particular level. This is a meta-question that collects all those links together. ...
292
votes
17
answers
83k
views
What really allows airplanes to fly?
What aerodynamic effects actually contribute to producing the lift on an airplane?
I know there's a common belief that lift comes from the Bernoulli effect, where air moving over the wings is at ...
- 77.6k
277
votes
12
answers
58k
views
Why are four-legged chairs so common?
Four-legged chairs are by far the most common form of chair. However, only three legs are necessary to maintain stability whilst sitting on the chair. If the chair were to tilt, then with both a four-...
- 2,971