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1500 questions
45
votes
3 answers
What is the origin of elements heavier than iron?
In all the discussions about how the heavy elements in the universe are forged in the guts of stars and especially during a star's death, I usually hear that once the star begins fusing lighter atoms to produce iron (Fe) that's the end of the star's…
Zubin
- 563
45
votes
11 answers
How do we measure time?
I'm having a little trouble trying to put to words my problem and I apologize in advance for any causation of trouble in trying to interpret it.
We define periodic events as those events that occur over equal intervals of time. But, don't we use…
Sathvik R.
- 575
45
votes
17 answers
Why does one experience a short pull in the wrong direction when a vehicle stops?
When you're in a train and it slows down, you experience the push forward from the deceleration which is no surprise since the force one experiences results from good old $F=m a$. However, the moment the train stops one is apparently pulled…
Tobias Kienzler
- 6,768
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45
votes
10 answers
Why can't the Earth's core melt the whole planet?
Earth core temperature is range between 4,400° Celsius (7,952°
Fahrenheit) to about 6,000° Celsius (10,800° Fahrenheit).
Source
Why can't the Earth's core melt the whole planet? In other words, what is stopping Earth from being melted up to its…
Dean Moxley
- 567
45
votes
9 answers
Intuitively, what actually is the cause of resonance?
Please don't explain it mathematically. I have been searching for the reason for a long time.
I have watched Walter Lewin's video giving an example of resonance, but I didn't get the reason behind the intuition. I am confused if the reason exists.
Nandani Kumari
- 606
45
votes
4 answers
How does Fermat's principle make light choose a straight path over a short path?
This is a thought experiment where I have made a "C" shaped hole inside diamond. The refractive index $(\mu)$ of diamond is 2.45. Say we shine a laser from top of the "C" as shown.
My calculations show that light reaching A can reach B in the least…
Rishab Navaneet
- 2,000
45
votes
8 answers
What is the reason that Quantum Mechanics is random?
We know quantum mechanics gives a random result when we observe a particle that's in a superposition, but why is it random? One of the explanations I've heard is that because light comes with those discrete energy packets called photons, when a…
Andrew.Wolphoe
- 639
45
votes
11 answers
Why does moving air feel colder?
If temperature is just the average kinetic energy of particles, why would moving air feel colder rather than warmer?
BOUNCE
- 565
45
votes
11 answers
Birds on a wire (again) - how is it that birds feel no current? They are just making a parallel circuit, no?
I have been thinking about this and I know that other people have answered this on here, but there's one part that still baffles me, and it has to do with parallel circuits.
If I connect a battery to a resistor, and connect another in parallel to…
Jesse
- 895
45
votes
2 answers
Does a star need to be inside a galaxy?
Must a star belong to a galaxy, or could it be completely isolated?
In case it can be isolated (not belong to a galaxy), could it have a planet orbiting around it?
cooper
- 453
45
votes
4 answers
What would happen if Jupiter collided with the Sun?
This question is inspired by a similar one asked on Quora. Let's say a wizard magicked Jupiter into the Sun, with or without high velocity. What happens?
The Quora question has two completely opposed answers: one saying "nothing much happens" and…
Allure
- 20,501
45
votes
3 answers
Why isn't the entropy of gas infinite if there are infinite microstates available?
How could it be that the entropy of gas is not infinite? If we use the formula $S=k\ln(\Omega)$ we get infinity because there are an infinite number of possible situations (because there are infinite possibilities of position and momentum for each…
Jacob
- 1,503
45
votes
5 answers
Speed of light vs speed of electricity
If I arranged an experiment where light raced electricity what would be the results? Let's say a red laser is fired at the same time a switch is closed that applies 110 volts to a 12 gauge loop of copper wire with a meter at a distance of ten…
Lambda
- 4,721
45
votes
6 answers
Does pure yellow exist in variations we can't discern?
If you add red light (~440 THz) and green light (~560 THz), you get what we perceive as yellow light (~520 THz). But I assume what you really get is a mixed waveform that we perceive as yellow? Suppose the red is a perfect sine wave, and so is the…
commonpike
- 579
45
votes
1 answer
Does the mass of a battery change when charged/discharged?
If so, how much? Is it possible to detect it, or is it beyond any measurement?
I'd say there are two possible scenarios (depending on the battery type) and both seem interesting:
The battery reacts chemically with its environment.
The battery…
Petr
- 3,069