Most Popular
1500 questions
37
votes
5 answers
How do LIGO and Virgo know that a gravitational wave has its origin in a neutron star or a black hole?
It is being said that gravitational-wave detectors are now able to distinguish neutron star waves from those originating from black holes.
Two Questions:
How do LIGO and Virgo know that a gravitational wave has its origin in a neutron star or a…
João Bosco
- 441
37
votes
3 answers
Is there a frame of reference in which I was born before I was conceived?
I'm struggling to understand the relativity of simultaneity and position.
If my conception and birth are separated by time but not space, a frame of reference in which my birth and conception are simultaneous should exist right?
If another observer…
IchVerlore
- 750
37
votes
6 answers
What is the probability for an electron of an atom on Earth to lie outside the galaxy?
In this youtube video it is claimed that electrons orbit their atom's nucleus not in well-known fixed orbits, but within "clouds of probability", i.e., spaces around the nucleus where they can lie with a probability of 95%, called "orbitals".
It is…
Klangen
- 479
37
votes
7 answers
Reading list in topological QFT
I'm interested in learning about topological QFT including Chern Simons theory, Jones polynomial, Donaldson theory and Floer homology - basically the kind of things Witten worked on in the 80s. I'm looking for pedagogical reviews rather than…
Sudip Paul
- 731
37
votes
1 answer
Can I eat myself into a black hole?
This was a humorous thought experiment that occurred while chatting about black holes. The person that I was talking to assumed that a black hole required a specific density to be achieved. I pointed to the formula for the Schwarzschild radius. …
badjohn
- 2,073
37
votes
3 answers
Could a powerful gravitational wave cause electrons to emit light?
I imagine electrons being accelerated by passing gravitational waves, say from a nearby kilonova, so I would expect the electrons to emit light. Am I right?
user6760
- 12,980
37
votes
6 answers
How many times has the matter in our Solar System been recycled from previous stars?
I've got a basic understanding of these facts:
The Universe is a little over 13 billion years old. Our Galaxy is almost that old.
Our Solar System is roughly 4.6 billion years old.
The heavier elements (carbon, oxygen, etc...) are only produced by…
Clinton Pierce
- 473
37
votes
3 answers
Nuclear Fusion: Why is spherical magnetic confinement not used instead of tokamaks in nuclear fusion?
In nuclear fusion, the goal is to create and sustain (usually with magnetic fields) a high-temperature and high-pressure environment enough to output more energy than put in.
Tokamaks (donut shape) have been the topology of choice for many years.…
Valentina
- 495
37
votes
1 answer
How far away are we from probing Planck scale physics directly?
There are three related questions here:
Given the current limits of technology how far away are we from probing Planck scale physics directly?
It's well known, at least in some circles, that atoms were thought of in Antiquity; given the limits of…
Mozibur Ullah
- 12,994
37
votes
3 answers
Symmetrical twin paradox in a closed universe
Take the following gedankenexperiment in which two astronauts meet each other again and again in a perfectly symmetrical setting - a hyperspherical (3-manifold) universe in which the 3 dimensions are curved into the 4. dimension so that they can…
vonjd
- 3,701
37
votes
3 answers
Is it possible to estimate the speed of a passing vehicle using a musical ear and the doppler effect?
I've found a number of questions that concern the Doppler effect, but none that seem to address my question.
I have a background in music. People with a musical ear can generally tell the ratio between two frequencies (as a musical interval). For…
M_M
- 481
37
votes
3 answers
Why do nuclei decay so fast and slow?
Why do nuclei like Oganesson (also known as Ununoctium, this is the 118th element on the periodic table) decay in about 5 milliseconds? This is weird that they decay. In comparison, why do elements like uranium take about 200,000 years to decay, or…
science error
- 339
37
votes
6 answers
If the moon had a mirror surface, would the earth be equally illuminated as by the sun during full moon, or would it require a different mirror shape?
Suppose the apparent diameters of the sun and the moon are exactly the same (which in fact very close to the real situation). If the moon had a perfect mirror surface, would the reflected visible light of a full moon (at night) illuminate the earth…
37
votes
1 answer
Nuclear bomb mushroom cloud with trumpet formation
I have found this specific image here (Loong found out that it is the Soviet Joe 4 test of the 400 kiloton RDS-6 warhead at the Semipalatinsk test site on August 12, 1953):
Also an impressive Youtube Video of the same explosion
As you see, an…
Thorsten S.
- 2,020
37
votes
5 answers
Why do people rule out local hidden variables?
I bet the automatic response to my question would be "Bell's theorem" and of course I am not disputing Bell's proof. I am however uncertain of one of his assumptions.
The so called "no conspiracy" assumption states that we somehow posses this…
QuestionAnswers
- 895