Unanswered Questions
158 questions with no upvoted or accepted answers
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Why MIT's Benjamin Rackham says "nearby ultracool dwarf SPECULOOS-3" would look "purplish-red, spotted, and flaring" from an airless orbiting planet?
May 15, 2024 MIT News article Newly discovered Earth-sized planet may lack an atmosphere includes the following:
“We can say from our spectra and other observations that the star has a temperature of ...
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Gravitational recoil with stars/planets...?
When two black holes are merging, the resulting merge can be ejected if one of the black holes had less mass than the other one, so the gravitational waves emitted by both of them is unbalanced, and ...
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Kinetic energy in cosmology?
Spacetime expands at an accelerated rate due to the Hubble flow. In many papers that I've read, objects coupled to the Hubble flow are treated as if they have some velocity and kinetic energy ...
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Potential energy in an expanding universe
A question you wonderful geniuses can hopefully answer. Imagine a piece of string drawn between two galaxies. Space between the galaxies is expanding. What force is being applied to the string? Where ...
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Deviations of conservation laws in the context of cosmological evolution?
If energy is "not conserved" in General Relativity (or at least, it is difficult to define it) in the context of an accelerating expanding spacetime (like it happens in our Universe), are ...
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Cosmic microwave background the same as the first visible light at 379,000 yrs after the Big Bang? How do these measure the age of the universe?
Was the CMB emitted at the same time as visible light at 379,000 yrs after the BB ? Was this a one time event ? If headed away from us, how does it measure the age of the universe?
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How can a busy high school student get into learning Astronomy?
I'm a high school student that has loved physics for quite some time, but have only started dabbling with the more complex things. I know a fair bit about quantum mechanics and such as I like it, but ...
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What is the main difference between cyclotron, synchrotron, and gyrosynchrotron radiation?
How are these various types of radiation generated? What is the main difference between them? Can someone suggest a book related to these radiations?
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How much mass to make a shperical object?
I was googling around for info for D&D campaign I am going to run. I was wondering about the mass required for a object to pull itself into a shperical shape and it seems that the answer varies ...
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Why are CMB peak heights sensitive to the physical densities
A very simple question: why should it be that the CMB power spectrum allows constraints to be placed on the combination of parameters
$$\omega_c = \Omega_c h^2$$
$$\omega_b = \Omega_b h^2$$
as opposed ...
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New evidence against the existence of dark matter?
I've just read and heard about an article which gives new evidence for MOND - Modified Newtonian Dynamics, which is an alternative to dark matter by proposing that our gravitational law should be ...
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Gravity on Mercury's highest elevation?
This post answers what is Mars' gravity at its highest point (Olympus Mons) compared to the Earth's and Mars' standard, it's 0.3736 g (Mars standard is 0.3794 g). This also seems to be the lowest ...
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Superconducting space dust; what transient fields could induce persistent current loops?
Science Alert's Superconductivity Has Been Discovered in Meteorites For The First Time quotes from Superconductivity found in meteorites (Wampler et al. PNAS March 23, 2020)
The paper describes the ...
CommunityBot
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Information on Planetary nebula formed from the death of our star the 'Sun'!
I want to know the expansion rate, composition, mass and density of hydrogen present of a Planetary nebula similar to that which will be formed after the death of our star the sun.
Knowing these ...
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Combined mass of binary stars
This is Question 17 from USAAAO Practice Round 2015. The answer is D. It would be best if someone can detail out the workings.
In a nearby star system, two stars are seen to orbit each other every
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