# All Questions

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### Existence of multiple universe?

In this youtube video, Prof. Michio Kaku mentions there can be multiple universe and if it is there, then there can be a worm hole to reach out other universe. My question is, still we are not sure ...
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### How would we thrive on a planet whose rotational period is different than Earth's?

Atmospheric pressure/composition, temperature, or gravity wouldn't be considered, or let's assume that all of that is the same as Earth's. Would we "rest/stay awake" however long or short it takes to ...
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### From Mean Moon to True Moon in an old procedural calendar

This is a follow-up to How to interpret this old degree notation? It is about an old calendar system which generates a luni-solar calendar with a procedural method, using a handful of calculations ...
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### Can you see pleiades and sirius at the same time on the sky?

I am would like to know if you can see pleiades and sirius on the sky at the same time from Greece? What time of the year would that be? And I would be very greatful if someone knows some interactive ...
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### What happens when two black holes collide?

There are many hypothesis saying that there will a collision between the milky way and Andromeda galaxy...so what happens when two black holes will collide?? And how will it effect the other objects ...
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### How would the explosion and fallout of a nuclear bomb on the moon compare to one on earth?

What effects would the atmospheric and gravitational differences between the earth and the moon have on a nuclear bomb explosion and fallout?
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### Eclipses of Jupiter's Moon during Retrograde motion

When Jupiter is undergoing retrograde motion as seen from the Earth, would you expect the eclipses of Jupiter’s moons to occur several minutes early, several minutes late, or neither? Can someone ...
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### Double Planet Orbiting Wide Binary Star?

Right now I'm writing a sci-fi story that develops in a double planet. But that's not all, the double planet (along with a couple more planets) orbit a big star and the whole system is orbited by ...
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### If a person were to die on the Moon or Mars, would the body decompose?

There wouldn't be enough oxygen for any bacteria to decompose the body, right? Not to mention, the radiation of space might kill off most organisms on it. So would it decompose, given millions of ...
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### Why is metallicity important in the death of stars?

I always thought that mass was the sole determinant of a star's fate. Then I saw the table here. So why does metallicity influence a star's ability to become a black hole or neutron star? Does it have ...
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### What are the cosmological ramifications if we probabilise and continuify the order of differentiation in $F=\frac{d(mv)}{dt}$? [migrated]

Newton's second law of motion states that $F=\frac{d(mv)}{dt}$. This is a first-order differential equation, in which the order of differentiation of momentum is 1. So we can write it ...
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### dataset of stars in the milky way galaxy [duplicate]

Does anyone have any idea were I can get a dataset of stars in the milky way galaxy, their mass and their planets and distance of planets from their star? I have tried various catalogs of NASA. I ...
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### How does gradual crossing over of the Roche limit transform a planet or moon?

Some cartoon simulations (an example) of an object (assume here a large moon with Earth-like density) which crosses the Roche limit of a much more massive giant planet, illustrate a circle suddenly ...
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### Luminosity Schechter function for galaxies

Just a question I am having trouble understanding. I have the Schechter luminosity function for galaxies, given as: ...
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### Low precision GMST formula clarification

According to the website http://aa.usno.navy.mil/faq/docs/GAST.php, a low-precision way of calculating the GMST is via the following formula: GMST = 18.697374558 + 24.06570982441908 D The website ...
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### Distribution of Stars in Milky Way and globular cluster analogy

Just a quick (and hopefully simple) question on the distribution of stars in the Milky Way and in globular clusters. I was wondering why it IS NOT possible to describe the distributions of stars in ...
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### How does gyrochronology deal with differential rotation and axial tilt?

K2 seems to become an even better mission than what a continuation of Kepler would have been, at least to some astronomers. By what means is differential star rotation being dealt with? The rotational ...
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### Definition question: continuum-subtracted spectrum

What is the exact definition of a "continuum-subtracted spectrum", such that one finds in SDSS spectra? http://classic.sdss.org/dr7/dm/flatFiles/spSpec.html#specmask Is there a definition ...
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### Could Pluto and Charon have extra-Solar origin?

Pluto and Charon seem to have surprisingly young surfaces, considering that resurfacing events were expected to be rare for them. Could the explanation be that they actually are young? Formed later ...
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### What places on Pluto and Charon are facing each other?

What places on Pluto and Charon are facing each other? Are Pluto and Charon perfectly tidally locked, or is there a slow rotation over time? And how long after formation should they have become ...
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### Relationship between the Casimir force and dark energy

This is related to another question I asked. Might we actually be observing dark energy when we do experiments that verify the Casimir effect?
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### How to get from the earth to another planet/ the moon? What happens on the way? [on hold]

I have a problem explaining for my students how to get from the earth to the moon? Is there someone who can give a good explanation? I Think these are words that might be included. Escape velocity, ...
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### Why can falling stars only be seen moving down towards horizon not up away from horizon?

Are falling stars as we know only just space debris entering and burning up in the atmosphere and not a star at all?
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### Telescope collimation issue

Recently I purchase Chinese 8 inch reflector telescope from local store. When I observing starts and planets I've been having trouble getting really sharp image from this telescope. I observe Venus ...
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### How much heat is generated from waxing and waning of reflected radiation from the Sun?

According to this article, the greatest cause of global warming would be from the waxing and waning of reflected radiation from the Sun. (Placing carbon emissions at 10-20%) So really, how much heat ...
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### Moving from computerised to normal amateur telescope?

A few years ago I purchased a Celestron Nexstar 130 SLT computerised telescope thinking that it would be a perfect to get me into astronomy. The issue is the computer doesn't work at all and manually ...
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### How many constellations in the Zodiac?

The astronomical zodiac contains a bunch of constellations along the ecliptic. Some sources say there are 13 constellations in the astronomical zodiac. Other sources claim there are 12. According ...
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### I'm making a presentation for a planetarium, any topic ideas? [on hold]

As part of a project I'm making a presentation that will be displayed on my university planetarium dome, using the Nightshade software. I'm looking for topic ideas... The subject I thought about ...
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### Calculate Local Sidereal Time

I am trying to follow this guide and move to a programming language but I have doubts. What means the strings A, B and C in this manual? ...
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### How is the Lithium Depletion Boundary used to determine the age of a stellar cluster?

According to my understanding of Soderblom et al. (2014), lithium ages of stars are determined as follows: Determine lithium abundance from equivalent width measurement of Li$_{\mathrm{I}}$ ...
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### How do proto-planetary nebulae gain momentum?

currently I am curious about proto-planetary nebulae. At first I was curious about how planets spin but I read in a couple of articles that they got their spin from when they were in a proto-planetary ...
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### Realistic space environments [on hold]

You've seen it in all kinds of science fiction, be it books, games, movies, and such. Space is depicted all sorts of ways, with asteroids far too close together, nebula thick enough to hide in and ...
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### What's the bleeding-edge model for how Population III stars are born and evolve?

I'm trying to do a brief literature review to find out what the best current models for population III stellar evolution are. I was hoping that someone with more expertise in the area could perhaps ...
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### What would happen if a rocket traveling at speed of light would collide with a planet (like earth)?

Let's assume it is possible for a spacecraft to travel at the speed of light (I've read the interstellar book by Kip Thorne, apparently this is theoretically possible if you swing around two black ...
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### How special is the Solar system compared with other planetary systems? [closed]

For example: Most planets have circular orbit What else?
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### Does liquid water on Mars means life?

We need to figure if liquid water is present throughout a Mars year, and how long the planet has been at its current distance from Sun. That will give us the length of time that liquid water has been ...
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### What would happen if we stepped on the Sun?

I mean in intrinsic detail. What would happen to our bodies besides "burst into flames"?
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### Is liquid water on Mars such a big leap compared with ice?

I thought we have found bacteria or other kinds of life on Mars. Now it is liquid water. Is there such a big difference between liquid water and iced water?
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### Could there be dark matter black holes?

Could dark matter compress and form black holes? Since dark matter is even more abundant than normal matter, a dark matter black hole should not be rare...right?
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### Are planets moving away from the sun?

I saw on the tv show Through the Wormhole (hosted by Morgan Freeman) that the planets in our solar system have been continuously moving away from the sun for millions of years. however, when I try to ...
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### What is the brightest star (relative magnitude) in M31?

I am wondering what the brightest individual star is in M31, the Andromeda Galaxy. Specifically, brightest as seen from Earth (so relative magnitude).
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### Estimation of average rock and asteroid mass associated with different stars

There is a lot of information on different star types and compositions. Can we make estimates of the total mass of rock, ice, and non stellar matter that orbits stars based on star evolution models? ...
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### What are the most valuable meteorites and asteroids in terms of precious metals?

There were some suggestions that asteroids could one day be mined for precious metals. I have found an outdated study that says that some siderites contain as much as 0.001% of gold: ...
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### How can one explain the apparent motion of the Sun from a heliocentric point of view?

From a horizontal frame of reference, the path of the Sun looks like a part of a circle in a tilted plane, as shown in this picture: ...
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### Pyrokinesis? Explain the cause [closed]

-A candle is lit on a table -A 2"1/2 book is placed in front of candle -the candle is obstructed by the book by 3" in each direction except the bottom -I rub my hands together like there cold 4" in ...
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### Can all areas on Earth experience a total solar eclipse?

A solar eclipse only puts part of Earth at a time in shadow, so I'm not talking about a solar eclipse that casts a shadow over all of Earth. What I mean is: are there any areas on Earth where, no ...
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### What light source can cause a shadow of a cloud onto the next cloud above?

Scenario- -Time & Environment-11:00pm Super Moon small town population 40,000 in Central Ca. -Nearest body of water is 80 miles away 4 small lakes of about 1 mile in diameter. -Pacific Ocean is ...
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### How important is the size of an astronaut [migrated]

It seems to me that weight and size would be important in choosing spacefarers for many reasons. I came across this wikipedia article where the Chinese Astronauts have to be between 50 and 70 kg, ...