# All Questions

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### Might the universe be really small yet seem infinite from spherical reflections? [closed]

if a single source of light quite small, was placed somewhere inside a completely reflective sphere, quite large, what would the reflections look like from the light source's point of view within that ...
577 views

### Formulas to determine the illuminated phase and orientation of the Moon

The phase of the Moon (the bright limb) looks different depending on where on Earth the observer is located and the time of the observation. I've located this video and the accompanying spreadsheet ...
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### What Is The Great Attractor?

I've heard that there is something called the Great Attractor which seems to have some kind of gravitational influence on objects in the Universe. Is this some kind of theoretical notion posited in ...
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### If we were to see the Sun with our naked eyes from the Orion belt, would all planets be encompassed inside the star? Is this calculable?

When we see a star it looks much bigger in diameter to us than it really is, this picture (extracted from here) explains what I mean: Notice that the point we see in the skynight, represented by ...
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### How can absolute value of azimuth exceed distance from pole?

I'm sure I'm just doing something dumb, but: Yildun has a declination of approximately 86.5. This puts it 3.5 degrees from the celestial north pole. Per the snapshot below, Yildun's azimuth can ...
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### On analogies between gas and stellar systems

Analogies between (typically) ideal gas and stellar systems are not only intuitively valid to some extent, but have been established and used in the studies of stellar clusters and galactic systems, ...
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### Are we still in the Solar Maximus stage? Will this winter 2013/14 be a good aurora-viewing season?

I remember reading in 2011 that 2013/2014 would be the peak of the current solar maximus, but I want to confirm whether that is still ongoing. Will the upcoming winter season be a good time to see ...
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### How can I observe the Orionid Meteor Shower?

I would like to see the orionids sometime this week (October 20-26, 2013). What is the best way for me to observe them by naked eye? Also, would I be benefitted by trying to look at them with a ...
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### If we found evidence of life on Mars, how would we know that it originated on Mars rather than Earth?

Consider this scenario. One of the probes sent to Mars either very soon, or within the next century, finds conclusive micro-fossil evidence that life once existed on Mars. One theory today that is ...
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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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### What makes a really good observatory site, besides altitude?

Let's limit this to optical telescopes. I understand that the higher you are, the less atmosphere is above you to get in the way of observations. From reading around, there seem to be a few more but ...
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### Astronomical databases for machine learning?

I was reading this question about open problems in astronomy. The bounty-receiving answer says that I have just left the field where some colleagues are trying to develop some software to use ...
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### Meteorites bring water

The latest information suggests that Earth's water came from Meteorites . The Moon was also bombarded by Meteorites and yet it has no water. Is this because it lacks an atmosphere and its water was ...
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### Tide on the Moon

If the Earth's Moon had a water ocean of depth 2-4 Km, how high would the tides rise due to the Earth's gravity? (Just a hypothetical question.)
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### Basic DIY Telescope

I am looking for a design of a cheap and easy telescope to build with my 9yo daughter with the only basic requirement being that I'd love to be able to see detail on the moon. Looking around, there ...
234 views

### Given a date obtain latitude and longitude where is the sun zenith

Searching is easy to find terminator line (frontier between day and night) or the position of the sun in the sky given a position on the earth and a time; but I can't find how to obtain where is the ...
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### How to compute satellite coordinates (lat,long) given antenna's coordinates, angles and satellite height

Given an Earth station (antenna) coordinates (in lat,long) ant its Elevation (El) and Azimuth (Az), how to compute the satellite coordinates (lat,long), known its height? For simplification purposes, ...
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### Composition of planets' core

It is often possible to find a list of the materials that compose the cores and the mantle of plantes (often they are iron and/or nickel). How can these materials be determined in our Solar system? ...
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### Could a space radio telescope fill multiple purposes?

Dream for a while and imagine that there will be a flagship+ mission within a decade to put a large radio telescope in space: What kind of different tasks could the same radio equipment feasibly be ...
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### Galactic Habitable Zone

Do galaxies have habitable zones the same as stars do? Say in a galaxy with a very active nucleus producing a lot of heat and radiation, would there be a point at which no star's planets could harbor ...
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### Would it be possible to calculate the expected frequency of impact craters of all sizes on Earth

Can the expected frequency of all sizes of impact craters on Earth be calculated based on the preservation of impact craters seen on the Moon? Taking into account the difference in gravity and ...
309 views