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What will happen to life on Earth when the Andromeda and Milky Way galaxies collide?
19 votes

4 billion years is the same timeframe of the life remaining to our Sun. So if we have not yet invented interstellar voyages, we're screwed, with or without Andromeda. Besides, stars do not interact ...

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Why can we sometimes see the moon during the day?
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14 votes

The Moon makes a full orbit around the Earth once per month. From full moon to full moon, it is 29.53058886 days (synodic month). Full moon happens when the Moon is at one side of the Earth (right ...

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Could gravity waves be used to confirm the existence of a ninth planet?
13 votes

No, they can't. Gravity waves from a small, simple object moving slowly are very, very faint, to the point of being undetectable with current (or foreseeable) technology. The waves that have been ...

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Why is the observable Universe larger than its age would suggest?
12 votes

In short: things can not move faster that light by theirselves, but they can move faster than light due to universal expansion. The more far away, the faster they go away.

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Why is the speed of light 299,792,458 meters/sec?
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10 votes

Speed of light being finite is one of the fundamentals of our Universe. If it were infinite, this would have a major implication in causality. Besides, in non-quantum physics, light is just an ...

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Any possibility for life on moons of planets in our Solar System
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10 votes

If you check 2001 A Space Odyssey saga, Europa is actually a satellite with Life. Coming back to real space, the "comfort zone" for life is approximately from Venus' orbit to Mars' orbit. There, only ...

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What's the largest non-spherical astronomical object in the universe?
10 votes

I think, by his mention of asteroids, that the OP means an object in the scale of asteroids or dwarf planets, that is, almost-solid objects. In this case, asteroids the size of 2 Pallas or 4 Vesta are ...

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Why do the planets in the Solar system stay in the same orbital plane?
9 votes

Answer to the NEW question: the Angular Momentum Conservation Law states that, for any moving body, its angular momentum does not change unless you exercise an external force different from the ...

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Doesn't gravity attract objects in space until they collide?
9 votes

There are other formulas at work, but not any other forces. You need to take into account ont only the force, thus the acceleration, but also the current velocity of a body orbiting another. To put ...

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Is the Hubble Ultra-Deep Field image representative of the entire sky?
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8 votes

Short answer: both. HUDF is representative on the type of galaxies we can find at that distance (and remember that distance also means time ago). On the other hand, we do not really know how the ...

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Pluto's orbit overlaps Neptune's, does this mean Pluto will hit Neptune sometime?
8 votes

No, their orbits do not cross. They are just tangled, but in no point they coincide.

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Does a planet's mass or gravity affect the height of it's mountains?
8 votes

Yes, gravity definitely affects the maximum heigh of mountains. Think on a solid bar of steel. It sticks straight because of the electronic forces. But when you make it larger and larger gravity ...

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Motion of the sun as observed from mercury
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7 votes

Both effects combined. Day being longer than year would just have retrograde motion of the Sun on sky, but no direction change. Variation of the distance alone happens on Earth, and we have no such ...

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Is there a pattern between the mass of a body and the mass of orbiting objects around it?
7 votes

No, there is no pattern on 1%. There are cases of double stars and (allegedly) of double planets. In our Solar System, Charon has a mass of 11.6% of that of Pluto.

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Astronomy questions I wondered for hours
6 votes

If you think on Big Bang as an explosion IN space, you are plain wrong. It was not. It was an explosion OF space itself. And time, for that matter. What happened before the big bang according to ...

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Is there a flaw with the newer purposes and correlations attributed to the HR diagram? (And would a third axis of mass correct the enclosed flaw?)
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6 votes

Yours is a very, very interesting work. If you publish it it may happen that 3D diagrams will be used in the future. Please publish it. But this does not mean that there is a flaw in the H-R diagram. ...

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Regarding the curvature of the Earth
6 votes

About curvature, you can see it. Just look at a ship some hundred meters away: you'll notice if you are careful that you can not see where the ship touches water. You can see at http://mathcentral....

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Why is liquid water considered a requirement for life?
6 votes

The reason for which water is needed for Life as we know it (and we have not been able to successfuly imagine a different model from that of DNA that has ability to self-replicate, react to the ...

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Can there be a 2nd possibility deduced from the fact that galaxies are moving away from us?
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6 votes

Galaxies are moving away from us in every direction. If it were like your race, galaxies at our same distance from the central point will be slowly approximating. That is, we will note that galaxies ...

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What distance has the moon been from earth at the closest?
Accepted answer
6 votes

If we accept the Giant impact hypothesis, which says that the Moon was once a part of the Earth pushed away by a big impact, the answer is obviously 0.

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apparent size of an astronomical body
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6 votes

Angular size. That is, the vieving angle that the body spans on sky.

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What is the physical, geometric shape of the universe?
6 votes

Ok, maybe you have some misconceptions. The Universe has no center at all. It looks the same from avaery point, to wherever you look to. It is approximatedly as follows: This image represents a very ...

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Official registry of lunar placenames?
6 votes

http://planetarynames.wr.usgs.gov/Page/MOON/target Official list endorsed by IAU

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Find distance from star to star?
Accepted answer
6 votes

If you know distance from Earth to both objects and the angle between them viewed from Earth, it is just a matter of trigonometry.

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Has life been discovered outside of Earth?
6 votes

No life has been discovered out of the Earth. It is still discussed that bacteria once existed at Mars.

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How was Io not torn apart by tidal forces during its formation?
6 votes

No, it is not just a matter of migration. You need to take into account two facts. One is that (as experience shows) Io's own gravity is enough to avoid it breaking by tidal forces. It has been like ...

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Why is right ascension measured in hours?
Accepted answer
5 votes

In order to know when a star will be above horizon, you'll need an equation with times, not "celestial latitudes". So you end up adding RA and sidereal time. EDIT In order to find out the position ...

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How did the reionization epoch make the universe "transparent"?
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5 votes

Nowadays, the universe is mostly ionized, and transparent. Transparent means that photons are able to travel long distances. So there comes the confusion: How could it be that recombination made the ...

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What is the orientation of planetary orbits?
Accepted answer
5 votes

No, the planet orbits do not have their major axis aligned. http://en.wikipedia.org/wiki/Orbital_elements You have Inclination and Longitude of the ascending node defining the plane, and Argument of ...

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Do all moons orbit their planets on the ecliptic?
Accepted answer
5 votes

Of course not. See Neptune's moons. Triton's orbit has a tilt of 157º from Neptune's rotation plane, which is in itself tilted 30º from Neptune's orbit, just 2º away from the Ecliptic. Or look at ...

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