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25
votes
11answers
5k views

What is the simplest way to prove the Earth is round?

Assume you've come in contact with a tribe of people cut off from the rest of the world, or you've gone back in time several thousand years, or (more likely) you've got a numbskull cousin. How would ...
10
votes
1answer
58 views

Why did the june 2011 lunar eclipse last so long?

It was kind of hard to miss the lunar eclipse this week, although I didn't see it in person (Sod's law means that on every relatively major astronomical event clouds cover where I am). From what I ...
25
votes
4answers
4k views

Why is a new moon not the same as a solar eclipse?

Forgive the elementary nature of this question: Because a new moon occurs when the moon is positioned between the earth and sun, doesn't this also mean that somewhere on the Earth, a solar eclipse ...
8
votes
1answer
263 views

Could the earth have another moon?

First, to clarify: I'm not asking if perhaps there's a moon that we haven't found yet. The question is, theoretically, would the earth be able to have another stable moon in addition to the current ...
16
votes
4answers
997 views

Does the Moon's core still contain significant heat?

On earth, using earth-sheltering techniques can significantly reduce the temperature fluctuations on a structure. Would the same statement be true as well on the Moon? Does the Moon's core still ...
-4
votes
1answer
228 views

How can the Earth's day increase and its rotation slow down at the same time? [closed]

I heard that the Earth rotation is slowing down, but I also heard the Earth's length of day is increasing. Does the two theories go together or conflict with each other?
13
votes
2answers
510 views

Is the length of the day increasing?

In Frontiers of Astronomy, Fred Hoyle advanced an idea from E.E.R.Holmberg that although the Earth's day was originally much shorter than it is now, and has lengthened owing to tidal friction, that ...
12
votes
5answers
3k views

Does Earth have a code name?

Everything we discover in the sky get eventually a code name, like NGC 7293, Simeis 147, etc. Does Earth/Moon have a code name too? Or it is just Earth/Moon, etc.?
-5
votes
1answer
13k views

What is the extent of Earth's gravitational pull? [closed]

Where the gravitational pull of Earth exist up to? What distance from Earth it will be zero? How do the skydivers fly at a same altitude? Won't they feel gravitational pull? What is the Earth's ...
-3
votes
1answer
420 views

Gravity anomaly in Lacnov, Slovakia: Gravity ashamed

http://www.youtube.com/watch?v=4qxwqNqL-Nc http://tvnoviny.sk/sekcia/spravy/technologie/v-lacnove-sa-predmety-kotulaju-do-kopca.html (Sorry: above links in Slovak.) Can someone explain this to me? ...
3
votes
3answers
288 views

Ozone Hole in the South Pole

Perhaps this should be a chemistry question, but it seems to have physics attributes. There's a perennial ozone "hole" around the south pole created by destruction from Cl based chemicals like CFCs. ...
20
votes
8answers
31k views

Why doesn't the Moon fall upon Earth?

Why doesn't the Moon, or for that matter anything rotating another larger body, ever fall into the larger body?
8
votes
4answers
5k views

How long would a lever have to be to move the planet Earth?

Give me a lever long enough and a fulcrum on which to place it, and I shall move the world. -Archimedes How long would that lever have to be? That is to say, how long a lever ...
4
votes
6answers
4k views

How fast is Earth moving through the universe?

As the galaxy is moving and the solar system orbiting the galaxy and the Earth orbiting the sun. So how fast is each object moving and what is the fastest we move at? Do we even know how fast the ...
20
votes
4answers
4k views

Would you be weightless at the center of the Earth?

If you could travel to the center of the Earth (or any planet), would you be weightless there?
5
votes
5answers
2k views

What sustains the rotation of earth's core (faster than surface)?

I recently read that the earth's core rotates faster than the surface. Well, firstly, it's easier to digest the concept of planetary bodies, stars, galaxies in rotation and/or orbital motion. But, ...
6
votes
6answers
990 views

Escape velocity from long ladder

The escape velocity of earth is roughly $11 kms^{-1}$. However, what if a long ladder was built extending out of Earth's atmosphere and considerably more. Then if something was to climb up at much ...
4
votes
1answer
681 views

Formula for getting time of sunrise at a particular location?

Is there a formula that can get sunrise at a particular latitude and longitude (and elevation from sea level)? If so, what it is? (Why does it work?)