Why does the world turn?

 

Well ya see......one God decided he was tired of looking at the same place on earth so he decided to spin it so he could see the whole thing. :P

 

Hi Jimmy, glad to see that someone is awake. You must be on duty.

 

An object in motion tends to stay in motion...something like that?

 

Naw, its just all the Ford trucks are sitting still, spinning tires and make the Earth rotate.

 

Why is the sky blue and the grass green, and not the other way around? It's just one of those questions nobody really asks, so there isn't a real answer for it. Here's a thought for you- the moon doesn't turn. Actually, it has held still for so long, that the gravitational pull of the earth has made it somewhat egg-shaped.

 

Sorry Mike, yes I am on-duty, will be for the next hour 1/2...I did not respond as I am swithing between 4 differant forums.....just got back to this one. :P
oh yeah, and working at thge same time.

 

I learned that when the planets were formed from parts of the sun, it was spun as it seperated.

 

There is actually a reason for both of those, though.

 

Ford 6, I don't mean to be smart, but the moon does spin. Once a month. Actually, every 27.9 days, but who's counting? The rate of spin makes it appear to remaing still.

 

I think it's because Jimmy Dean farter, and everyone was trying to run away, and the earth just kept spinning

 

very big bearings

 

I think I know where you came up with this one. Yes the moon rotates on an axis. The interesting part is that the moon rotates once for every time it revolves around the Earth so we always see the same side of the moon, giving the appearance that the moon is not rotating.

The sky is blue because the "short" blue light waves are scarttered in the atmosphere and thereby give the sky a blue appearance.

I'm not sure why Chlorophyl is green but it is the substance that makes grass green.

The world turns like other bodies in space because they are "spiraling in" to whatever is gravitationally superior.

 

The Answer
The Earth spins because of conservation of angular momentum. The classic example of this is a figure skater. When a figure skater pulls in her arms, she spins faster. The Earth formed when gas left over from making the Sun condensed into the planets. As this gas cooled and condensed, it started to spin faster. Now that it is spinning (and not condensing any more), it will keep spinning at a steady rate unless something stops it.

The Moon, of course, rotates--at the same speed as it orbits the Earth. So, in the 27.32 days it takes the Moon to go around Earth, the Moon also spins about its axis one full revolution. That's why we always see the same face of the Moon.

Now, the interesting part: why does the Moon spin about its axis at the same rate it orbits? In the distant past, the Earth's tidal pull on the Moon slowed the Moon's rotation to match the time it takes to go around Earth.

This is tricky stuff. You know about the tides on Earth. The same forces work on the Moon. It isn't obvious there because the Moon lacks water but it happens. The Earth's gravitational attraction is stronger on the side of the Moon nearest to Earth and weaker on the opposite side. Since the Moon isn't perfectly rigid, it stretches out, like a ball of taffy, along the line between Earth and Moon. If we were on the Moon, we could, theoretically, see two bulges--one on the side facing Earth and the other directly opposite.

Long ago when the Moon spun much faster, the Moon's tidal bulge preceded the Earth-Moon line because the Moon couldn't "snap back" its bulges quickly enough to keep its bulges in line with Earth, says James Hilton, Astronomer, U.S. Naval Observatory. The rotation swept the bulge beyond the Earth-Moon line. This out-of-line bulge caused a torque, slowing the Moon spin, like a wrench tightening a nut. When the Moon's spin slowed enough to match its orbital rate, then the bulge always faced Earth, the bulge was in line with Earth, and the torque disappeared. That's why the Moon rotates at the same rate as it orbits and we always see the same side of the Moon.

In our solar system, almost all moons spin at the same rate as they orbit. We think the exceptions are ex-asteroids captured so recently that tidal forces have not yet equalized the orbital and rotational periods.

"Not only did the Earth slow down the Moon's rotation," says Hilton, "but the Moon is slowing down the rotation rate of the Earth." The Moon, being small in relation to Earth, has a long ways to go before it slows Earth's spin rate to the Moon's orbital rate. It will take "twice the age of the solar system", says Hilton.

One planet, Pluto, is small enough in relation to its moon that it's already happened. Pluto and its moon both always show the same face to each other.

 

great stuff CTrunkSlammer. Conservation of angular momentum. I think I've forgotten more than I remember about most things. Sucks getting old.