TRUE OR FALSE : The same side of the moon always faces Earth. Explain?
No one who has answered so far got it right. The answer is TRUE, and the reason is because the moon rotates on its axis in exactly the same amount of time it takes it to make one revolution around the earth. No one seems to get this.
The moon revolves around the earth, but doesn't rotate/spin on its own axis. Why not?
The moon DOES rotate. The reason you cannot detect it is because it is in a synchronous rotation, meaning that it takes the same ammount of time to revolve as it does to rotate, meaning that the same face (the Light side) is always facing us. It may be hard to visualize at first, but imagine you are the moon. Now, stand facing an object, like a pole which will be the Earth. Now, practice spinning around (revolving) so that you can do it in exactly 10 seconds. Now, practice walking around the pole so that you are rotating for exactly 10 seconds. Now, do them both together. From your perspective (as the moon) you ARE rotating, but you'll notice that your face (the Light side of the moon) is always facing the Earth.
Wich pole is facing the milky way spin direction ?
The angle between the north galactic pole and the north ecliptic pole is 119.8°, which is the same as -60.2°. In other words, the SOUTH ecliptic pole is 60.2° from the north galactic pole. That's a long way from "perpendicular". The Earth is going around the sun in a direction opposite to the spin of the galaxy. More precisely, the angle can be decomposed as 75% perpendicular and 25% anti-parallel to the galactic plane. That's not north or south -- it's more like counterclockwise, while the galaxy spins clockwise (as viewed from the north side). KennyB wrote >> ... at the right time of the year, our north pole is are aligned (more or less) with the galactic "north" and six months later we are tilted about 50 degrees "away" from galactic north. No, it doesn't work like that. The Earth's north pole always points at the same place in space (the movement from precession is less than 0.8' per year, and can be ignored for this problem). The north pole's angle to the galactic pole is approximately 27° at any time of the year.
How did the planets got their rotations and order?
The planets spin on their own axis' in the same manner as the Sun (with the exception of Venus, which spins counter-clockwise) due to the fact that this is the direction the Sun started spinning at the dawn of its creation. Had the Sun began to spin in the opposite direction instead, so too would have followed the planets. Now, Mercury is not tidally locked as it was earlier suggested. It does in fact spin clockwise as most of the other planets in our solar system do, but it does so at such a slow rate (it takes about 2 Mercury years to complete one rotation on its axis) that it mimicks the attributes of a tidally locked planet. Why does Venus spin the opposite way? The latest theory on that is that it isn't actually spinning counter-clockwise at all. It's actually spinning clockwise, but upside-down, meaning it started off spinning in the same direction as all of the other planets and was flipped 180 degrees on it's axis due to the gravitational and frictional effects between the Sun and the planet's thick atmosphere. How did the planets form in the order they are in now? With a little observation, you'll notice that all of the inner planets are rocky and all of the outer planets are gas/ice giants. There is a reason for this. When the Sun finally ignited at the start of the nuclear fusion process, it gave off a blast of solar radiation, which acts like a wind. The wind blew out a large percentage of the lighter elements and a small amount of heavier elements in the disk that circled the Sun. That left most of the heavier elements and a small amount of lighter elements in the inner solar system to form planets, which is why they are rocky planets. Just the same, the planets that formed further out were made primarily of these lighter elements that were pushed out by the solar winds, which is why they formed as gas giants. On a side note, the planets weren't always in the order they are in now. Jupiter was actually further out than Saturn, and at some point about 4.5 billion years ago they switched orbits. This massive shift in high gravity planets disturbed the asteroid belt and sent billions of asteroids screaming into the inner solar system. This is known as the Late Bombardment period, and you can see the remains of this event on all of the inner planets and moons which are covered heavily with craters.