petebro Posted March 16, 2008 Posted March 16, 2008 having spent a year in the southern hemisphere my perception of earth and its rotation has certainly altered so i pose the question which way around are we all facing . given that the northern hemisphere is rotating in a anti clockwise direction and the south the opposite is there a definitive answer to my question the is no right and wrong way around . but having said that is the universe acting in that fashion is the equator the centre of our universe if we sliced though it like an orange do we end up with two pieces the same in which case is the two pieces acting in the same fashion . is time in relation to this acting in the same way . can someone give me a explanation ? this then poses another question how is the universe expanding in relation to this if things are rotating in opposite directions. mr confused
ecoli Posted March 16, 2008 Posted March 16, 2008 there is no 'right or wrong way around.' Position and motion through any space depend on your reference frame.
Bignose Posted March 16, 2008 Posted March 16, 2008 Because the Earth is all one piece, the Northern hemisphere and the Southern hemisphere don't "rotate in opposite directions". They rotate in the same direction. It's not like if you jump over the Equator, you have to suddenly change directions. The sun rises in the East and sets in the West in both hemispheres -- if they were rotating in opposite directions, that couldn't be. Now, if you look at the Earth rotating from atop the North Pole and compared that with looking from the South Pole, then, yes, it will look like it is rotating in opposite directions. But, that is all a matter of perspective. Just like if I threw a ball at you, the perspective is that the ball is coming towards you, but my perspective is that the ball is leaving me. Which is correct? They both are, from our perspectives. On top of that, ecoli's point about reference frames being arbitrary is still valid too. In one reference frame, the Earth would appear to have a certain rotation. In a second reference frame, one that is rotating more, the Earth may have a slower rotation speed. In a third we could choose a reference frame where the Earth had no rotation or a reference frame where the Earth actually spun the opposite way. All of these are equally valid points of view. The exact same thing can be done with lateral movement, too. In one frame, the Earth sits still, in another the Earth is zooming through space. It's just like that example if the ball I threw to you. In one frame, yours, the ball has a negative velocity in my frame the ball has a positive velocity. It's all a matter of perspective.
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