Quote:
Originally Posted by Zada Knight
Has anyone else noticed lately the changes in the sky? Its seems to be cocked sideways, the stars seem to be in different places.
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You are correct in noticing changes and that the stars seem to be in different places. Here's why:
First, a couple of basic facts. The Earth orbits the Sun once a year. In other words, we make a great big circle around the Sun and it takes 365 days to do that.
Now, while we're going around the Sun we also have a spinning rotation which gives us our day-and-night process. So we can establish the fact that as we face the Sun, it's daytime, and facing away from the Sun we have night.
As we go through the daily rotation (day and night), we're also moving ever so slightly around the Sun in our yearly Big Circle. And because of both movements, our sky changes ever so slightly from night to night.
Here's how that works:
We'll use our current time as an example. It's now early April. Let's say you look at the sky at say 11pm. So you can see what's in the sky at this current time of the night and month. Because we make a little movement around the Sun, the sky tomorrow night will have a slight westerly shift to it when viewed at the same time of the night. Here's a way to see this happening:
Go outside and pick a place to stand where you can see a bright star (it does not matter which one) in relation to a reference point like say a phone pole or building, or roof line of a house. Just anything you can use as a reference point. And let's say the time you do this is 11pm.
When you go out the next night at the VERY SAME TIME and stand in the EXACT same place to see the same star, you'll see the star has moved a little west from where it was the night before. And the night after at the same time, it will have moved a little more west. And the night after that, the same thing, and so on and so on.
This slight shift is equal to four minutes of time. So every day, the sky shifts a little west which means everything rises and sets 4 minutes earlier than it did the day before. And here how this is viewable. Pick your place and time (again 11pm for the example) to view the star you picked like before. But this time, the next night go out and look at it at 10:56pm and you'll see it in the same place as it was the night before. The next night go out at 10:52pm, the star will be in the same place. Next night it will be there at 9:48, night after that 9:44 and so on.
So after a full month the sky has shifted by 2 hours (4 minutes x 30 days = 120 minutes). What you were seeing at 11pm is now in the same position at 9pm. The month after that it will be in the same position at 7pm and so on.
So in 6 months time (half a year) we have gone halfway around the Sun which means that what we now see at night (April) will not be visible at night (October) because that area of the sky will be occupied by the Sun. And what we now see as the daytime sky (April) will be visible as stars at night (October).
I hope I have explained this so everyone understands and is not confused.