If the moon orbits the Earth approximatly every 24 hours why am I seeing the moon in the middle of the day?
Because the Moon doesn’t orbit the Earth every day. It takes about 29 days to go around our planet.
If it zipped around us every day, it would be moving mighty frigging fast! And it would appear in the same spot in the sky, because that’s called geo-stationary orbit.
I’m sure you can find much more about that celestial body over at the site maintained by our very own Bad Astronomer.
The moon orbits the earth roughly once a month (“roughly” because you can quibble about different types of months, and days). The earth rotates once a day. So you sometimes get the moon up in the daytime. If you get an astronomical calendar, you can see exactly what’s going on.
whoops, screwed up the coding. try http://www.badastronomy.com
Because the moon changes its path slightly every day, having an elliptical orbit, so 24 hours later it’s not exactly in the same spot it was 24 hours previously. So every so often, you see the moon at noon.
It takes the moon exactly 27.32 days to orbit our planet. Since this is true, it (the moon) should only be visible to me every other 13.66 days, since the other 13.66 days the moon is on the opposite side of the planet. Yet I am fairly certain that the moon is visible to me far more than that. I know that I am wrong here, somewhere, but (maybe because its friday) I just don’t get it.
anyone?
Sigh…
But you’re on the Earth’s surface, rotating every 24 hours. So the moon appears at least once a day at different times for its rising and setting as your position rotates under it. (Its rise and set times progress about 1 [sup]1[/sup]/[sub]8[/sub] hours per day because its orbiting in the same direction as the Earth’s rotation.)
The sun does the same thing. But since its position is the basis for our time of day, we don’t notice that its position actually regresses a few degress every time the Earth rotates 360[sup]o[/sup]. We just wait about another 4 minutes, and the sun is at the same approximate azimuth as the day before.
Er… I misspoke. The Sun doesn’t do the same thing as the moon. I was just trying to point out that nothing’s simple in considering orbital geometry.
Mothman, try this. Think of an analog clock. So instead of the hour hand making a complete 360 degree circle in twelve hours we are going to slow down the clock motor so it goes around the face of the clock once every twenty four hours.
Now let’s take a cardboard cut out of the moon and put it at say… 12 o’clock. We are going to move the cardboard cut-out around the clock at a rate of once every 27.32 days. So in 13.66 days it will be sitting at 6 o’clock etc, etc, etc.
We can also put a cardboard cut-out of the sun at the 12 o’clock position, but the scissors are hurting my fingers. Since it does not move from the 12 o’clock position, let’s just use our imaginations.
Ok, so when our slowed down clock reads 12 o’clock, the earth (where you are) is facing the sun. At 6 o’clock the earth is facing away from the sun and it is the middle of the night.
Just to make it easy, let’s say you can see the moon if it is 90 degrees from the hour on the clock. Therefore, if the clock reads 12 o’clock, you can see the moon if the cardboard cut-out is anywhere between 9 o’clock and 3 o’clock. (The top side of the clock, obviously.)
Now we need to fast forward a bit. Since we started with the moon cut-out at noon, we cannot see it since the sun is too bright. Let’s move the cut-out to 6 o’clock and start time from there.
Ok, day one, card-board cut-out is at 6 o’clock. As the earth rotates and hits the 3 o’clock mark, we start to be able to see the moon (moon-rise). Also, since we are getting more than ninety degrees from the Sun, we are unable to see it anymore (sunset). (This is, coincidentally, a full moon, but that is more indepth than I can get right now.)
Time moves on. The clock sweeps from the 3 o’clock position to 9 o’clock, the moon sets, the sun rises, and Cecil said it was good.
Now update the moon position. In that one day, it only moved a slightly more than a third of the way from the 6 o’clock position to the 7 o’clock position. Not very far at all, really. As the hands continue to sweep, the sun sets at the 3 o’clock position but the moon does not start to come up until about a third of the way between the 3 and 4 o’clock positions.
Now here is where I believe the answer to your question actually starts. I think you are saying (please correct me if I am wrong) that if the moon is anywhere between the 9 o’clock and the 3 o’clock position you cannot see the moon because the sun is too bright. This is incorrect and here is why:
Let’s move the moon to the 11 o’clock position. As the hands of the clock sweep to the 8 o’clock position, the moon begings to rise but the sun will not rise yet for a little bit. Since it is still dark where you are on the earth, you can see the moon without it being washed out by the Sun. (Actually, only a sliver of it at that point, but you can still see it.)
Now continue the progression and you will see that about the only time the moon would not be visible would be when it is at the 12 o’clock position. (Called the new moon, BTW.)
I hope this helps. If not, then I will count my blessings I took up accounting instead of teaching or astronomy as a profession.
This reminds me of the Stephen Wright line: “How come the Moon is sometimes out in the day, but you never see the Sun out at night?”