How do both of us see the moon at the same time?

Question

If it is daytime here and we see the moon (sometimes) during daylight hours, how is it that people who are in the night hemisphere of the earth see the moon as well? Or do they not? Do they just not have a moon on those nights?

Always wondered about this. I've considered asking my Exploration of Space instructor, but I can't seem to word the question right verbally.

haha, cute, Thin Kaboudit. I don't live with my parents anymore, so the fruit in my refrigerator is mine =) I like your analogies, though.

Answer 1

The only celestial body that you cannot see at night is the Sun. This is the one and only requirement for night to happen: that the Sun not be there.

Not so for the Moon, which is visible both when the Sun is in the sky (daytime) and when the Sun is not in the sky (night time). If, in the sky, the Moon and the Sun are less than 180 degrees apart then it follows that part of the Earth that is facing the Moon will be in darkness (night), and part of it will be in sunlight (day). The people on the dark side will see the Moon in a night sky and the people on the sunlit side will see the Moon in a daytime sky.

There are only two places in the lunar cycle where this cannot happen, and that is at full moon, when the Moon is directly opposite the Sun in the sky, and therefore only visible to the people on the night side of the Earth, and at and around new moon, when the moon is very close to the Sun in the daytime sky, and invisible to everyone, day and night (except during a solar eclipse).

Another way to get your head around this is to look up at the Moon in the sky, and imagine people up there on the Moon looking back at Earth. Unless it's a full moon which only happens one day each month, you are looking at a Moon that is only partly lit. Well the people on the lit up part of the Moon can see the Sun in their sky and the people on the unlit or dark part of the Moon, don't see the Sun, and it is night for them.

But ALL the people you are imagining up there, whether they are on the sunlit part of the Moon or not, can see the Earth, because they're facing us.

BTW, people on the Moon see the Earth in phases too, and at any given time, the phase of the Earth as seen from the Moon would be exactly opposite to the phase of the Moon seen from where we are.

It's all because of the perpetual movements of the Earth, Moon and Sun relative to each other, and the fact that one of these three bodies lights up the other two. It's complicated.

Answer 2

The night hemisphere is half the Earth. Now clearly there is a dividing line between the day and night half. It is called the terminator. Clearly one person can be only a few kilometers away and still be on the other side of that line. So one person is seeing the Sun just about to set and the other just saw it set a little while ago. But if the Moon is not close to the Sun in the sky, then it is not close to setting, so it is high in the sky and you could both see it. The Moon will be slightly higher for one of you than the other, slightly closer to setting for the person who just saw the sun set, but you can both see it. The farther apart you get, the more difference in how high in the sky it appears to one of you. If one of you was exactly 180 degrees away, exactly on the one exact spot half way around the world, then you and that person could not see it at the same time. But people on most of the planet that isn't exactly half way around from where you are can see it at the same time as you for at least part of a day.

It isn't hard to visualize, especially if you use a globe and a couple balls to represent the Moon and Sun.

Answer 3

To answer this question get a balloon and colour half of it black and leave the other side white. Place the balloon on the table (the line between the colors is vertically upward) and an orange about an arms length away.

Put one dot on the evening side of the line (the dot goes on the light side of the balloon; about 1 cm from the dark edge).

Put another dot on the black side of the balloon around when it just becomes night (the dot goes on the dark side of the balloon directly opposite the dot on the light side and about the same distance (except 1cm from the light edge))
Place a flash light so that it more or less shines only on the light side of the balloon, notice the pattern that might be seen if you were one of the dots on the surface of the balloon looking up at the orange.

Roll the orange (keeping it at arm’s length from the balloon) and imagine when the two dots both can see the moon and when they cannot. Remember the dots separated by 2 cm might represent thousands of kilometres in the actual world.

That experiment should explain why two people can see the moon at the same time. Your astronomy club may have models that are much cooler to look at and explain the same thing I have above.

Good luck

Answer 4

The moon is only on one side of the Earth or the other at any given time. When a person on one side of the Earth can see the moon, a person on the opposite side of the Earth cannot. It doesn't matter whether it's day or night.

A new moon rises around 6 a.m.
A waxing moon rises around noon.
A full moon rises around 6 p.m.
A waning moon rises around midnight.

Often, like now, we see the waxing moon rising in the east during the afternoon. Also, we often see the full moon setting in the west after sun-rise in the morning.

From what ever side of the Earth you're on, it takes the moon about 12 hours to pass over your portion of the sky. So some of that time is bound to be daylight hours, especially in the summer when days are longer and nights are shorter.

Answer 5

When you see the moon during the daytime, the people where it is night cannot see it.

Hold an orange in one hand, and a grape between the finger & thumb of the other. Now move the orange slowly around a table lamp. (The lamp is the sun, the orange Mother Earth)...Now orbit the moon (the grape) around the orange...remember, the same side of the grape always faces the orange....

At the right spot, every so often, you will see how a fly on the orange could look up and see both the light bulb AND the grape, and notice that on the other side of the orange it is dark, and they can't see the grape!

Now put the fruit back before your Mom catches you & gets mad!

Answer 6

Surprising answers you got there!

It depends where the Moon and the two observers are. If you see the Moon soon after sunset or soon before sunrise, then people who are still in the lighted hemisphere of Earth will see it too. And vice versa.

Answer 7

sometimes the moon rises around 3 or 4 PM usually when it is waxing gibbous. On those days it can be seen in the afternoon and still later after sunset.

Answer 8

The moon is relatively stationary in the sky with respect to Earth's rotation. If the moon is in the daylight sky, it will be there for all. It will not be seen at night on one part of the planet and daylight on another.