I know it’s sun’s light that reflect back on earth, but how sometimes we see it on bright day? And why full moon wouldn’t be eclipse if it’s the phase the moon is right in front of the earth and the sun illuminating right behind? Shouldn’t it also depend of earth rotation, seeing slightly different angle by sunrise or sunset?
In: Physics
The moon is a ball in space. The sun is always shining on it, so exactly half of the moon is lit by the sun at any given time.
The moon also orbits the earth, and it takes a month to do so. So for a few days each month it’s on the “sun” side of the earth, and for a few days it’s on the “night” side of the earth, and for a few days in between it’s off to each side.
So when it’s on the “sun” side, it’s up in the daytime, and the half of the moon lit up by the sun is on the far side of the moon and we can’t see it (new moon). When it’s on the “night” side, it’s up at night, and the lit half of the moon is fully visible to us (full moon). When it’s off to the side, we see half of the lit side and half of the dark side (quarter moon).
Sometimes the new moon wanders *exactly* between the sun and the earth, and then you get a solar eclipse. And sometimes the earth wanders *exactly* between the sun and the full moon, and you get a lunar eclipse.
> how sometimes we see it on bright day?
There’s no rule stating that the Moon has to stay on the night side of the Earth. It orbits around the Earth once every four weeks, spending half its time on the Sunward side of Earth. The closer to a New Moon it gets, the more time it spends visible in daylight hours.
> why full moon wouldn’t be eclipse if it’s the phase the moon is right in front of the earth and the sun illuminating right behind?
Like the Earth’s spin, The Moon’s orbit is tilted relative to the plane of the Earth’s orbit. This means that for most of the year, the Earth, Moon, and Sun cannot fall perfectly in line with each other. Roughly twice per year, the Moon’s orbit intersects the Earth-Sun alignment and eclipses become possible (see [Eclipse season](https://en.wikipedia.org/wiki/Eclipse_season)).
Late to the party, but the simple answer is that the moon isn’t behind the earth when you can see it during the day. It’s more off to the side [like this.](https://www.schoolsobservatory.org/sites/default/files/astro/esm_all.gif)
Latest Answers