It is always fully lit and always fully dark, and you are seeing the terminator
The Half Moon holds a 4.3 from sixteen hundred and seventeen reviews, and the object in the name is never half.
The moon is always fully lit
Which is the fact everything follows from.
Because the sun is always shining on one entire hemisphere of it – exactly half the sphere, all the time, without exception.
And the other half is always in darkness.
That never changes. It is always a half-lit ball.
What changes is where you are standing
Which is the whole of the phases, and it is the thing people find genuinely difficult.
Because as the moon goes round the earth, we see the lit hemisphere from a different angle.
Sometimes we are looking straight at the lit side – and that is a full moon.
Sometimes we are looking straight at the dark side – and that is a new moon.
And in between, we see part of the lit half, at an angle – and it looks like a crescent, or a half, or a gibbous.
The moon is not changing shape. We are changing seat.
And the line has a name
The terminator.
Which is the boundary between the lit side and the dark side – and it is a shadow line, and it is where the sun is rising or setting on the moon.
And it is the most interesting part of the moon to look at with a telescope, because the shadows are long there – and the craters and mountains show up in relief.
At the full moon, the sun is directly overhead and there are no shadows at all, and it looks flat.
The moon is most three-dimensional when it is least full.
And there is no dark side
Which is the last correction, and it is the one everybody gets wrong.
The moon is tidally locked – the same face always points at us.
So there is a far side we never see.
But it is not dark. It gets exactly as much sunlight as the near side does. It has days and nights like anywhere else.
Eight postcodes and thirteen hundred and thirty-eight articles.
The sign is not the thing – and the half moon is a whole moon, seen from the side, and the dark side is not dark.
And it is called a quarter
Which is the last confusion, and it is a good one.
Because astronomers call the half-lit moon the first quarter and the last quarter.
And it looks like a half.
Because they are not describing the shape. They are describing where it is in its orbit – one quarter of the way round, and three quarters of the way round.
The name refers to the journey, and the shape is a side effect – and everybody who has ever looked up has assumed the opposite.
Verdict
Good pub, honest number on a large sample.
I need the next 800 to bnexte