ELI5. I’ve always been told moonrise for a new moon is around dawn and for a full moon around sunset, but also that it takes about 29.5 days for the lunar cycle. Are both these true? Shouldn’t the new moon rise around dawn one month and then around sunset the next month?
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After thinking about this it occurred to me you might be hung up on the “.5” part.
The new moon and full moon are *moments* in the moon’s orbit. There is a precise time at which the sun and moon reach a certain position that it’s *exactly* new moon or *exactly* full moon. These moments will *not* coincide with your *local* horizon. They will coincide with a local horizon *somewhere* on Earth, but likely not where you are, and it changes every month.
When we say “tonight is a full moon” it’s because the moon stays “full-ish” for a day or so, where you can’t tell with the naked eye if part of the near side is in shadow. The exact moment of full moon might occur when it’s over your head, or an hour before it rises or an hour after it sets, but it’s still “full.”
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