There are many adults who don't know what causes the Moon phases. The purpose of this task is to make sure you're not one of them.

Before the lecture, make sure you can explain the correct cause for the phases. If you are 100 % sure you can do this, great, and you're done! However, if you have even slight doubt, continue to do the rest of the preliminary work.

Start by watching the following video that shows the Moon's phase (and other things) throughout 2024. Pay attention to details such as the Moon's orbit position and tilt/angle, varying distance from the Earth at true scale, the direction of sunlight on the Moon and the Earth at different times of the year, at least. Full screen and good resolution recommended!

The video is part of NASA's Scientific Visualization Studio  you can use to study how our view of the Moon (what parts we see at a given time) changes over time. You already know the Moon phases, but what other phenomena are there, and how do our view depend on Moon's place on it's orbit around the Earth, Moon's distance (that varies all the time), etc.?

To be fully sure you can explain the phases, watch also the video below or read this website , or use your favourite search engines to find some of the other million websites explaining it well. Use source criticism, however, when looking for information --  don't just accept anything you find in the Internet as a fact.


Also, make yourself a mnemonic ("muistisääntö", memory rule, in Finnish) to remember the moon phases and to determine whether the moon is waning or waxing, based on the shape of the crescent. Or what do you think, is it better to have a mnemonic of the Moon phases (in order to quickly remember), or to be able to deduce the answer from physical principles?

Last modified: Wednesday, 3 January 2024, 10:45 AM