## Phases of the Moon (with an infrared twist)

Posted: May 24, 2014 in Institute of Physics, Thoughts and ideas
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I recently was asked about the phases of the Moon and why the Moon appears to change in shape in its orbit around the earth. So I thought a good point to start from was to establish what misconceptions people have on this topic and I found this great video by Veritasium (but I would stop it at the end of the interview without revealing the explanation initially).

The most common misconception in the video seems to be that the earth blocks the sunlight reaching the Moon, hence, we see the phases of the Moon when it is behind the earth with respect to the sun. At this point I would slide two circles of card, a white and a black one (with the black one bigger than the white one) past each other (black on top). If the black card is the shadow cast on the Moon by the earth (essentially what happens in a lunar eclipse), the shapes of the Moon due to the light reflected back to earth are considerably different than the shapes we observe from the phases of the Moon. So, we have establish that this model is a misconception.

Now we can introduce a better model and I use the pingpong ball in the image below with the students in the centre of the room. They are the observers on the earth and the light from the sun is coming from the left hand side in the photo.

If you go around the learner in the middle of the class making sure the “lit” face of the pingpong moon is always facing the wall on the left in this case, your students will see the same shapes we observe during the phases of the moon.

To reinforce this demonstration you could show the students this great animation by Keith Gibbs (also available in HTML5 if using an iPad).

Ok, now for the icing on the cake that you’ve all been waiting for! Check out the video below that shows a cresent moon through an infrared camera. You can see the crescent really bright, but you also see the other parts of the side of the moon facing the earth. I believe that is what is emitted by the moon in the infrared spectrum and that gets picked up by the IR camera. It is really awesome.

Last night we had our first TeachMeet entirely dedicated to the teaching of Physics in Gloucestershire and despite the inclement weather and illnesses a few teachers from the region managed to come and give some great presentations! A particular thank you goes to Helen Rogerson (@hrogerson) who took the time to record two videos for us to watch. And that’s what we did! In fact, the TeachMeet began with Helen’s 7 minutes video which showed some great stuff she does wit their learners and parents with revision. Of particular interest to the participants was the part on Electromagnetic Induction, which sparked a series of interesting discussions and caused us to go back and watch the lovely demonstrations several times. This was indeed a lovely part of our TeachMeet that I believe stood out from others I have attended and organised in the past. In fact, it is quite easy to rush through all the presentations trying to fit everyone in and forget about allowing the participants time for discussion and to network. But last night ideas on alternative ways to use the equipment and extensions to the demos were freely flowing and created a very relaxed atmosphere from the very beginning.

Next, IoP award winner Kevin Betts showed a great demo of “Dancing Waves” on custard on the cone of a speaker. You can see his Magic in the video below.

Steve Rice was up next showing us how he uses  a sparkler attached to a drill to simulate the gravitational attraction between the earth and the moon. As the sparkler spins around the drill, the sparks fly along the tangent to the circle drawn by the sparkling tip, which helps the learners visualise what would happen if the gravitational pull between the two heavenly bodies suddenly disappeared. I liked this demonstration because it allows the learners to think outside the box and stretch their understanding in the realm of the abstract.

Below is a video of these two lovely demonstrations.

After that it was my turn to talk about how I used one of the best iPhone/iPad apps I have ever come across, the Vernier Video Physics, with my learners. You can find this resources on the TES website here. It was also the first time I publicly announced my new role as Science Lead at TES commencing in January and I explained that, although I occasionally use it already, I will actively interact with the Twitter sphere using @TESScience from then.

We closed the TeachMeet with our sponsors’ raffle, which included a very generous box full of Nelson Thornes books, ranging from GCSE revision guides to a Muncaster tome 4th edition. ThinkBuzan also offered a free copy of their Mind Mapping software iMindMap 5 Ultimate (the last two links are affiliate links, so Google iMindMap 5 instead, if you are bothered by this sort of thing).

Two other teachers emailed me apologising they couldn’t attend due to illness, but they sent links to interesting stuff that they would have shared in person, if they had been there. The first is the YouTube video below about mixing colours with glow sticks shared by Bernadette Willey.

The other tool is Poll Everywhere shared by Lewis Matheson, which seems a really neat tool to use with mobile devices!

I thoroughly enjoyed myself last night and I learnt a lot (as usual) from innovative colleagues in the Gloucestershire Network. I hope to see many more at our next events in the new year.