I thought a few recent videos on Sixty Symbols were worth highlighting.
They've been filmed with Professor Mike Merrifield, the head of astronomy at the University of Nottingham.
He's regular contributor to my videos.
Like many on the Sixty Symbols team, Mike's a science "all-rounder" and a good sport.
He's willing to tackle many areas of astronomy and physics - from the planet Mars to Einstein's theories of relativity.
However the last few videos we've done are really in his area of expertise - galaxies.
The most recent is this one about "pattern speed" and why many galaxies have spiral arms.
We were really dealing with his everyday work.
In fact, the diagrams and graphs used in the video are from real scientific papers that Mike has co-authored.
There's more information in this Test Tube "additional footage" video.
A couple of weeks back Mike also helped with this video about the Milky Way's twin.
It seemed the perfect time to ask about Mike's little hobby business (something I knew about but had never had reason to discuss on camera!)
Mike makes replicas of astronomical objects, sculpted in glass cubes with lasers.
Among others, his collection includes the Sun and The Milky Way.
It was not my intention to "advertise" the cubes.
But when making a video about the Milky Way's structure, it would've been stupid to ignore the fact Mike makes sculptures of the galaxy.
It added a personal and unexpected touch to the video... And yes, Mike did sell a few extra cubes.
But I don't think he'll be retiring to the Bahamas just yet.
PS: A piece of trivia... Mike featured in the first ever Sixty Symbols video... It was about the speed of light.
PPS: To some viewers, Mike is best-known for having the controversial Atlas of Creation on his bookshelf... It has been so contentious, we even made a video about it.