As a welcome alternative to the tedium of Hallowe’en (which I usually post about in this fashion), I notice that today (31st October 2017) has been officially designated Dark Matter Day. I would have sent some appropriate greetings cards but I couldn’t find any in the shops…
All of which gives me the excuse to post this nice video which shows (among other things) how dark matter plays a role in the formation of galaxies:
P.S. Lest we forget, today is also the 500th anniversary of the day that Martin Luther knocked on the door of All Saints’ Church in Wittenberg and said `Trick or Theses?’ (Is this right? Ed.)
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In the Dark 