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dark matter and dinosaurs

7 January 2016

Lisa Randall, a particle physicist, has written an interesting book with the title, 'Dark Matter and the Dinosaurs' (Ecco:2015) – see www.sciencenews.org/article/dark-matter-helped-destroy-dinosaurs-physici… … it seems the dinosaur bit is an add-on, something to persuade people to look at her book, a colourful window on what she has to say as she goes on to suggest that dark matter could have been a trigger factor in the K/T event. It is an interesting book it would seem as Randall lays out on the table such things as Big Bang, inflation of the universe, and orbital dynamics – and says dark matter could be to blame for mass extinctions. Sounds like an overall theory to explain everything but it is interesting if you want to get inside the head ofa cosmologist and have wondered how all those theories coalesced.

Basically, her hypothesis is that every 35 million years or so the solar system moves through a concentrated disc of dark matter in the Milky Way. This jostles the comets and sends them towards the inner solar system. I was struck how similar this was to the Clube and Napier theory of the solar system periodically moving through the galactic spiral arms. In an article by them in Nature volume 282 (29th November 1979) they say that if spiral arms contained planetesimals each solar system passage would dislodge comets and create temporary Oort Clouds which in time would cause some of those comets to enter the inner solar system and threaten the earth.

The problem with Randall's theory is that the nature of dark matter is unknown – and a product of modelling. Napier has recently suggested the Centaurs are planetesimals that become comets when they are dislodged and adopt an orbit taking them into the inner solar system. Presumably the centaurs have an origin in the spiral arms of the galaxy in their theory – but it is not necessary to push such an origin as centaurs are a fact observable in telescopes.

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