You may be thinking of the Earth's magnetic field reversing itself (although I have no idea if it had anything to do with the dinos dying out).
I was thinking earth.
Been watching the How the Earth formed series on History of late... the formation of both Yosemite and Death Valley is fascinating...
It is one of many theories on how and why they went extinct. One being, of course the asteroid that smashed into Mexico’s Yucatán Peninsula, another being volcanic ash spewing into the atmosphere and blocking the sun and the other being the reversing of the earths poles, which has been proven to have taken place by drilling core samples and from evidence found in places where a lot of dino skeletons have been found. BTW the earths poles switch about every 700,000 years.. and there is there is a theory that large scale volcanic activity is more common at a time when there are many reversals of the earths magnetic field so the two may be inter-related.
