A science presenter, writer, speaker & former TV host; author of The Skeptic's Handbook (over 200,000 copies distributed & available in 15 languages).


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Is a rock on the way? (and a Weekend Unthreaded)

50,000 years ago a bit of wayward rock about 50m across met Earth and left this 1200m wide crater in Arizona.

Ponder the momentum of 50m bit of rock that left a hole over a kilometer wide and 200m deep.

If one was coming. Would we know?

…(Click to enlarge) Photo not by JoNova


Thanks to NASA and The Earth Observatory

UPDATE: JoeV in comments adds an interesting link to Tracking space junk at An old satellite is coming in right now. It’s over Alaska (moving fast) at 153km high and falling quickly. Cosmos 1220, a Soviet era military surveillance satellite.  Eddie adds a different link which suggests Cosmos is expected to crash into the Pacific in hours. Amazing what you can find out on the Internet.


Two asteroids in one day but we spend 6000 times as much to change the climate

The two asteroids were going in opposite directions, so were not related.

While everyone was expecting and watching Asteroid 2012DA14, which missed Earth by 26,000 km (17,000 miles), another asteroid blasted through the atmosphere in Russia, injuring more than 1,000 people (mostly by shards of glass caused by the sonic boom). One estimate makes it out to be a 10 tonner (seems a bit small), traveling at 30 kilometers a second. Another astronomer, Margaret Campbell-Brown, claims ultrasound stations show it was 15m wide and around 40 tonnes. Nature quotes the same researcher talking about 15m and 7,000 tonnes. You can see we have a good grip on what happened. [UPDATE: Now it's 10,000 tons and 55 feet wide and stone. The largest object to hit in a century. WUWT. What about the ones that fell over the ocean wonders Jo? How would we know?]

It left a “contrail” and a flash that could be seen for 700km (see these videos –why are people filming while they drive?).  It only “missed” by 30 – 50 kilometers and nobody knew it was coming. How little we know. One part of it broke off and smashed into a frozen lake, leaving a 6m [...]