# How fast do large asteroids usually travel?

I have just watched this video made by discovery channel, and you can hear the narrator at 0:51 saying that : "even though it is moving at 720 THOUSANDS kilometers per hour..."

I stopped once I heard this, because I never thought an asteroid would ever travel that fast. So, is it a mistake since in the beginning of the video someone said "an object moving 20 kilometers a second.." or it could be correct ?

Also, if it is a mistake, then would a 20 km/s asteroid of that size cause the damage mentioned in the video ?

• Fast compared to what? – jinawee Feb 8 '14 at 23:23
• Did you read what I just posted above ? – Abanob Ebrahim Feb 8 '14 at 23:26
• If you do the arithmetic, 720,000 km/hr= 200km/sec... Earth travels around the Sun at about about 30km/s. Solar escape velocity is around 600km/s at its surface, but only about 42km/s at Earth orbit, so a 20km/s delta-V with respect to Earth would not be exceptional for an object gravitationally bound to the Sun (such as a comet or asteroid), but a 200km/s delta-V would. Seems like the narrated value is a mistake, unless the origin of the asteroid is extrasolar, in which case its delta-V could be just about anything. – Anthony X Feb 9 '14 at 0:12
• I don't claim to speak for anybody else (i.e. moderator hat very much off), but I never follow a link to watch a video to find out what someone is asking. It just doesn't happen; you are asking me to put time into your question before I know if I am interested in it. See meta.physics.stackexchange.com/questions/5028/… and meta.physics.stackexchange.com/questions/4918/… for how others feel about that. – dmckee Feb 9 '14 at 2:08
• @AbanobEbrahim - I don't know. I found this which might provide some insight: impact.ese.ic.ac.uk/ImpactEffects – Anthony X Feb 9 '14 at 15:42