# Re: Theories on the extinction of dinosaurs

```-----Original Message-----
From: James R. Cunningham <jrccea@bellsouth.net>
To: larryf@capital.net <larryf@capital.net>; dinosaur@usc.edu
<dinosaur@usc.edu>
Date: Tuesday, November 16, 1999 8:06 AM
Subject: Re: Theories on the extinction of dinosaurs

>
>
>Larry Febo wrote:
>
>> How do they know the object was 6 mi in diameter?
>
>They don't, but estimate it from the size of the crater.  I suspect it was
>less.  If it were 3 mi in diameter, the kinetic energy would have been
reduced
>by a factor of 8.
>
>> How did they know it was
>> traveling at 30 miles per sec???
>
>Again, they don't.  The minimum velocity would have been about 11
miles/sec, max
>about 50 miles/sec.  The two limits average to 30.5 miles/sec which implies
too
>much accuracy, so it gets rounded to 30, give or take about 20.  Raising
the
>velocity from 11 to 50 will increase the energy by a factor of 20.7, from
30 to
>50 by a factor of 2.8.  Reducing it from 30 to 11 reduces the energy by a
factor
>of 7.4.  This all assumes the body originated in the solar system.  If it
were
>an interloper, the velocity could have been much, much higher.
>
>

It seems that the size of the crater would be determined by both the mass of
the object, and it`s speed. directly proportional to the mass, and
proportional to the speed raised to the power of two. If they could
(perhaps???) predict the size of the bolide from the amount of Iridium
spread around (or some other method), then they would know the speed from
the size of the crater. Seems better than trying to average the speed over
that huge range of values (which translates into an even greater range of
energy produced,  being the square of the velocity).

I personally would suspect a larger bolide, and much less speed. This way
you get the appropriate sized crater, with less energy produced by the
impact.

```