CHIN, Chien Ting (chin@tch.fgg.eur.nl)
Wed, 28 Mar 2001 12:59:54 -0800 (Pacific Standard Time)


Dafydd Neal Dyar wrote:
> The canonical size of the crater is 500 km (300 miles) diameter,
> approximately 16% or one-sixth of the continental land mass, resulting
> from an impact force given as 60,000 megatons (2.5104e+20 Joules /
> Watt seconds = 2.38099e+017 BTU [thermal]).

Correct me if I am wrong (I am losing memory in my advanced age :) Didn't
we calculated that the colony drop (using sensible mass of the
colony cylinder) should be only about 60-600 megatons?

> But a given volume of seabed and land mass doesn't correspond to an
> equal volume of particulate matter in the atmosphere. A significant
> percentage of the material will be vaporized into reactive gasses and
> plasma, a percentage of which will become pure energy in the form of
> heat and radiation -- look at the energy released here! -- which for
> all intents and purposes ceases to exist as matter. Some of the
> heavier elements will fission and some of the lighter elements will
> fuse and the shockwave will travel two to five times the speed of
> sound, turning much of the remaining material into dust so fine that
> it'll act (and react) like a fluid.

There are several things that I am pretty sure you are wrong here.

1. Massive impact may or may not be more likely (compared to nuclear
blast) to vaporize and plasmarize rocks. But vaporized rocks and plasma
are definitely more likely to cause climate change. Most of the
simulation models focus on submicron particles, which are formed from
vaporized rocks and plasma. Particles larger than 1 micron clear out of
the atmosphere fairly quickly due to gravity and rain. See the second
link in my previous post about this.

2. Nuclear blast and asteroid impact(*) are not hot enough to cause rocks
(Si, O, Ca, K, P, N, Fe, Cu etc) to split or fuse atomically.
Plasmarization is as far as you get. Nuclear blasts make rocks
radioactive by neutron (and sometimes proton) bombardment, which is a
nasty thing for living creatures. But neutron bombardment doesn't affect
climate directly. I doubt asteroid impact can make anything radioactive.

(*) I am 99% sure that even an impact big enough to break Earth into a
million pieces is not hot enough to split or fuse the atoms making up
rocks. You can do the lightest and heaviest elements (H, He, U, Pu etc)
but not the middle elements.

3. If any bits of matter is converted into pure energy, then by Einstein's
famous E = mc^2 equation, it would make the climate change even more
disastrous. Putting any extra energy into the mix could only kick up even
more dust into the air, and as I said, vaporized rocks are bad bad bad.

> If you really want comparable effects, I'd look less at the nuclear
> scenarios and more at the great seismic and volcanic events,
> especially the explosive eruptions of the islands of Krakatoa (east of
> Java) and Santorini (west of Crete).

Well nuclear blast is a bad example because it's too concentrated and too
hot (I think), seismic and volcanic events are also bad example because
they are too distributed and too cold. Best example is of course asteroid
impact. The only difference between asteroids and colony/space station is
that colony cylinders and space stations are mostly hollow.

In fact, historically the nuclear winter scenario was proposed from the
hypothesized asteroid impact that caused mass extinction that killed a
huge number of plant and animal species, including the dinosaurs. As I
understand it, the asteroid impact => dinosaurs extinction scenario was
90% confirmed but still debated amongst some scientists, but asteroid
impacts causing multiple episodes of climate changes and mass extinctions
is pretty much accepted by everyone.

> On 4 January 0079, Island Iffish broke up into four pieces over the
> Persian Gulf. The three smaller pieces fell on unpopulated areas of
> North America (which took it in the shorts in both the OYW and the
> Delaz Turmoil) and only the fourth and largest piece fell on Sydney.
> Add to that the fact that it was falling from west to east, in the
> same direction as the Earth's rotation.
>
> But on 13 November 0083, Island Ease passed over Jaburu in the central
> Amazon basin to hit northern Kansas just south of the Nebraska border
> almost totally intact, traveling in a SSE to NNW trajectory, a polar
> orbit slightly counter to the Earth's rotation.

Where the hell did you get the orbital data??? I suppose you can find
some info from freeze-framing 0083, but you obviously got more data from
other sources.

Anyway I still argue that (1) colony drops shouldn't make such a big
Sydney crater, (2) if a crater as big as Sydney were made, then you can't
avoid a drastic change in Earth's climate and the ecosphere.

PS: since you are the expert, can you enlighten us about the colony's mass
compared to Mir? Also only 27 out of 100+ ton of Mir reached sea level,
do you expect a higher ratio with a colony? The answer is obviously yes,
but how much?

PPS: [OT] I just like to counterbalance a bit the negative press given to
the Mir drop. The Russians did an excellent job controlling the drop. I
am not so sure NASA could have done as well. Imagine if NASA mix up
metric and imperial again...

Dr. Core
Brain Surgeon
Newtype Asylum
http://side7.gundam.com/newtype_asylum

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