Re: (Fwd) Gravity

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From: adalby@ccs.carleton.ca (Andrew Dalby)
Subject: Re: (Fwd) Gravity
To: paleonet-owner@nhm.ac.uk
Date: Wed, 25 Oct 95 11:05:03 EDT
Status: O

Roy E. Plotnick writes:
>
> Folks:  Here is an interesting one!  My question is, how should I handle
> this kind of thing?  I'm torn between blowing it off and making a long,
> reasoned
> reply.  Suggestions?  How do the rest of you handle off-the-wall inquiries?
> -Roy Plotnick
>
> --- Forwarded mail from Tim Taylor <kj7az@coffey.com>
>
> Date: Tue, 24 Oct 95 04:21:23 -0700
> From: Tim Taylor <kj7az@coffey.com>
> To: plotnick
> Subject: Gravity
>
> Here's a theory for you.  I have for a long time been
> wondering about how the dinosours all died off.  I've had a
> hard time believing the comet theory's.  I have wondered
> about a sudden change in the earths gravitational pull.
> The gravity increased suddenly, the dinosaurs just couldn't
> support their own weight and collapsed.
> Some of the water dinosaurs lived on which gives us whales
> and sharks.  Some of the smaller reptiles lived on for
> birds and the close to the ground dinosaurs are todays
> lizards.
> Just something to think about.  I'm not a scientist, just a
> normal person who wonders about stuff.
>
> Thanks
>
> Tim/KJ7AZ
> Rawlins Wyoming
>
>
>
>
> ---End of forwarded mail from Tim Taylor <kj7az@coffey.com>
>
> --
> Roy E. Plotnick
> Geological Sciences
> University of Illinois at Chicago
> 845 W. Taylor St.
> Chicago, IL 60607
>
> plotnick@plotnick.geol.uic.edu
>
> phone: 312-996-2111
> fax: 312-413-2279
>

        I have many friends and relatives who ask me many, many questions
about geology and palaeontology.  These people may be laymen, but they
are genuinely interested, so my philosophy is "no question is too
stupid".  Professors who take this approach generally find that their
students learn more, mainly because they are not afraid to get
clarification when they desparately need it.  I believe that it would be
arrogant presumption to disregard honest and interested inquiries.
        You wanted to know how to answer this person's query?  Why not
let the paleonet people help you by submitting their view, briefly,
that is.  Then you can forward the ensuing discussion to Mr.Tim
Rawlings especially if your research does not afford you the time to
write him a long and drawn out thesis to answer his questions:

Tim,
        I used to have similar questions and interests, which is why
I'm studying palaeontology.  It is fascinating stuff.  Like you, I
have difficulty in accepting that a comet killed off the dinosaurs.  I
would much rather a deterministic explanation, one that takes into
account a number of unrelated effects or events.  A dramatic climate
change could have changed ecosystems so much so that this could have
been a contributing factor.  Another scenario is volcanism.  At the
end of the Permian Period (the biggest extinction of all time - about
245 million years ago) there is evidence of massive lava flows now
known as the Siberian traps.  Imagine a giant scar on the Earth
hundreds of kilometers across.  Now imagine a volcano like Pinatubo in
the Phillipines spewing out enough garbage to affect our weather for
years.  Now imagine that on a very much larger scale.  That amount of
volcanic debris in the atmosphere would certainly block out the sun
for some time.
        Another similar volcanic event at the end of the Cretaceous (66
m.y.a. - the dinosaur extinction) also happened.  (Please forgive me if
I've mixed up the Deccan and Siberian traps)  This may have been the largest
cause of that extinction, and there are huge aerial lava flows that
date to that time to prove it.  The comet theory's evidence consists
of some shocked quartz and a crater-like formation in the Yucatan
Peninsula area in Mexico.  These may be evidence of a meteorite impact.
        My feeling is that the lava flows are a more likely contributing
explanation of these major extinction events.  As for a radical shift
in gravity, I feel that this is unlikely.  Perhaps a geophysicist
could help you out better.
        Did dinosaurs become whales, birds and sharks?  Firstly,
sharks evolved in the early Paleozoic (550-360 million years ago).
Dinosaurs or dinosaur-like reptiles didn't show up well into the
Triassic (245-208 million years ago), so there's no close link there.
Birds DID evolve from reptiles, but not necessarily dinosaurs.  They
arose from a group that also gave rise to dinosaurs, so they are kin,
but one didn't become another.
        Whales are mammals.  Mammals evolved from synapsids (mammal-like
reptiles) in the Permian (before the Triassic) which much later gave rise to
whales, so marine reptiles from the dinosaur era had nothing to do
with the subsequent rise of whales.
        As you will probably find out soon enough, scientists do not
know for certain what caused the great extinctions, although many have
their single pet theories, which is good.  This is how science
progresses.  Hypothesize why something happened, and see if the
evidence supports it.  Personally, I think we should look at the bigger
picture and take many events and effects into account.  In my opinion,
no one single event killed off the dinosaurs, but a combination of
events that happened at about the same time.
        Keep asking questions.

Andrew Dalby
Carleton University
Ottawa, Ontario