The large dinosaurs went extinct around the
end of the Cretaceous Era.
The usual story is that a meteoroid struck
Earth,
filling the air with soot that made it hard
for plants to harvest the sun's energy,
causing a cascade of death up the food chain.
Under this theory, herbivores should have
fared better than carnivores.
But then why did giant plant-eaters go extinct
while puny meat-eating mammals survived?
Most suspiciously, why were all creatures
heavier than 55 pounds purged?
I propose that what killed the big dinosaurs
was no meteoroid
but a brief reversal of Earth's gravitational
field.
Cosmologists posit that something called "dark
energy" exhibits gravitational repulsion with
itself;
we know almost nothing about dark energy or
how it interacts with ordinary matter,
so it's 100 percent consistent with our state
of ignorance to hypothesize
that a pulse of dark energy could have temporarily
infused our planet and its inhabitants,
causing the gravitational force between them
to reverse sign.
If gravity suddenly became repulsive rather
than attractive, animals would fall upward
and then, when gravity became attractive again
a short time later, fall back down to Earth.
A Gravitational Reversal Event, or GRE, of
about a minute's duration
wouldn't harm animals during the first 99
percent of the round trip,
because they wouldn't get high enough to suffocate.
But what about that last second?
There's evidence that animals the size of
cats or smaller might just be able to stick
the landing.
In an observational study of 132 cats that
fell out of open windows in New York City
—
observational study! —
some plummeting hundreds of feet at a terminal
velocity of 60 miles per hour,
it was found that a full 30 percent required
no medical attention at all.
That's good enough odds for Darwin.
A typical 55-pound animal would probably die,
but enough of its kind would survive to repopulate
the species.
But really large animals wouldn't fare so
well.
This comes down to basic biomechanics:
bone-strength is governed by the cross-sectional
area of bone,
which grows roughly like the square of an
animal's length,
whereas the impact caused by hitting the Earth
after a GRE
would be governed by the animal's mass, which
grows roughly like the cube of an animal’s
length.
What about large flying animals?
When gravity reverses, a winged creature can
just flip and keep flying.
But, but the air isn't a safe place to be
during a GRE
because of all the boulders and brontosauruses
and whatnot hurtling upward and then downward.
if you're flying around during a GRE, you
want to have as small a lateral area as possible.
Now the weight of a flying animal grows like
the cube of its length,
while the lift provided by a wing is proportional
to the area of the wing,
so bigger flying animals don't just need proportionately
bigger wings;
they need disproportionately bigger wings,
making them easier targets to hit.
The pterodactyls that didn't get killed by
things falling up around them
were probably too dumbfounded to dodge them
when the things fell back down.
Going back to the land dwellers: why are cats
so good at surviving falls?
Some cats pounce on their prey, but never
from hundreds of feet up.
Could the feline ability to survive a long
fall stem from evolutionary bottleneck that,
an evolutionary bottleneck
that only the torso-twisting kind of a cat,
or proto-cat, was able to survive?
To test the GRE, to test the GRE extinction
hypothesis,
I modeled occurrence of GRE's as a Poisson
process,
tuning the intensity parameter lambda based
upon the number of GRE's
postulated to have occurred during Earth’s
history, namely, one.
If the GRE extinction hypothesis is true,
the expected number of GRE's
to have occurred in recorded history would
be 0.000002.
On the other hand, the number of GRE's described
by historical sources is exactly 0.000000.
Note that the first five digits after the
decimal point are the same.
Such phenomenal agreement between theory and
evidence is no mere coincidence.
Now some of you may be thinking that such
a radical proposal needs to meet
a higher evidentiary bar than your run-of-the-mill
theory of dinosaur extinction.
To you I say: Even if you think my theory
has only a one-in-a-million chance of being
true,
the consequences of a future GRE would be
so dire
that humankind should unite to explore the
theory now while there's still time.
Current engineering practice protects buildings
from seismic events,
but does nothing to prevent a building from
falling up to, and then down from, a great
height.
All it takes to level a city is a few rogue
skyscrapers that plunge up and then plunge
down again,
causing other buildings to topple like dominos.
We should create back-up systems that would
use electromagnetism
to keep our buildings anchored in place.
Public transit should make use of maglev rail
technology
that can be switched from "levitate" to "de-levitate".
In cities, we need swarms of smart mobile
trampolines
that can adaptively place themselves so as
to save the greatest possible number of lives.
For people in areas with no trampoline network,
those personal jetpacks that we were promised
as part of our 21st century birthright
will be not a luxury but a necessity.
And maybe some of you have ideas of your own.
We all need to come together on this.
If we as a species take these steps, and calamity
strikes a prepared planet,
what a monumental triumph that would be for
the human spirit!
And if we as a species take these steps, and
calamity doesn't strike, that's fine too.
Because hey: we'll have jetpacks!
In conclusion: A motto of an earlier age was
"Indication of harm, not proof of harm, is
our call to action."
Given what's at stake, I put it to you that
in this matter,
science-flavored speculation of harm must
be our call to action.
Otherwise, the next dinosaurs could be us.
Thank you.
