the amount of smoke coming out of it
like a barbecue that is not something
that you would see when it hits the
ground it's actually really cold i am
professor gretchen benedict i have been
studying meteorites and asteroids for
about 20 years today we're going to be
looking at asteroid disasters in movies
and on tv and judge how real they are
now we can get asteroids that are fully
metallic but with all the canyons and
things the asteroids that we do see do
not have this kind of debris cloud
around them an asteroid
will generally not have too much of this
gas coming off of it it may have some
ice in it that's not going to be the
majority of it
i'm pretty sure that we would see
something that size headed for us well
before it got to that point very
unrealistic
the biggest myth is that you actually
have to steer
your spaceship to avoid asteroids
there's a ton of bodies out there it's a
huge amount of space it's really hard to
kind of
get into a situation where you might hit
something accidentally
you could potentially land on it it's
not like landing on earth
you're dealing with a totally different
gravity regime you know we've had a
couple of really tiny asteroids that
we've got uh missions from japan and the
us and they have these little touchdown
things um and it's really really really
hard just to do this tiny little drone
size thing and land it down on the
surface of the asteroid and then get it
back off
the amount of
power you'd need to actually explode it
is impossible we don't have enough
explosive material on the earth so there
have been some studies done that have
shown that if you take an asteroid 20
kilometers across
you need something like 200 gigatons of
explosion to break that apart completely
now the biggest thing that we've ever
exploded on earth was 50 megatons so
you'd need 4 000 of those to blow up
something 20 kilometers across this
thing in this movie is a thousand
kilometers across you'd need a hundred
and thirty thousand fifty megaton bombs
to try and blow that particular asteroid
up
a shock wave it's a pressure sound wave
you need atmosphere to have sound so
when the sound is playing in the movie
about this explosion happening that's
possible because there is a lot of what
we can see is atmosphere there so
there's there's some gas molecules and
that's going to cause that sound wave to
travel but it's space so usually there's
a whole lot of space in between all of
these these molecules so the sound is
not going to be what we hear
here on earth you will have a shock wave
but it won't travel out both sides of
the thing it'll only travel out one
direction that's not how you would
actually try to
destroy an asteroid that's coming for
you so i would give it a one out of ten
[Music]
65 million years ago
is not when the asteroid got knocked out
of the asteroid belt that is when the
asteroid actually hit the earth number
two wrong the asteroid belt does not
look like that it's not a doughnut of of
rocks that are that close together
sometimes can get an asteroid family so
you can get one asteroid that has like
maybe three or four other asteroids kind
of close to it so this asteroid gets
knocked out you can have collisions
every once in a while they do get the
size of the rock correct over time
the sizes of the rocks that are out in
space have actually gotten smaller
because they do run into each other but
they're really far away from earth so
not all of them are going to get onto a
collision course with earth and they
don't necessarily impart enough energy
to stick it on a direct collision course
to the inner solar system the collisions
that occur out there over time have
gotten fewer and fewer because we've
kind of um gone from a really chaotic
system four and a half billion years ago
to now it's pretty quiet there's a
mission called dart they're trying to
take a small asteroid they're going to
push it with their little spacecraft and
see if it will change its orbit in any
way
the movie takes a different tact and
says well it missed the orbit was such
that it kind of got close but it it flew
by
now we do have objects that fly by that
that's kind of cool and that i do i
don't think a six mile asteroid would
actually
skim the atmosphere and then bounce out
again but you can do that with smaller
sized objects again one out of ten
for realism
i love this show and in terms of the
realism about everything else they
actually use real asteroid shape files
they have coated it with material that
would make it hard to see
the amount of light that's reflecting
off the surface is the only way we can
tell that that thing is there so we can
see it moving and if it's moving fast
and it's bright enough the the amount of
light it reflects from the sun is how we
tell it's there so if they've coated it
with this this coating that's stealthy
then system that they have in place to
detect incoming asteroids that would
fail so that actually makes sense
i would be surprised if he didn't hear
it to be honest because that would be a
very loud rumbly noise that you would
kind of notice before you saw the light
there have been fireballs that have come
across we get images of them and people
don't see hear them or see them or
sometimes people will hear something but
never see the fireball itself for this
particular scene all of that makes sense
you'd feel the thermal radiation before
you felt the shock wave that's that's
definitely realistic so even if you're
like 500 kilometers away you might feel
the thermal radiation in
maybe a minute
whereas you might not feel the shock
wave for a half an hour or more an hour
and the effects of the thermal radiation
would be
burning uh your clothing could burn off
your skin might not but i i imagine that
it would it would just depend on how far
away from the impact you are it's at
least an 8 out of 10 for realism
pause on the comment let's talk about
that first there's this whole bunch of
smaller bodies in between mars and
jupiter that we called asteroids and
asteroids are really rocky metallic
bodies comets come from farther out in
the solar system comets are composed
primarily of ice and dust the fireball
that we're seeing here these these bits
of material are fragmenting off and they
are still moving fast enough so that
they can
exhibit a glow as well that is a normal
thing that you would see
just
not at
this
size and distance the size of this rock
is about the same size as the rock that
caused the extinction of the dinosaurs
so
having shelters is a good idea because
we know what that asteroid did
we'd want to be underground potentially
could
devolve into that level of governments
making choices about randomly picking
people to save and then finding shelters
for them to go into
what we're seeing is that the entire
earth has been
wrecked and poisoned there would be
potentially a global dust layer on top
of everything but you would not
necessarily see the level of shock
damage or structural damage that is
being shown here for every place on the
planet you could potentially have
sunlight be blocked for quite a while
and then that could settle down two or
three out of ten we've never witnessed
something this size hit a terrestrial
planet
what we're seeing is
the smoke trail we're not actually
seeing
the fireball and then an explosion
that's not how it works it would be
something that is like a fireball and
then a trail of smoke behind it you know
we have evidence of this in 2015 this
several
tens of meters wide object came through
the atmosphere in russia
and it fragmented and people caught the
the whole thing on dash counts
so the impact itself would potentially
cause a lot of material to come out i
don't think it would go straight up like
that it would more spill out sideways
and then the shock wave would come after
certain impacts can burst your eardrums
because of the air burst afterwards so
if it's big enough yeah you can get
noise
levels that are well beyond you know
breaking your eardrums
there's a trail a skidded track to the
end of the trail no that doesn't happen
with impacts impacts are an all or
nothing thing even if they come in at a
really steep angle
it will still make a single hole and it
won't have a gouge in the earth leading
up to it that's gonna be zero on this
one
does that look like a problem to you
in your shower they call this a meteor
shower the size of that thing is is not
a meteor those are big rocks and we now
know meteors are really tiny small
specks of dust so meteors are different
than asteroids and
comets and meteorites
we're talking about tiny dust particles
that are between the size of sand grains
to maybe a small pebble size that are
burning up in the atmosphere so this is
a fireball or even we could even call it
a bolide if we're feeling super
scientific
if you see a fireball and it looks like
it's headed for you
stand there until the very last possible
second because
if it's small you might be able to jump
out of the way
but but probably not and if it's big it
doesn't matter i get this a lot i saw a
fireball over there so it must have just
landed over on the other side of my
field no if you see a fireball it's
actually really far away because it's
very high in the atmosphere
you would not be catching fireballs
and if a fireball hit you like it hit
those two
you would be
fried you'd be in the crater that was
left behind from the perspective of
science it's not realistic so i give
this a um i think a one out of ten
from the perspective of a rock hitting
the ground that came from space yes
that's a meteorite bring your phone come
on
don't go in there don't go near it
glowing on the ground no that's wrong so
that means there's something inside of
it it might glow as it's coming through
the atmosphere because the chemistry of
the rock might interact with the
atmosphere so you could get different
colors that way purple would tell you
something about the the elements that
are in it meteors that glow different
colors but again those are just small
pieces of dust smells
the amount of smoke coming out of it
like a barbecue that is not something
that you would see a meteorite coming
through the atmosphere it heats up but
only the outside so when it hits the
ground it's actually really cold because
space is cold and it's been out in space
and there have been reports of people
finding meteorites very shortly after
they've fallen and having them having
ice on them and if you're going to get
burned from it it's going to be freezer
burn not
not a heat burn you can get close to
them as long as they haven't come in at
a massive speed peak scale meteorite in
the us
october 1992
when it the meteor was seen across about
16 states it actually hit the boot of a
car in new york
and
punched a hole through the car
did you plant those
no
it would not be
something that is actually alive after
having gone through that atmospheric
thing unless the meteorite is somehow a
spaceship which
generally they're just rocks the idea
that there could be life on a meteorite
that's one area of study in our world we
check for
evidence of either organic material or
like the precursors of organic things
that could potentially harbor life we
haven't found any so far so we've we've
found precursor materials but no actual
evidence of life the color
it doesn't glow on the ground at all i'm
going with 0 out of 10 on this one
this is the comet and it is hitting
water the odds of anything hitting water
are really high on the earth
that tsunami wave looks very high to me
but i think you could get a tsunami wave
that was something like 600 meters high
with the size of that object
the running away park in general you're
gonna have some time before the tsunami
hits as we know from recent events with
volcanoes in the middle of the pacific
it takes a long time for the tsunami to
get to wherever it's going if the impact
is upon you
you have no warning the only way that
happens is if we haven't tracked it and
the only way that happens is if we're
not looking and so none of those things
are happening
you wouldn't have this level of water
coming inland as far as i think this is
so even if the impact had happened very
close to shore
the depth of the water would be less so
the wave would be lower this is
completely no i would probably head for
the middle of
a continent if i knew it was gonna hit
water
deep impact for realism i give it a one
out of ten
why does the ephemeris keep getting
lower and lower
professor mindy
so this is really good i like this
aspect of it we're going to
run through the numbers and we're going
to do the calculations from first
principles 0.0 means we're getting close
to the earth that doesn't mean it's
going to hit because
0.05 au is still farther away than the
moon the way we currently check for
things that might be potentially
hazardous is when we do these
calculations we work out well if it's
going to be closer than .05 a u from the
earth then we call it potentially
hazardous there's a good chance it'll
never hit so
his worry is
probably not unfounded it happens
several times a year that you'll get
something
at this .05 or less
but generally the sizes of the objects
are only a few meters or tens of meters
across
[Music]
[Applause]
this particular size comet would not
completely decimate it would not take
out the earth it would destroy it but it
wouldn't break it apart it would make it
a mess but it wouldn't even wobble it
off its orbit i think they said it's
like 10 to 15 miles across even the moon
forming event which was a mars-sized
object smacking into the earth
did not destroy the earth the
probability of something this the the
size of what these things show
actually hitting is so infinitesimally
small at this point um because the solar
system has evolved over time so don't be
afraid we're doing a really good job of
tracking things we have a much better
handle on how we look out in space
thanks so much for watching if you
enjoyed this video click on the one
above