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for the last couple decades nuclear
weapons and mostly stayed out of the
news as the Cold War's kind of started
to fade to the back of our minds but
they're back in the news now and back on
our minds most of us are hoping that any
threats are just empty threats but at
some point you might start to wonder
what would happen if there were a
nuclear missile heading for us of course
the latest in military defense is
classified like any sort of defense the
more people know about it the easier it
is to circumvent but we do know a lot
about the basics and the good news is
that an incoming nuclear missile doesn't
necessarily mean doom because we have
some options when it comes to the most
important part of stopping an incoming
attack hitting it before it hits us the
only nuclear bombs ever used in the war
were dropped from planes that could
definitely still happen but most people
today aren't worried about planes that
worried about missiles missiles are
faster and harder to stop than planes
and some types can launch from pretty
much anywhere
the most famous are intercontinental
ballistic missiles or ICBMs which rocket
into space before speeding down at their
target they can hit something halfway
around the world within an hour after
launch and if you're curious about the
challenges involved in building one you
can check out our video about that other
types of missiles are less famous but
each is designed to go a different
distance and carry a different amount of
weight no matter what type it is the
best time to stop a missile is before it
even launches so countries constantly
use spy planes and radar and satellites
to monitor each other for any signs of
missiles being prepared sometimes the
first hint of a missile is the launch
itself missile launches are bright and
hot and the missiles stay hot while
they're screaming through the atmosphere
so the US has a worldwide network of
satellites on the lookout for unusually
hot objects known as this space-based
infrared system SBIRS and its
predecessors have monitored missiles for
decades although it's heat-seeking eyes
can track wildfires and watch volcanoes
for signs of impending eruptions when
there isn't a missile to watch but if
one sees a missile you can bet those
other jobs go out the airlock other
countries have their own missile defense
systems but they pretty much all share
the same goal making sure that if a
missile is being launched anywhere we
know about it once a missile is in the
air there's really only one way of
stopping it hit it with something
usually another missile it isn't ideal
to have a nuclear bomb explode up in the
atmosphere and rainfall out on the world
below but that's still way better than
letting it reach its target plus the
nuke might not even explode when
rest of the rocket does a lot of modern
bombs don't bring the explosive parts
near each other known as arming until
they're about to land to make sure that
nothing goes wrong during the launch or
the flight so the nuke might be
destroyed by the explosion or it might
end up like that unarmed hydrogen bomb
that accidentally fell into a North
Carolina swamp in 1961 nothing happened
when it landed and its uranium core is
probably still 50 or so meters beneath a
farm to track their target missile
interceptor systems use radar and the
same heat signature that SBIRS uses but
hitting a missile with another missile
definitely isn't easy it's like shooting
a bullet with a bullet except each
bullet is moving six or seven kilometers
per second and missiles are way more
complicated to build a manned launch
than bullets are make it even harder
missiles often carry decoy parts that
fall off during descent to distract
defensive systems from hitting the real
thing with so many factors to take into
account it's not too surprising that
missile defenses need a lot of testing
but you don't want to test any defense
too many times even if it's not quite
perfect to an outside observer every
test reveals a bit more about how it
works and how to get around it it's
expensive to each ICBM defense test
costs tens of millions of dollars and
takes months to prepare for altogether
the u.s. is probably equipped to stop a
couple dozen ICBMs at once but it's hard
to know for sure because the military
tends not to go around telling people
exactly how many missiles it would take
to overwhelm our defense systems we do
know that single networks and groups of
submarines in places like South Korea
and Japan are capable of tracking a
hundred smaller missiles at once but
even they aren't perfect missiles are so
hard to hit that it's next to impossible
for every interceptor system to stop
every missile 100% of the time military
strategy is always evolving so some
places will end up less defended than
others so the military is always trying
to develop new technologies to block
those holes and one technology that was
first imagined back in the 70s and 80s
might make a comeback lasers back then
people figured that satellites with
ultra powerful lasers could overheat and
blow up missiles mid-flight it was
incredibly impractical at the time for
one thing lasers powerful enough to
overheat a missile from so far away just
didn't exist of the American military
recently announced that it was testing
laser mounted drones for missile defense
today's lasers are a lot stronger and
smaller than those from decades ago and
drones could quickly get within 10 or a
hundred kilometers of a missile without
endangering lives powerful lasers still
aren't quite compact
to be carried by a drone but a laser
defense system might not be too far off
or maybe we already have one and it's
just not public information either way
generations of brilliant scientists and
engineers have spent their careers
trying to make sure that no nuclear
weapon ever hits another city and we
have their defense systems in place
let's just hope we never need them
thanks for watching this episode of
scishow if you'd like to learn more
about the science of nuclear weapons or
the science of anything else you can go
to youtube.com/scishow and subscribe
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