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alright let's establish this up front we
are not here to rag on science teachers
their jobs are very difficult and they
are making the world so much better by
doing that and when science gets blown
out of proportion or oversimplified it's
almost never their fault so science
teachers we love you thank you for your
hard work now that said thanks to
misleading Articles oversimplified books
or plain old misunderstandings sometimes
you walk out of elementary school with a
few misconceptions about the world ones
that stick around for the rest of your
life and we've debunked many of these
over the years so now it's time to lay
them out let's start way up in space the
first time you learned about astronauts
on the International Space Station you
might have heard that they're weightless
because there's no gravity up there and
from their perspective they definitely
feel weightless but it's not because
there's no gravity here's a very old
video from Hank with more
we spend our lives stuck to this planet
the best of us can jump on astounding 2
meters off the ground the record for a
land animal is the tiger with a vertical
leap of barely double that that's some
serious force dragging us down into this
thing and we don't usually think about
it because we're always under its spell
our entire lives unless of course we get
to space because everyone knows that
space has no gravity
except of course everyone is wrong ok
probably not everyone in fact you may
have seen a number of YouTube videos
that have set you straight on this topic
but if not let's get down to it
space is packed wall-to-wall with
gravity without gravity everything would
just shoot off in straight lines there
would be no galaxies or solar systems or
planets in the universe would be a
supremely boring place so let's talk
real quick about how gravity works this
equation was figured out by Sir Isaac
Newton and he used it to do all sorts of
awesome stuff there are three variables
in this equation the mass of two objects
say the earth and the moon and the
distance between them there's also a
constant the gravitational constant
which Newton just worked out by
observation so according to this
equation the gravitational force between
two objects is dependent upon the mass
of both of the objects and the distance
between them
the masses are divided by the distance
so as the distance increases the force
decreases at 370 kilometers above the
earth the height of the Space Station
there is still plenty of gravity indeed
without that gravity it would just fly
off into deep space so it's good that
there's gravity the space station is in
orbit stuck there by the Earth's gravity
the astronauts are not weightless they
are falling a lot sounds weird because
they're safe I mean relatively they're
not as safe as I am but they aren't
about to crash into the earth that's
because they are falling at the speed of
gravity while moving horizontally enough
to continually miss the earth instead of
plummeting toward the earth they're
plummeting around it that's what we call
an orbit and just like when in a plane
you don't feel like you're moving 400
miles per hour the astronauts have
already done all of their acceleration
and are at a constant speed so to them
it feels like they're weightless and
motionless
their only frame of reference is inside
of the spacecraft the same sensation can
be experienced without being in space by
getting in a plane having the plane drop
toward the earth at the same
acceleration
gravity it looks to all the world like
you're floating in the plane because the
fuselage is your frame of reference but
really you're crashing toward the earth
a terrible speed plane and everything
inside all the objects and people
everything is falling toward the earth
at the same rate so the contents of the
plane appear to float because gravity is
acting on all the objects equally so
let's go back to Isaac's equation no
matter what we do to that distance
number no matter how big how far apart
things are it always exists that force
never goes to zero that means that every
object in the universe is constantly
attracting every other object in the
universe so hypothetical situation for
you there are two things in the universe
nothing else just one planet and you it
doesn't matter how far away you are if
you're sitting there motionless you're
not floating you are falling and
eventually you will fall into that
planet it may take longer than the life
of the universe but you will eventually
fall into the planet
man since 2013 scishow has grown a lot
now in your first science classes you
may have started learning about physics
while you probably didn't get too far
into the weeds there's a good chance you
at least saw this diagram of an atom
it's a really popular symbol and it
would be easy to think that's what atoms
look like it turns out that atoms are a
lot more complicated than that but I'll
let Olivia explain
have you ever looked carefully at the
intro for this show I mean really
carefully if you have you might have
noticed that there's a diagram of an
atom with little electrons orbiting the
nucleus but here's the thing atoms don't
actually look like that over the years
scientists have come up with different
atomic models based on what we know
about how they work the atomic model
that's in the scishow intro was one of
them and it has a lot of history behind
it but the most accurate atomic models
are a little more complicated because
atoms are complicated by the start of
the 20th century scientists knew that
atoms were made up of negatively charged
electrons plus some sort of positive
charge the tricky part was figuring out
how these charges fit together the
running theory was that the electrons
were embedded in a positive sphere which
was called the plum pudding model
because it looked like a traditional
Christmas pudding but that all changed
around 1911 when a scientist named
Ernest Rutherford along with his team at
Manchester University published the
results of the famous gold foil
experiment Rutherford and his colleagues
fired alpha particles which are
positively charged at thin gold foil
according to the plum pudding model the
alpha particles should have just passed
straight through the foil because atoms
would be mostly empty space with some
charges scattered around and atoms are
mostly empty space so most of the alpha
particles did pass straight through the
foil but to Rutherford surprise some
alpha particles were deflected by a lot
he concluded that an atoms positive
charge was concentrated in a tiny
central nucleus and these nuclei were
deflecting alpha particles that bounced
off of them he also predicted that the
electrons were orbiting around the
nucleus kind of like how planets orbit
the Sun that's why this model is
sometimes called the planetary model
Rutherford was right about protons being
in the middle with electrons around them
and you'll still see his model used
today to explain the very basics of the
atom it's the one in the scishow intro
but there was one major problem with the
planetary model it predicted that
orbiting electrons would lose energy in
the form of radiation which would make
them spiral inward and eventually crash
into the nucleus this implied that all
atoms would eventually collapse
but we know that stable atoms do exist
so there had to be something missing
just two years later in 1913 Danish
scientist Niels Bohr proposed an
adjustment to the Rutherford model that
solved this problem Bohr's model
predicted that electrons orbit at very
specific energy levels which he called
orbits the electrons could only orbit at
precisely those levels and so they
couldn't spiral inwards an electron
could switch levels if it absorbed or
released some energy but only specific
discrete levels were allowed and
electrons couldn't go below the lowest
level that explained why stable atoms
didn't just collapse Bohr's model
quickly became the most popular model of
an atom and it's often used today to
show the basic way that an atom is
arranged but it still wasn't totally
right one breakthrough was in 1932 when
English physicist James Chadwick
discovered that neutrons exist neutrons
weren't electrically charged and they
helped explain why the nucleus was so
heavy another breakthrough involved
quantum mechanics and the idea that
electrons don't necessarily orbit the
nucleus at all in fact electrons aren't
even really in a specific place at any
given time instead they're kind of in
lots of different places at once within
a bigger area then when you actually
measure an electron suddenly it's in one
specific spot within that area
it's a weird concept that's very
different from the way that we normally
experience the world but that's quantum
mechanics for you the area where you
might find it if you tried to measure it
is called the electron cloud in diagrams
normally the cloud is drawn darker where
there's a high probability of the
electron being there when you measure it
with the most basic atoms like hydrogen
and helium this cloud looks kind of like
a big sphere and it turns out that
electrons have the highest probability
of being in one of Bohr's orbits which
is why you can use Bohr's model to
simplify things but when you get into
bigger and bigger atoms with more and
more electrons these clouds begin to
interfere with each other and start to
have weirder shapes so the electron
cloud model is the most up-to-date model
of an atom and it's used by scientists
around the world but that doesn't make
the other models useless like Bohr's
model can be helpful if you need to
focus on energy levels and radiation but
if you
studying chemical bonds you might need
the electron cloud model to know where
the electrons are and if you want a
model that shows off the fundamentals
and still looks pretty cool you might
want to go for the planetary model
now back in elementary school there's
also a chance you first learned about
the human body in death stuff like how
your body makes urine to get rid of
waste and along the way you might have
picked up this idea that urine is
sterile maybe from some kid on the
playground who'd been watching survival
documentaries with their older siblings
and it's understandable I mean it's what
people were taught for a long time but
the next time you or one of your friends
gets stung by a jellyfish you should
probably hold your bladder here's Hank
to explain why
for some reason the TV seems to be full
of guidance about what you can do with
your pee like maybe you're watching one
of those wilderness survival shows and
the guy falls down into the ravine and
gets a big gash on his leg and he's like
oh no worries others pee on it a little
urinal spruce that right up maybe you're
watching lost and Hurley steps on a sea
urchin or jelly vision or whatever and
he's like bit suddenly pay on my front I
Got News for you
despite televisions teachings and in
fact what many doctors and nurses were
taught there's increasing evidence that
your urine is not sterile the idea that
urine and by extension your bladder is
free of bacteria stems from the fact
that under normal circumstances it won't
produce results in a laboratory culture
that means is that if a sample of your
urine is added to a growth medium and
incubated in the right conditions it
won't produce big flourishing colonies
of bacteria if you're healthy doctors
have been using these urine cultures for
generations because they're really good
at detecting large amounts of certain
kinds of bacteria like e-coli and
Klebsiella that can cause infections in
your bladder or urethra however if your
culture comes back negative that does
not mean that there's nothing there for
one thing the threshold that labs used
to diagnose bacterial infection in your
urine is kind of high to get your
results lab technicians count colonies
of bacteria and each colony is basically
a little speck growing on the growth
medium and if there are fewer than
100,000 colonies growing in a single
milliliter of your urine that's about
one-fifth of a teaspoon they will give
that a negative result they just assume
that those germs were picked up on the
way out of your body or simply aren't
statistically significant and they want
to avoid reporting a false positive but
even then the bacteria that show up in
these cultures are only the ones that we
can test for fact is only a small
percentage of bacteria can actually be
cultured in labs there are entire
general of bacteria thriving out there
in nature eating and being eaten
recycling elements and basically making
the world work that we don't know how to
grow in petri dishes
it's also worth considering that you're
literally teeming with bacteria right
now I'm talking on the order of
trillions of microorganisms inside and
out
forming what scientists call your human
microbiome basically the habitats your
body provides for lots and lots of tiny
livestock and recent research has shown
that your bladder
is part of it several studies in the
past few years have found lots of uncle
trouble bacteria swimming around in the
urine of otherwise healthy people and
they found them not by using the old
petri dish technique but by scanning the
pee for tiny sequences of DNA
specifically telltale genetic markers
that we use to identify and classify
bacteria one study urine was sampled
from two groups of women one who had
some symptoms of urinary infections and
another healthy control group all of the
women had already tested negative for
bacteria by conventional means but 91%
of them turned out to have bacteria
living in their pee including some kinds
that cause infections and a separate
experiment similar techniques were used
to compare the urine of healthy women
with that of women who had overactive
bladder syndrome a condition that makes
patients feel like they have to be
frequently even when their bladders
aren't full results showed that both
groups had two ample bacteria growing in
their urine but the populations and the
women with overactive bladder --zz were
different than those in the control
group suggesting that the syndrome might
be microbially caused in the end the
researchers say your urine may well have
some bacteria in it that are causing
problems they're just hard to detect but
it's even more likely that it contains
bacteria that pose no danger and who
knows some of them might even be
beneficial the next time you pass your
pee test at the doctor's office keep in
mind that that doesn't mean your pee is
sterile so don't do anything crazy with
it and if you happen to skin Unni while
you're out in the woods wash it with
soap and water
not with pee
okay next up animals because if there's
anything kids love learning about its
animals especially their pets if you had
a dog when you were a kid or even if you
didn't somebody probably told you that
dogs can't see color maybe in a
show-and-tell presentation or in some
program about animal biology and you can
probably guess where I'm going with this
there is a little truth to that idea but
it's still not quite right
here's Michael with more
maybe you've heard that dogs can only
see in black and white it's one of those
fun factoids that people like to toss
around sometimes but this like so many
things we talked about on quick
questions is a misconception and the
misconception stems from the fact that
dogs are from a human perspective
colorblind but that doesn't mean they
can't see color we perceive color
through a series of receptors in the
retinas of our eyes called cones and
humans have three kinds each of which is
activated by a specific wavelength of
light corresponding to a certain set of
colors most humans have cones that can
detect blue green and red wavelengths of
light but dogs kind of like humans who
are colorblind only have two kinds of
cones that work for dogs the two colors
they can register are blue and yellow so
dogs can't see the color red but they
can see and distinguish between various
shades of yellow blue gray and something
that probably comes through as a dirty
greenish Brown so while we see this your
dog sees something more like this
it's not exactly Technicolor but it's a
lot more information than just black and
white and setting the record straight
about dogs partial color vision is
teaching us a lot about how pups
experience the world recent experiments
have found that dogs who are trained to
find dark yellow objects could still
find them even if they were replaced
with very light yellow ones and they
didn't mistake dark blue objects for the
dark yellow ones either suggesting that
dogs can clearly distinguish between
many different shades and colors and
don't just see in greyscale so the next
time you ask your dog to fetch your blue
slippers and he comes back with a pair
of bananas he's not colorblind he's just
messing with you
yeah all this time we've been selling
dogs short now there's a lot of things
we could put into this episode but for
now let's end on a big one your senses
in grade school you likely learned that
you have five senses and you may have
even done games and activities to really
help you remember what they are well
it's time to break out the markers and
popsicle sticks again because you've got
at least three more senses to add to
your list here's one last video in which
Hank explains
at some point you've probably learned
about the five senses sight sound smell
taste and touch these five don't explain
all of our sensations how can we tell
how hot or cold we are keep ourselves
balanced now scientists are beginning to
add more senses to that classic list
here are three of those it's probably no
surprise that sensing temperature is
pretty important which we call thermo
ception it helps us keep our body
temperature constant and lets us know
when our environment is too hot or too
cold so we can avoid tissue damage like
from burns or frostbite so how do we do
it scientists have found a couple of
potential mechanisms connected with the
transient receptor protein channel or
trip family there are lots of these
channels and they react to lots of
different stimuli we're still trying to
figure out what they all do but one
thing's for sure a lot of them help us
respond to changes in temperature
scientists aren't exactly sure how these
channels work but with the physical
stimuli of the environment getting
warmer or colder depending on the
channel they're more likely to open one
of these channels trip v1 plays a role
in the sensation of painful heat the
receptor is activated when temperatures
get uncomfortably warm around 40 degrees
Celsius trip m8 on the other hand
response to cold stimuli below 20
degrees Celsius so pretty much anything
below room temperature these channels
and others can be found throughout our
bodies but when they're on nociceptors
or pain sensing nerves activation of the
channel triggers a rush of calcium into
the cell and sends a signal to the brain
about painful temperature all that
information goes to the primary
somatosensory cortex a thick fold of
tissue on the top of the brain where
most of the mechanical sensations like
touch pain and vibration are processed
then you can consciously process the
temperature and yank your hand away from
that campfire or decide whether you want
to put on a jacket now have you ever
thought about how you just know where
your body is in space
well that's proprioception the word
comes from the Latin for one's own grasp
it's how you can type without looking at
a keyboard and walk without looking at
your feet and there are a bunch of
specialized receptors in our skin joints
and muscles that help us do it for
example muscle spindles respond to
changes in muscle length and the speed
of muscle movement while Golgi tendon
organs send signals about muscle tension
and exertion and then cutaneous
mechanoreceptors respond to
Treach and pressure in the skin and
joints all of these receptors work
together to provide the brain especially
the cerebellum with information about
your movement and the positions of your
Lin the cerebellum is responsible for
coordinating things like balance posture
and voluntary movement weirdly though
scientists recently discovered a case of
a woman born without a cerebellum who
has some balance and movement issues but
seems to be doing relatively fine so
there is still a lot to understand about
how our brains process proprioceptive
information separately we have
equilibria ception our sense of balance
and we need balance whenever we move
like walking and running ears are
important for our sense of hearing but
they're also a key part of equilibria
ception especially the inner ear it
contains the vestibular system which
includes three fluid-filled semicircular
canals lined with tiny hair cells your
head moves these hair cells are sloshed
around by the fluid and sends signals to
the brain specifically to the vestibular
nuclei in the brainstem each canal is
responsible for a different kind of
movement one for up and down one for
left and right and one for side-to-side
Oh Duluth organ is located just below
the semicircular canals are similar but
in addition to liquid they have tiny
crystals made of calcium carbonate as
the head moves these crystals rub
against the hair cells attached to the
membrane which send information to the
brain stem brain then sends information
out to your eyes joints and muscles so
they can respond accordingly and help
you navigate the world now problems with
this system can lead to issues with
balance vertigo for example can be
caused by loose stones in the otolith
organs they can also fall into the
semicircular canals disrupt the normal
fluid movement and put unexpected
pressure on the hair cells that pressure
conflicts with what your eyes are seeing
which can make you feel dizzy when you
move your head together these three
senses are really important in helping
us navigate our environments
successfully and safely so even though
they don't make the list of our
traditional senses I think we do
ourselves a disservice by forgetting
about them
so in a lot of ways the world is way
cooler than we learned when we're kids
and that's okay it doesn't mean your
teacher did a bad job or that you should
have definitely learned what Adams
really look like when you were seven or
eight especially when you're first
learning about science it can be easier
to take things one step at a time
and then as we get older we can learn
that things are more complex than they
see thank you for watching this episode
of scishow and thank you to all of our
patrons who have made this show possible
over the years if you want to learn
about more misconceptions that you might
be carrying around you can check out our
episodes about animal misconceptions
right after this
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you
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