April 1, 2010 • 22 mins
Gravity is a pervasive and ambiguous force -- we still don't understand everything about it. Yet every physical act on our planet involves gravity. Join Allison and Robert as they explore exactly how gravity affects the average person in this podcast.
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Episode Transcript
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Speaker 1 (00:01):
Welcome to Stuff from the Science Lab from how stuff
works dot com. You guys, welcome to the podcast. This
is Alison. I don't know if the science editor at
how stuff works dot com. And there is Robert Lamb,
science writer and how stuff works dot com. So, Alison,
(00:23):
have you seen the movie Phantasm? I've not seen it.
It's a nineteen seventies flick, right, yeah, harror flick. You
haven't seen it. I have not, but you've mentioned it before, right, Well, okay,
it's awesome. It's um. I mean it's it's horrible, but
it's awesome. It's um. The basic plot line here is
you have a mortuary where some funny things are happening.
(00:44):
There silver balls flying around, stabbing people in the head. Uh.
And there are these dwarves running around in these little
like I think they're yellow, little yellow robes, okay, like
evil dwarves. Right, And you come to find out that
all of this basically has to do with gravity. There's
a really tall man, like a scary old man. It's
really tall, Okay. And it turns out he's from another
(01:06):
planet where the gravity is more intense, like a larger world. Okay,
so that's why he's taller when he comes to this world, okay,
and the deal with the dwarves, he's taking corpses and
smushing them down, making a more compact and bringing him
back to life a zombies and then sending them to
this other world to be like slaves. All right, So
(01:31):
dwarves are being used as as as zombies. Dwarves are
being used as slave labor on another world where there's
more gravity. And so this all occurs thanks to gravity. Yes,
like it Like for me anyway, as as a kid.
You know, it's like, you know, gravity is, They're great,
but I never think about it. But then somebody comes
along and shows me how gravity is affect you know,
(01:51):
zombie dwarves and uh and it it really you know,
unders it really resonated with me and underlining how amazing
gravity is. I mean, um, like I said, we take
it for granted because it's everywhere, because every pretty much
every physical act on the planet um involves gravity in
somewhere and within another. So that's what we're going to
(02:14):
talk about the day. We're gonna We're gonna basically talk
about four examples um of technologies that utilize gravity in
a way that highlight just how amazing it is. But
of course to do that, we need to talk briefly
about about gravity itself. Now, we have an excellent article
on how Stuff Works dot Com about this um and
(02:36):
I recommend checking that out if you want more details.
But basically, two schools of thought. There's there's Newton Newton's
uh a theory of universal gravitation from back in the
sixt eighties, and this is the idea. The gravity is
a predictable force that acts on all matter in the universe,
(02:56):
and it's a function of both mass and distance. Right. Basically,
each particle of matter attracts every other particle of matter,
all right. Whether we're talking about a great or a
massive sign. Okay, whether we're talking about a spaceship or
I don't know, a dog, everything has gravity, all right.
(03:17):
And if ever, and if the only two things you
had in the universe were a dog and a spaceship,
they would each have a great gravitational pull and it
would be drawn to each other. Okay, um, go ahead.
And then along comes Einstein. Yes, along comes Einstein, and
he says, fooie to this whole dog and spaceship business.
(03:37):
And he says that, he says that gravity isn't even
a force, all right, he's a he's seeing it more
as a distortion in the shape of space time, all right,
as the you know, a distortion in the fourth dimension.
And in Einstein's footsteps. You have some more modern theories
(03:58):
as well, okay, that are less even even less proven.
There's the idea that UM that gravity is due to
little particles called gravitons that that cause objects to be
attracted to one another. And there's another theory that there's
gravitational radiation UM, which which is supposedly the ideas that
gravitational radiation is generated when an object is accelerated by
(04:20):
the external force. Basically, the idea here is that gravity
is is awesome and every day it's mysterious. Um. Basically,
the idea here that it is that as every day
as gravity is, there's a lot we don't know. There's
a lot we don't know about it. It's still kind
of a mystery in many ways. All right. So with that,
let's kick off with four cool things that gravity can
(04:41):
do for you. Yeah, what do you got? What can
gravity do for you? Well, if you listen to our
Fighting Asteroids podcast, we touched on this briefly but gravity
can actually I could save the Earth from being destroyed
by some crazy space rock and always good. Yeah, I
like this. Um, So this thing called a gravity tractor,
and I'm not talking about the the grateful dead cover
(05:03):
band that seems to be located in upstate New York
of the same name. This gravity tractor, actually, um might
have a might have a chance of being built. According
to the BBC, there's this British company by the name
of E. A. D. S Astrium that they finally started
taking concrete steps to make the graph tractor reality. So
it's the graph tractor gonna do it well. It's a
(05:26):
robotic spacecraft weighing roughly ten tons or so, and it
has a has a particularly daunting task. Once it's launched
into space, it has to get within forty eight m
so roughly a hundred fifty feet of the space rocking question.
And once it gets within that range, it has to
pull the rock toward it, and the two of them
march happily off on a path that's not kind of
(05:48):
coincide with the Earth and now in theory though it
could also if you had a New York area jam
band floating in space. It could also use its immense
gravity to to pull them aside as well. Right right,
and I think if you pull the string cheese incident
on there, I mean it could just do crazy winners
with a space rocks headed our way. Um. And the
(06:09):
other chicky thing about the tractors, it's gonna we have
to launched. The other chicky thing about the tractors that
has to be launched fifteen years ahead of time. So
we're kind of we're kind of stuck. This is what
we're relying on right now. So gravity, it can it
can save you from a space rock someday. Perhaps what
else can it do out in space? Well, gravity can
also help you fire a spaceship to some distant corner
(06:31):
of the Solar System. I like the way that sounds. Yeah,
this is something we call gravity assist. Sometimes you see
it referred to as a gravity slingshot, but that's a
little misleading. Um, so just think of it. It's gravity assist,
all right. And to understand that, you need to think
of the Solar System in terms of the Sun's gravity. Well, okay,
(06:52):
imagine a bathtub, all right, It's filled with water and
it has a little boat in it. Okay, you pull
the drain, the water begins to to to go to
to leave the bathtub in the form of a whirlpool.
The little boat is going to be pulled towards the whirlpool,
all right. In the scenario, the Sun is the whirlpool.
It's the object of the most mass and if it
(07:12):
has the most gravitational pool and spacecraft, right, and it's
gonna if it's if the little toy boat is moving
towards the world pool, it's gonna go faster to move
away from the world pool. It has to work harder
and it's going slower. Okay, that's basically the gravity well.
So if we want to send something farther out into
(07:32):
the gravity well, out to one of the outer planets, um,
we need to we need a little help, all right,
and and it and it uh, it's more effective if
we don't have to depend on say, you know, thrusters
and rockets to do all of the work and take
a take advantage of inherent force. Right. So that's where
the gravity assist comes in. And this is a fly
(07:53):
by technique where we can add or subtract momentum to
increase or discrete decrease the energy of a spacecraft. Orbit,
so we've used it. Yes, UM. Take, for for example,
Voyager two launched in um, we flew it by Jupiter.
Will first, just you know, to see Jupiter, that was
one of its mission objectives. But also um, by flying
(08:16):
flying by Jupiter, this provided traject trajectory boost to shoot
it towards Saturn. Now again go back and going back
to the spaceship and the dog. You know, both both
the spaceship and the dog have mass and therefore have
their own gravitational pool. Right, So Voyager two has its
own gravitational pool, as does Jupiter. All right. So when
(08:38):
the spacecraft actually tugs on Jupiter as it goes past,
all right, and actually decreases the planet's orbital momentum by
a tiny amount, very tiny amount. In return, the spacecraft
acquires momentum from Jupiter. Except as we're talking, a significant
amount of momentum, and uh, and it it shoots it
(08:58):
off in this new trajectory. Okay. Uh. One of the
more useful analogies, uh that that you find for this
is imagine a kid standing next to um a train track, okay,
and he has a softball in his hand. The softball
is a spacecraft, all right, And then hurtling down the
train track is a locomotive, al right. The locomotive is Jupiter.
(09:22):
If you were to throw the softball and hit the
front of the coming train, then the softball would would
veer off into another direction with the momentum of the train.
So it's it's very useful for for shooting off any
number of probes UH into into the surrounding Solar system
and uh A lot of people have even looked at
(09:45):
considered possibilities of using it for the future use of
man space spacecraft being able to like use the the
Sun's gravity to shoot an aircraft off to a not
an aircraft, of using the Sun's gravitational poole to um
to shoot a spaceship off towards another system. Have you've
(10:06):
seen Star Trek or any number of science fiction properties,
then you've you've you've heard examples of this, So I'd
say that's a cool thing. Gravity shooting you to a
distant corner of the galaxy. On a more earthly level,
gravity can perhaps let your home someday. And this is
an idea that's been around for quite a while. Back
in the nineteen seventies, there are a bunch of fellows
at the Lawrence Livermore lab who thought we should try
(10:27):
to harness the energy potential of gravity courtesy of black hole.
So this is what they had in mind. You guys,
remember that a black hole forms when this big old
star is dying and it's collapsing inward, and the end
result is this tiny object that's just unspeakably dense. So
the gravitational force of a black hole is large, so
large that not even light can escape it. I know
(10:49):
you guys know this, but let's just reiterate it. So
the idea was, according to these scientists, was well, let's
locate a black hole, well, get it to orbit the Earth.
That's now that that's the point I think where you
just you cancel this plan like that just sounds like
the worst idea ever. Hey, let me just okay, it
gets better, Okay, Okay. So you're gonna get the said
(11:10):
black hole to orbit the Earth with the help of
a spaceship, and once it's in permanent orbit, just you know,
kind of hanging out like black hole does, you're gonna
tap the power of said black hole by firing matter
into it. Okay. So the whole plan is we're going
to go and find the most destructive force in the universe.
We're going to bring it home and then we're going
(11:30):
to feed it. Yes, yes, and then wait, it gets better.
So you know that things get really tiny, as are
you know, hurtling towards their on their death spiral towards
a black hole. Well, all that getting tiny business generates
an amounse amount of energy, and they thought that this
amount of energy could in fact be enough to start
a fusion reaction. So this one, this idea of a
(11:53):
black hole gravity thing, actually never came to fruition. I
think probably the the first point of business was moving
the black hole, or actually maybe even locating black hole
and then moving black hole. So a couple of a
couple of a couple of holes in this plan. Yes,
the latest incarnation of gravity power is a lamp. It's
a little bit simpler and a black hole. No no, no, no, um.
(12:19):
Let me explain. It's conceived of by this grad student
at Virginia Tech, and I think he entered his invention
in some sort of TEO thousand in a green Tech award.
And it's a guy by the name of claymont. Well.
Clay calls his lamp the gravity So conceptually, here's how
Clay's gravity powered lamp works. If you picture kind of
a cylinder shaped floor lamp, maybe about five feet tall. Um,
(12:43):
Now imagine that there are these like five ten pound
brass swats sitting there at the top. And for those
of you guys who don't know what one is, there's
a ball screw in in the in the floor lamp.
And what is the what is ball screw? I had
no idea before I started doing this podcast. Well, it's
a it's a linear screw and um, something rotates downward
on it. So it's kind of like falling on the
(13:05):
ball screw. It's moving downward on the ball screw. And
as these brass weades moved downward on the ball screw,
the screw rotates, and that rotational motion is able to
spin a generator and convert the motion into electricity. So
if you can't quite picture, you can always check out
the illustration. We have a good one on our how
gravity powered lamps were an article. So anyway, this electricity
(13:28):
powers ten led bulbs which light up and whaila you
have light. And do you think, well, how long is
that going to take? Because gravity can happen relatively fast right,
falling objects might be down to the bottom and lamp,
but actually it takes four hours, so that would be
a good amount of light. Would it would work faster
on the the phantasm planet with the dwarves? Sure would, Surewood.
(13:51):
It's also worth noting here that the hour glass is
actually a gravity powered timetelling device. Yeah, and it seems
like a little bit of a simple concept than the
The gravity powered lamp also cuckoo clocks, but are also
worth considering that they're actually powered by black holes. So anyway,
(14:11):
the thing with Poort Clay's lamp is that the d
technology isn't quite where it needs to be, and the
LEDs aren't as efficient as they need to be, and
so that means the weights would have to be much heavier.
And that's about where we are with the gravity powered lamp.
So you cannot buy one at your local lamp star.
It sounds promising, though, I like the idea of gravity
powered electronics. Well, I'll tell you another thing that gravity
(14:35):
can do for us. What gravity can help us understand
what's going on underneath the Earth surface. And how many
do that? Well, think of it this way. Imagine an
appetizer sampler platter. All right, you know it's it's covered
with fried cheese sticks, hush puppies. What are the what's
the meat on the stick called? Oh, chicken settee? Chicken
(14:57):
sette all right, all of idea of different foods. Now,
something late and fluffy too, right? Yeah? Like, well, hush
puppies are lighting fluffy? Right? Well, what's something light and
fluffy do you get as an appetizer? Um, we'll see.
I think that's the thing. Most appetizers, they're so hideously
unhealthy that you get them in small portions first, right, okay,
(15:19):
So imagine something light and fluffy appetizer, but hush puppy.
So so you have all these different items on the plate, right,
and all of them have different densities, okay, which means
and all of them have gravitational pools, all right, And
the more dense the appetizer item, the more gravitational pool
(15:40):
it has. Okay, Okay, all right, Well, our planet is
basically an appetizer platter when it comes to gravity. All right,
there are our planet has is covered with varying densities
of rock. Um, you have you have water that's cold,
you have water that's hot, and of course there's different
(16:01):
tensity there. Um. You know, you look under the Earth,
they're gonna be they're gonna be empty caverns, they're going
to be uh, you know, blocks of solid bedrock. There's
going to be you know, liquid magma. So gravity is
gonna vary according to where are you on there. That's
interesting because I guess I just think of it as
such a constant uniform Yeah. Yeah, we think of it
more as uh, you know, a pizza with a pizza's
(16:24):
worth of you know, of a uniform gravitational pool. But
like if you go up to Hudson Bay in Canada, Um,
the gravity is actually less there. And I need to
stress that it's not not less in the sense that
that you can go to, uh to Hudson Bay and
uh and feel like you lost weight. It's right, You're
not gonna be able to fit in your skinny jeans,
(16:45):
are right. The Earth's gravity is still pretty uniform, um,
all all across the globe, but it varies um to
it to a slight degree um wherever you go. All right,
So um, you know, most people say, well, what does
what does that matter? Right? It matters when you start
looking into fluid dynamics, alright. The ocean, for instance, Um,
(17:09):
you have it dictates the flow of hot and cold water,
all right. I think of it as a topography, okay,
Like if you have a hill next to a plane,
you know water is gonna flow down that hill. All right.
Well you have the same kind of topography going on
across the planet, except in terms of gravity, with fluids
drawn towards the areas of higher gravity. Okay. So we're
(17:33):
very interested in finding out exactly what this uh, this
secret topography looks like. We in fact, we've launched to
um Um orbiting a spacecraft. There's a European Space Agencies
Gravity Field and Steady State Ocean Circulation Explore and this
is up there right now, um, yes, called GHOS. See
(17:54):
that one went up in two thousand nine. And then
there's NASA's Gravity Recovery and Climate experiment that's called Race
and Grace went up in two thousand two. All right, ghost.
These mission has been to take a picture of what
this uh, the secret topography of gravity, which we call
the geode, to take a picture of what that looks
like right at nay moment of time, Like what are
(18:16):
the highs, what are the lows? Uh? Grace has been
looking at how the geo changes, because it's always changing too.
It's not like like you can you know, you'll be
able to go here, and oh, the gravity is always
going to be this, especially when it comes to the ocean.
And why do we care if the geo changes? Because
the more we understand how the ocean transports heat and water,
the more we understand how the ocean moves, And the
(18:38):
more we understand how the ocean moves, the more we
understand how the atmosphere moves. See, it's all a part
of Earth's outer layer of fluid, all right, and that
is where our weather takes place. UM and uh and
you know everything from from fierce hurricanes, two patterns of
drought and uh floods and what have you? All right, UM,
(18:58):
so it helps us a better understanding of global climate.
On a more specific note, UM scientists think it will
be able to look, uh, look at changes in in gravity,
changes in density too, to determined shifts and water mass
caused by droughts or floods. And it will also also
allow us to better understand plate tectonics, UH, seismic activity.
(19:22):
You know, what's what's happening underneath underneath the soil um
in the crust to you know, the leads to two
two earthquakes and uh another phenomena and uh and just
the geological geophysical processes that underlie the the Earth. Sorry,
but it's pretty it's pretty I'm getting a little long
winded here, but it's pretty pretty, pretty awesome, and that's
why we're looking into it. So I hope you've inspired
(19:44):
some reverence for gravity and you besides the kind of
gravity that trips you up and makes you fall flat
on your face and gravity is pretty cool. Um. So
now we would like to take a moment to imagine
a world without gravity. Oh, we were going to talk
about it or just imagine it, because I was just
going to picture it. Yeah. One thing that's really gonna
(20:05):
suck is that all the atmosphere is going to drift
off into space and we're not gonna be able to breathe. Yeah. Also,
I don't think I don't think our hair is gonna
look right. I mean, how do you style your hair
for that? That's true? I mean what kind of products
could could combat that effect? Um? I think that it
(20:25):
would suck if the the oceans boiled away and just
kind of float it off into the void um. On
a more mundane level, I think eating would kind of
pose a number of challenges. Only the astronauts. They'd be
sitting there, happy as you please, eating their dinner out
of their bags. Everybody else would just be in full
freak out mode. Yeah, like trying to run after their
(20:48):
hamburger which had floated off into bun Yeah, and the
chop bits of onion and I'm sorry, catch ups. Just
a globular thing floating out there. Yeah, yeah, that would
be bad. So that would be a world without gravity,
and we hope that we may never encounter it. So
if you want to tell us why you think gravity
is cool or maybe not so cool, send us an
(21:09):
email at science stuff at how stuff works dot com,
or go read about gravity where we're at site. Yeah,
and when you got to check out the blogs where
we handle any number of scientific specs, including zombies from
time to time. Thanks for listening, guys. For more on
(21:32):
this and thousands of other topics, is that how stuff
works dot com. Want more how stuff works, check out
our blogs on the house stuff works dot com home
page
Welcome to Stuff from the Science Lab from how stuff
works dot com. You guys, welcome to the podcast. This
is Alison. I don't know if the science editor at
how stuff works dot com. And there is Robert Lamb,
science writer and how stuff works dot com. So, Alison,
(00:23):
have you seen the movie Phantasm? I've not seen it.
It's a nineteen seventies flick, right, yeah, harror flick. You
haven't seen it. I have not, but you've mentioned it before, right, Well, okay,
it's awesome. It's um. I mean it's it's horrible, but
it's awesome. It's um. The basic plot line here is
you have a mortuary where some funny things are happening.
(00:44):
There silver balls flying around, stabbing people in the head. Uh.
And there are these dwarves running around in these little
like I think they're yellow, little yellow robes, okay, like
evil dwarves. Right, And you come to find out that
all of this basically has to do with gravity. There's
a really tall man, like a scary old man. It's
really tall, Okay. And it turns out he's from another
(01:06):
planet where the gravity is more intense, like a larger world. Okay,
so that's why he's taller when he comes to this world, okay,
and the deal with the dwarves, he's taking corpses and
smushing them down, making a more compact and bringing him
back to life a zombies and then sending them to
this other world to be like slaves. All right, So
(01:31):
dwarves are being used as as as zombies. Dwarves are
being used as slave labor on another world where there's
more gravity. And so this all occurs thanks to gravity. Yes,
like it Like for me anyway, as as a kid.
You know, it's like, you know, gravity is, They're great,
but I never think about it. But then somebody comes
along and shows me how gravity is affect you know,
(01:51):
zombie dwarves and uh and it it really you know,
unders it really resonated with me and underlining how amazing
gravity is. I mean, um, like I said, we take
it for granted because it's everywhere, because every pretty much
every physical act on the planet um involves gravity in
somewhere and within another. So that's what we're going to
(02:14):
talk about the day. We're gonna We're gonna basically talk
about four examples um of technologies that utilize gravity in
a way that highlight just how amazing it is. But
of course to do that, we need to talk briefly
about about gravity itself. Now, we have an excellent article
on how Stuff Works dot Com about this um and
(02:36):
I recommend checking that out if you want more details.
But basically, two schools of thought. There's there's Newton Newton's
uh a theory of universal gravitation from back in the
sixt eighties, and this is the idea. The gravity is
a predictable force that acts on all matter in the universe,
(02:56):
and it's a function of both mass and distance. Right. Basically,
each particle of matter attracts every other particle of matter,
all right. Whether we're talking about a great or a
massive sign. Okay, whether we're talking about a spaceship or
I don't know, a dog, everything has gravity, all right.
(03:17):
And if ever, and if the only two things you
had in the universe were a dog and a spaceship,
they would each have a great gravitational pull and it
would be drawn to each other. Okay, um, go ahead.
And then along comes Einstein. Yes, along comes Einstein, and
he says, fooie to this whole dog and spaceship business.
(03:37):
And he says that, he says that gravity isn't even
a force, all right, he's a he's seeing it more
as a distortion in the shape of space time, all right,
as the you know, a distortion in the fourth dimension.
And in Einstein's footsteps. You have some more modern theories
(03:58):
as well, okay, that are less even even less proven.
There's the idea that UM that gravity is due to
little particles called gravitons that that cause objects to be
attracted to one another. And there's another theory that there's
gravitational radiation UM, which which is supposedly the ideas that
gravitational radiation is generated when an object is accelerated by
(04:20):
the external force. Basically, the idea here is that gravity
is is awesome and every day it's mysterious. Um. Basically,
the idea here that it is that as every day
as gravity is, there's a lot we don't know. There's
a lot we don't know about it. It's still kind
of a mystery in many ways. All right. So with that,
let's kick off with four cool things that gravity can
(04:41):
do for you. Yeah, what do you got? What can
gravity do for you? Well, if you listen to our
Fighting Asteroids podcast, we touched on this briefly but gravity
can actually I could save the Earth from being destroyed
by some crazy space rock and always good. Yeah, I
like this. Um, So this thing called a gravity tractor,
and I'm not talking about the the grateful dead cover
(05:03):
band that seems to be located in upstate New York
of the same name. This gravity tractor, actually, um might
have a might have a chance of being built. According
to the BBC, there's this British company by the name
of E. A. D. S Astrium that they finally started
taking concrete steps to make the graph tractor reality. So
it's the graph tractor gonna do it well. It's a
(05:26):
robotic spacecraft weighing roughly ten tons or so, and it
has a has a particularly daunting task. Once it's launched
into space, it has to get within forty eight m
so roughly a hundred fifty feet of the space rocking question.
And once it gets within that range, it has to
pull the rock toward it, and the two of them
march happily off on a path that's not kind of
(05:48):
coincide with the Earth and now in theory though it
could also if you had a New York area jam
band floating in space. It could also use its immense
gravity to to pull them aside as well. Right right,
and I think if you pull the string cheese incident
on there, I mean it could just do crazy winners
with a space rocks headed our way. Um. And the
(06:09):
other chicky thing about the tractors, it's gonna we have
to launched. The other chicky thing about the tractors that
has to be launched fifteen years ahead of time. So
we're kind of we're kind of stuck. This is what
we're relying on right now. So gravity, it can it
can save you from a space rock someday. Perhaps what
else can it do out in space? Well, gravity can
also help you fire a spaceship to some distant corner
(06:31):
of the Solar System. I like the way that sounds. Yeah,
this is something we call gravity assist. Sometimes you see
it referred to as a gravity slingshot, but that's a
little misleading. Um, so just think of it. It's gravity assist,
all right. And to understand that, you need to think
of the Solar System in terms of the Sun's gravity. Well, okay,
(06:52):
imagine a bathtub, all right, It's filled with water and
it has a little boat in it. Okay, you pull
the drain, the water begins to to to go to
to leave the bathtub in the form of a whirlpool.
The little boat is going to be pulled towards the whirlpool,
all right. In the scenario, the Sun is the whirlpool.
It's the object of the most mass and if it
(07:12):
has the most gravitational pool and spacecraft, right, and it's
gonna if it's if the little toy boat is moving
towards the world pool, it's gonna go faster to move
away from the world pool. It has to work harder
and it's going slower. Okay, that's basically the gravity well.
So if we want to send something farther out into
(07:32):
the gravity well, out to one of the outer planets, um,
we need to we need a little help, all right,
and and it and it uh, it's more effective if
we don't have to depend on say, you know, thrusters
and rockets to do all of the work and take
a take advantage of inherent force. Right. So that's where
the gravity assist comes in. And this is a fly
(07:53):
by technique where we can add or subtract momentum to
increase or discrete decrease the energy of a spacecraft. Orbit,
so we've used it. Yes, UM. Take, for for example,
Voyager two launched in um, we flew it by Jupiter.
Will first, just you know, to see Jupiter, that was
one of its mission objectives. But also um, by flying
(08:16):
flying by Jupiter, this provided traject trajectory boost to shoot
it towards Saturn. Now again go back and going back
to the spaceship and the dog. You know, both both
the spaceship and the dog have mass and therefore have
their own gravitational pool. Right, So Voyager two has its
own gravitational pool, as does Jupiter. All right. So when
(08:38):
the spacecraft actually tugs on Jupiter as it goes past,
all right, and actually decreases the planet's orbital momentum by
a tiny amount, very tiny amount. In return, the spacecraft
acquires momentum from Jupiter. Except as we're talking, a significant
amount of momentum, and uh, and it it shoots it
(08:58):
off in this new trajectory. Okay. Uh. One of the
more useful analogies, uh that that you find for this
is imagine a kid standing next to um a train track, okay,
and he has a softball in his hand. The softball
is a spacecraft, all right, And then hurtling down the
train track is a locomotive, al right. The locomotive is Jupiter.
(09:22):
If you were to throw the softball and hit the
front of the coming train, then the softball would would
veer off into another direction with the momentum of the train.
So it's it's very useful for for shooting off any
number of probes UH into into the surrounding Solar system
and uh A lot of people have even looked at
(09:45):
considered possibilities of using it for the future use of
man space spacecraft being able to like use the the
Sun's gravity to shoot an aircraft off to a not
an aircraft, of using the Sun's gravitational poole to um
to shoot a spaceship off towards another system. Have you've
(10:06):
seen Star Trek or any number of science fiction properties,
then you've you've you've heard examples of this, So I'd
say that's a cool thing. Gravity shooting you to a
distant corner of the galaxy. On a more earthly level,
gravity can perhaps let your home someday. And this is
an idea that's been around for quite a while. Back
in the nineteen seventies, there are a bunch of fellows
at the Lawrence Livermore lab who thought we should try
(10:27):
to harness the energy potential of gravity courtesy of black hole.
So this is what they had in mind. You guys,
remember that a black hole forms when this big old
star is dying and it's collapsing inward, and the end
result is this tiny object that's just unspeakably dense. So
the gravitational force of a black hole is large, so
large that not even light can escape it. I know
(10:49):
you guys know this, but let's just reiterate it. So
the idea was, according to these scientists, was well, let's
locate a black hole, well, get it to orbit the Earth.
That's now that that's the point I think where you
just you cancel this plan like that just sounds like
the worst idea ever. Hey, let me just okay, it
gets better, Okay, Okay. So you're gonna get the said
(11:10):
black hole to orbit the Earth with the help of
a spaceship, and once it's in permanent orbit, just you know,
kind of hanging out like black hole does, you're gonna
tap the power of said black hole by firing matter
into it. Okay. So the whole plan is we're going
to go and find the most destructive force in the universe.
We're going to bring it home and then we're going
(11:30):
to feed it. Yes, yes, and then wait, it gets better.
So you know that things get really tiny, as are
you know, hurtling towards their on their death spiral towards
a black hole. Well, all that getting tiny business generates
an amounse amount of energy, and they thought that this
amount of energy could in fact be enough to start
a fusion reaction. So this one, this idea of a
(11:53):
black hole gravity thing, actually never came to fruition. I
think probably the the first point of business was moving
the black hole, or actually maybe even locating black hole
and then moving black hole. So a couple of a
couple of a couple of holes in this plan. Yes,
the latest incarnation of gravity power is a lamp. It's
a little bit simpler and a black hole. No no, no, no, um.
(12:19):
Let me explain. It's conceived of by this grad student
at Virginia Tech, and I think he entered his invention
in some sort of TEO thousand in a green Tech award.
And it's a guy by the name of claymont. Well.
Clay calls his lamp the gravity So conceptually, here's how
Clay's gravity powered lamp works. If you picture kind of
a cylinder shaped floor lamp, maybe about five feet tall. Um,
(12:43):
Now imagine that there are these like five ten pound
brass swats sitting there at the top. And for those
of you guys who don't know what one is, there's
a ball screw in in the in the floor lamp.
And what is the what is ball screw? I had
no idea before I started doing this podcast. Well, it's
a it's a linear screw and um, something rotates downward
on it. So it's kind of like falling on the
(13:05):
ball screw. It's moving downward on the ball screw. And
as these brass weades moved downward on the ball screw,
the screw rotates, and that rotational motion is able to
spin a generator and convert the motion into electricity. So
if you can't quite picture, you can always check out
the illustration. We have a good one on our how
gravity powered lamps were an article. So anyway, this electricity
(13:28):
powers ten led bulbs which light up and whaila you
have light. And do you think, well, how long is
that going to take? Because gravity can happen relatively fast right,
falling objects might be down to the bottom and lamp,
but actually it takes four hours, so that would be
a good amount of light. Would it would work faster
on the the phantasm planet with the dwarves? Sure would, Surewood.
(13:51):
It's also worth noting here that the hour glass is
actually a gravity powered timetelling device. Yeah, and it seems
like a little bit of a simple concept than the
The gravity powered lamp also cuckoo clocks, but are also
worth considering that they're actually powered by black holes. So anyway,
(14:11):
the thing with Poort Clay's lamp is that the d
technology isn't quite where it needs to be, and the
LEDs aren't as efficient as they need to be, and
so that means the weights would have to be much heavier.
And that's about where we are with the gravity powered lamp.
So you cannot buy one at your local lamp star.
It sounds promising, though, I like the idea of gravity
powered electronics. Well, I'll tell you another thing that gravity
(14:35):
can do for us. What gravity can help us understand
what's going on underneath the Earth surface. And how many
do that? Well, think of it this way. Imagine an
appetizer sampler platter. All right, you know it's it's covered
with fried cheese sticks, hush puppies. What are the what's
the meat on the stick called? Oh, chicken settee? Chicken
(14:57):
sette all right, all of idea of different foods. Now,
something late and fluffy too, right? Yeah? Like, well, hush
puppies are lighting fluffy? Right? Well, what's something light and
fluffy do you get as an appetizer? Um, we'll see.
I think that's the thing. Most appetizers, they're so hideously
unhealthy that you get them in small portions first, right, okay,
(15:19):
So imagine something light and fluffy appetizer, but hush puppy.
So so you have all these different items on the plate, right,
and all of them have different densities, okay, which means
and all of them have gravitational pools, all right, And
the more dense the appetizer item, the more gravitational pool
(15:40):
it has. Okay, Okay, all right, Well, our planet is
basically an appetizer platter when it comes to gravity. All right,
there are our planet has is covered with varying densities
of rock. Um, you have you have water that's cold,
you have water that's hot, and of course there's different
(16:01):
tensity there. Um. You know, you look under the Earth,
they're gonna be they're gonna be empty caverns, they're going
to be uh, you know, blocks of solid bedrock. There's
going to be you know, liquid magma. So gravity is
gonna vary according to where are you on there. That's
interesting because I guess I just think of it as
such a constant uniform Yeah. Yeah, we think of it
more as uh, you know, a pizza with a pizza's
(16:24):
worth of you know, of a uniform gravitational pool. But
like if you go up to Hudson Bay in Canada, Um,
the gravity is actually less there. And I need to
stress that it's not not less in the sense that
that you can go to, uh to Hudson Bay and
uh and feel like you lost weight. It's right, You're
not gonna be able to fit in your skinny jeans,
(16:45):
are right. The Earth's gravity is still pretty uniform, um,
all all across the globe, but it varies um to
it to a slight degree um wherever you go. All right,
So um, you know, most people say, well, what does
what does that matter? Right? It matters when you start
looking into fluid dynamics, alright. The ocean, for instance, Um,
(17:09):
you have it dictates the flow of hot and cold water,
all right. I think of it as a topography, okay,
Like if you have a hill next to a plane,
you know water is gonna flow down that hill. All right.
Well you have the same kind of topography going on
across the planet, except in terms of gravity, with fluids
drawn towards the areas of higher gravity. Okay. So we're
(17:33):
very interested in finding out exactly what this uh, this
secret topography looks like. We in fact, we've launched to
um Um orbiting a spacecraft. There's a European Space Agencies
Gravity Field and Steady State Ocean Circulation Explore and this
is up there right now, um, yes, called GHOS. See
(17:54):
that one went up in two thousand nine. And then
there's NASA's Gravity Recovery and Climate experiment that's called Race
and Grace went up in two thousand two. All right, ghost.
These mission has been to take a picture of what
this uh, the secret topography of gravity, which we call
the geode, to take a picture of what that looks
like right at nay moment of time, Like what are
(18:16):
the highs, what are the lows? Uh? Grace has been
looking at how the geo changes, because it's always changing too.
It's not like like you can you know, you'll be
able to go here, and oh, the gravity is always
going to be this, especially when it comes to the ocean.
And why do we care if the geo changes? Because
the more we understand how the ocean transports heat and water,
the more we understand how the ocean moves, And the
(18:38):
more we understand how the ocean moves, the more we
understand how the atmosphere moves. See, it's all a part
of Earth's outer layer of fluid, all right, and that
is where our weather takes place. UM and uh and
you know everything from from fierce hurricanes, two patterns of
drought and uh floods and what have you? All right, UM,
(18:58):
so it helps us a better understanding of global climate.
On a more specific note, UM scientists think it will
be able to look, uh, look at changes in in gravity,
changes in density too, to determined shifts and water mass
caused by droughts or floods. And it will also also
allow us to better understand plate tectonics, UH, seismic activity.
(19:22):
You know, what's what's happening underneath underneath the soil um
in the crust to you know, the leads to two
two earthquakes and uh another phenomena and uh and just
the geological geophysical processes that underlie the the Earth. Sorry,
but it's pretty it's pretty I'm getting a little long
winded here, but it's pretty pretty, pretty awesome, and that's
why we're looking into it. So I hope you've inspired
(19:44):
some reverence for gravity and you besides the kind of
gravity that trips you up and makes you fall flat
on your face and gravity is pretty cool. Um. So
now we would like to take a moment to imagine
a world without gravity. Oh, we were going to talk
about it or just imagine it, because I was just
going to picture it. Yeah. One thing that's really gonna
(20:05):
suck is that all the atmosphere is going to drift
off into space and we're not gonna be able to breathe. Yeah. Also,
I don't think I don't think our hair is gonna
look right. I mean, how do you style your hair
for that? That's true? I mean what kind of products
could could combat that effect? Um? I think that it
(20:25):
would suck if the the oceans boiled away and just
kind of float it off into the void um. On
a more mundane level, I think eating would kind of
pose a number of challenges. Only the astronauts. They'd be
sitting there, happy as you please, eating their dinner out
of their bags. Everybody else would just be in full
freak out mode. Yeah, like trying to run after their
(20:48):
hamburger which had floated off into bun Yeah, and the
chop bits of onion and I'm sorry, catch ups. Just
a globular thing floating out there. Yeah, yeah, that would
be bad. So that would be a world without gravity,
and we hope that we may never encounter it. So
if you want to tell us why you think gravity
is cool or maybe not so cool, send us an
(21:09):
email at science stuff at how stuff works dot com,
or go read about gravity where we're at site. Yeah,
and when you got to check out the blogs where
we handle any number of scientific specs, including zombies from
time to time. Thanks for listening, guys. For more on
(21:32):
this and thousands of other topics, is that how stuff
works dot com. Want more how stuff works, check out
our blogs on the house stuff works dot com home
page
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