07x20 - Light Speed, Docking and Weightlessness

[bunniefuu]

[Dallas] This is
the Science of Stupid in space.

[alarm blares]

For millennia, humankind
has looked to the stars and wondered

and now through space exploration

we travel billions of miles
to seek answers

to our greater scientific mysteries,

but you don't have to go that far,
thanks to this lot.

[man, off-screen] Ohh!

[Dallas] Yes, space science is confusing,

but don't worry, just watch...

as our amateur astronauts
show that much of it

can be learned right here on Earth.

Through their mishaps,

we'll unlock mysteries of the universe

with some help from cosmic principles

such as the rocket launch,

the effect of gravity,

not to mention G force.

It's not rocket science...

it's the Science Of Stupid in space.

[debris whizzing]

[crashing]

In this episode, we'll be
looking at weightlessness,

the speed of light,

and what this has got to do
with docking a space station,

but first this.

[creaks]

There is a planet in our solar system
populated entirely by robots.

Yes, I'm talking about Mars.

NASA has sent four rovers to Mars,

the latest, largest and most capable
is called Curiosity.

Its primary objective is to find out

whether Mars is or was suitable for life,

impressive considering that
even our cutting-edge autonomous robots

aren't yet...

[laughter]

...entirely foolproof.

Right now the Curiosity rover
is roving Mars' landscape

powered by a nuclear generator

and containing a laser
that can vaporize rock.

It's exciting stuff.

To get to Mars takes a journey
of between eight and nine months,

and that's the easy bit.

To reach the surface
requires a combination of parachute,

which relies on the thin atmosphere,
and retrorockets,

which don't.

The mission uses radio relays
via Mars orbiters to control Curiosity,

but due to the distances involved
the delay is about 20 minutes,

so it helps if it can work
somewhat independently.

Curiosity now uses
autonomous navigation or "auto nav"

to calculate the safest path.

Let's for a moment imagine
you'd like to send your own rover to Mars,

what problems would you need to overcome?

Well, your first issue
is getting to the surface.

[man, off-screen] So high.

[Dallas] Three minutes before landing

the space craft uses a parachute,
just like this guy.

-Okay, maybe not exactly like this guy.
-[man, off-screen] Are you all right?

[man, off-screen]
Are you okay?

[Dallas] But the principle is the same,

use what atmospheric
air resistance you can

to slow your descent before landing.

He could have done with
some of those retrorockets.

[man, off-screen] Are you okay?

[Dallas] So, you've managed
that gentle landing,

what's your next issue?

-[man] Oh!
-[man laughs]

[Dallas] It's communication delay.

Thirty five million miles away
means a communication delay

of about 20 minutes,

and even with getting
instant feedback, remote control...

-[man] Oh!
-[man laughs]

[Dallas] ...can be tricky.

Then, of course, you'll need to
negotiate the alien landscape,

Curiosity has
a rocker-bogie suspension system

that's designed to keep
all six of its wheels on the ground.

[man, off-screen] Oh!

[Dallas] You can see
why that would be useful.

[man, off-screen] You all right?

[Dallas] He was all right later.

So many of the advances
made in our effort to explore space

end up helping us down here on Earth,

from smartphone cameras to baby formula,

so that $2.5 billion the rover cost
is already looking like a bargain.

[electricity crackling]

[creaking]

Our exploration of space
has encouraged scientists

to push technology to its known limits
and then beyond.

Advances that have led
from landing on the moon...

[Neil Armstrong over radio]
It's one small step for man...

[Dallas] ...to living in space
in just over 30 years.

Up here everything's just a... a bit odd.

Whether it's
the morning bathroom routine...

or having a spot of lunch.

Yep, there's something distinctly floaty

about life on-board
the International Space Station,

AKA the ISS,

but we all know why, don't we?

There's no gravity, right?

Well, wrong.

The ISS is on average 240 miles from Earth

where gravity is about 90%
of what it is down here,

so why don't they feel it?

Well, the ISS and the astronauts aboard it

experience weightlessness
because they're constantly falling.

To understand how that's all possible

I'm going to ask you to think
of the Space Station as a plastic cup

and the astronauts as the water within it,

and then watch this.

When the cup is held
water pours through the holes

and is accelerated downwards by gravity,

but when the cup's dropped,

it can also accelerate towards the ground

and as the water and the cup
are accelerating at the same speed

the water stays in the cup.

As there are no contact forces
acting in the opposite direction

both water and cup
experience weightlessness

until they reach the ground.

So, gravity accelerates objects
towards the Earth

which can be painful,

but astronauts aboard the ISS are in orbit

and so are effectively falling around
the Earth and cleverly missing it.

[whooping]

When Al from the research team
asked for tickets to a theme park

I was dubious, but I warned him,

"Don't take any valuables."

He didn't listen.

[man, off-screen] Oh, no!

[Dallas] As they go over the hump,
they briefly feel weightlessness

as their downward acceleration
is equal to gravity,

because they're strapped in

they're then accelerated downwards
by the roller coaster,

but the phone isn't.

At least I know why Al's
not been returning my calls now.

This is one of our most
expensive experiments to date

with the final costs
adding up to several... dollars.

It was well worth it.

[screams]

With no contact forces
acting on our researcher,

he achieves a cosmic experience
of weightlessness...

for a bit.

So, that's weightlessness,
great science...

great fun.

[debris whizzing]

[crashing]

Moon buggies remain the most expensive
land vehicle of all time,

and they didn't even go that far.

The first one used
on the Apollo 15 mission

cost in today's money
around $13.5 million a mile,

so not the ideal commuting vehicle.

A more economical option
is the golf buggy,

but what science is this one
about to show us?

[creaks]

We asked you
what space-related science

this golf buggy
was about to demonstrate.

Yes, it's gravitational attraction.

The gravitational attraction
an object exerts depends on its mass,

and as the moon is 81 times
less massive than the Earth,

it has a lot less gravity.

So, this has a lot less impact
on landing...

than this.

[men, off-screen] Ohh!

[debris whizzing]

[crashing]

[Dallas] When searching for who might
have the right stuff to be an astronaut,

space agencies discovered

that you not only
need to be mentally strong

but also physically in good shape.

So, if you want to do this...

you'll need to do an awful lot of this.

Pre-mission training can last 18 months

focusing on a highly functional form
of fitness essential for life in space,

but the exercise doesn't stop
at blast off.

In microgravity, your bones and muscles

no longer have to support
the weight of your body

as they would do on Earth,

as a result you experience loss
in muscle mass and bone density.

Then there's your heart, which weakens

because it doesn't have to work so hard
to counteract gravity

as it pumps blood to the head,

so to help keep in shape

astronauts typically exercise
two hours a day whilst in space.

With the dawn of a new space age upon us,
we thought we'd do our bit

and help out in finding
the next batch of astronauts.

So, where do we start?

Pre-mission prep is focused on
building functional fitness,

kettlebells are great for this,

so does this guy have the right stuff?

[people laughing]

I think that probably
answers that question.

Despite their exercise regimes,
astronauts still lose

about one to two percent
of bone density a month,

so staying in shape up there
is even more important than it is...

-down here.
-[people laughing]

Astronauts use planking
to build core strength.

[screams]

[laughter]

But they prefer not to do it on trains.

During a space walk,
astronauts clench their hands

thousands of times as they loosen
and tighten bolts and screws.

One of the best forms
of terrestrial training for this

is considered to be rock climbing.

[woman, off-screen]
Britney is being awesome.

[Britney] Oh, my God!

[groans]

[Dallas] We can only pray
Britney has dense bones.

[electricity crackling]

[creaking]

Space stations are our
farthest human outposts,

the International Space Station, the ISS,

is an incredible achievement.

The coordinated effort of 15 nations

and the most expensive
single object ever built.

But it's not all good

being in a hermetically sealed container,

all the toilet water
is recycled for drinking.

Don't worry, that's coffee.

Getting astronauts and supplies
up to the ISS is a tricky business,

not surprising when you consider

that it's moving almost
five miles a second.

A joining of two vehicles in space
is called "docking."

To achieve this,
you first need to maintain

a near-zero relative velocity.

What's that?

Well, here comes the science.

Imagine this skateboarder
is one orbiting object

and his board the other,

to successfully dock

his trajectory must intersect
with the path of the other object.

He also needs a relative velocity
of near zero,

achieved here by traveling
at the same horizontal speed

as the other object.

And he's safely docked.

So, it's largely about
controlling relative velocities,

good to know in case
you ever find yourself in a situation

where you need to dock
with a space station.

But will any of this come in useful
down here on Earth?

[man, off-screen]
Chaz on the hard hat challenge.

Go!

[Dallas] Well, yes...

-[Chaz groans]
-[man laughs]

...but not very.

Chaz does get the right trajectory
for his hard hat,

so it's heading in the right direction

but hasn't calculated
the relative velocities, and that...

-[Chaz groans]
-[man laughs]

...is what gives him a headache.

Of course docking is somewhat
harder high above terra firma

where there is a greater range
of possible trajectories,

like this paraglider's and that eagle's.

[eagle squawks]

[paraglider screaming]

The relative velocities of man
and eagle are radically different,

hardly surprising
as neither seems to expect the other,

so when their trajectories intersect...

[eagle squawks]

...it's at a far from
zero relative velocity.

[paraglider screams]

[eagle squawking]

[yells]

Okay, they're still docked,
but don't worry,

our eagle eventually managed to fly free.

-[inaudible]
-Was he all right?

[paraglider] I'm okay.

[Dallas] Good.

In space, the docking process
happens in two stages,

first a soft dock
where the vehicles make initial contact

and then a hard dock
where they lock together

to create an airtight pressurized tunnel.

Soft docking is a very delicate business
which requires minute adjustments.

The last thing you want to do
is jar on contact.

[man screaming]

Yeah, I'd say that was
more of a hard dock.

[creaks]

Okay, time to really mess with your head.

How big is space?

It's difficult to grasp, isn't it?

In galactic terms,
our solar system is tiny

and yet the distance from the sun to Pluto
is just shy of 3.7 billion miles.

To put that into perspective,

if you were cruising
at American highway speeds

it would take you about 6,000 years
to get there...

[men, off-screen] Ohh!

[Dallas] ...or a bit longer
if you were in that car.

[man, off-screen] Oh, my God. Oh, my
God.

[Dallas] That's just the start of it.

The edge of the Oort Cloud

in the furthest reaches
of our solar system

is over nine trillion miles from the sun,

with those distances,
measurements like miles become redundant

so scientists use light instead.

Light travels at 186,282 miles per second,

that's the equivalent of
seven and a half times around the world

in a single second.

Scientists measure distances in space

by how far light travels
in a certain time,

more specifically they use light-years.

And if you're interested
a light-year is 5.9 trillion miles.

It's a weighty concept,

but one that we can shed
a little more light on

with the help of some
high speed activities

right here on Earth.

This car is traveling
at about 190 miles an hour.

You might guess
what's about to happen next

but just be assured the driver was okay...

which is incredible.

In fact he only suffered minor injuries.

Just as incredible is that
he'd have to have been traveling

three and a half million times faster
to achieve the speed of light.

Imagine what that roll
would have looked like.

Okay, this is more like it.

It seems a bit boring,
I know, but watch and listen.

Fortunately that rocket
didn't have anyone onboard.

[expl*si*n]

But did you spot the delay between
seeing the rocket crash back on Earth

and the sound of the expl*si*n?

Because light travels 874,000 times
faster than sound

we see the expl*si*n before we hear it.

In fact, the ten second delay
allows us to calculate

that the rocket was two miles away
when it crashed.

[expl*si*n]

Or what I like to call
a sensible distance.

Right, we know how fast light travels,

but space is so vast
that when you look at the night sky

the light from some of the stars you see

has taken thousands of years
to reach your eyeballs.

To help you understand
the concept, here's Ellen

from our science communications team.

She's not lost her mind,
this is a genuine demo.

[Ellen] Oh!

[Dallas] If we were watching Ellen
smash the light bulb

from 5.9 trillion miles away,

it would be a year
before we saw it go out.

[Ellen] Oh!

[Dallas] Mind you, to see it
in the first place

it would have to be pretty bright.

[electricity crackling]

[creaking]

If gravity depends on mass

and the most massive thing
in the solar system

by a long way is the sun,

then why isn't everything else
pulled into it?

Well, it's all to do
with celestial mechanics.

Celestial mechanics can explain
the great orbital ballet

that is our universe.

The moon orbits the Earth,
the Earth orbits the sun,

and our sun orbits
the center of our galaxy.

In fact, up here pretty much everything
is orbiting something,

the scales are so large

it can seem an overwhelming concept
to get your head around.

So, let's simplify things.

Exactly.

An orbit is basically
a regular repeating path

that one object takes
around another one.

There'll be an extra carrot
in your nose bag tonight.

Now, if he gets it then so can you.

We just need some clear examples
to guide us through the science

and the first step
is to imagine that this is a satellite,

now it could be a man-made satellite
like the International Space Station

or a natural one like the moon.

They're all still satellites,
even when they're tennis ba*ls.

A constant tug of w*r takes place
between a satellite's tendency

to move in a straight line,
what we call momentum,

and the tug of gravity
pulling the satellite back.

Represented here by the string.

When gravity and a satellite's momentum
are in balance

it's always falling towards the planet

but because it's moving sideways
fast enough it never hits it,

so it maintains a stable orbit.

If it doesn't have enough momentum

it'll be pulled down by gravity
and crash into the planet.

And if it gains too much momentum
it will escape from a planet's orbit.

So, you need the perfect amount
of momentum to stay in orbit,

but amazingly
there are thousands of objects

orbiting us right now.

Imagine one of them
as this athlete's hammer.

Okay, it's not a perfect analogy.

The hammer isn't held in orbit by gravity

but by the centripetal force
being provided by the wire

accelerating it in a circle,

but without that centripetal force

momentum means the hammer
carries on in a straight line.

[man, off-screen] Oh.

[Dallas] Let's imagine
that this guy is orbiting Earth,

what would happen if he gained
too much momentum?

[screams]

Yes, that's right.

He'd be going too fast
to be trapped in orbit

and he'd fly off into space.

[screams]

A bit like that.

So, that's orbits, always predictable...

[woman, off-screen] See it now.

[screams]

[Dallas] ...and occasionally painful.

[debris whizzing]

[crashing]

What have we learned?

Well, to truly understand space
you need to understand science.

And Elon Musk put it,
well, slightly differently when he said,

"I would like to die on Mars,
just not on impact."

-[man over radio] Last call...
-[Dallas] That's me.

[man over radio] Ten, nine...

-[man] Oh!
-[man laughs]

[screaming]

[people laughing]

[paraglider screams]

[men, off-screen] Ohh!

[Ellen] Oh!

[screams]

[grunts]

[man, off-screen] Ohh!

[yells]

[neighs]