Transcript for NASA Connect - The Venus Transit


[Jennifer] Hi.

I'm Jennifer Poli, and
welcome to NASA Connect,

the show that connects you to math,

science, technology, and NASA.

Today, we are at NASA
Kennedy Space Center,

on the east coast of Florida.

And behind me is the Vehicle
Assembly Building, or VAB.

This is where NASA
assembles all the components

of the space shuttle system.

Kennedy Space Center is also a
site where NASA launches satellites

that study the Earth
and our solar system.

In fact, the satellite Voyager 1
which was launched right here back

in 1977 is very close to
leaving our solar system.

It's over 13 billion kilometers,
or 8 billion miles, from Earth.

Can you imagine that?

13 billion kilometers?

Whew! It would be hard
to count that high.

Just look at all the digits
that 13 billion represents.

I don't know about you,
but it's hard for me

to imagine just how far a
way 13 billion kilometers is.

I mean, how large
is the solar system?

It would probably
make more sense to us

if we could see a scale
model of the solar system.

This would give a
better understanding

of how far away Voyager
1 or the other planets

in the solar system are from Earth.

The focus of today's program is
to learn why we use a scale model

to determine the size
and distance of objects

in our solar system and beyond.

In order to learn how to
scale the solar system,

we must first understand
the concept of scaling.

During the course of the
program, you will be asked

to answer several
inquiry based questions.

After the questions
appear on the screen,

your teacher will cause the
program to allow you time to answer

and discuss the questions.

This is your time to explore
and become critical thinkers.

Students working in
groups, take a few minutes

to answer the following questions.

What does it mean to scale?

Why is it sometimes necessary
to use scale models or drawings?

List some math terms associated
with scale models or drawings.

It's now time to pause the
program and answer the questions.

A scale model or drawing is
used to represent an object

that is too large or too small to
be drawn or built at actual size.

The scale gives the ratio of
the measurements in the model

or drawing to the measurement
of the actual object.

Remember guys, a ratio is
a fraction that is used

to compare the size of
two numbers to each other.

Let's look at an example.

One of the most common types
of scale drawings is a map.

Maps are very useful when planning
a trip, but it is across town

or across the country.

Norbert and Za are
planning to drive

from NASA Kennedy Space
Center to Washington, DC.

Norbert wants to estimate the
distance he and Za will travel.

The scale in Norbert's map
reads 1 cm equals 100 km.

How can he estimate the distance
in kilometers from the space Center

to Washington, DC,
using the given scale?

The scale can be written as
the fraction 1 cm over 100 km.

The first number, 1 cm,
represents the map distance.

And the second number, 100 km,
represents the actual distance.

First, using a metric
ruler and the given a map,

measure the linear distance

from Kennedy Space
Center to Washington, DC.

In Norbert, this distance is
approximately 13 1/2 centimeters.

Now we have all the information
we need to set up our proportion.

Remember guys, I proportion
is a pair of equal ratios.

The first ratio is
of the map scale.

And the second ratio
is the distance

from Kennedy Space
Center to Washington, DC.

Let's set these two
ratios equal to each other.

N represents the distance that
we are trying to calculate.

This proportion can be
read as 1 cm is to 100 km

as 13 1/2 centimeters
is to N kilometers.

In a proportion, the cross products
of the two ratios are equal.

In other words, the product of
the top value from the first ratio

and the bottom value from
the second ratio is equal

to the product of the top
value of the second ratio

and the bottom value
from the first ratio.

We can write the cross product

as 1 cm times N km equals 100
km times 13 1/2 centimeters.

Using multiplication, Norbert
calculated the actual distance

between the Kennedy Space
Center at Washington,

DC to be about 1350 km.

Students, here is an important
point for you to remember.

Proportions often include
different units of measurement.

Units must be the same
across the top and bottom

or down the left and right sides.

If the units only match diagonally,

then the ratios do
not form a proportion.

So guys are you still
having trouble trying

to understand scaling?

OK, let's look at another example.

This time, using a scale model.

Right behind me is a
replica of the space shuttle.

And this right here?

This is a scale model
of the space shuttle.

The actual space shuttle
has a length of 37.2 m,

a height of 17.3 m, and
a width or wing span

of 23.8 m. Now the shuttle
model is a 1:100 scale

of the actual space shuttle.

Now that is 1 m equals 100
m. So using that scale,

let's set up a proportion
to calculate the length

of the space shuttle model.

The first ratio is the model scale.

And the second ratio is
the length of the model

to the actual shuttle length.

N represents the length
of the shuttle model.

We set these two ratios
equal to each other.

Now remember, in a
proportion, the cross products

of the two ratios are equal.

We write the cross products

as 1 m times 37.2 m equals
100 m times N meters.

Dividing 37.2 x 100 gives us
the length of the shuttle model,

which is 0.3 72 m, or
approximately 14 1/2 inches.

That wasn't too bad, was it?

Do you think you can handle
the other two dimensions?

So now it's your turn to calculate
the height, and the width,

or wing span, of the shuttle
model, using the given scale.

Remember, the height of the actual
shuttle is 17.3 m. The width

or wing span is 23.8 m. And the
scale is 1 m equals 100 m. It's now

time to pause the program
to calculate the height

and width of the shuttle model.

So guys, how did you do?

Let's check your answers with mine.

Earlier, we calculated the
length of the shuttle model

to be 0.372 m. I calculated the
height of the model to be 0.1 73 m,

or approximately 7 inches.

And the width or wing
span to be 0.2 38 m,

or approximately 9 1/2 inches.

Did you get the same answers?

If you did, great job.

And if you didn't,
don't be discouraged.

Just go back and checked
over your work carefully.

Make sure you set
up your proportions

and multiplied correctly.

You know, scientists and
engineers learned a great deal

from making mistakes.

Now that you have a better
understanding of scaling,

let's turn our attention to
the focus of today's program,

which is scaling the solar system.

Dr. unclear, an astronomer
and scientist

at NASA's Goddard space
flight Center, has the scoop.

[Stan] Thanks, Jennifer.

When we talk about the differences
between points of interest,

we instinctively use the
units that make sense

to us and our convenient.

For example, what unit
of measure would you use

to describe the distance
from Washington,

DC to Los Angeles, California?

Would you use miles, inches,
kilometers, or meters?

What about your height?

Would you measure it
in inches or feet?

And how about the width
of your classroom?

Do you use kilometers,
meters, or feet?

You can use any unit of measure you
wish, as long as it's convenient

for everyone to understand.

When describing distances of
the scale of the solar system,

even units like miles and
kilometers lead to numbers that are

in the millions or the billions,

and that makes it very
hard to understand them.

For example, the distance
between the Earth and the sun is

about 149 million kilometers.

Between the Sun and Pluto,
this is about 5.9 billion km.

But suppose we wanted to
compare these two numbers.

It's not easy to see that
Pluto is about 40 times as far

from the sun as birthdays.

It would make sense to use
a smaller scale in order

to get a better idea of the
distances between the planets.

To come up with that scale,
we have to define a baseline.

The baseline that
astronomers use is the distance

between the Earth and the sun.

This distance is known
as the astronomical unit.

The astronomical unit or
AU represents the distance

between the Earth and the sun,
which is about 93 million miles.

The astronomical unit is the
baseline that astronomers use

to determine the distances to
the planets in our solar system

and to the stars beyond.

So let's have a look at the
scale of the solar system

where one astronomical unit
equals 93 million miles.

Based on the astronomical unit,
it's easy to compare the distances

between all the other
objects in the solar system.

The accompanying chart shows
the distances to the planets

from the sun in terms
of astronomical units.

Let's look at Mars.

We can quickly see that Mars is
one of a half times further away

from the sun and Earth is.

So how far is Mars
from the sun in miles?

Remember the process and Jennifer
demonstrated earlier in the program

to solve problems
involving scaling?

We can solve the Mars distance
problem using a proportion.

The first ratio is the scale,

and the second ratio is the
distance of Mars to the sun.

And Miles represents the
distance from Mars to the sun.

After setting these two
ratios equal to each other,

let's find the cross products.

The equation becomes one times
N equals 93 million times 1.52.

Multiplying, we get the
distance from Mars to the sun

to be approximately
141 million miles.

Using the astronomical
unit instead of a mile

or the kilometer makes it
easier to compare the distances

between the planets and the sun.

For example, it's easier to
remember that Mars is one

of the half times further away
from the sun than the Earth

than it is to remember that it's
48 million miles further away

from the sun than the earth.

If you recall from
earlier in the program,

the Voyager spacecraft
is 8 billion miles

or 13 billion km from the earth.

It's at the far edge of our
solar system, ready to head

out into interstellar space.

Based on what you've learned about
scaling and the astronomical unit,

can you estimate the distance
of a Voyager 1 from the earth

in astronomical units?

Working with a partner,
take a few minutes and see

if you can solve this problem.

Voyager 1 is over 8 billion
miles away from Earth.

Estimate how far in astronomical
units Voyager 1 is from the earth.

Remember the scale is one
astronomical unit equals 93

million miles.

Teachers, you may
now pause the program

so students can answer the problem.

OK, so what did you come up with?

If you said that Voyager was
86 astronomical units away

from the earth, you're correct.

Do you have a sense
for how far that is?

The planet Pluto is 40 astronomical
units away from the earth.

So that means that Voyager is
twice as far away from the earth

than the planet Pluto.

Suppose that Voyager 1 were
stationary, and you were able

to ride in a car traveling
at 55 mph to get to it.

The trip would take you
over to 16,000 years,

just to reach the satellite.

That would be quite a lengthy
and expensive vacation.

Jennifer, I think the
students are ready

for that hands-on activity now.

Could you send them back to
me when I you're finished?

I have a real tough
question for them to answer.

[Jennifer] Thanks, Stan.

We'll get back to you a
little later in the program.

But first, students from Brewster
Middle School at Camp Lejeune,

North Carolina, will preview
this program's hands-on activity.

[Voices] Hi.

NASA Connect has asked us
to show you this program's

hands-on activity.

In this activity, you will
use graphing, measurement,

and ratios to construct a
scale model of the solar system

and relate each planet to the sun.

And you will explore the skills
needed to represent the size

of the planets and the
distances to the sun.

You can download a copy

of the educator guide containing
directions and a materials list

from the NASA Connect web site.

Working in groups, students
will complete the activity

by using a scale model chart
and the planet templates.

Each group will be
a signed a planet.

Cut out your assigned planet
using the planet template.

The scale for this activity
is one toilet paper sheet

equals 30,102,900 km.

Using the scale, students complete
column 4 in the scale model chart.

Remember the math concepts you
learned earlier in the program?

This is your chance to put
your math skills to the test.

Next, you will complete column
5 on the scale model chart.

The scale needed to
complete this column is 1 AU

or astronomical unit equals
five toilet paper sheets.

Groups should check
each other's work

to make sure all values
are correct.

After completing the scale model
chart, each group should roll

out the number of toilet
paper sheets needed

for it is signed planet.

Now it's time to head
to the staging area.

This could be in a gym,
hallway, or even outside.

Place the sun in a
central position.

Students, attach your pre-measured
toilet paper strip to the sun.

And let it extend outward
in various directions.

Don't forget to tape your assigned
planet on the end of the strip.

You will need about 23 m or
75 feet in one direction.

Based on your solar system
model, you'll be asked

to answer several critical
thinking questions.

Graphing is a great way to
visually represent data.

Each group will construct

and analyzed two graphs using
an appropriate type of grass

and scale of your choice.

Be careful with the type
of graphs you choose.

Don't forget to check out the
Web activity for this program.

You can download it from
the NASA Connect web site.


[Jennifer] Great job,
Brewster Middle School.

OK. Now that you guys
have a preview

of this program's hands-on
activity, now it's time

to pause the program and see

if you can construct a scale
model of the solar system.

So, how was the activity?

Hopefully, it helped reinforce the
math concepts you learned earlier

in this program.

Now, let's review.

In the beginning of the program,
we talked about the importance

of scaling, especially when
it comes to maps and models.

You learned that fractions,
decimals, ratios,

and proportions are all
important math concepts

when in dealing with scales.

Stan introduced you to the
astronomical unit, the unit used

to scale the solar system.

Later in the program, I have an
interesting challenge for you.

But before we get to that, Stan
has a few more questions for you.

Let's head back to stand
now, and learn more

about scaling the solar system.

[Stan] Hey, it's great
to have you back.

In the last segment, we introduced
scale of the solar system

and the astronomical unit.

Believe it or not, astronomers once
knew only what the distances were

in astronomical units,
not an actual miles.

Recall the following chart,
that shows the distance

of the planet to the sun.

Between 1609 and 1619,

the astronomer Johannes Kepler
used precise measurements

of the planets in the sky
to determine their orbits.

But his geometric model was based
on the scale of the Earth's orbit,

not in its actual diameter
in a kilometers or miles.

He determined the ratio of
the distance of each planet

to the sun relative to
Earth's distance to the sun.

His baseline unit, the
distance from Earth to the sun,

was designated as exactly 1
AU, or one astronomical unit.

The problem is that Kepler could
not accurately determine the

distance between the
Earth and the sun.

The best estimates that at that
time ranged from 50 million miles

to over 200 million miles.

But by the 1890s, as farmers began
to know that number very precisely.

How did scientists, without
modern space technology

and rockets, do this?

You can't just send a
spacecraft to the sun and back

to determine the distance.

Human life, including
Norbert and Za,

could survive the intense
heat produced by the sun.

So the question for this segment of
the program is how did we determine

that the earth is 93 million miles

or 149 million kilometers
from the sun?

This would be a good
time to pause the program

and discuss the question with
your teacher and your peers.

So, did you come up
with any good ideas?

If you didn't, don't
worry about it.

After all, it took
astronomers about 2000 years

to figure out how to do it.

The answer is that astronomers
used a geometric technique called

parallax to determine the distance
between the Earth and the sun.

Parallax is the apparent change of
position of an object when you look

at it from two different
stations or points of view.

It sounds mysterious, but we
use this technique all the time.

For example, let me show you how
parallax works by using my thumb

and that rocket in the background.

First, hold your thumb
out at arm's length.

Now look at your thumb
with your left eye open

and your right eye closed.

What do you notice about
the position of your thumb?

There seems to be an apparent
change in position of your thumb

from two points of view.

Your left eye and your right eye.

Your brain uses this
information to figure

out how far away things
are from you.

Actual parallax calculations
can be quite complicated,

but here's an example of how
we can determine the distance

to that rocket using many of
the same geometric principles.

Suppose we wanted to
approximate the distance

between where I'm standing right
here and that rocket over there.

And suppose also that there
was a body of water in between

that we couldn't get across.

Would you believe that we could
do that by just using a pencil,

a piece of paper, a ruler, a
piece of rope, and a protractor?

The first thing we do is to
lay a rope in a straight line.

The rope will serve as our
baseline, and is 10 m in length.

Standing on the left
end of the rope,

which we will call position
A, hold the protractor

so that it is parallel
to the baseline.

Place the pencil on the
inside of the protractor,

and move it along the curve until
it lines up with the object.

Being careful not to move your
pencil, have a partner read

and record the angle measurement.

You then need to repeat
the same procedure

on the other side of the rope.

We will call this position B. We
now have to angle measurements

and our baseline measurement,
which is 10 m,

the length of our rope.

In a sheet of paper a long the
bottom, we draw a line 10 cm long

to represent our baseline.

For this exercise, let the
scale be 1 m equals 1 cm.

Mark one end of the drawn line
as point A, and the other end

as point B. Using our protractor
at point A, we measure an angle

that is the same number of degrees
as the angle measured outside

for point A. Let's mark
and draw the angle.

At point B, we do the same thing.

Now measure an angle that is the
same number of degrees as the angle

that we measured outside
for point B. As you can see,

the two lines intersect.

We mark the point of intersection

as point C. Now we draw a line
perpendicular form point C

to the baseline.

Using our metric ruler, we
can measure the distance

of this perpendicular line.

Finally, using the scale
of 1 m equals 1 cm,

we can approximate the
distance the actual object was

from the baseline.

For our case, the object
is approximately 20 m away.

In this example, we used a
geometric technique called

triangulation, which assumes
that we know the baseline length

and the two bit angles.

When astronomers use parallax,

they measure the baseline
length and the vertex angle.

It is hard to use the parallax
method in the classroom

because you can't measure
the vertex angle exactly.

With proper measuring technology,

this is not a problem
for astronomers.

To refine the actual sun/Earth
distance, parallax observations

of the transit of Venus were
made between 1761 and 1882.

The transit of Venus occurs
whenever the planet Venus passes

in front of the sun, as
viewed from the earth.

But observing the apparent
shift in position of Venus,

against the background
of the solar disk as seen

from two different places on
earth, astronomers were able

to use the parallax shift
to determine the distance

from the earth to the sun.

The last Venus transit occurred in
1882, and we are fortunate enough

to have another transit of Venus
happening on Tuesday, June 8, 2004.

This is an historic event
because no one alive today was

around when the last one occurred.

To learn more about the transit of
Venus, let's visit Dr. Janet Lerman

at the University of
California's space science lab

in Berkeley, California.

[Dr. Lerman] Venus transit occurs
when Venus crosses the disc

of the sun as seen by an observer.

It's like a solar eclipse in
that Venus is located on the line

between the sun and the earth,

and therefore blocks
some of the sun's light.

However, in a Venus transit,

the sunlight blocked is very
small compared to a solar eclipse.

And so the observer who is
unaware will never notice it.

Venus's circular shadow is much,

much smaller than
our moon's shadow.

Even though Venus is nearly
the size of the earth,

it is much farther
away than the moon.

In clear weather, Venus transits
are visible with the naked eye

or with a small telescope,

which is why they became
popular in the 1600s.

Before the advent of radar,
Venus transits were used mainly

for the measurement of
the astronomical unit,

or the Sun/Earth distance,
as you've heard earlier.

The biggest activities surrounding
the June 2004 Venus transit will be

the International Network
of Amateur Astronomers.

These astronomers will
measure the astronomical unit

with the Venus transit using
the same techniques as used

by the early observers.

An innovative aspect of this time,
however, not available in 1882,

is the widespread
use of the Internet

to organize international

and the ease of access
to the tools needed

to make the parallax calculations.

There also will be a few
astronomical researchers

who will try to exploit
state-of-the-art observing tools

to see what can be learned
about these transits

to investigate planets
around other stars.

Transits are currently being
used to search for such planets.

Perhaps this Venus transit
will lead to some new technique

or measurements that will
allow future researchers

to further study the terrestrial
planets during long-range

planet finding missions.

The Venus transit will
also serve to remind us

of Earth's place in the cosmos.

The tiny dot crossing the solar
disc is a terrestrial planet

with an atmosphere, and yet
it is far from an Earth.

Venus was once called a twin earth,
in part because of its similar size

and distance from the sun.

It is now known to be a place
that is extremely hostile to life

for reasons that are
still under study.

One can speculate how our
own pale blue dot would look

to some distant alien astronomer
as it passed across the sun

in transit, and whether it
has ever been so observed.

Maybe one day humans will be able
to observe the earth transit.

To learn more about the planet
Venus, and the Venus transit,

check out the sun/Earth connection
education forum web site.

Take it away, Jennifer.

[Jennifer] They say you learn
something new every day.

And I sure did.

I had never heard
of transits before.

And how astronomers and
scientists used them

to determine the astronomical unit.

Thanks, Janet.

OK, guys. Remember
earlier in the program

when I said I had an
interesting challenge for you?

Well, it's now time for
scaling the solar system.

Now, the astronomical unit or a
you currently in use is derived

from the average mean distance
between the Earth and the sun.

Which is approximately
93 million miles.

Working in groups, your
task is to make a proposal

that uses the average mean
distance between the sun

and another planet in our
solar system as the basis

for determining the
astronomical unit.

In other words, is there a
better baseline distance to use,

rather than the Sun/Earth baseline?

What about using a Sun/Jupiter
baseline or a Sun/Pluto baseline?

You choose another planet, you
will have to recalculate the scale

of the solar system using
your new chosen baseline.

And then explain why your new
baseline is a better choice

than the Sun/Earth baseline.

What are the advantages and
disadvantages to your new scale?

Detailed instructions
and tips on how

to make your proposal
can be located

at the NASA Connect web site.

From the web site, we encourage
you to submit your proposal.

Your proposal will
be seen by millions

of students across the country.

We look forward to
your some medals.

Well, guys, that wraps up
another episode of NASA Connect.

I hope you have a better
understanding of how

and why astronomers and
scientists use scale models

of the solar system.

We'd like to thank everyone who
helped make this program possible.

Got a comment, question,
or suggestion?

Well, then e-mail them

Or pick up a pen and mail them to
NASA Connect, NASA Langley Center

for Distance Learning, NASA
Langley Research Center,

Mail Stop 400, Hampton,
Virginia, 23681.

So until next time,
stay connected to math,

science, technology, and NASA.

Bye from sunny Florida.