Transcript for NASA Connect - The Venus Transit

[00:00:40.918]
[Music]

[00:00:40.948]
[Jennifer] Hi.

[00:00:41.418]
I'm Jennifer Poli, and
welcome to NASA Connect,

[00:00:44.348]
the show that connects you to math,

[00:00:46.728]
science, technology, and NASA.

[00:00:49.798]
Today, we are at NASA
Kennedy Space Center,

[00:00:52.308]
on the east coast of Florida.

[00:00:53.508]
And behind me is the Vehicle
Assembly Building, or VAB.

[00:00:57.248]
This is where NASA
assembles all the components

[00:01:00.778]
of the space shuttle system.

[00:01:02.488]
Kennedy Space Center is also a
site where NASA launches satellites

[00:01:06.478]
that study the Earth
and our solar system.

[00:01:09.138]
In fact, the satellite Voyager 1
which was launched right here back

[00:01:13.188]
in 1977 is very close to
leaving our solar system.

[00:01:17.238]
It's over 13 billion kilometers,
or 8 billion miles, from Earth.

[00:01:22.198]
Can you imagine that?

[00:01:24.038]
13 billion kilometers?

[00:01:26.328]
Whew! It would be hard
to count that high.

[00:01:28.648]
Just look at all the digits
that 13 billion represents.

[00:01:36.438]
I don't know about you,
but it's hard for me

[00:01:39.028]
to imagine just how far a
way 13 billion kilometers is.

[00:01:43.718]
I mean, how large
is the solar system?

[00:01:47.668]
[00:01:49.648]
It would probably
make more sense to us

[00:01:51.708]
if we could see a scale
model of the solar system.

[00:01:57.568]
This would give a
better understanding

[00:01:59.768]
of how far away Voyager
1 or the other planets

[00:02:03.088]
in the solar system are from Earth.

[00:02:05.928]
[00:02:07.188]
The focus of today's program is
to learn why we use a scale model

[00:02:11.528]
to determine the size
and distance of objects

[00:02:14.618]
in our solar system and beyond.

[00:02:16.938]
In order to learn how to
scale the solar system,

[00:02:19.578]
we must first understand
the concept of scaling.

[00:02:22.498]
During the course of the
program, you will be asked

[00:02:24.838]
to answer several
inquiry based questions.

[00:02:27.508]
After the questions
appear on the screen,

[00:02:29.608]
your teacher will cause the
program to allow you time to answer

[00:02:33.168]
and discuss the questions.

[00:02:34.698]
This is your time to explore
and become critical thinkers.

[00:02:38.358]
Students working in
groups, take a few minutes

[00:02:41.208]
to answer the following questions.

[00:02:43.368]
What does it mean to scale?

[00:02:46.098]
[00:02:47.148]
Why is it sometimes necessary
to use scale models or drawings?

[00:02:51.918]
[00:02:53.018]
List some math terms associated
with scale models or drawings.

[00:02:58.218]
It's now time to pause the
program and answer the questions.

[00:03:02.318]
A scale model or drawing is
used to represent an object

[00:03:06.818]
that is too large or too small to
be drawn or built at actual size.

[00:03:13.288]
The scale gives the ratio of
the measurements in the model

[00:03:16.908]
or drawing to the measurement
of the actual object.

[00:03:21.088]
Remember guys, a ratio is
a fraction that is used

[00:03:25.288]
to compare the size of
two numbers to each other.

[00:03:28.398]
Let's look at an example.

[00:03:30.388]
One of the most common types
of scale drawings is a map.

[00:03:33.638]
Maps are very useful when planning
a trip, but it is across town

[00:03:37.438]
or across the country.

[00:03:39.288]
Norbert and Za are
planning to drive

[00:03:41.478]
from NASA Kennedy Space
Center to Washington, DC.

[00:03:44.708]
Norbert wants to estimate the
distance he and Za will travel.

[00:03:49.158]
The scale in Norbert's map
reads 1 cm equals 100 km.

[00:03:53.948]
How can he estimate the distance
in kilometers from the space Center

[00:03:59.428]
to Washington, DC,
using the given scale?

[00:04:02.518]
The scale can be written as
the fraction 1 cm over 100 km.

[00:04:08.568]
The first number, 1 cm,
represents the map distance.

[00:04:13.208]
And the second number, 100 km,
represents the actual distance.

[00:04:18.968]
First, using a metric
ruler and the given a map,

[00:04:22.438]
measure the linear distance

[00:04:24.088]
from Kennedy Space
Center to Washington, DC.

[00:04:26.598]
In Norbert, this distance is
approximately 13 1/2 centimeters.

[00:04:33.968]
Now we have all the information
we need to set up our proportion.

[00:04:38.238]
Remember guys, I proportion
is a pair of equal ratios.

[00:04:43.238]
The first ratio is
of the map scale.

[00:04:46.178]
And the second ratio
is the distance

[00:04:48.688]
from Kennedy Space
Center to Washington, DC.

[00:04:52.258]
Let's set these two
ratios equal to each other.

[00:04:56.428]
N represents the distance that
we are trying to calculate.

[00:05:00.448]
This proportion can be
read as 1 cm is to 100 km

[00:05:06.508]
as 13 1/2 centimeters
is to N kilometers.

[00:05:11.398]
In a proportion, the cross products
of the two ratios are equal.

[00:05:16.888]
In other words, the product of
the top value from the first ratio

[00:05:22.198]
and the bottom value from
the second ratio is equal

[00:05:26.938]
to the product of the top
value of the second ratio

[00:05:31.118]
and the bottom value
from the first ratio.

[00:05:34.358]
We can write the cross product

[00:05:36.158]
as 1 cm times N km equals 100
km times 13 1/2 centimeters.

[00:05:44.808]
Using multiplication, Norbert
calculated the actual distance

[00:05:48.618]
between the Kennedy Space
Center at Washington,

[00:05:51.048]
DC to be about 1350 km.

[00:05:55.738]
Students, here is an important
point for you to remember.

[00:05:59.408]
Proportions often include
different units of measurement.

[00:06:03.718]
Units must be the same
across the top and bottom

[00:06:08.388]
or down the left and right sides.

[00:06:11.918]
If the units only match diagonally,

[00:06:14.938]
then the ratios do
not form a proportion.

[00:06:18.608]
So guys are you still
having trouble trying

[00:06:20.578]
to understand scaling?

[00:06:22.138]
OK, let's look at another example.

[00:06:24.758]
This time, using a scale model.

[00:06:27.208]
Right behind me is a
replica of the space shuttle.

[00:06:29.778]
And this right here?

[00:06:31.028]
This is a scale model
of the space shuttle.

[00:06:33.178]
The actual space shuttle
has a length of 37.2 m,

[00:06:37.808]
a height of 17.3 m, and
a width or wing span

[00:06:45.418]
of 23.8 m. Now the shuttle
model is a 1:100 scale

[00:06:52.098]
of the actual space shuttle.

[00:06:53.848]
Now that is 1 m equals 100
m. So using that scale,

[00:06:59.508]
let's set up a proportion
to calculate the length

[00:07:02.738]
of the space shuttle model.

[00:07:04.938]
The first ratio is the model scale.

[00:07:07.438]
And the second ratio is
the length of the model

[00:07:10.418]
to the actual shuttle length.

[00:07:13.078]
N represents the length
of the shuttle model.

[00:07:16.548]
We set these two ratios
equal to each other.

[00:07:19.998]
Now remember, in a
proportion, the cross products

[00:07:23.488]
of the two ratios are equal.

[00:07:26.418]
We write the cross products

[00:07:28.018]
as 1 m times 37.2 m equals
100 m times N meters.

[00:07:37.018]
[00:07:37.088]
Dividing 37.2 x 100 gives us
the length of the shuttle model,

[00:07:42.658]
which is 0.3 72 m, or
approximately 14 1/2 inches.

[00:07:47.398]
That wasn't too bad, was it?

[00:07:49.318]
Do you think you can handle
the other two dimensions?

[00:07:52.248]
So now it's your turn to calculate
the height, and the width,

[00:07:59.448]
or wing span, of the shuttle
model, using the given scale.

[00:08:03.398]
Remember, the height of the actual
shuttle is 17.3 m. The width

[00:08:09.218]
or wing span is 23.8 m. And the
scale is 1 m equals 100 m. It's now

[00:08:18.218]
[00:08:18.768]
time to pause the program
to calculate the height

[00:08:22.038]
and width of the shuttle model.

[00:08:24.508]
So guys, how did you do?

[00:08:25.798]
Let's check your answers with mine.

[00:08:29.508]
Earlier, we calculated the
length of the shuttle model

[00:08:33.268]
to be 0.372 m. I calculated the
height of the model to be 0.1 73 m,

[00:08:40.758]
or approximately 7 inches.

[00:08:43.498]
And the width or wing
span to be 0.2 38 m,

[00:08:48.548]
or approximately 9 1/2 inches.

[00:08:50.868]
Did you get the same answers?

[00:08:52.508]
If you did, great job.

[00:08:54.148]
And if you didn't,
don't be discouraged.

[00:08:56.818]
Just go back and checked
over your work carefully.

[00:08:59.608]
Make sure you set
up your proportions

[00:09:01.758]
and multiplied correctly.

[00:09:04.118]
You know, scientists and
engineers learned a great deal

[00:09:07.338]
from making mistakes.

[00:09:09.008]
Now that you have a better
understanding of scaling,

[00:09:11.638]
let's turn our attention to
the focus of today's program,

[00:09:14.388]
which is scaling the solar system.

[00:09:17.208]
Dr. unclear, an astronomer
and scientist

[00:09:19.978]
at NASA's Goddard space
flight Center, has the scoop.

[00:09:23.398]
[00:09:25.668]
[Stan] Thanks, Jennifer.

[00:09:26.478]
When we talk about the differences
between points of interest,

[00:09:29.658]
we instinctively use the
units that make sense

[00:09:31.598]
to us and our convenient.

[00:09:33.278]
For example, what unit
of measure would you use

[00:09:36.078]
to describe the distance
from Washington,

[00:09:37.678]
DC to Los Angeles, California?

[00:09:40.198]
Would you use miles, inches,
kilometers, or meters?

[00:09:44.428]
What about your height?

[00:09:45.988]
Would you measure it
in inches or feet?

[00:09:48.738]
And how about the width
of your classroom?

[00:09:50.918]
Do you use kilometers,
meters, or feet?

[00:09:54.188]
You can use any unit of measure you
wish, as long as it's convenient

[00:09:57.948]
for everyone to understand.

[00:09:59.848]
When describing distances of
the scale of the solar system,

[00:10:02.598]
even units like miles and
kilometers lead to numbers that are

[00:10:05.578]
in the millions or the billions,

[00:10:07.258]
and that makes it very
hard to understand them.

[00:10:09.818]
For example, the distance
between the Earth and the sun is

[00:10:12.928]
about 149 million kilometers.

[00:10:15.778]
Between the Sun and Pluto,
this is about 5.9 billion km.

[00:10:20.668]
But suppose we wanted to
compare these two numbers.

[00:10:23.748]
It's not easy to see that
Pluto is about 40 times as far

[00:10:27.098]
from the sun as birthdays.

[00:10:29.278]
It would make sense to use
a smaller scale in order

[00:10:32.718]
to get a better idea of the
distances between the planets.

[00:10:35.718]
To come up with that scale,
we have to define a baseline.

[00:10:38.648]
The baseline that
astronomers use is the distance

[00:10:41.138]
between the Earth and the sun.

[00:10:43.068]
This distance is known
as the astronomical unit.

[00:10:45.998]
The astronomical unit or
AU represents the distance

[00:10:49.748]
between the Earth and the sun,
which is about 93 million miles.

[00:10:53.858]
The astronomical unit is the
baseline that astronomers use

[00:10:57.028]
to determine the distances to
the planets in our solar system

[00:11:00.208]
and to the stars beyond.

[00:11:02.138]
So let's have a look at the
scale of the solar system

[00:11:04.678]
where one astronomical unit
equals 93 million miles.

[00:11:08.388]
Based on the astronomical unit,
it's easy to compare the distances

[00:11:11.608]
between all the other
objects in the solar system.

[00:11:14.458]
The accompanying chart shows
the distances to the planets

[00:11:16.938]
from the sun in terms
of astronomical units.

[00:11:20.178]
Let's look at Mars.

[00:11:21.758]
We can quickly see that Mars is
one of a half times further away

[00:11:24.898]
from the sun and Earth is.

[00:11:26.918]
So how far is Mars
from the sun in miles?

[00:11:30.218]
Remember the process and Jennifer
demonstrated earlier in the program

[00:11:33.188]
to solve problems
involving scaling?

[00:11:35.728]
We can solve the Mars distance
problem using a proportion.

[00:11:39.118]
The first ratio is the scale,

[00:11:41.068]
and the second ratio is the
distance of Mars to the sun.

[00:11:44.598]
And Miles represents the
distance from Mars to the sun.

[00:11:48.598]
After setting these two
ratios equal to each other,

[00:11:50.858]
let's find the cross products.

[00:11:52.858]
The equation becomes one times
N equals 93 million times 1.52.

[00:11:59.768]
Multiplying, we get the
distance from Mars to the sun

[00:12:02.438]
to be approximately
141 million miles.

[00:12:06.258]
Using the astronomical
unit instead of a mile

[00:12:08.768]
or the kilometer makes it
easier to compare the distances

[00:12:11.528]
between the planets and the sun.

[00:12:13.458]
For example, it's easier to
remember that Mars is one

[00:12:16.178]
of the half times further away
from the sun than the Earth

[00:12:19.048]
than it is to remember that it's
48 million miles further away

[00:12:21.978]
from the sun than the earth.

[00:12:24.118]
[00:12:25.608]
If you recall from
earlier in the program,

[00:12:27.498]
the Voyager spacecraft
is 8 billion miles

[00:12:29.958]
or 13 billion km from the earth.

[00:12:32.578]
It's at the far edge of our
solar system, ready to head

[00:12:35.158]
out into interstellar space.

[00:12:37.768]
Based on what you've learned about
scaling and the astronomical unit,

[00:12:41.148]
can you estimate the distance
of a Voyager 1 from the earth

[00:12:43.798]
in astronomical units?

[00:12:45.908]
Working with a partner,
take a few minutes and see

[00:12:48.118]
if you can solve this problem.

[00:12:49.618]
Voyager 1 is over 8 billion
miles away from Earth.

[00:12:53.098]
Estimate how far in astronomical
units Voyager 1 is from the earth.

[00:12:58.488]
Remember the scale is one
astronomical unit equals 93

[00:13:02.258]
million miles.

[00:13:04.248]
Teachers, you may
now pause the program

[00:13:06.108]
so students can answer the problem.

[00:13:08.578]
OK, so what did you come up with?

[00:13:10.698]
If you said that Voyager was
86 astronomical units away

[00:13:13.748]
from the earth, you're correct.

[00:13:15.758]
Do you have a sense
for how far that is?

[00:13:18.178]
The planet Pluto is 40 astronomical
units away from the earth.

[00:13:21.818]
So that means that Voyager is
twice as far away from the earth

[00:13:24.838]
than the planet Pluto.

[00:13:26.348]
Suppose that Voyager 1 were
stationary, and you were able

[00:13:29.288]
to ride in a car traveling
at 55 mph to get to it.

[00:13:33.318]
The trip would take you
over to 16,000 years,

[00:13:36.358]
just to reach the satellite.

[00:13:38.258]
That would be quite a lengthy
and expensive vacation.

[00:13:41.358]
Jennifer, I think the
students are ready

[00:13:42.838]
for that hands-on activity now.

[00:13:44.828]
Could you send them back to
me when I you're finished?

[00:13:46.658]
I have a real tough
question for them to answer.

[00:13:49.768]
[00:13:52.178]
[Jennifer] Thanks, Stan.

[00:13:53.028]
We'll get back to you a
little later in the program.

[00:13:55.228]
But first, students from Brewster
Middle School at Camp Lejeune,

[00:13:58.638]
North Carolina, will preview
this program's hands-on activity.

[00:14:03.088]
[00:14:04.268]
[Voices] Hi.

[00:14:04.958]
NASA Connect has asked us
to show you this program's

[00:14:08.138]
hands-on activity.

[00:14:09.858]
In this activity, you will
use graphing, measurement,

[00:14:12.918]
and ratios to construct a
scale model of the solar system

[00:14:16.418]
and relate each planet to the sun.

[00:14:19.858]
And you will explore the skills
needed to represent the size

[00:14:23.878]
of the planets and the
distances to the sun.

[00:14:27.398]
You can download a copy

[00:14:28.578]
of the educator guide containing
directions and a materials list

[00:14:31.528]
from the NASA Connect web site.

[00:14:33.338]
Working in groups, students
will complete the activity

[00:14:36.408]
by using a scale model chart
and the planet templates.

[00:14:41.268]
Each group will be
a signed a planet.

[00:14:43.858]
Cut out your assigned planet
using the planet template.

[00:14:47.548]
The scale for this activity
is one toilet paper sheet

[00:14:50.728]
equals 30,102,900 km.

[00:14:55.498]
Using the scale, students complete
column 4 in the scale model chart.

[00:15:00.378]
Remember the math concepts you
learned earlier in the program?

[00:15:03.478]
This is your chance to put
your math skills to the test.

[00:15:06.768]
Next, you will complete column
5 on the scale model chart.

[00:15:10.508]
The scale needed to
complete this column is 1 AU

[00:15:14.088]
or astronomical unit equals
five toilet paper sheets.

[00:15:18.788]
Groups should check
each other's work

[00:15:20.518]
to make sure all values
are correct.

[00:15:23.088]
After completing the scale model
chart, each group should roll

[00:15:26.518]
out the number of toilet
paper sheets needed

[00:15:28.828]
for it is signed planet.

[00:15:30.218]
Now it's time to head
to the staging area.

[00:15:33.078]
This could be in a gym,
hallway, or even outside.

[00:15:36.938]
Place the sun in a
central position.

[00:15:39.438]
Students, attach your pre-measured
toilet paper strip to the sun.

[00:15:43.168]
And let it extend outward
in various directions.

[00:15:46.358]
Don't forget to tape your assigned
planet on the end of the strip.

[00:15:50.508]
You will need about 23 m or
75 feet in one direction.

[00:15:55.208]
Based on your solar system
model, you'll be asked

[00:15:57.968]
to answer several critical
thinking questions.

[00:16:00.968]
Graphing is a great way to
visually represent data.

[00:16:04.628]
Each group will construct

[00:16:06.198]
and analyzed two graphs using
an appropriate type of grass

[00:16:10.088]
and scale of your choice.

[00:16:11.968]
Be careful with the type
of graphs you choose.

[00:16:14.388]
Don't forget to check out the
Web activity for this program.

[00:16:17.398]
You can download it from
the NASA Connect web site.

[00:16:19.738]
[Music]

[00:16:20.738]
[00:16:23.858]
[Jennifer] Great job,
Brewster Middle School.

[00:16:26.098]
OK. Now that you guys
have a preview

[00:16:27.968]
of this program's hands-on
activity, now it's time

[00:16:30.838]
to pause the program and see

[00:16:32.518]
if you can construct a scale
model of the solar system.

[00:16:36.188]
So, how was the activity?

[00:16:38.858]
Hopefully, it helped reinforce the
math concepts you learned earlier

[00:16:42.798]
in this program.

[00:16:44.168]
Now, let's review.

[00:16:45.358]
In the beginning of the program,
we talked about the importance

[00:16:49.158]
of scaling, especially when
it comes to maps and models.

[00:16:53.058]
You learned that fractions,
decimals, ratios,

[00:16:56.868]
and proportions are all
important math concepts

[00:17:00.318]
when in dealing with scales.

[00:17:02.218]
Stan introduced you to the
astronomical unit, the unit used

[00:17:06.568]
to scale the solar system.

[00:17:08.388]
Later in the program, I have an
interesting challenge for you.

[00:17:11.708]
But before we get to that, Stan
has a few more questions for you.

[00:17:15.298]
Let's head back to stand
now, and learn more

[00:17:18.468]
about scaling the solar system.

[00:17:21.098]
[00:17:23.448]
[Stan] Hey, it's great
to have you back.

[00:17:25.268]
In the last segment, we introduced
scale of the solar system

[00:17:28.148]
and the astronomical unit.

[00:17:30.028]
Believe it or not, astronomers once
knew only what the distances were

[00:17:33.588]
in astronomical units,
not an actual miles.

[00:17:36.898]
Recall the following chart,
that shows the distance

[00:17:39.568]
of the planet to the sun.

[00:17:41.468]
Between 1609 and 1619,

[00:17:44.548]
the astronomer Johannes Kepler
used precise measurements

[00:17:47.438]
of the planets in the sky
to determine their orbits.

[00:17:50.648]
But his geometric model was based
on the scale of the Earth's orbit,

[00:17:53.848]
not in its actual diameter
in a kilometers or miles.

[00:17:57.518]
He determined the ratio of
the distance of each planet

[00:17:59.718]
to the sun relative to
Earth's distance to the sun.

[00:18:02.358]
His baseline unit, the
distance from Earth to the sun,

[00:18:06.038]
was designated as exactly 1
AU, or one astronomical unit.

[00:18:10.708]
The problem is that Kepler could
not accurately determine the

[00:18:13.368]
distance between the
Earth and the sun.

[00:18:15.408]
The best estimates that at that
time ranged from 50 million miles

[00:18:18.648]
to over 200 million miles.

[00:18:20.808]
But by the 1890s, as farmers began
to know that number very precisely.

[00:18:26.148]
How did scientists, without
modern space technology

[00:18:28.978]
and rockets, do this?

[00:18:30.658]
You can't just send a
spacecraft to the sun and back

[00:18:33.348]
to determine the distance.

[00:18:34.378]
Human life, including
Norbert and Za,

[00:18:37.788]
could survive the intense
heat produced by the sun.

[00:18:40.448]
So the question for this segment of
the program is how did we determine

[00:18:44.038]
that the earth is 93 million miles

[00:18:45.878]
or 149 million kilometers
from the sun?

[00:18:49.188]
This would be a good
time to pause the program

[00:18:51.388]
and discuss the question with
your teacher and your peers.

[00:18:54.948]
So, did you come up
with any good ideas?

[00:18:57.138]
If you didn't, don't
worry about it.

[00:18:58.778]
After all, it took
astronomers about 2000 years

[00:19:01.158]
to figure out how to do it.

[00:19:03.258]
The answer is that astronomers
used a geometric technique called

[00:19:08.288]
parallax to determine the distance
between the Earth and the sun.

[00:19:11.298]
Parallax is the apparent change of
position of an object when you look

[00:19:14.628]
at it from two different
stations or points of view.

[00:19:17.588]
It sounds mysterious, but we
use this technique all the time.

[00:19:20.928]
For example, let me show you how
parallax works by using my thumb

[00:19:25.238]
and that rocket in the background.

[00:19:27.188]
First, hold your thumb
out at arm's length.

[00:19:30.268]
Now look at your thumb
with your left eye open

[00:19:32.428]
and your right eye closed.

[00:19:34.168]
What do you notice about
the position of your thumb?

[00:19:36.388]
There seems to be an apparent
change in position of your thumb

[00:19:39.258]
from two points of view.

[00:19:41.118]
Your left eye and your right eye.

[00:19:43.318]
Your brain uses this
information to figure

[00:19:45.558]
out how far away things
are from you.

[00:19:47.768]
Actual parallax calculations
can be quite complicated,

[00:19:51.138]
but here's an example of how
we can determine the distance

[00:19:53.508]
to that rocket using many of
the same geometric principles.

[00:19:56.798]
Suppose we wanted to
approximate the distance

[00:19:58.818]
between where I'm standing right
here and that rocket over there.

[00:20:02.548]
And suppose also that there
was a body of water in between

[00:20:05.368]
that we couldn't get across.

[00:20:07.208]
Would you believe that we could
do that by just using a pencil,

[00:20:10.018]
a piece of paper, a ruler, a
piece of rope, and a protractor?

[00:20:14.398]
The first thing we do is to
lay a rope in a straight line.

[00:20:17.918]
The rope will serve as our
baseline, and is 10 m in length.

[00:20:22.168]
Standing on the left
end of the rope,

[00:20:24.118]
which we will call position
A, hold the protractor

[00:20:27.078]
so that it is parallel
to the baseline.

[00:20:29.688]
Place the pencil on the
inside of the protractor,

[00:20:32.438]
and move it along the curve until
it lines up with the object.

[00:20:35.588]
Being careful not to move your
pencil, have a partner read

[00:20:38.528]
and record the angle measurement.

[00:20:40.788]
You then need to repeat
the same procedure

[00:20:43.058]
on the other side of the rope.

[00:20:44.658]
We will call this position B. We
now have to angle measurements

[00:20:48.918]
and our baseline measurement,
which is 10 m,

[00:20:51.348]
the length of our rope.

[00:20:52.028]
In a sheet of paper a long the
bottom, we draw a line 10 cm long

[00:20:57.028]
to represent our baseline.

[00:20:59.348]
For this exercise, let the
scale be 1 m equals 1 cm.

[00:21:05.558]
Mark one end of the drawn line
as point A, and the other end

[00:21:09.758]
as point B. Using our protractor
at point A, we measure an angle

[00:21:14.908]
that is the same number of degrees
as the angle measured outside

[00:21:18.888]
for point A. Let's mark
and draw the angle.

[00:21:22.908]
At point B, we do the same thing.

[00:21:26.198]
Now measure an angle that is the
same number of degrees as the angle

[00:21:29.448]
that we measured outside
for point B. As you can see,

[00:21:33.528]
the two lines intersect.

[00:21:35.908]
We mark the point of intersection

[00:21:37.448]
as point C. Now we draw a line
perpendicular form point C

[00:21:43.018]
to the baseline.

[00:21:44.718]
Using our metric ruler, we
can measure the distance

[00:21:47.398]
of this perpendicular line.

[00:21:49.448]
Finally, using the scale
of 1 m equals 1 cm,

[00:21:53.328]
we can approximate the
distance the actual object was

[00:21:56.198]
from the baseline.

[00:21:57.748]
For our case, the object
is approximately 20 m away.

[00:22:01.868]
In this example, we used a
geometric technique called

[00:22:04.528]
triangulation, which assumes
that we know the baseline length

[00:22:07.978]
and the two bit angles.

[00:22:09.748]
When astronomers use parallax,

[00:22:11.458]
they measure the baseline
length and the vertex angle.

[00:22:14.278]
It is hard to use the parallax
method in the classroom

[00:22:17.278]
because you can't measure
the vertex angle exactly.

[00:22:20.268]
With proper measuring technology,

[00:22:21.858]
this is not a problem
for astronomers.

[00:22:24.458]
To refine the actual sun/Earth
distance, parallax observations

[00:22:28.268]
of the transit of Venus were
made between 1761 and 1882.

[00:22:33.368]
The transit of Venus occurs
whenever the planet Venus passes

[00:22:36.388]
in front of the sun, as
viewed from the earth.

[00:22:39.298]
But observing the apparent
shift in position of Venus,

[00:22:42.008]
against the background
of the solar disk as seen

[00:22:44.138]
from two different places on
earth, astronomers were able

[00:22:47.198]
to use the parallax shift
to determine the distance

[00:22:50.018]
from the earth to the sun.

[00:22:51.498]
The last Venus transit occurred in
1882, and we are fortunate enough

[00:22:55.008]
to have another transit of Venus
happening on Tuesday, June 8, 2004.

[00:22:59.578]
This is an historic event
because no one alive today was

[00:23:02.608]
around when the last one occurred.

[00:23:04.718]
To learn more about the transit of
Venus, let's visit Dr. Janet Lerman

[00:23:08.388]
at the University of
California's space science lab

[00:23:11.158]
in Berkeley, California.

[00:23:13.318]
[00:23:16.858]
[Dr. Lerman] Venus transit occurs
when Venus crosses the disc

[00:23:19.818]
of the sun as seen by an observer.

[00:23:22.188]
It's like a solar eclipse in
that Venus is located on the line

[00:23:25.478]
between the sun and the earth,

[00:23:27.298]
and therefore blocks
some of the sun's light.

[00:23:29.858]
However, in a Venus transit,

[00:23:32.068]
the sunlight blocked is very
small compared to a solar eclipse.

[00:23:35.718]
And so the observer who is
unaware will never notice it.

[00:23:38.878]
Venus's circular shadow is much,

[00:23:40.938]
much smaller than
our moon's shadow.

[00:23:42.918]
Even though Venus is nearly
the size of the earth,

[00:23:45.438]
it is much farther
away than the moon.

[00:23:47.328]
In clear weather, Venus transits
are visible with the naked eye

[00:23:50.698]
or with a small telescope,

[00:23:52.598]
which is why they became
popular in the 1600s.

[00:23:56.208]
Before the advent of radar,
Venus transits were used mainly

[00:23:59.908]
for the measurement of
the astronomical unit,

[00:24:02.388]
or the Sun/Earth distance,
as you've heard earlier.

[00:24:05.088]
The biggest activities surrounding
the June 2004 Venus transit will be

[00:24:09.208]
the International Network
of Amateur Astronomers.

[00:24:12.848]
These astronomers will
measure the astronomical unit

[00:24:15.478]
with the Venus transit using
the same techniques as used

[00:24:18.148]
by the early observers.

[00:24:19.588]
An innovative aspect of this time,
however, not available in 1882,

[00:24:23.868]
is the widespread
use of the Internet

[00:24:25.648]
to organize international
participation,

[00:24:28.248]
and the ease of access
to the tools needed

[00:24:30.358]
to make the parallax calculations.

[00:24:32.478]
There also will be a few
astronomical researchers

[00:24:35.218]
who will try to exploit
state-of-the-art observing tools

[00:24:38.108]
to see what can be learned
about these transits

[00:24:40.668]
to investigate planets
around other stars.

[00:24:43.368]
Transits are currently being
used to search for such planets.

[00:24:46.898]
Perhaps this Venus transit
will lead to some new technique

[00:24:49.808]
or measurements that will
allow future researchers

[00:24:52.348]
to further study the terrestrial
planets during long-range

[00:24:55.448]
planet finding missions.

[00:24:56.868]
The Venus transit will
also serve to remind us

[00:24:59.558]
of Earth's place in the cosmos.

[00:25:01.638]
The tiny dot crossing the solar
disc is a terrestrial planet

[00:25:04.798]
with an atmosphere, and yet
it is far from an Earth.

[00:25:07.618]
Venus was once called a twin earth,
in part because of its similar size

[00:25:11.788]
and distance from the sun.

[00:25:13.558]
It is now known to be a place
that is extremely hostile to life

[00:25:16.858]
for reasons that are
still under study.

[00:25:18.798]
One can speculate how our
own pale blue dot would look

[00:25:21.778]
to some distant alien astronomer
as it passed across the sun

[00:25:25.098]
in transit, and whether it
has ever been so observed.

[00:25:28.398]
Maybe one day humans will be able
to observe the earth transit.

[00:25:31.618]
To learn more about the planet
Venus, and the Venus transit,

[00:25:35.078]
check out the sun/Earth connection
education forum web site.

[00:25:38.698]
Take it away, Jennifer.

[00:25:40.698]
[00:25:43.058]
[Jennifer] They say you learn
something new every day.

[00:25:44.798]
And I sure did.

[00:25:46.248]
I had never heard
of transits before.

[00:25:48.668]
And how astronomers and
scientists used them

[00:25:51.468]
to determine the astronomical unit.

[00:25:53.498]
Thanks, Janet.

[00:25:54.828]
OK, guys. Remember
earlier in the program

[00:25:57.168]
when I said I had an
interesting challenge for you?

[00:25:59.628]
Well, it's now time for
scaling the solar system.

[00:26:03.468]
Now, the astronomical unit or a
you currently in use is derived

[00:26:07.998]
from the average mean distance
between the Earth and the sun.

[00:26:11.248]
Which is approximately
93 million miles.

[00:26:13.478]
Working in groups, your
task is to make a proposal

[00:26:17.508]
that uses the average mean
distance between the sun

[00:26:21.408]
and another planet in our
solar system as the basis

[00:26:25.018]
for determining the
astronomical unit.

[00:26:27.128]
In other words, is there a
better baseline distance to use,

[00:26:31.208]
rather than the Sun/Earth baseline?

[00:26:33.478]
What about using a Sun/Jupiter
baseline or a Sun/Pluto baseline?

[00:26:39.158]
You choose another planet, you
will have to recalculate the scale

[00:26:43.238]
of the solar system using
your new chosen baseline.

[00:26:46.948]
And then explain why your new
baseline is a better choice

[00:26:50.408]
than the Sun/Earth baseline.

[00:26:51.878]
What are the advantages and
disadvantages to your new scale?

[00:26:55.708]
Detailed instructions
and tips on how

[00:26:58.218]
to make your proposal
can be located

[00:27:01.008]
at the NASA Connect web site.

[00:27:02.578]
From the web site, we encourage
you to submit your proposal.

[00:27:06.238]
Your proposal will
be seen by millions

[00:27:08.188]
of students across the country.

[00:27:09.798]
We look forward to
your some medals.

[00:27:11.838]
Well, guys, that wraps up
another episode of NASA Connect.

[00:27:14.788]
I hope you have a better
understanding of how

[00:27:17.558]
and why astronomers and
scientists use scale models

[00:27:21.508]
of the solar system.

[00:27:22.908]
We'd like to thank everyone who
helped make this program possible.

[00:27:26.208]
Got a comment, question,
or suggestion?

[00:27:28.448]
Well, then e-mail them
to connect@LARC.NASA.gov.

[00:27:32.268]
Or pick up a pen and mail them to
NASA Connect, NASA Langley Center

[00:27:36.838]
for Distance Learning, NASA
Langley Research Center,

[00:27:39.458]
Mail Stop 400, Hampton,
Virginia, 23681.

[00:27:43.338]
So until next time,
stay connected to math,

[00:27:46.298]
science, technology, and NASA.

[00:27:49.038]
Bye from sunny Florida.

[00:27:50.178]
[Music]

[00:27:50.178]