Transcript for NASA Connect - Ancient Observatories: Timeless Knowledge

In this episode of NASA Connect,

learn how ancient cultures
observed seasonal cycles

and how the Sun played a
part in their observations.

We'll also conduct a cool hands-on
activity measuring shadows created

by the Sun and a gnomon.

Stay tuned for another exciting
episode of NASA Connect:

Ancient Observatories.


Cama'i tawow, or welcome,
to NASA Connect.

I'm Jennifer Pulley, and
this is the National Museum

of the American Indian.

And I'm Dr. Sten Odenwald at an
archaeological site in Mexico.

Hola, this is NASA Connect, the
show that connects you to math,

science, technology -- and NASA.

On today's program, you will
see how ancient cultures found a

connection to the stars.

You will also learn how many

of these societies
were very sophisticated

when making celestial observations.

You'll also learn about the
mathematics and geometry used

by these ancient peoples
to make their observations.

What you will learn today
will absolutely astound you.

But first, Jennifer, tell us about
that building that you're in.

Sten, this is the newest
museum in our nation's capital.

As you enter the museum, hundreds
of written and spoken words meaning

"Welcome" in native languages
throughout the Americas are

projected onto this wall.

These people -- not only
here in the Americas,

but also their brothers and
sisters in Africa, Asia, Europe,

and the Pacific -- looked
at our starry skies.

All of these people had
a connection to the Sun.

In the museum, this
room celebrates the Sun.

From this circle, the four cardinal
directions -- north, south, east,

and west -- extend
out of the building.

The angles of solstices and
equinoxes are mapped on the floor.

A light spectrum is
cast by the Sun,

which shines through the prisms
set into the south-facing wall.

Each prism is sighted to the Sun

for a particular time
of day and season.

The dramatic designs in this
modern museum show the connection

between astronomy,
nature, and people.

That connection is the key

to understanding how the
ancients looked at our universe,

which is the theme
of today's program.

Today we will talk to
Native American astronomers.

Dr. Sten Odenwald will treat us
to the foundations of astronomy

as we know it today,
and he will fill us

in on the celestial
accomplishments of the Mayans.

Throughout the program,
you will be asked

to answer several
inquiry-based questions.

After the questions
appear on the screen,

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

and discuss the questions.

This is your time to explore
and become critical thinkers.

Now let's learn more about
ancient observatories.

The science of interpreting the
relationship between the Sun

and the daily lives of primitive
people is called archeoastronomy --

"archeo" meaning "archeology,"

and "astronomy" meaning
"the study of stars."

Observing celestial
phenomena is the one constant

that unifies humankind
throughout space and time.

Ancient man knew celestial events
followed cycles -- circles --

and these events could be recorded.

Approximately 5,000 years ago,
they devised a way to place stones

in certain positions to align
for lunar and solar events.

Events like seasons were noted
and found to recur regularly

with certain positions
of the Sun and stars.

The earth spins on its
axis once every day

and gives us the familiar

of daytime and nighttime.

For thousands of years, humans
have used this cosmic cycle

to regulate their workday,
their meals, and their sleep.

The earth orbits the
Sun once every year,

and from this we get the
familiar 365 day cycle.

Earth's orbit around
the Sun is an ellipse --

basically, that means an
oval with the Sun offset

from the center of the ellipse.

Does this mean that we have
summer when the earth is closest

to the Sun and winter when the
earth is farthest from the Sun?

The surprising fact is that
the distance from the earth

to the Sun has absolutely nothing
to do with the changing seasons.

Our northern hemisphere is
closest to the Sun in January

and farthest from the Sun in July.

So what is causing the
change in temperature?

Earth's axis is tilted
by 23 1/2 degrees

from a line perpendicular
to Earth's orbit.

What does this mean?

To understand this tilt, we have
to use a bit of basic geometry.

An angle has two sides
and a vertex.

The sides are rays that share a
common endpoint called the vertex.

The angle formed by two rays can
be named in a variety of ways.

For example, the angle
formed by ray AB

and ray AC can be named angle BAC,
angle CAB, or angle A for short.

Notice that A must be the middle
letter in both three-letter names

because it's the vertex.

You can measure angles
using a protractor.

The unit of measure is degrees.

Angles can be classified
by their measures as acute,

right, obtuse, and straight.

If the earth rotated on
its axis perpendicular to,

or at a right angle to the orbit,

there would be no
changes in temperature.

The earth rotates at
an angle 23 1/2 degrees

from this perpendicular line.

It's a very small tilt, but enough

to affect the Sun's
rays hitting the earth.

This is a great time to
pause the program and think

about the following questions:

Why is the area near
earth's equator hotter

than the areas near the poles?

If the tilt of earth's axis
measured 33 degrees rather

than 23 1/2, how might
seasonal changes

and temperature ranges differ?

Teachers, it's now time
to pause the program.

The tilt of the earth's
axis gives us our seasons,

and because of the extremes in
heat and cold, it's very important

to keep track of the changing
seasons if you're growing food.

This seasonal cycle is important
to ancients and even modern people.

In some parts of the world,
like the arid climates

of the southwest states of the
USA, the growing season was

so short that people could not
waste much time getting the seeds

in the ground at the
start of spring.

But how do we predict when
the growing season will begin

in the spring?

For that matter, how can we tell

when the other seasons
begin and end?

It turns out that just by keeping
track of how high up the Sun gets

over the horizon at noon,
you can determine the start

of the seasons exactly.

Almost all ancient
people that relied

on planting times discovered
this little relationship.

The start of the four seasons --
summer, fall, winter, and spring --

are noted by what astronomers
call the summer solstice,

the fall equinox, the winter
solstice, and the spring equinox.

At the start of summer --

around June 21 in the
northern hemisphere --

the Sun is at its highest point
above the horizon at noon.

As the Sun begins its movement
back away from its maximum height,

the number of daylight hours
has declined to an equal number

of daylight and nighttime hours.

This is the fall equinox,
near September 21.

A few months later, the
path of the Sun arrives

at its lowest point at noon.

The Sun spends very little
time above the horizon

of the northern hemisphere, and
the night is much longer than day.

Welcome to the winter solstice,

or start of winter,
around December 21.

After a few more months, the path
of the Sun works its way higher

in the sky, eventually
arriving at a path

where day and night are equal.

This happens March 21
at the spring equinox,

a vital time for planting crops.

Archeoastronomers have found three
types of early observatories:

simple markers, circles of
stone and wood, and temples.

Early on, markers were used to
create sight lines to the horizon

so that during the equinox or
solstice, the Sun would appear

to rise exactly on the sight line.

Stonehenge, in England, was set
up this way, as were a number

of ancient Native American
buildings, such as the ones

at Chaco Canyon in New
Mexico, and Hovenweep in Utah.

England's Stonehenge is one
of the earliest examples

of an observatory in Europe.

Stonehenge is a large
calendar capable

of predicting the
equinoxes and the solstice.

Before Stonehenge in 3,000 BC,

the ancient Egyptians had devised
a solar calendar of 365 days,

the starting point of which
hinged on the helical rising

of the star Sirius, which
also happened to coincide

with the summer solstice and
the annual flooding of the Nile.

By being in touch with
celestial phenomenon

and their natural surroundings,
the ancient Egyptians were able

to predict events of
great significance

in their desert environment.

At Abu Simbel, massively
carved statues

of Ramses the Great face east

to greet the Sun god Ra,
the bringer of light.

As the Sun rises each day, the
statues are illuminated again,

perhaps a sign of
rebirth for Ramses.

But the most compelling
is a passage

to the temple's inner sanctuary,
which is aligned so that

on October 18, the Sun
filters into the sanctuary,

illuminating a statue of Ramses.

While October 18th doesn't mean
much to us in the Western world,

this October date
corresponds to the beginning

of the Egyptian civil
year and the celebration

that occurred during the
time in which Ramses lived.

It was the Greeks, however,

that created the first portable
cosmological tool for keeping track

of these motions -- a stick.

The Greeks actually called
it a gnomon, and it was used

to keep track of the
shadow of the Sun.

Actually, it's a little bit
more difficult than that,

because the shadow
depends on your latitude.

Again, if you were
not near the equator,

the shadow will be shortest
during the summer solstice

and longest during
the winter solstice.

For the spring equinox and fall
equinox, the shadow will be halfway

between the shadow
lengths at the solstices.

In the southern hemisphere,
the shadows will be reversed,

just as you all know the
seasons are reversed.

When it's summer in the United
States, it's winter in Argentina.

This all works pretty well
if you're not at the equator.

At the equator, the summer
solstice Sun casts a shadow

in a southerly direction, and the
winter solstice Sun casts a shadow

in the northerly direction.

During the equinox, at the
equator, the shadow disappears.

Oh, and another thing that
they were used for is sundials.

And it looks to me like it's
time to go back to Jennifer.

Okay, guys, let's take a
look at how a gnomon works

and see the angle of the Sun at
certain times during the day.

Students from Newcomb Elementary
School in Newcomb, New Mexico,

will preview this
show's hands-on activity.


Hello. We are students from
Newcomb Elementary School.

We are located on the
Navajo Reservation

in the Four Corners
Region of New Mexico.

Tracking the passage of the
Sun in the sky continues

to play a very important role in
the life of our Navajo culture.

Traditional Navajos
still use this system

of tracking the Sun's
shadows to tell time

and to tell the changing
of the seasons.

For example, when my
grandfather herds sheep,

he does not wear a watch like this.

He uses the Sun's
shadow to tell time.

It also helps him to tell when
to take the sheep back home

in their corral.

It also helps him to
tell when to plant corn

and watermelon on his farm.

NASA Connect asked us to show you
this program's hands-on activity.

In this activity, the students will
make Sun shadow plots every half

hour, marking the ends
of the shadows made

by the Sun and a gnomon.

You can download a copy
of the educator guide

from the NASA Connect website for
directions and a list of materials.

Turn a cardboard box upside down.

Tape a large piece of
paper to the cardboard box.

Draw two lines that are
perpendicular to each other:

from top to bottom,
and the other from left

to right across the paper.

Mark its center with a dot,
and make a very small hole

in the center of the box
using the point of a scissors.

Stick the gnomon through the dot
and the hole in the cardboard.

Secure it with tape so that 10
centimeters is sticking straight

up out of the box.

Use a protractor to make sure the
gnomon is perpendicular to the box.

On a clear, sunny day,
find a large, flat area.

Tape the box to the
ground on all four sides.

Starting as early in
the morning as possible,

mark the end of the gnomon's
shadow every half hour

until the end of the day.

Next to the dot, label the
time of the day it was marked.

You will analyze the
data you collect

by measuring angles and length.

Remove the gnomon and draw a
straight line from each dot

to the hole that the
gnomon was placed in.

Measure and record the angle
between the horizontal line drawn

through the center of the
paper and each marked shadow.

Then measure and record
the length of each shadow.

Using geometry, find and label
true north on your Sun shadow plot.

Verify local solar noon
using shadow length times

and sunrise/sunset times.

How do the lengths, positions,
and angles of the shadows change?

What do the changes tell
you about the position

of the Sun throughout the day?

Would the curve change if you
used a different sized gnomon

to cast the shadow?

And don't forget to check out this
cool web activity for this program.

You can download it from
the NASA Connect website.

Great job, you guys.

All right.

Let's review.

We've seen how ancient cultures
used the Sun/Earth connection

to mark the season.

And you've seen an activity which
uses the placement of shadows

to record the movement of
the Sun across the sky.

Research regarding Native American
astronomy has recently begun

to gain headway in archeoastronomy.

Let's look at the
ways native cultures

in the Americas used the
Sun/Earth connection.

Nancy Maryboy and David Begay
are two indigenous astronomers

from the Navajo Nation.


Hello. We're in Hovenweep
National Park in southern Utah.

I'm a Cherokee Navajo, I
live not far from here,

and I'm an educator
on the Navajo Nation.

A "cultural astronomer" means
you deal with the astronomy

of your own culture, and we
put things within the context

of a Native worldview.

Right behind me, on the boulder,

you can see an indication
of a solar phenomena.

On the boulder, there's two images:

one's a concentric
circle, one's a spiral.

As the Sun begins to
rise, shafts of light come

in from each direction, and
as the Sun continues to rise,

the lights meet in the center.

This only happens once a year.

This phenomenon occurs on
the longest day of the year

and is a very appropriate
way to mark time.

This can be a very harsh
environment to live in.

It can be hot, it can be
cold, and it can be very dry.

In order to survive, people
had to live in accordance

with the natural environment,

and that meant the natural
cosmic environment: the Sun,

the Moon, and the stars.

It was very important to track
the path of the Sun and the Moon

and certain constellations,
and to do that,

people used natural
markers like petroglyphs

and Sun and Moon alignments.

Remember, there was no watches,
there was no timekeepers,

there was no calendars.

My name is David Begay.

I am a cultural astronomer.

I've been living out
here for many years.

My clan is Midishkisinee.

This clan is a descendant
from the Jemez Pueblo people.

And here is one of the structures
at Hovenweep National Monument.

This structure had many purposes,
one of which was an observatory.

The ancient had a profound
respect for the movement

of the Sun and the stars.

On the longest day of the year,
the Sun shines through an opening,

and the light falls on a marker.

What people experience here is
really a cultural experience.

It's a whole life experience.

People felt the movement
of the Sun.

People felt the movement
of the Moon.

It was a daily experience.

Among the Navajo people,
for the Sun,

when it reaches summer solstice,
it's a total life experience.

People used to talk about
the solstice being a

four-day phenomenon.

People used to say,

[speaking Native], the sun spent
four days before it starts moving

back the other way.

So it's really something
that was experienced.

It was talked about.

It was a part of the
culture that's been passed

down through the generations.

I think people talk about these
movements in terms of days.

I'm not really sure if you can
really call it "special" math.

I don't think tracking the Sun

down to the second was
important at that time.

These buildings and boulders are
remnants of ancient civilizations,

much like the ruins in Rome,
the ruins in Greece, and today,

they're still very relevant to
us out here in the Southwest.

We still see the same sky, and
we're in awe of the technology

that was employed to
build these buildings

and capture these solar
and lunar alignments.

Today we look in the sky.

We use some of the same knowledge
that the ancestral Pueblans used.

We use it for planting, we
use it for setting ceremonies,

and we use it to keep
the earth in order.

The balance between earth and
sky is still very important

to Native peoples.

Thanks, Nancy.

And thanks, David.

You know, guys, one of the
earliest Native American structures

to observe the Sun and the
stars is Casa Rinconada.

Located in the Chaco Cultural
National Historical Park,

Casa Rinconada is a large kiva.

Kivas are large circular
rooms used for ceremonies

by Native American cultures.

Like Hovenweep, on the day of the
summer solstice, a beam of light

from an opening in the kiva
precisely illuminates a niche

in the far wall.

For years, Chaco Canyon was
primarily seen as a trade center,

but with the advent of
archeoastronomy, Chaco is beginning

to be seen as a center of
astronomy and cosmology.

So far on today's program, we
have seen how the relationship

between the Sun and the
earth weaved a connection

between all ancient cultures.

Now, much of the information from
those cultures has been lost to us.

However, other cultures have
recorded that information,

and now that information
is being interpreted.

For a look at one of
these ancient cultures,

let's return to Dr. Sten Odenwald.

Thanks, Jen.

Perhaps the greatest ancient
astronomers were the Mayans,

who lived right here
where I'm standing.

The Mayans inhabited the Yucatan
Peninsula in Mexico and Guatemala.

These people made astronomical
and seasonal observations,

which rivaled anything seen

in Europe during the Roman
Empire or the Dark Ages.

These amazing people
mapped the heavens,

they evolved the only true writing
system native to the Americas,

and they were masters
of mathematics.

They invented calendars that
are still accurate today,

and without metal tools, beasts
of burden, or even the wheel,

they were able to construct vast
cities with an amazing degree

of architectural perfection
and variety.

The largest structure at this site
is El Castillo -- "the castle."

That these temple builders
were mathematically precise

in their architectural designs is
borne out by the natural phenomena

which occur during the
fall and spring equinoxes.

In the spring, as the Sun rises,
the shadow cast on the steps appear

to form the body of a serpent
which slithers down the stairs.

Here at Chichen Itza, there is a
structure unlike anything else ever

created by the ancient Mayans.

It's called El Caracol,

and it actually looks
like a modern observatory.

Its design didn't function the same
way as our modern observatories.

Instead, its walls
contain many windows.

Inside the dome, stones
could be removed,

enabling the Mayan astronomers to
observe different parts of the sky.

The Mayans looked at
the sky differently

from any other civilization.

Being near the equator, the
equinox passages were easier

and more accurate to determine
because the Sun casts no shadow

at local noon during this time.

They also had great
veneration for the Milky Way.

They called it "the world tree."

The star clouds that form the Milky
Way were seen as the tree of life,

from which all life came.

The Mayans also had their
unique constellations.

Like today's zodiac,
they had their scorpion.

Gemini, which appears
to us as twins, however,

was seen as a peccary, a
nocturnal animal in the pig family.

Other zodiac symbols were
a jaguar, a bat, a turtle,

the tail of a rattlesnake,
and a sea monster.

Because they looked
at things differently,

perhaps it's not surprising

that the Mayans had a
different mathematics as well.

We use a numbering system
based on ten digits,

but the Mayans used a system
based on the number 20.

Sounds a little bit complicated,
but in fact, it was more efficient

for counting than some
of the older systems used

in Europe a long time ago.

The Mayan counting system
required only three symbols:

a shell representing 0, a dot
representing a value of 1,

a bar representing 5, and a shell

with a dot representing
the base number 20.

There are two advantages to
the Mayan counting system.

The first of these is the idea
of zero, which many civilizations

at that time did not have.

Second, they only
used three symbols

to represent lower
and higher numbers.

In Rome, multiple
symbols were used.

I is for 1, V for 5, X for 10, L
for 50, C for 100, and M for 1,000.

Mayan numbers were
written from bottom to top,

so the number 19 becomes
bars of 5, 5, 5,

with four dots above the bars.

To complete the first set
of 20, a dot was raised

over a shell-like symbol.

To get 21, the elevated
placement of the dot remained

to represent 20, and a dot was
added underneath to represent 21.

Then the counting cycle for
the next 20 began again.

So what do you think the number
40 or 41 would look like?

In Europe at this time,
people still struggled

with the Roman numeral system.

That system suffered
from two serious defects.

First, there was no zero.

And second, Roman numbers
were entirely symbolic,

having no direct connection to
the number of items represented.

So are you ready for a challenge?

Okay, working together, try adding
21 and 33 using the Mayan system.

Then try adding 21 and
33 using Roman numerals.

This is a good time
to pause the program.

So how did you do?

Let's check your work.

In Mayan, the number 21 is
represented as dot, dot.

33 is two bars, equalling
10, three dots, for units,

and an elevated dot
representing 20.

Adding together, you get 54,
which is two bars, four dots,

and two elevated dots.

Easy to decipher.

In Roman, you have XXI
plus XXXIII equals LIV.

Unless you actually know what
the Roman symbols stand for,

you have no idea what
you are seeing.

In Mayan, you can actually add
up the dots, bars, and shells.

Mayan merchants often
used cocoa beans, sticks,

and shells to do these

From these three symbols, the
Mayans could do everything

from the simplest arithmetic
needed for trade to keeping track

of astronomical events
both past and future.

Speaking of astronomy, remember how
I said the earth's axis was tilted

at 23 1/2 degrees?

If you round that to 24, how
would you write that in Mayan?

The Mayan system of
counting using dots, bars,

and shells can be compared
with the ones and zeroes used

by modern computers, and it
was all done 1,500 years ago.

With all the advances that the
Mayans made, it's interesting

to speculate what
would have happened

if the Mayans had sailed east
to discover Europe instead

of the Europeans sailing west
to the discover the Americas.

To learn more about
Mayan mathematics,

go to the following websites.

Back to you, Jennifer.

Thanks, Sten.

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

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

Got a comment, question,
or suggestion?

Then email them to
"connect at"

I'd like to leave you guys
with a thought and a challenge.

What is impressive about
these sites is the accuracy

of their observations and
the time and effort they put

into building these observatories.

Looking back at these
buildings and places,

we see that the ancients
had a natural connection

to their environments, and
that they were also capable

of high-tech accomplishments
in their own times.

So now, here's my challenge.

How do you think people
300, or even 1,000 years

from now will see us through the
artifacts that we leave behind?

Until next time, stay
connected to math,

science, technology, and NASA.

Good-bye for now.

Finally, they picked
one star out and said,

"this one will be the morning
stars, it will give us direction

that the daylight is coming,
it will give us direction

that it's in the east."

And the next one is
the evening stars.

They will tell us it's
in the west direction.

It's almost nighttime.

They liberated more, like
the Dipper and all that.

It revolves in different positions.

It will tell us if it's fall,
spring, or summertime, wintertime.


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