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Parallax - Contenido educativo

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Subido el 28 de mayo de 2007 por EducaMadrid

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NASA Connect segment explaining how scientists determined the distance between the earth and the sun. The video also explores the geometric technique called parallax.

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So, how was the activity? 00:00:00

Hopefully it helped reinforce the math concepts you learned earlier in today's program. 00:00:03

Now, let's review. 00:00:08

In the beginning of the program, we talked about the importance of scaling, 00:00:10

especially when it comes to maps and models. 00:00:14

You learned that fractions, decimals, ratios, and proportions 00:00:17

are all important math concepts when dealing with scales. 00:00:22

Sten introduced you to the astronomical unit, 00:00:26

the unit used to scale the solar system. 00:00:29

Later in the program, I have an interesting challenge for you. 00:00:32

But before we get to that, Sten has a few more questions for you. 00:00:35

Let's head back to Sten now and learn more about scaling the solar system. 00:00:39

Hey, it's great to have you back. 00:00:47

In the last segment, we introduced the scale of the solar system and the astronomical unit. 00:00:49

Believe it or not, astronomers once knew only what the distances were in astronomical units, 00:00:54

not in actual miles. 00:00:59

Recall the following chart that shows the distances of the planets to the sun. 00:01:01

Between 1609 and 1619, 00:01:05

the astronomer Johannes Kepler used precise measurements of the planets in the sky 00:01:08

to determine their orbits. 00:01:13

But his geometric model was based on the scale of the Earth's orbit, 00:01:15

not on its actual diameter in kilometers or miles. 00:01:18

He determined the ratio of the distance of each planet to the sun 00:01:21

relative to Earth's distance to the sun. 00:01:24

His baseline unit, the distance from Earth to the sun, 00:01:26

was designated as exactly 1 AU, or 1 astronomical unit. 00:01:29

The problem is that Kepler could not accurately determine the distance between the Earth and the sun. 00:01:34

The best estimates at that time ranged from 50 million miles to over 200 million miles. 00:01:39

But by the 1890s, astronomers began to know that number very precisely. 00:01:44

How did scientists without modern space technology and rockets do this? 00:01:49

You can't just send a spacecraft to the sun and back to determine the distance. 00:01:54

Human life, including Norbert and Zott, 00:01:58

couldn't survive the intense heat produced by the sun. 00:02:01

So the question for this segment of the program is, 00:02:04

how do we determine that the Earth is 93 million miles, or 149 million kilometers, from the sun? 00:02:07

This would be a good time to pause the program 00:02:12

and discuss the question with your teacher and your peers. 00:02:15

So, did you come up with any good ideas? 00:02:19

If you didn't, don't worry about it. 00:02:21

After all, it took astronomers about 2,000 years to figure out how to do it. 00:02:23

The answer is that astronomers used a geometric technique called parallax 00:02:29

to determine the distance between the Earth and the sun. 00:02:33

Parallax is the apparent change in position of an object 00:02:35

when you look at it from two different stations or points of view. 00:02:38

It sounds mysterious, but you use this technique all the time. 00:02:41

For example, let me show you how parallax works 00:02:45

by using my thumb and that rocket in the background. 00:02:48

First, hold your thumb out at arm's length. 00:02:51

Now look at your thumb with your left eye open and your right eye closed. 00:02:54

What do you notice about the position of your thumb? 00:02:58

There seems to be an apparent change in position of your thumb from two points of view, 00:03:01

your left eye and your right eye. 00:03:05

Your brain uses this information to figure out how far away things are from you. 00:03:07

Actual parallax calculations can be quite complicated, 00:03:12

but here's an example of how we can determine the distance to that rocket 00:03:15

using many of the same geometric principles. 00:03:18

Suppose we wanted to approximate the distance between where I'm standing right here 00:03:21

and that rocket over there. 00:03:25

And suppose also that there was a body of water in between that we couldn't get across. 00:03:27

Would you believe that we could do that by just using a pencil, a piece of paper, 00:03:31

a ruler, a piece of rope and a protractor? 00:03:35

The first thing we do is to lay our rope in a straight line. 00:03:38

The rope will serve as our baseline and is 10 meters in length. 00:03:42

Standing on the left end of the rope, which we will call position A, 00:03:46

hold the protractor so that it is parallel to the baseline. 00:03:50

Place the pencil on the inside of the protractor 00:03:54

and move it along the curve until it lines up with the object. 00:03:56

Being careful not to move your pencil, have a partner read and record the angle measurement. 00:04:00

We then need to repeat the same procedure on the other side of the rope. 00:04:05

We will call this position B. 00:04:09

We now have two angle measurements and our baseline measurement, which is 10 meters, 00:04:11

the length of our rope. 00:04:15

On a sheet of paper along the bottom, we draw a line 10 centimeters long 00:04:17

to represent our baseline. 00:04:21

For this exercise, let the scale be 1 meter equals 1 centimeter. 00:04:23

Mark one end of the drawn line as point A and the other end as point B. 00:04:29

Using our protractor at point A, we measure an angle that is the same number of degrees 00:04:35

as the angle we measured outside for point A. 00:04:40

Let's mark and draw the angle. 00:04:44

At point B, we do the same thing. 00:04:47

Now measure an angle that is the same number of degrees 00:04:50

as the angle we measured outside for point B. 00:04:53

As you can see, the two lines intersect. 00:04:56

We mark the point of intersection as point C. 00:05:00

Now we draw a line perpendicular from point C to the baseline. 00:05:04

Using our metric ruler, we can measure the distance of this perpendicular line. 00:05:09

Finally, using the scale 1 meter equals 1 centimeter, 00:05:13

we can approximate the distance the actual object was from the baseline. 00:05:17

In our case, the object is approximately 20 meters away. 00:05:22

In this example, we used a geometric technique called triangulation, 00:05:26

which assumes that we know the baseline length and the two base angles. 00:05:30

When astronomers use parallax, they measure the baseline length and the vertex angle. 00:05:34

It is hard to use the parallax method in the classroom 00:05:39

because you can't measure the vertex angle exactly. 00:05:42

With proper measuring technology, this is not a problem for astronomers. 00:05:45

To find the actual Sun-Earth distance, 00:05:49

parallax observations of the transit of Venus were made between 1761 and 1882. 00:05:51

The transit of Venus occurs whenever the planet Venus 00:05:57

passes in front of the Sun as viewed from the Earth. 00:06:00

By observing the apparent shift in position of Venus 00:06:03

against the background of the solar disk as seen from two different places on Earth, 00:06:06

astronomers were able to use this parallax shift 00:06:10

to determine the distance from the Earth to the Sun. 00:06:13

The first Venus transit occurred in 1882, 00:06:16

and we are fortunate to have another transit of Venus happening on Tuesday, June 8, 2004. 00:06:18

This is an historic event because no one alive today was around when the last one occurred. 00:06:24

To learn more about the transit of Venus, 00:06:29

let's visit Dr. Janet Luhmann at the University of California's Space Science Lab in Berkeley, California. 00:06:31

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Idioma/s:

Materias:

Matemáticas

Niveles educativos:

▼ Mostrar / ocultar niveles

- - Nivel Intermedio

Autor/es:

NASA LaRC Office of Education

Subido por:

EducaMadrid

Licencia:

Reconocimiento - No comercial - Sin obra derivada

Visualizaciones:

389

Fecha:

28 de mayo de 2007 - 16:52

Visibilidad:

Público

Enlace Relacionado:

NASAs center for distance learning

Duración:

06′ 36″

Relación de aspecto:

4:3 Hasta 2009 fue el estándar utilizado en la televisión PAL; muchas pantallas de ordenador y televisores usan este estándar, erróneamente llamado cuadrado, cuando en la realidad es rectangular o wide.

Resolución: