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Space #2: Scale & Measurement in Astronomy

By LAUREN JILBERT
Last updated over 6 years ago
35 Questions
Note from the author:
SHMS
SCALE AND MEASUREMENT IN ASTRONOMY

This Formative assignment will be done partly as classwork and partly as homework over a week. Work you do not finish in class automatically becomes homework.

Points Possible: 50 assignment points
SECTION #1: SCALE AND MODELS OF THE SOLAR SYSTEM
The picture above shows a model of our solar system. You have probably seen similar models before. Models are representations of things that are very large, very small, or very complex so we can study and understand them. Models are never perfect.

This model does show that the Sun is the largest object in our solar system. We can see that Jupiter is a larger planet than Earth. The order of the planets is also correct. However, the sizes and distances between these objects are not correct or "to scale" at all. When objects are to scale, it means they are the correctly proportionate sizes or distances compared to each other.

You may wonder why someone doesn't just make a better model of our solar system that is to scale. The truth is that objects in space are much, much bigger, smaller, or far away than you realize.

This model (shown below) is to scale for size. These are the correct sizes of the Sun and planets compared to each other. The terrestrial planets are so small! If we wanted to show to scale distances between the Sun and planets, we would need A LOT of space. This would make the objects even harder to see. This is why almost all models of the solar system are not shown to scale.

Watch the video below to see a to scale model of our solar system for size AND distance. You will find the planets are much smaller and farther apart than you ever realized!
SECTION #2: SIZING UP THE UNIVERSE

In this activity, you will see selecting different objects to represent objects in a model of our solar system. Complete steps 1-14 on this interactive activity comparing the sizes of objects in our solar system and beyond.

As you go through the interactive activity, make sure you answer the questions below. It helps to split your screen. You will have a choice of objects so your answers will vary from other people in the class. Be sure to click on all the videos and information for each step. You can click back to the steps you already have done if you need to go back.

Get a pair of headphones or earbuds. Open a new tab in your browser and copy and paste in the link below if the hyperlink does not work:

http://learning.si.edu/idealabs/sizinguptheuniverse/#intro/
1.

If the Earth is the size of a ______________, then the Moon would be the size of a _____________.

2.

Compared to the object you chose to represent Earth in your scale model, what object would best represent the size of the Sun?

3.

After you click on “Map Orbit” for the objects you chose to represent the Earth, Moon, and Sun, describe how much space you would need to make this model showing the proportionate distances between those objects? (You can describe places shown on the map or describe using miles). Are you surprised?

4.

If the Earth is the size of a ___________, then Pluto, a dwarf planet in our solar system, would be the size of a __________.

5.

To make an accurate model of our solar system using the objects you chose to represent the sizes and positions of the Sun, Earth, and the dwarf planet Pluto, how much space would you need? (You can describe places shown on the map or describe using miles). Are you surprised?

6.

Using the information provided, how many Plutos could fit inside the planet Jupiter? ____________

After you click on the pink arrow that says, “Then It’s on to the Stars”, answer the following questions:
7.

About how many stars are in our galaxy, the Milky Way?

8.

After the Sun, what is the name of the next closest star to the Earth? How far away is it?

9.

Using the objects you chose for this model, how much space would you need to show the correct distance between the Sun and Proxima Centauri?

10.

What is an Astronomical Unit (AU)? How big is 1 AU?

11.

How wide across is our solar system?

12.

How wide across is our galaxy, the Milky Way?

13.

If the solar system was the size of a ____________, then our galaxy, the Milky Way, would be the size of a __________________.

After you watch the video about the Milky Way, click on the green arrow that says, “Now on to Other Galaxies”
14.

What is the name of the galaxy that is closest to the Milky Way?

15.

If you shrunk down each galaxy to a few inches, how far apart would they be?

16.

Eventually, the Milky Way and Andromeda galaxies are going to collide and become one big galaxy (over a VERY long time). What will happen? Will it necessarily be the end of any life in those galaxies?

Watch the video clip about galaxies and answer the following questions:
17.

Do galaxies move or hold still?

18.

Are most galaxies getting closer together or spreading farther apart?

SECTION #3: SCALE OF THE UNIVERSE

When things are the correctly proportionate measurements compared to each other, it means those objects are "to scale". Those measurements might be for size, the distance between things, or amounts of something.

This interactive activity is a way to compare the sizes of objects in the universe when they are to scale. You begin by looking at objects as you see them in the real world--as compared to the size of you. The human figure is the correct size compared to the objects around it, such as the humming bird. As you scroll to the right, objects will get bigger and bigger as the image of the person becomes smaller and smaller by comparison. Eventually, you can zoom all the way out to the observable universe. If you understand what you are looking at, you will end up feeling very small!

Go to: http://htwins.net/scale2/
If the link does not work, Google "Scale of the Universe 2" and make sure the Flash Player is enabled on your Chromebook.
Note: The chicken in the picture above is NOT shown to scale. The chicken is not the correct size compared to the man or other objects in the scene.
19.

How many meters (m) tall is the average human?

20.

Scroll the bar slightly to the left. What is the length of the hummingbird? How many times a minute can a hummingbird flap its wings?

21.

Now scroll to the right. Which is taller--the Hoover Dam or the Washington Monument?

22.

How much larger is Halley's Comet than Mount Everest?

23.

Click on Hydra. What is Hydra?

24.

What is Earth's largest continent? Is it larger in length than Earth's Moon?

25.

How much larger is the Sun in diameter than the Earth?

26.

Click on the Star WOH G64. What's so special about this star?

27.

What is the Kuiper Belt? (Pronounced "KY-per")

28.

List TWO things in the universe that are larger than a light year.

29.

Click on at least one nebula (huge space cloud of dust and gases) and describe something interesting about it.

30.

Click on at least one galaxy and describe something interesting about it.

SECTION #4: MEASUREMENT IN ASTRONOMY

By now, you should have some idea that space is so huge, it's kind of hard to wrap your head around just how big it is. Let's consider an object that is very close to the Earth: the Sun. On average, the Sun is about 152,000,000 kilometers or 94,500,000 miles away from Earth.

That's a pretty big number, but what about something that is farther away, like the next closest star to Earth after the Sun, Proxima Centauri? It's about 24,800,000,000,000 miles away from us. That's a much bigger number.

Now, about how far away is our "next door neighbor" galaxy, Andromeda? It is... approximately 151,200,000,000,000,000,000 miles away. Yikes! That number is so big that it is too hard to understand that amount or to even say the number out loud. This is why studying astronomy requires units of measurement that are bigger than miles and kilometers.

When we study individual planets, moons, stars, asteroids, comets, and other small space objects, we do use kilometers (km) to measure length or distance. For example, the average distance between the Earth and the Moon is 369,510 km or 229,605 mi. That is a large number but not so big that it can't be understood or difficult to communicate.

ASTRONOMICAL UNITS (AU)

When we study greater distances within our solar system, we use Astronomical Units (AU). 1 AU is the distance between the Earth and the Sun, which we have already seen is 152,000,000 kilometers or 94,500,000 miles. So, 1 AU = 152,000,000 km. Everyone can agree it's a lot easier to say and understand 1 AU than 152,000,000 km.

If we use Astronomical Units to measure the distance between the Sun and each planet in our solar system, you can see how using this unit makes things simpler. By this unit of measurement, Mercury and Venus are less than 1 AU away from the Sun because they are closer to the Sun than Earth. Objects farther away from the Sun than the Earth have a measurement greater than 1 AU.

If you look at the second picture below, you can see its a lot easier to compare the distances of the planets using Astronomical Units than it would be to compare several distances that are millions or billions of kilometers.
LIGHT YEARS (ly)

Light sets the speed limit of the universe. Nature does not allow any matter or other form of energy to travel as fast as light moves through empty space--186,000 miles/second or 300,000 kilometers/second. At this speed, light can go all the way around the Earth seven times in just one second. Light does not speed up or slow down as it moves through space, so it is what scientists call a "constant" value that can be used in math. This allows astronomers to calculate distances in space, like how far away a newly discovered exoplanet is from Earth.

A light year is a way to measure large distances in space. Usually, light years are used to measure distances between objects in the same galaxy. Even though it has the word "year" in it, a light year is not a measurement of time. A light year is how far light, the fastest thing there is, travels in one year. In one year, light travels about 5,880,000,000,000 miles or 9,460,000,000,000 kilometers. So, 1 light year (ly) = 9,460,000,000,000 km. At the beginning of this section, it was mentioned that the next closest star to Earth after the Sun, Proxima Centauri, is about 24,800,000,000,000 miles away. If we use light years instead of miles, the distance between Earth and Proxima Centauri is 4.3 light years. In other words, a beam of light leaving Earth would have to travel for 4.3 years to reach that star.

In addition to light years (ly), there are also light seconds, light minutes, and light hours for smaller (but still really big) distances. For very large distances, the metric unit prefixes kilo, mega, and giga can be put in front of light years. You should know that "kilo" means a unit multiplied by 1,000. So, a kilolight-year is 1,000 light years. A megalight-year is 1,000,000 light years and a gigalight-year is 1,000,000,000 light years.
Parsecs (pc)

Eventually, even light years become too small to measure the really, REALLY big distances in the universe. A parsec is a special unit of measurement in astronomy that helps scientists understand and communicate even larger distances, such as the distances between galaxies.

1 parsec = 3.26 light years, or 19.7 trillion miles. I'm not even going to type that one out with all the zeros. As with light years, the metric measurement prefixes kilo, mega, and giga can be used with parsec to make it represent even larger and larger distances.

It was mentioned earlier that our closest neighboring galaxy, Andromeda Galaxy, is approximately 151,200,000,000,000,000,000 miles away. If we use light years instead of miles, that same distance is about 2,571,000 ly. If we use parsecs, that distance is 788,333 pc.
31.

Put the units of measurement in order from smallest on the top to the largest on the bottom

  1. Kilometer (km)
  2. Light year (ly)
  3. Meter (m)
  4. Astronomical Unit (AU)
  5. Parsec (pc)
  6. Kiloparsec (kpc)
  7. Centimeter (cm)
  8. Foot (ft)
32.

Which unit of distance would be best for measuring the diameter of Mars?

33.

Which unit would be best for measuring the distance between the Sombrero Galaxy and the Topsy Turvy Galaxy?

34.

Which unit would be best for measuring the distance between the planets Venus and Jupiter?

35.

Which unit of distance would be best for measuring the distance between the Sun and other stars in the Milky Way Galaxy?