Title Bar - Cosmology

Scaling Activity Introduction

We begin by creating a scaled-down map of the classroom to familiarize students with scaling and distance on a very familiar level. We continue by scaling the size of the solar system and continue this model out to the edge of the local group. Also, in another model the distance to the edge of the known universe is scaled to a comprehensible size by setting the distance between the Sun and the Earth to the thickness of a sheet of paper. It is presumed that students have some knowledge of the planets and workings of the solar system, and also a general idea of the scale of the solar system. This exercise builds on this knowledge and extends it to scale the universe including the nearest star to the Sun, the distance to the center of our galaxy, the diameter of the galaxy, the distance to the next galaxy, the diameter of the local group and the distance to the edge of the known universe.

Tables I, II & III, which are to be used in the activities which follow, show statistics of the planets in metric units, Earth units, and scaled units, respectively. The scaled units are calculated based upon scaling the diameter of the Sun to 3 inches. This convenient size is demonstratable in a large classroom, and also familiar to students as ordinary objects, like oranges or tennis balls. It also allows for conceivable scaled distances to astronomical objects. The first two tables are included mainly for reference and comparison, and to encourage familiarization with scientific units.

 

Table I. Astronomical Object Properties in metric units


Mass (kg)

Equatorial Diameter (km)

Distance from

Sun (106 km)

Rotation Period

(days)

Orbital period

(years)

Sun

1.99 x 1030

1390000

0

Mercury

3.30 x 1023

4,880

58

59

0.241

Venus

4.87 x 1024

12,100

108

243

0.615

Earth

5.97 x 1024

12,756

150

1

1

Mars

6.42 x 1023

6,790

228

1.03

1.88

Jupiter

1.90 x 1027

142,984

778

0.4

11.86

Saturn

5.69 x 1026

120,536

1427

0.4

29.46

Uranus

8.66 x 1025

51,118

2871

0.7

84.01

Neptune

1.02 x 1026

48,528

4497

0.6

164.8

Pluto

1.31 x 1022

2,300

5910

6.4

248

Proxima Centauri

40500000

Distance to Center of Galaxy

2.5 x 1011

Diameter of Galaxy

9 x1011

Distance to Andromeda

2 x 1013

Diameter of Local Group

3 x 1013

 

Table II. Astronomical Object Properties in Earth Units (based on Earth mass and diameter)



Mass (Me)

Equatorial Diameter (De)

Distance from Sun (AU)

Rotation Period (days)

Orbital period (years)

Sun

333000

109

0

Mercury

0.06

0.38

0.39

59

0.241

Venus

0.81

0.95

0.72

243

0.615

Earth

1

1

1

1

1

Mars

0.11

0.53

1.52

1.03

1.88

Jupiter

317.9

11.2

5.2

0.4

11.86

Saturn

95.18

9.4

9.54

0.4

29.46

Uranus

14.5

4.0

19.19

0.7

84.01

Neptune

17.1

3.8

30.06

0.6

164.8

Pluto

0.002

0.18

39.5

6.4

248

Proxima Centauri

270000

Distance to Center of Galaxy

1600

Diameter of Galaxy

6000

Distance to Andromeda

140000

Diamter of Local Group

200000

 

Table III. Astronomical Object Properties in Scaled Units (based upon scaling the diameter of the Sun to 3 inches)



Mass

Equatorial Diameter (Scaled Inches)

Distance from Sun (Scaled inches)

 

Rotation Period (days)

Orbital period (years)

0

Sun

3

0

Mercury

0.011

10 ft.

59

0.241

Venus

0.026

19 ft.

243

0.615

Earth

0.027

27 ft.

1

1

Mars

0.015

41 ft.

1.03

1.88

Jupiter

0.31

140 ft.

0.4

11.86

Saturn

0.26

260 ft.

0.4

29.46

Uranus

0.11

520 ft.

0.7

84.01

Neptune

0.10

810 ft.

0.6

164.79

Pluto

0.0050

1100 ft.

6.4

247.69

Proxima Centauri

1400 miles

Distance to center of galaxy

8400000 miles

Diameter of galaxy

31000000miles

Andromeda

730000000 miles

Diameter of Local Group

1000000000 miles




Because this exercise concentrates on distance scale, you may want to begin the lesson with an exercise demonstrating the relative masses and radii of the planets. For a good example of this comparison, consult the New Jersey Science Curriculum Framework in the list of learning activities for standard 11 under Planet Gravities. This exercise uses relative numbers of pennies in empty soda cans to represent the weight of a full soda can on other planets. The number of pennies in each can changes based upon how massive the particular planet is and how big its radius is.


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