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Our View of the Universe

Discussion: Scale

Lots of people have worked to try and understand the size and scale of objects in Astronomy.

Choose one of the links listed here to, watch or explore the demo, and share something interesting you learned with your dicsussion pod.

  • How Far Away is the Moon? (The Scale of the Universe) by Veritasium (YouTube) If the Earth were the size of a basketball and the moon a tennis ball, how far apart would they be? Diagrams that are not to scale make us think that they're closer than they really are.
  • Powers of Ten™ (1977) by Eames Office (YouTube) Powers of Ten takes us on an adventure in magnitudes. Starting at a picnic by the lakeside in Chicago, this famous film transports us to the outer edges of the universe, returns to Earth, and ends inside a proton of a carbon atom within a DNA molecule in a white blood cell.
  • How big is the Universe? by BBC Ideas (YouTube) Revisiting ‘Powers of Ten’: what we've learned about the Universe since 1977. Professor Brian Cox takes us on a journey from a small picnic on Earth... to the deepest depths of space over ten billion light years away.
  • Solar System Size and Distance by NASA JPL Edu (YouTube) How big are the planets and how far away are they compared to each other? See how the sizes of planets and the distances between them compare. And find out why it's so hard to create a scale model of the solar system that accurately represents both size and distance on a single screen or the page of a book.
  • Scale of the Solar System Demo (web page) This page shows a scale model of the solar system. The Sun and planets are shown in corresponding scale. Unlike most models, which are compressed for viewing convenience, the planets here are also shown at their true-to-scale average distances from the Sun. That makes this page rather large - on an ordinary 72 dpi monitor it's just over half a mile wide.

Lecture Tutorial: Position

Work through the Position Lecture Tutorial on pages 1-2. Read carefully, and discuss any questions with your group. Make sure you check agreement on Question 8 in the tutorial book!

Check Your Lecture Tutorial Understanding

A dome-shaped local sits above the horizon, with Earth at the center and Earth’s equator marked. The north celestial pole and North Star are indicated along the tilted rotation axis. Arrows indicate the direction of celestial sphere rotation, and dashed lines illustrate the stars’ circular paths around the celestial pole. Two example stars (Star A and Star B) trace curved paths across the sky. Star B traces a circular path from the back of the dome (1), the zenith (2), front of dome (3), and above the horizon directly below the North star. Star A follows a larger circle from the farthest point of the horizon (1), to high on the rightmost edge of the dome (2), to the front point of the horizon(3), to down below the horizon (4).

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Which star(s) will set on the Western Horizon?

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What direction would you face to see Star A when it is highest in the sky?

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Where in the sky does the observer look to see Star A at the position marked?

A dome-shaped local sits above the horizon, with Earth at the center and Earth’s equator marked. The north celestial pole and North Star are indicated along the tilted rotation axis. Arrows indicate the direction of celestial sphere rotation, and dashed lines illustrate the stars’ circular paths around the celestial pole. Two example stars (Star A and Star B) trace curved paths across the sky. Star B traces a circular path from the back of the dome (1), the zenith (2), front of dome (3), and above the horizon directly below the North star. Star A follows a larger circle from the farthest point of the horizon (1), to high on the rightmost edge of the dome (2), to the front point of the horizon(3), to down below the horizon (4). Star A is marked on the back half of the dome, between points 1 and 2.