Natural Science - Year II
Unit 63: Hubble and Galaxies
History Weblecture for Unit 63
| This Unit's | Homework Page | History Lecture | Science Lecture | Lab | Parents' Notes |
Unit 63: Hubble and the size of the Galaxy
For Class
- Period: 1750-2000 A.D.
For the interactive timelines, click on an image to bring it into focus and read notes.
Click on the icon to bring up the timeline in a separate browser window. You can then resize the window to make it easier to read the information.
Click here: Timeline PDF to bring up the timeline as a PDF document. You can then click on the individual events to see more information if you want. Exploring this version of the timeline is optional!
- Geographic Location: USA
- People to know: Heber Curtis, Harlow Shapley, Edwin Hubble, Henrietta Leavitt
- See science topics: Astronomy: Measuring distances in space
Lecture:
The Size of the Galaxy
The Curtis-Shapley Debate
Science textbooks often present theories as obvious and dominant, the "true" explanation. As we've seen, however, most scientific theories were formed slowly, and were often subject to resistance by other scientists, or by groups within the culture. The estimation of the size of the universe was no exception. In the 1920s, two astronomers used what is now realized as erroneous data to support opposing theories. Heber Curtis of the Lick Observatory claimed that many nebulae were much further away than individual star systems, and were themselves island systems of stars. Harlow Shapley used data that supported a smaller galaxy and required an interpretation of nebulous objects as gas clouds.
Read about the Curtis-Shapley debate at the NASA site. You can skip the bibliography sections.
- What was the debate about? Why was it important?
- What were the problems with the evidence used to support Curtis' position?
- What were the problems with the evidence used to support Shapley's position?
Leavitt and Variable Stars
Henrietta Leavitt was one of the women astronomers working on projects like Pickering's survey of stars. In her work, she started to notice a relationship between certain kinds of stars and their intrinsic brightness.
- What is the problem in determining distance to a star from a photograph of a star?
- What is a standard candle?
- What is a Cepheid variable?
- What is the period-luminosity relationship?
- How can we use the P-L relationship to determine distances to stars and star systems?
Edwin Hubble
Read about Edwin Hubble at NASA's site on the Hubble Telescope.
- Where did Hubble work?
- How was Hubble able to show that Andromeda lay outside the bounds of the Milky Way?
- What is a "Doppler velocity"?
- What do Doppler velocities for near and distant galaxies indicate about the the universe?
Study/Discussion Questions:
- How does our concept of size shape our idea of man's importance?
- How can scientific data be reviewed for accuracy?
Further Study/On Your Own
- Look at some of the other topics on the history of stellar classification at Harvard.
© 2005 - 2025 This course is offered through Scholars Online, a non-profit organization supporting classical Christian education through online courses. Permission to copy course content (lessons and labs) for personal study is granted to students currently or formerly enrolled in the course through Scholars Online. Reproduction for any other purpose, without the express written consent of the author, is prohibited.