1. New Core Curriculum week 4, class-2 Foundations of Scientific Process The Birth of the Universe

2. Hubble’s Law Proxy for velocity  Doppler shift Distance Measurement  Parallax or other more sophisticated methods

3. Proxy for velocity  Doppler shift Distance Measurement  Parallax or other more sophisticated methods

4. Fall 2007 Hubble’s Law What are the ramifications of Hubble’s discovery?

6. Cosmic Microwave Background Radiation (CMB) Additional Evidence for Big Bang & Expanding Universe? background temperature of the Universe

7. Exploring Hubble’s Law Balloon Activity What are Models? help us visualize aspects of nature that seem fairly abstract & build intuition Models provide a conceptual framework for interpreting the data we collect. They help understand what is happening in the otherwise to us invisible world.

8. Tips before you start: don’t place marks too close to the neck or far end of the balloon - it doesn’t stretch uniformly in these areas blow the balloon up as much as reasonably possible! measure the distance between points along the shortest path when done, add your data points to the plot on the board. Each group use a different type of symbol/color so we can distinguish the data sets. Modeling the Big Bang and the Expansion of the Universe with a Balloon

10. How is it a good model? How is it a bad model?

11. Modeling the Big Bang and the Expansion of the Universe with a Balloon How is it a good model? How is it a bad model? -the balloon is finite -the surface of the balloon is only 2- dimensional + curved -the marks drawn on the balloon also expand (they shouldn’t, as galaxies are held by gravity) -the balloon may not expand uniformly (especially if not inflated fully) -it produces an expansion law qualitatively similar to Hubble's Law, in that the velocity of expansion (with respect to the origin) is proportional to distance (from the origin) - it shows that no matter where you draw the origin (i.e., no matter your location), you will always observe that all points are moving away from YOU Another model  rising loaf of bread better, since the resins (“galaxies”) do not expand as loaf expands

13. This plot can be thought of as a calibrating relationship for using velocity as a proxy to measure distance Velocity is proportional to distance

14. What does it mean that distance and velocity are proportional? Can we trace the expansion back to the point where it began? If the Universe is expanding, does that also mean that the Galaxy and the Solar system are expanding?

15. balloon is stretched (multiplicatively) by some factor - we need to think of the Universe the same way that “point” is now the whole balloon/whole Universe... so no. What does it mean that distance and velocity are proportional? Can we trace the expansion back to the point where it began? If the Universe is expanding, does that also mean that the Galaxy and the Solar system are expanding? no, they are bound by gravity - they represent parts of the Universe that have been gravitationally extracted (for now) from the initial expansion

16. What is the importance of Hubble’s law? Universe expands, changes over time Universe had a beginning in time: observable Universe is finite – we can measure its age! once relationship is established, it can be used as an easy way to measure distances to galaxies

17. Think to the sinusoidal wave drawn on the balloon… wavelengths get stretched longer wavelength radiation becomes more red

18. Galaxy voids and Galaxy Clusters Expansion competes with gravity: galaxies = places where gravity “wins” voids = places where expansion “wins”

19. Key Concepts for Week-4, Class-2: (what You need to know, as You will be tested on this material):  Hubble’s Diagram & Hubble’s Law  The significance of Hubble’s constant (inverse time)  Implications behind Hubble’s Law  Big Bang Theory  Evidence for Big Bang Theory  Recall modeling the expansion of the Universe with Balloons  (recall good & bad aspects of this model). The Birth of the Universe