New Core CurriculumNew Core Curriculum

week 4, class-2week 4, class-2

Foundations of Scientific ProcessFoundations of Scientific Process

The Birth of the UniverseThe Birth of the Universe

Hubble’s LawHubble’s Law

Proxy for velocity Proxy for velocity Doppler shift Doppler shift

Distance Measurement Distance Measurement Parallax or other more Parallax or other more sophisticated methodssophisticated methods

Proxy for velocity Proxy for velocity Doppler shift Doppler shift

Distance Measurement Distance Measurement Parallax or other more Parallax or other more sophisticated methodssophisticated methods

Fall 2007

Hubble’s LawHubble’s Law What are the ramifications of Hubble’s discovery?

Cosmic Microwave Background Radiation (CMB)Cosmic Microwave Background Radiation (CMB)

Additional Evidence for Big Bang Additional Evidence for Big Bang & Expanding Universe?& Expanding Universe?

background temperature of the Universe

Exploring Hubble’s LawExploring Hubble’s Law

Balloon ActivityBalloon Activity

What are Models?What are Models?help us visualize aspects of nature that seem fairly abstract & build intuition

Models provide a conceptual framework for interpreting the Models provide a conceptual framework for interpreting the data we collect. They help understand what is happening in data we collect. They help understand what is happening in

the otherwise to us invisible world. the otherwise to us invisible world.

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

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?

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)

-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

-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 breadbetter, since the resins (“galaxies”) do not expand as loaf expands

This plot can be thought of as a calibrating relationship for using velocity as a proxy to measure distance

Velocity is proportional to distance

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?

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

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

Think to the sinusoidal wave drawn on the balloon…

wavelengths get stretched

longer wavelength radiation becomes more red

Galaxy voids and Galaxy Clusters

Expansion competes with gravity:Expansion competes with gravity:

• galaxies = places where gravity “wins”

• voids = places where expansion “wins”

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 UniverseThe Birth of the Universe