The Expanding Universe

Age

Middle School, High School

Format

Hands-on

Materials

   Data from Hubble's 1929 publication
   A chalkboard or whiteboard 

Safety Precautions

Science Theatre demonstrators must keep the safety of themselves and their audience in mind at all times. All Science Theatre demonstrators must have read through the Safety Training page. The ST Safety Box with first aid kit, fire extinguisher, etc. should always be available to demonstrators. Always wear safety gloves, glasses, and a labcoat if handling chemicals; always perform potentially dangerous demonstrations at a safe distance from the audience; and always keep a very close eye on any volunteers you call from the audience.

Preparation

This demonstration should be preceded by a discussion of the Doppler effect (e.g. the Doppler Ball demo). The audience should understand how a galaxy's redshift can indicate it's radial velocity (speed towards or away from Earth). You can also precede this with the standard candle demonstration so the audience understands how distance to galaxies are estimated.

Copy some of the data from Hubble's 1929 paper onto the whiteboard for the audience to consider. You don't need to write down every data point - just make sure you have enough to illustrate the linear trend.

Demonstration

Present the audience with the galaxy distance and velocity data from Hubble's paper. Guide them through the discussion described below.

What to Say

1. Discussion of what the data is and how it was gathered.

2. Discussion of overall trend - Hubble's law.

3. Discussion of what universal expansion means.

4. Discussion of local group velocities vs Hubble flow.

Why It Is

More recent observations and other lines of evidence for expanding universe.