General

Lab#2: Modeling the Big Bang

Background: According to the big bang theory, almost all galaxies are moving outward from all other galaxies.

Objective: Demonstrate the principles of this expansion with a simple model.

Materials: Large uninflated round balloon; water-based felt-tip pen, string 20 cm long; metric ruler

Procedure:

Experiment 1:

  1. Mark a pair of dots 0.5 cm apart across the middle of the uninflated balloon. Label them A and B. Mark a third dot 5.0 cm away from B. Label this dot C.
  2. Blow into the balloon for approximately 5-10 seconds. Record your elapsed time. Pinch the end of the balloon between your fingers to keep it inflated.
  3. Use the string and ruler to measure the distance between A and B and C and B.
  4. Calculate the rate of change in the distances between A and B and between C and B.
  5. Allow your balloon to deflate.

Experiment 2:

  1. Obtain a string that is 100 cm long. Mark 10 cm intervals on your string. Inflate the balloon so that it is 10 cm in circumference at the widest point. Measure the distance between A and B.
  2. Repeat this step every 10 cm until you have a minimum of 5 data points.
  3. Create a table in your lab note nook to record your data. Be sure to give your table a title, headings, and units where needed.
  4. Graph the relationship between distance and circumference using the Create-a-Graph website.

Data (Copy the tables and formula into your notebook)

Table 1: Distances

Uninflated distance (cm) / Inflated Distance (cm)
Distance between A and B
Distance between B and C

Inflation Time: ______(seconds)

To calculate the rate of change:

Distance (inflated balloon)-Distance (uninflated balloon)

Balloon inflation time

Table 2: Rate of Change

Rate of Change between A and B (cm/sec) / Rate of change between B and C (cm/sec)
Group data
Class Average

Analysis and Conclusions

  1. S 16.1 Look at all of the class data. How can we make sense of all these numbers? Do some numbers not look like the others? Why do you think this is? Why is it a good idea for scientists to collect a lot of data?
  1. I 20.2 In the first experiment, did the distance between A and B or between C and B show the greatest rate of change? Use your data to explain your answer.
  1. E 20.1 Suppose dots C and A represent galaxies and dot B represents Earth. How does the distance between the galaxies and Earth relate to the rate at which they are moving apart?
  1. I 16.4 In experiment 2, describe how the distance between point A and B changes as the circumference increases? Describe the “line” in your graph.
  1. E 20.2 Your balloon is considered a “model”—it helps explain how the universe works. In what ways is your model like the actual universe and in what ways is it not like the universe?