In the textbook section 13.2 you find four stories about scientific hypotheses. We're going to focus on the story of atmospheric pressure. Here is a video on YouTube that also talks about the story. https://youtu.be/EkDhlzA-lwI

Read that section of the textbook and watch the video. After you've done that, read through this assignment and answer the 10 included questions. Your goal as you answer these questions is to apply the concepts from Chapter 13. This is your chance to show me that you understand the material and can apply the ideas to this specific piece of science history. Each question is worth 10 points. You will be graded on accuracy, relevance, and completeness.

Before you submit your response make sure that each answer is numbered correctly and that you have fully answered each part of every question.

The Three Hypotheses

In this story about the discovery of atmospheric pressure, we find three hypotheses discussed. For your reference, I'm including a list of the three hypotheses here.

- Aristotle's hypothesis: Nature abhors a vacuum. (Vacuums are impossible in nature.)

- Galileo's hypothesis: Vacuum suction. (Vacuums are possible and they exert force.)

- Torricelli's hypothesis: Atmospheric pressure. (Air has weight and exerts downward pressure.)

The story begins with Aristotle's hypothesis, because this was a theory that was accepted for around two thousand years. Aristotle believed that it was impossible to create an vacuum in nature. In this context "vacuum" means a perfectly empty space. We're going to start by looking at an experiment that was designed to test Aristotle's hypothesis.

Testing Aristotle's hypothesis:

The experiment was designed by Gasparo Berti. You can see it illustrated around 1:37 in the video. Feel free to watch that section again as you answer the following questions.

1. Explain Berti's experiment. How is it set up? How is the experiment supposed to demonstrate that creating a vacuum is possible?

2. What is the implication of Aristotle's hypothesis? In other words, imagine that Aristotle is there when the experiment is set up, but Berti hasn't opened the bottom of the tube yet. Given Aristotle's hypothesis, what does he think will happen when Berti opens the bottom of the tube? Explain the implication and why the implication follows from Aristotle's hypothesis.

3. Explain the results of the experiment and what it proved about Aristotle's hypothesis. What actually happened when Berti opened the bottom of the tube? Does this prove or disprove Aristotle's hypothesis? (You need to show that you understand how experiments are used to test hypotheses by testing the implications of the hypothesis.)

Two new hypotheses:

Berti's experiment led to two new hypotheses. These hypotheses are both proposed to explain the result of his experiment. One hypothesis came from Galileo, the other came from Torricelli.

Let's start with Galileo's hypothesis. We could call it the "Vacuum suction hypothesis".

4. What is Galileo's hypothesis and how is it supposed to explain the results of Berti's experiment?

Testing Galileo's hypothesis with the "Two Tube" experiment (3:32 in the video). Torricelli creates this experiment to test Galileo's hypothesis. The experiment consists of two tubes filled with mercury. One is a standard tube, the other has a bulb at the top, making it hold more mercury. Watch the experiment in the video.

5. Imagine that the experiment is set up, but the tubes haven't been opened yet. What is the implication of Galileo's hypothesis? In other words, what does Galileo think will happen when both tubes are opened?

6. What actually happens when the experiment is run and does this confirm or disprove Galileo's hypothesis? Explain the results and what those results tell us about Galileo's hypothesis.

Atmospheric Pressure:

The final hypothesis we need to consider is Torricelli's "Atmospheric Pressure" hypothesis. This hypothesis was proposed to explain the results of Berti's experiment. (The one with a single tube of water from 1:37 in the video).

7. Describe Torricelli's hypothesis and how it is intended to explain the results of Berti's experiment.

There were at least three experiments described that tested Torricelli's hypothesis. Let's start with the "Two Tube" experiment we were thinking about in the previous section. (This is the experiment with two tubes of mercury shown around 3:32 in the video).

8. Imagine that the experiment is set up, but the tubes haven't been opened yet. What is the implication of Torricelli's hypothesis? In other words, what does Torricelli think will happen when both tubes are opened?

9. What actually happens when the experiment is run and does this confirm or disprove Torricelli's hypothesis? Explain the results of the experiment and what those results tell us about Torricelli's hypothesis.

Up the Mountain:

The final experiment to test Torricelli's atmospheric pressure hypothesis was conducted when Blaise Pascal took a barometer up a mountain. You can find this around 3:50 in the video.

10. Explain this experiment and how it is supposed to test the atmospheric pressure hypothesis. Be sure you talk about the implications of the atmospheric pressure hypothesis and how those implications are tested in this experiment. How does the experiment confirm or disprove Torricelli's hypothesis?