Displays and experiments

1. Expanding circles of knowledge
A diagram depicts the increase of scientific knowledge in terms of the areas of concentric circles. Inner circles represent the old theories and their regions of applicability. Outer circles represent new theories which encompass all previous knowledge, and hopefully anything we will encounter in the future. As knowledge expands, sometimes it overtakes the theory, requiring a new one (a new outer circle). (This model implicitly contradicts popular historian of science Thomas Kuhn and his paradigm/revolution model.)

2. Black boxes of reality
Our knowledge of the “world as it really is” can be compared with our knowledge of a “black box:” a container with inputs and outputs but unknown contents. The visitor is presented with three black boxes with two buttons and a light each. We can act in the world (push the buttons) and observe the results through our senses (see the light light up). But we can’t know what’s inside the box (the thing as it really is, or the “thing in itself” as Kant said). The visitor is invited to theorize about what’s in the boxes. Upon peeking, it is found that the boxes (which all exhibit the same behavior) have three different internal mechanisms, including one with a smaller black box inside.

3. The white crow
An standard example of the limitations of knowledge based on experience is that of the bird watcher who hypothesizes that all crows are black, after seeing only black ones so far. Maybe there is a white one out there no one has seen, it’s impossible to be certain. Still, it’s a good bet to say the next one you see will be black. The visitor can pull a lever to spin a jackpot-like wheel with (almost all) black crows on it. The visitor can form a hypothesis and test it by spinning the wheel multiple times. The more black crows come up, the more the hypothesis is confirmed, even if there was a white one somewhere not yet seen.

4. The game of life
This computer game demonstrates how life could spring from “dead matter” without a soul. The computer has many square “cells” that follow a simple set of rules that connect adjacent cells. The viewer can change the arrangement of cells or preload patterns, resulting in surprising action that never could have been predicted based on the simple rules. Patterns emit other patterns that move across the screen and are absorbed by other patterns, as some grow and others change. It’s an example of “emergence” and another argument for a big picture approach to complex systems.

5. Photon counting interferometer
This ambitious experiment reveals the utter strangeness of quantum particles. A light source emits light particles one at a time. The light signal splits into two parallel paths that recombine by crossing. A slight change in the length of one of the paths (controlled by the visitor) determines which final output path all the light appears in. It is argued that only a wave that was simultaneously in both paths could behave this way. Upon examining the signals in each path, the visitor only finds particles in one or the other, not a wave in both. How could this be? This experiment confronts the visitor with deep issues concerning knowledge, existence and time. 

6. Optical illusions
Illusions are the bane of knowledge based on sense experience. How do you know your perceptions are not just illusions? Well, you can test them. The viewer sees a hologram, which is convincing until one puts one’s hand through it. An illusion of motion is created by a pattern that is clearly stationary when you look closely at its parts. An illusory color is found to be comprised of three primary colors when the visitor can turn each off and on at will. We needn’t be afraid that illusions dominate our experience of the world, because they have the hallmarks of illusions rather than the hallmarks of reality, which careful tests reveal.

7. What is a wave
It can be strongly argued that the entire universe consists of waves of one sort or another. What is a wave? The visitor can manipulate some electronic and sound waves to see how amplitude (loudness), frequency (tone), phase (delay), resonance (ringing) and interference (mutual cancellation) work. These concepts apply to everything from earthquakes to atoms. The concept of a wave is one of the most powerful explanatory tools in physics. We recognize wave phenomena from experience with sound, so sound is emphasized in this exhibit, which allows the visitor to play until the concepts become intuitive.

8. The famous uncertainty principle
In quantum physics (the study of the smallest pieces of matter and energy), there are pairs of related quantities that can’t be measured perfectly. That is, the more precisely you know one of these quantities, the less you know the other. Some uncertainty is always present. This is because on this level, everything consists of waves. Two examples are given the visitor: one shows that the more you constrain a light beam in a narrow slit, the more it spreads out after going through. This is really due to the quantum light particles and the real uncertainty principle. The other example is an analogy using sound. The visitor varies the tone and duration of repetitive beeps. As the duration is decreased, it becomes harder to discern a change in tone. As uncertainty in time is reduced, uncertainty in frequency is increased and vice versa. The uncertainty principle has been one of the most philosophically controversial discoveries in quantum physics, and a source of much popular confusion.

9. Introduction
One display will be devoted to orienting the visitor and describing what’s being presented. Questions that should remain in the visitors mind as they view the displays will be emphasized.