ISME is intended for science museum audiences: ages 8 to adult, with a focus on about age 12.
Use of Sound
The use of sound is integral to ISME. The Arecibo signal and other example radio signals are played as sound (radio waves have much higher frequency than sound; the exhibit shifts the frequencies down into the audio range).
Sound provides a nice, tangible way of demonstrating ideas about signals (frequency, bandwidth, etc.). It adds pizzazz to the exhibit. It also connect with the SETI-related movie "Contact", which uses sound to represent radio signals at several critical points.
The exhibit constantly displays whatever sound is playing both as a waveform (like an oscilloscope) and as a 3-D graph of the spectrum over time.
The exhibit consists of four "pages", each of which teaches some concepts and offers an activity.
The exhibit's display is divided into three regions:
1) "Listen to Space"
Concepts: This page is supposed to a) attract attention, and b) get across the idea that we're "on-line", listening for radio signals from life on other stars.
Activity: the user listens to and watches the signal from Arecibo, checking for the narrow-bandwidth Gaussian pattern.
To Do: - Example of the pattern to look for? Maybe have two buttons: Listen to Space and What to Listen For - Explain that what you're seeing is probably noise from Earth. - Add Ron Hipschmann's QTVR views of Arecibo.
2) "What to Listen For"
Concepts: a) explains the ideas of frequency and bandwidth, b) explains why we're looking for narrow-bandwidth signals, and c) explains how a celestial source can be distinguished from man-made interference.
Activity: a) the user can click on several types of signals, hearing and seeing them; b) the user can click on a demonstration of the telescope beam passing over a point source.
To do: - More signal types, maybe a composite. - picture of TV transmitter
3) "Drake's Equation"
This a) explains that there may be many other intelligent races in the universe, even within our own galaxy, and b) shows how the number N of such races may be estimated using a simple formula.
Note: The real Drake's equation has seven terms rather than three, and it's a bit more complex: it involves time as well, e.g. the rate at which stars are born and the duration of a technological society. This is probably too complex for our target audience.
Activity: Fiddle around with the terms of the formula, leading to larger or smaller estimates or N. This estimate is shown graphically and sonically.
Graphics: The current value of N is shown by the number of specially-colored stars in a galaxy map.
Sound: You hear a signal, a sum of several pulsed and continuous sine waves, representing the sound of N alien signals being heard simultaneously.
4) "Play the ET Search Game"
This teaches a) that a radio telescope "hears" in a very narrow beam; b) the a SETI search program must have a strategy for where to point this beam (i.e. where to listen); c) two popular strategies: targeted search and sky survey.
Activity: Play a game where you control a radio telescope beam, moving it over an area of the sky. You develop your own search strategy to find as many alien signals as you can.
Graphics: The sky map currently has randomly-generated stars with a uniform distribution. Possible alternative: non-uniform distribution so there are distinct areas with lots of small stars. This is more like the real sky, since the dense part of the Milky Way occupies a small part of the sky, and it better differentiates the Targeted Search and Sky Survey strategies.
Sound: As you move the telescope, you hear the sound of the closest star. Alternative: play the combined sounds of all the stars in the telescope beam. This would emphasize the difficulty in picking signal out of noise.
To do: - Synthesized voice announces time left. - high scores of the day. - In game-over page: Sidebar on major SETI projects, pictures of scopes.