The Sunshine Curriculum

Sensor/Senses I

Objectives:

• To appreciate the role of the environmental sensors by considering them as an extension of human senses. Sensors sense the same phenomena as human senses, but:
  • they are there 24 hours a day;
  • they are there 365 days a year;
  • their measurements are more precise;
  • their measurements are reproducible.

• To understand (some of) the ways in which those parameters measured by the environmental sensors are important to the survival and welfare of mammals and other forest inhabitants.

Procedure:

• Students use their bodies to sense the same environmental parameters sensed by the sensors in an environmental monitoring station.

• Temperature:
  • Students feel air and attempt to estimate its temperature in degrees. Take average of all students' estimates and compare with thermometer reading.
  • Dig hole in soil 10cm deep. Feel soil. Do you think it is warmer or colder than air?
  • Feel water in pond. Do you think it is warmer or colder than air?
  • Suggest other ways, besides using the heat and cold sensors in your skin, to judge the temperature of your environment. (example: use eyes to determine whether the pond is frozen)

• Wind:
  • Students use the feel of the wind on their cheeks to determine wind direction. Extend arms out in front, and turn until wind feels equal on both cheeks. What sense is being used? (Sense of feel: pressure sensors and cold sensors in cheek skin.)
  • Suggest other ways to tell the wind direction without an instrument. (Look for direction that trees are bending, or direction of flag flapping, or direction of smoke rising.)
  • Suggest other ways to tell the wind speed without an instrument. (Vigor of trees and plants swaying, presence of ripple/waves/whitecaps on water; Beauford scale).

• Solar Radiation:
  • Blindfold students. Have them turn towards the direction from which they think the sun is coming. How can they do this? (heat sensors in skin, part of "sense of feel")
  • Blindfold student. Have him/her sit on ground. Have another student walk between blindfolded sitter and sun, casting shadow over sitter. Blindfolded student says when (s)he is in shadow, when in sun. How does (s)he do this? (heat sensors in skin, part of "sense of feel").
  • Suggest other ways, without using the heat sensors in your skin, to tell whether the amount of incoming solar radiation is high or low at a given time. (examples: distinctness of shadows, diameter of pupil of eye, amount of cloud cover).

• Barometric Pressure:
  • Barometric pressure changes due to weather systems occur too slowly for us to be able to detect them with our bodies. However, there are circumstances under which we can detect barometric pressure changes. Can you suggest what those circumstances are? (Going up or down in an airplane or elevator.)
  • What is the mechanism by which your body detects barometric pressure change when going up or down in an airplane or elevator. (Bulging in or out of ear drum, because air pressure in the inner ear is less or more than ambient.)

Points for possible discussion:

• Why did mammals evolve the five senses that we have?

• Of what use to a hominid in a hunting-gathering society is the ability to sense temperature? Of what use is the ability to sense wind speed and direction?

• Would you consider our ability to sense barometric pressure changes to be a "sense"? Why or why not?

• A human or an electromechanical environmental sensor needs to be "calibrated." There are differences between people and between cultures in the way the human "sensors" are "calibrated." For example, an Eskimo might call a room "too hot" that a child from New York calls "just right."

• A human or an electromechanical environmental sensor has a certain accuracy. There are differences between people and between cultures in the "accuracy" of our human "sensors." For example, in a seafaring culture with sailing ship era technology, most people's ability to sense wind speed and direction would probably be more accurate than in a landlocked culture.

• Are there environmental parameters that are important to our welfare and survival that cannot be sensed by the human senses? (Yes, examples: carbon monoxide, radon, radioactivity)

• It is possible to build electromechanical sensors that measure things that cannot be detected by our human senses (e.g. geiger counter for radioactivity).

• If you could have an additional sense in addition to the five you now have, what sense would you wish for? and why?

• Can you think of an environmental parameter that you can sense with your body that the environmental monitoring stations cannot detect? (Yes, examples: the direction of the sun, cloud type)