chapter 2 thinking critically about the environment

Chapter 2 Thinking Critically About the Environment

Basing our ideas and policies on SOUND SCIENCE, not opinion or conjecture.

Sound Science: continual refining of understanding by questioning and active investigations of questions.

A Brief History of Scientific Thought

Early History:1)Ancient Babylonia and Egypt:

-observations carried out to enhanceagriculture, and for religious reasons.-predictions of human events basedon natural occurrences, such as starposition.

Key: Ancients did not distinguish between science and religion.

2) Greeks: -developed more sound,theoreticalapproach to science. -knowledge for its own sake.

Key: gradual movement of pure science away from religion.

3) Modern Science: -late 16th, early 17th century-development of scientific method-first described by Francis Bacon in 1620. -Galileo was a big proponent of valid scientific investigation, ratherthan conjecture.

Key: Questions like “How?” increased.

Assumptions of Science1) Natural events follow patterns that can be understood by observation.2) Basic patterns in nature are the same in allplaces throughout the universe. 3) Science is based on induction; the extension of observations to generalizations. 4) Generalizations can be tested for validity.

5) Science can never offer absolute proof for any theory, only disproof.

What is PROOF?Deductive vs. Inductive Reasoning

Deductive reasoning is based on premises,which are initial assumptions about asubject.

If the initial premise is incorrect, the reasoning based on it will be incorrect.

Problem: D.R. does not require that the premise be true, only the reasoning.

Inductive reasoning is based on observation, which cannot usually be used with a 100% certainty.

Ex: “All swans are white”

What we really mean: “All the swans thatwe have observed were white”.

There may indeed BE black swans, but we have not seen any.

A proof in inductive reasoning, therefore,leads to a probability that the proof is valid.

This allows us to express our certainty about the conclusion, based on the initialquality of our observations.

Problem: this process is often mistaken for deductive reasoning, which leads tomisunderstanding of the meaning of science

Measurement and Uncertainty

Scientists know that ALL measurements are approximations, limited by the type of instrument used to take the measurement.

Uncertainties caused while performing an experiment are called experimental errors.

Errors can be systematic, or random

Systematic errors occur consistently, suchas when a machine is poorly calibrated. Ex: ALL temperature readings in anexperiment are low by 5 degrees C dueto a poorly calibrated thermometer. Random errors occur usually once, because of a recording error, or an errorin calculation of a single number. Ex: a transcription of 90 to 09

The Methods Of Science-Observation: made through any of the five senses, or by instruments that measure beyond our capability.

-an observation that is agreed upon is called a fact.

-an inference is an idea based upon an observation, but must first be confirmed.

Example: a white crystalline substanceis observed, and an inference is made thatthe substance is table sugar.

Before this inference can be made a fact, the inference must be tested for validity.

How could you test this inference?

A hypothesis is a way to test an inference.

Generally, a hypothesis is formed into an“ if-then” statement.

A hypothesis is held to be true until it isdisproved. Therefore, every hypothesismust be able to be tested for validity.

A Proper ExperimentFor an experiment to properly test aHypothesis, it has to be a Controlled Experiment.

A controlled Experiment has several keycomponents:1)A proper Control Group, which servesas a comparison of change.

2) An Experimental Group, upon which any changes will be applied.

Types of Variables-An Independent Variable is the one which is applied by the scientist. (Manipulated Variable)

-A Dependent Variable is one which ismonitored for change. (Responding Variable)

3) Replication of Groups

-Especially in Biology or Environmental Science, the number of Control andExperimental replicates should be as highas is feasible. -This accounts for natural variability, andallows proper statistical analysis of the data to be taken.

Precision vs. AccuracyPrecision is the degree of exactness with which a measurement is made.

Ex: a thermometer that measures to .001degrees is more precise than one that measures to .1 degree

Ex: a ruler marked in mm vs. cm

Accuracy is the degree to which measured values are correct, or agree with accepted values.

Ex: a watch that is set to the proper time.

Precision does not always guarantee accuracy!

Ex: a Rolex watch set to the wrong time.

The Need to DefineOperational Definitions describe partsof an experiment in a way so that other scientists can understand their meaning.

This allows for the experiment to be replicated by others, a key component of valid science.

Ex: common measurement values in recipes. (Cup, tablespoon, etc…)

For a valid experiment, the variables (dependent and independent) must be defined before the experiment is carriedout. Ex: We will measure the amount on CO2

in the atmosphere in ppm.

Taking DataDuring an experiment, data must be recorded. Data may be numerical, orquantitative data, or nonnumeric, or qualitative data.

Ex: Qualitative: relative sizes (s/m/l),colors, general weather observationsEx: Quantitative: measurements, weatherNumbers(inches of rainfall), temperature

Sometimes it is possible to convert qualitative data into quantitative data.

This makes it much easier to subject the data to statistical analysis. Ex: levels of plant disease on a crop-visually given a rating of 1-5, with 1having the least disease. It is VITAL that operational definitionsare given for performing this exercise.

Science vs. Technology

The terms “science” and “technology” are often interchanged, but this is wrong.

Science refers to the understanding of The natural world. Technology refers to the control of the natural world, for the benefit of humans.

Science often leads to new technology, and new technology often leads to newavenues of science, but they are distinctideas.

Science is often limited by the availabletechnology. When the technology matures,the science that uses it will also mature.

Ex: telescopes, satellites, Hubble

Objectivity in ScienceWhile the goal of science is to be value-free, it is understandable that a scientistssocial values and ethics will come into play. It is vital that a scientist understand theirbiases, and try to minimize rather than ignore them.

High standards for evidence are one wayof ensuring that objectivity is maintained.