The Scientific method. What is a:
- hypothesis
- theory
- law

 

 
 

Hypothesis

A hypothesis is an attempt to explain observations. It is really a best guess. A hypothesis must always be able to be tested by observation or experiment. Through experimentation or further observation a hypothesis can be refuted or supported but never proven. A hypothesis can never be proven as there might be some, as yet, undiscovered evidence to refute it.

Example: Galileo, with the use of a telescope, was able to observe moons orbiting Jupiter. During this time astronomers had a geocentric model of the Solar System. Earth was considered the stationary centre of the Solar System. This model predicted that if the Earth was not stationary the Moon would be left behind. By observing moons orbiting Jupiter Galileo was able to disprove this hypothesis and gave credibility to the heliocentric model of the Solar System.

 

Theory

A theory is a hypothesis or group of hypotheses that have been supported through repeated testing, can be considered a theory. A theory can always be disproved and is valid only as long as there is no evidence to dispute it. If evidence accumulates to support a hypothesis, it becomes accepted as a good explanation of a phenomenon. One can say that a theory is an accepted hypothesis.

Example: It is known that the dinosaurs died out unexpectedly about 65 million years ago. The best explanation so far is that an asteroid impacted the Earth. Evidence exists to support this hypothesis. Many hypotheses have been proposed for what caused the death of the dinosaurs, however, the evidence consistently supports the asteroid hypothesis. Hence the asteroid theory to explain the extinction of the dinosaurs is generally accepted to be true, however, it does not mean that evidence can not immerge in the future to refute the theory.

Is this theory fact? No.

Law

A law is proposed to fit a set of observations with no known exceptions. Scientific laws explain the relationship between its elements but they do not describe the elements or suggest, as theory would, why they behave in certain ways.

Example: Consider Keppler's Third Law. The time it takes for a planet to orbit the Sun is related to its average distance from the Sun according to the formula below.

P2(Earth years) = D3 (AU)

This law clearly gives the relationship between distance and time without the reason why.

 
Consider Newton's Law of Gravity. Newton could use this law to describe the motion of planets around the Sun, but there was no explanation as to why mass and distance were related in this way?

1) When a range of tests support a concept that explains a wide range of observations, this concept is known as a:
2) A set of observations is explained by a
3) A scientists records the path of a planet in the night sky. What skill is she using?
4) A statement that always describes the outcome given a set of conditions is called a scientific:
5) A good hypothesis must :
6) How does a scientist formulate and test a hypotheses?
7) The scientific method, shown above, outlines a set of procedures. What is the next step after objectively testing a hypotheses?
8) When a scientific theory is valid, it allows you to: