Theory & Law

• •MISCONCEPTION: If evidence supports a hypothesis, it is upgraded to a theory. If the theory then garners even more support, it may be upgraded to a law.

• In other words: Theories don’t graduate into laws and laws don’t get “down graded” into theories.

SCIENTIFIC LAWS• Are statements of fact meant to explain, in concise terms, an

action or set of actions.

• Are generally accepted to be true and universal, and can sometimes be expressed in terms of a single mathematical equation.

• Are similar to mathematical postulates. They don’t really need any complex external proofs; they are accepted at face value based upon the fact that they have always been observed to be

true.

Give me some examples of scientific laws!

• Newton’s Three Laws of Motion

• The Laws of Thermodynamics

• Boyle's law of gases

• The law of conservation of mass and energy

• Hooke’s law of elasticity

• Galileo's law of free fall

• Kepler's three laws of planetary motion

• Newton's law of gravitation

Laws, continued

• Great examples! But I’m still not sure I can identify a law if I saw one.

No problem! Here’s a quick way of classifying laws:

• They have the following universal form: "in all cases when condition of kind A are

realized, conditions of kind B are realized as well."

• This means laws are suited to mathematical formulas! So when one condition happens, the result can be predicted.

Example: If something is thrown up, then it will fall back to earth at a certain speed.

More law clarification• Not ALL laws can be expressed

mathematically, but they’re a good guide to classifying laws as statements of absolute truth.

•Example: Newton’s Third Law says “For every action, there is an equal and opposite reaction.”

• This can be expressed as: F12 = -F21

HYPOTHESIS

                                  Scientists design investigations based on testable questions they have developed. These questions list specific things that will be

involved in their investigation.

A hypothesis is a statement that predicts the outcome of an investigation.

(If we do this, then this will happen.)

The purpose of a hypothesis is to organize an experiment. If the hypothesis is carefully formed, all the steps of the scientific method follow

- the hypothesis provides the structure.

Give me some examples!

Examples are:

• If the temperature of a gas is increased, then the volume will increase.

• If the length of a pendulum increases, then the period of swing will decrease.

• If runners drink water and run in a race, then they will run faster than runners who drink a sports drink.

Notice a pattern?• Be careful - Not all "if-then" statements are

hypotheses.

• For example the statement:

"If you warm yeast, then more gas will be produced" is a prediction, not a hypothesis.

You have not answered the questions:• What is being tested? • What is related to what? • Is temperature a variable? • Is yeast a variable? • Is gas production a variable?

Hypothesis continued:The Differences between a Hypothesis, Theory, and Belief

HypothesisA hypothesis is a tentative explanation or idea about how things work. It guides you in further work to get a better answer.

• For example:"If a trip was made to the moon then it would be found that the moon is made of cheese."

How could we test this hypothesis?

• Construct a rocket to go to the moon and return with samples. • Make a cheese pizza substituting the moon samples for the

cheese. • Ask people to eat the pizza and see if they can tell any difference

from pizza made with real cheese. • Most likely conclusion: Hey, this pizza tastes like dirt.

SCIENTIFIC THEORIES

• This one is perhaps the most “controversial” of the terms we’ve looked at so far.

• Why? Simply because people mistake a scientific theory for the every day use of the term “opinion”.

SCIENTIFIC THEORIES• A "theory" is not an insult (as in the silly saying

"it's just a theory"). A theory is simply the most elaborate form of consistent scientific knowledge not yet disproved by experiment.

• In experimental sciences, a theory can never be "proved", it can only be "disproved" by experiment.

• This is precisely was makes a theory scientific. A statement that cannot be disproved by experiment may still be highly respectable but it's simply not part of any experimental science.

All of these theories are well documented and proved beyond

reasonable doubt: • The theory of evolution• The theory of relativity• The atomic theory• The quantum theory

A theory is more like a scientific law than a hypothesis. A theory is an explanation of a set of related observations or events based upon proven hypotheses and verified multiple times by detached groups of researchers. One scientist cannot create a theory; she can only create a hypothesis.

                 

   

Laws vs. Theories

• The biggest difference between a law and a theory is that a theory is much more complex and dynamic.

A law governs a single action, whereas a theory explains an

entire group of related phenomena.

An analogy can be made using a slingshot and an automobile.

• A scientific law is like a slingshot. A slingshot has but one moving part-the rubber band. If you put a rock in it and draw it back, the rock will fly out at a predictable speed, depending upon the distance the band is drawn back.

• An automobile has many moving parts, all working in unison to perform the chore of transporting someone from one point to another point. An automobile is a complex piece of machinery. Sometimes, improvements are made to one or more component parts. A new set of spark plugs that are composed of a better alloy that can withstand heat better, for example, might replace the existing set. But the function of the automobile as a whole remains unchanged.

• A theory is like the automobile. Components of it can be changed or improved upon, without changing the overall truth of the theory as a whole.

      

   

                

   

Putting it together

• Where do scientist begin? With the scientific method. Before conclusions can lead to a law or formula, it must be tested!

• Data and conclusions are drawn from data gotten from experimenting.

• Here are the steps to experimenting:

                                                                                               

             

What happens when people draw conclusions from nothing in

particular?Those are beliefs!

• Beliefs guide your actions because they’re based on your history. They’re not based on anything besides thinking a thing is so.

» Is this science? NO

• You may believe that all dogs are friendly and this might prompt you to pet any and all dogs you see. But not all dogs are friendly. So your belief may be based on your past experiences/family/religion/habits, etc. but are not at all scientific.

• The result – NO conclusions can be drawn from what you believe.

Science draws conclusions from the facts that are found from experimenting.

Everyday theories are not scientific. The conclusion is offered first, then facts are found to support that.

That’s not science folks.