Nature of Science• Observation v. Inferences• Hypothesis, Theories, & Laws• Variables & Controls

A Portrait: Take a moment to observe…

What do you see? Write it down.

How come we are looking at the very same drawing and seeing two different things?

How can it be that some of us see only one face and not the other?

Is it possible that some scientists may look at the same piece of evidence or set of data and see different things?

The Old Lady

The Young Lady

In the same manner that you were not able to see the face of the young lady in the drawing, scientists sometimes fail to `see' a certain set of evidence as relevant to their questions.

Scientists sometimes tend to infer different things from the same set of data in the same manner that you inferred totally different things from the same piece of evidence: The portrait.

How does this relate to science?

Investigating Tracks: Describe the scene…

Describe the scene…Observation orInference?

• Based on the same set of evidence- many equally warranted answers to the same question can be inferred.

• Scientists make similar inferences as they attempt to derive answers to questions about natural phenomena

• No single answer (or story) may solely account for that evidence...several answers are often plausible

• Scientists may simply never find the answer as to what has really happened.

Observation v. Inference

Observation:

When studying something describe only facts that you can see, touch, smell and hear. You are not making any guesses. THIS IS NOT AN OPINION!!

Ohh… This liquid is green and it is leaking from a brown can. I also smell it.

Inference: using your observations

to make a guess about an object or an outcome

THIS CAN BE A SCIENTIFIC

OPINION

Based on my observations, I think that this can is old and is leaking a toxic substance.

Describe the scene…

Define observation & inference…

Practice Please Make some observations and

inferences about the following picture.

LAWHYPOTHESISTHEORY

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Theories and laws are different kinds of knowledge- one can not become the other theories are inferred explanations for observable

phenomena laws are statements or descriptions of the

relationships among observable phenomena laws cannot be `proven theories', because in

addition to the fact that these are different kinds of ideas, neither scientific hypotheses,

nor theories or laws can be `proved'.

Hypothesis v. Theory A hypothesis, or set of hypotheses, can

develop into a theory or a law hypotheses explain relatively limited sets of

observations in a certain field of scientific research

theories often explain relatively huge sets of seemingly unrelated observations in more than one field of investigation.

Scientific Hypothesis

A hypothesis is an educated guess based upon observation. It is a rational explanation of a single event or phenomenon based upon what is observed, but which has not been proved. Most hypotheses can be supported or refuted by experimentation or continued observation.

Scientific Theory Scientific theory- Inferred explanation for

observable phenomenaA 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; he/she can only create a hypothesis. 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.

Examples: Theory of Evolution, Theory of Relativity

Scientific LawsScientific law: States, identifies, or describes relationships among observable phenomena

Laws must be simple, true, universal, and absolute. They represent the cornerstone of scientific discovery, because if a law ever did not apply, then all science based upon that law would collapse.

Example: Law of Gravity, Newton’s Laws of Motion