What is Inquiry in the Natural World”?

What is a “physical object”?

What are physical objects made of?

Aristotle (384 – 322 BC)

Another early idea: “atomism” Leucippus & Democritus (~ 500 BC) John Dalton, A New System of Chemistry

/SnowHydro/mol.html The quantum physics model of matter

How easy is it to measure physical objects?

What can’t we see?

Modern instruments have greatly extended our detection abilities

Why do physical objects behave the way they do?

Anthropomorphic explanation

Mechanistic explanation

Can we make predictions about the natural world?

Given a knowledge of the “laws” of physics, can you predict what will happen if I drop this ball? Given a knowledge of the “laws” of physics, can you predict what will happen if I drop this ball?

Do the results support your prediction? Do the results support your prediction?

Chaos Theory Chaos Theory

Types of Inquiry

Curiosity

Curiosity-driven science Basic or “pure” often leads to surprisingly practical discoveries

Problem Solving

Problem-solving science Applied or “practical” Gives us power over the natural world

How do we investigate the natural world?

Francis Bacon (1561 – 1626) if we understand nature we can dominate it Questioned authority Emphasis on incompleteness of knowledge Proposed a new method of studying nature observation over philosophical speculation

Hypothetico-deductive scientific method

Step 1: Observations

The “Where’s Waldo” problem

Step 1b: look for a general pattern This step uses a process called Inductive Reasoning ~ in which we develop a rule based on many individual examples

Step 2: Think up explanations (hypotheses) for the patterns observed 3. is generally applicable A useful hypothesis: 1. leads to accurate predictions 2. is as simple as possible

Step 3: Make a testable prediction This step uses a process called Deductive reasoning ~ in which we use the rules of logic to generate a prediction

Step 4: Make observations or do experiments to test our explanations

How can you tell if someone is a Witch?

A Witch! A Witch! We’ve got a Witch

What’s the general pattern here?

If she looks like a Witch and acts like a Witch she is a Witch - Nose like a Witch - Hat like a Witch - Wart like a Witch -Turned someone into a newt Must be a Witch!

What do you do with Witches? Burn them!

What do you burn other than Witches? Wood

Why do Witches burn? Because they’re made of wood? How can you tell she is made of wood? Build a bridge out of her

But can’t you also build bridges out of stone? Oh Yeah!

Does wood sink in water? It Floats Throw her in the pond

What else floats? Bread! Apples! Very small rocks! Gravy! A Duck Cider! Cherries! Mud! Churches! Lead!

So, logically... If she weighs the same as a duck She’s made of wood And therefore... SHE’S A WITCH!

Bring my large scales She DOES weigh the same as a duck SHE’S A WITCH!

 Witch  Wood Witch  burns Wood  burns

 Duck  Wood Wood  Floats Duck  Floats

Duck  Wood Girl’s weight  Duck’s weight Witch  Wood Girl  Wood  Girl  Wood  Girl  Witch

William of Ockham (1280 – 1347) “ Pluralitas non est ponenda sine necessitate” Translation  Entities should not be multiplied unnecessarily Ockham’s Razor “keep it simple”

Description of Motion of Planets around the Sun

Two Competing Models with Different Predictions

Kepler - elliptical Shape of Planetary Orbits Copernicus - circular

More accurate prediction is “better” Perform Experiment

Two Competing Models with the Same Predictions

Model # 1 Planets move around sun in ellipses

decreases as the square of the distance force between them and the sun

Model # 2 Planets move around sun in ellipses

decreases as the square of the distance force between them and the sun

Model # 2 Force is generated by will of powerful aliens

Models # 1 and # 2 Force between planets and sun determines motion of planets

Models # 1 and # 2 same type of force

Models # 1 and # 2 predicted motion of planets identical for both Models

Model # 2 has additional baggage (the will of aliens) that is unnecessary for description of system

Ockham’s Razor reject’s 2 nd model

motion of planets can be explained by simple idea of force Solar system may be permeated by alien intellect BUT no evidence of alien’s presence nor their absence

It does not guarantee that the simplest model is correct, it merely establishes priorities Application of Ockham’s Razor directs us to look to simplest model

Scientific Theories keep changing so where is the Truth?

Newton & Theory of Gravitation Newton’s theory “The Truth” 1666 – explained all the observed facts Predictions later tested and found correct to within accuracy of instruments used

Einstein & Theories of Relativity 19th century – more accurate instruments Slight discrepancies in Newton’s theories Einstein’s theory explained newly observed facts Found to be correct with accuracy of instruments used Einstein’s theory “The Truth”

Has the Truth changed? Theories can be shown to be incomplete No it hasn’t - Universe is still the same “Truth” means it agrees with all known experimental evidence

New Theories Devour and assimilate its predecessors Explain old and new data

Acknowledgements I would like to thank Dr. Ted Georgian for the use of a number of his slides and especially his idea to use Monty Python as a humorous example of the scientific method