Science is the means of studying the physical world

Science is the art of not fooling yourself (Richard Feynman)

The Scientific Method

The Scientific Method

• Study a problem (prior knowledge)

(e.g., why do more earthquakes occur during the summer in the Cascades?)• Observations, measurements, collect info

(Find patterns and regularities of behavior, e.g., object dropped fall towards the ground)• Formation of a hypothesis

(The beginning of a reasonable guess:• A reasonable statement that can be checked by anyone • Offers possibilities of prediction and tests)• Predict consequences of a hypothesis

• Experimental testing and formation of theory

(hypothesis that explains all available data may become a theory)

• Theory becomes principle/scientific law

(if theory withstands testing over long period of time, e.g., gravity, evolution, …)

The Scientific Method

What is a Theory?

• Must be capable of explaining a large number of different observations

• Must be testable, subject to new testing, and refinement as new data becomes available

• Theories, principles, and laws are not forever

• They get dropped or undergo revisions in the light of new evidence

• Good theories last a long time

What is a Theory?

An Example: “A Fire-breathing dragon lives in my garage”

(from The Demon-Haunted World by Carl Sagan)

Scientist Garage OwnerWhere’s the dragon Right here but it is invisible

Spreads flour on floor Good idea, but the dragon floats

Uses infrared sensors But the invisible fire is heatless

Spray-paints dragon tomake it visible

Great, but it is an incorporeal dragon, so the paint won’t stick

For every physical test that is proposed there is a special explanation of why it won’t work.

What’s the difference between an invisible, incorporeal, floating dragon who spits heatless fire AND no dragon at all?

Question:

If it is not testable and does not explaina large number of observations it is not a scientific theory, principle, or law!

from: www.astronomy.pomona.edu

The Mayans viewed the Earth as flat and four cornered, with one corner in each cardinal direction. Each direction had a color: red for east, white for north, blackfor west, yellow for south and green for the center. The sky was supported by four trees, one in each corner and one at the center. The trees were all different colors. The Earth was on the back of a giant crocodile resting in a pool of water lilies. The crocodile's counterpart in the sky was a double-headed serpent. This is probably because the Mayan word for sky was close to the Mayan word for snake. Heaven had 13 layers. Each layer was associated with a different god. The underworld had nine layers, each associated with a Lord of the Night. The underworld was a cold and unhappy place. Most Mayans went to the underworld after their death. (from: Jeremy Wertheimer, Archeoastronomy Project, Pomona College)

Example: Mayan’s world view

Scientific Uncertainty

Uncertainty in the prediction of Katrina’s path

x

y

Scientific Uncertainty

2 data points and “knowing” a line fit is required perfect fit

x

y

Scientific Uncertainty

2 data points and “knowing” some curve fit is required many fits possible

x

y

Scientific Uncertainty

More than 2 data points and “knowing” a line fit is required perfect fit only forvery unique situation: perfect data pointswithout errors all lining up perfectly (does not exist in reality)

x

y

Scientific Uncertainty

More than 2 data points and “knowing” a line fit is required fit is still possibleif uncertainties are considered ...

… but there are infinitely manypossible fits, althoughthe range of fitsmay be reasonableto make predictions

x

y

Scientific Uncertainty

More than 2 data points and “knowing” a line fit is required fit is still possibleif uncertainties are considered ...

Using so-called inverse theory wecan determine the best fit that minimizes the errors

… but there are infinitely manypossible fits, althoughthe range of fitsmay be reasonableto make predictions

x

y

Scientific Uncertainty

Similarly we can use uncertaintiesto determine the best curve fitfor a given model (curve type).

There are often many different models (curve types) possible and a good deal of science is about finding the model (i.e., the theory) that explains the data.

In fact one model (curve type)would be the special case of a curve called a line.

Scientific Uncertainty

x

ySo, uncertainties are our friends!

Without them we could not try and explain our data, develop scientifictheories, and make predictions.

And besides, it is betterto explain natural processes with a certain amount of uncertainty than not to predict(or try to explain)them at all!

Similarly with global warming

Many modelsand uncertaintiesbut ALL show globalwarming

axis?

zoomin onbox

departuresin temperaturein ºC (from the1990 value)

0.0

1.0

2.0

3.0

4.0

5.0

-1.0

0.25

departuresin temperaturein ºC (from the1990 value)

0.0

1.0

2.0

3.0

4.0

5.0

-1.0

0.25

1

2

3

2000 2100

year

Section 1 (door)

Section 2 (middle)

Section 3slope 1 =

slope 2 =

slope 3 =

rise over run

4.75 oC

100 yrs

= 0.0475 oC/yr

2.75 oC

100 yrs

= 0.0275 oC/yr

1.75 oC

100 yrs

= 0.0175 oC/yr

So how much higher would be the Earth’s averagetemperature in the year 2200 with respect to theyear 1990 for slopes 1, 2, and 3?

slope 1: ∆T = 0.25 oC + 200 yrs * 0.0475 oC/yr = 0.25 oC + 9.5 oC = 9.75 oC

slope 2: ∆T = 0.25 oC + 200 yrs * 0.0275 oC/yr = 0.25 oC + 5.5 oC = 5.75 oC

slope 3: ∆T = 0.25 oC + 200 yrs * 0.0175 oC/yr = 0.25 oC + 3.5 oC = 3.75 oC

Y = Y0 + ∆X * slope

x

y

Scientific Uncertainty

2 data points and “knowing” a line fit is required perfect fit

Y0

slope

run

rise

slope=rise/run

Y = Y0 + ∆X * slope

∆X

Geologic Time: Early Views

• CatastrophismEarth’s features (Mts., Volcanoes,

etc.) were formed quickly by a few catastrophic events

Do not have parallels in modern world

Earth is relatively young

Geologic Time: Early Views

• CatastrophismEarth’s features (Mts., Volcanoes,

etc.) were formed quickly by a few catastrophic events

Earth was relatively young

• Uniformitarianism

Catastrophism and Uniformitarianism

• Uniformitarianism Observations of James Hutton (1726-1797)

• All materials are products of two forces• Primary materials produced by Fire -

igneous rocks• Primary materials acted upon by water • Secondary materials such as sediments

were produced

The basic physical, chemical and biological laws of the present-day world also operated in the Earth’s past.

Implications: 1. Present day geological processes acting at slow

rates, but over long time periods, can produce

dramatic results.2. Based on the study of changes that are known to

occur gradually (e.g. wearing down of mountains),

the Earth must be very old.

Uniformitarianism: The present is the key to the past (Hutton, 1788)

• Same internal/external processes we see in action today have been operating over geologic time

• Many cycles of internal and external processes producing primary and secondary materials

Principle of Uniformitarianism

However: It is a misconception that all geologic processes are slow and gradual!Earth is shaped by both:

• slow and consistent processes• catastrophic events

Example of Slow Change: Green River, Utah

1871

1968

Modern example of volcanic Activity on Hawai’i

The present is the keyto the past (Hutton, 1788)

Ancient Example of Volcanic Activity

The present is the keyto the past (Hutton, 1788)

Modern ripple marks from Monument Valley

The present is the keyto the past (Hutton, 1788)

Ancient ripple marks

The present is the keyto the past (Hutton, 1788)

Modern cross bedding in trench cut through dune

The present is the keyto the past (Hutton, 1788)

Ancient cross bedding

The present is the keyto the past (Hutton, 1788)

Modern stromatolites, Shark’s Bay Australia

The present is the keyto the past (Hutton, 1788)

Ancient stromatolites1.5 billion years old

The present is the keyto the past (Hutton, 1788)

Catastrophic Event: Chicxulub Crater, Yucutan,

Mexico

Impact event: 65 million years agoCrater size: 180-280 km diameterProfoundly affected global climate due to atmospheric dustPossible cause of mass extinction (e.g., of dinosaurs)

Meteorite Crater, AZ

Catastrophic Event

Hutton’s Discovery - Siccar Point, Scotland

Hutton’s Discovery - Siccar Point, Scotland

Buried and tilted erosional surface

Fault scarpLanders Earthquake

Catastrophic event: Hurricane Katrina: Aug. 23-29, 2005

Catastrophic event: Hurricane Andrew: Aug. 25, 1992

Indonesian City ofBanda Aceh

Before thetsunami and …

… after thetsunami ofDec. 26, 2004

Catastrophic Event

Before thetsunami and …

… after thetsunami ofDec. 26, 2004

Catastrophic Event

Indonesian City ofBanda Aceh

The tsunami of Dec. 26, 2004 1/6

The tsunami of Dec. 26, 2004 2/6

The tsunami of Dec. 26, 2004 3/6

The tsunami of Dec. 26, 2004 4/6

The tsunami of Dec. 26, 2004 5/6

The tsunami of Dec. 26, 2004 6/6