Physics, Astronomy, Chemistry

Sebastian de Haro, fall 2012

Big Questions in Science, spring 2012. SdH, AUC 2

3a, 3b Time and relativity

5b Chemistry

4b, 5a Quantum mechanics

4a Our cosmic origins

1b Classical physics

Big Questions in Science, fall 2012. SdH, AUC 2

Class discussion:

List some of the essential properties of science as an academic activity (also properties that distinguish it from other activities).

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The following elements will have appeared in your definitions of science discussed in class:

Logic, rigor.

Scientific method.

Falsifiability .

Experimental verifiability.

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One goal of the course is to demystify some of the ideas about science that you may find in popular books or media:

Science is messy, with lots of guesswork, serendipity.

Theories are not falsified by one single observation.

Scientific products are presented in the strictly logical, rigorous way. But the actual scientific process (including research and scientific discussions) is usually rather different.

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Four generic properties I would like to emphasize, in addition to the ones already mentioned:

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Big Questions in Science, fall 2012. SdH, AUC 7 http://www.umsl.edu/~fraundorfp/stm97x.html http://ebooks.adelaide.edu.au/h/hooke/robert/micrographia/plates/scheme34.png

http://outreach.atnf.csiro.au/

http://inhabitat.com/new-mars-curiosity-science-laboratory-will-be-nuclear-powered-not-solar-powered/

Other important driving forces:

economic interests, technological

advance, societal and political needs,…

Key driving force behind scientific research:

human curiosity. We want to know what

nature around us looks like, both in the

worlds of the smallest, of the largest, and in

the intermediate scale of complexity.

Big Questions in Science, fall 2012. SdH, AUC 8 http://en.wikipedia.org/wiki/Las_Meninas http://www.blogmuseupicassobcn.org/2009/06/weve-got-something-special-to-celebrate-a-brand-new-addition-to-the-museu-picasso/?lang=en

If artists represent (or interpret) aspects of reality that usually cannot be grasped by

analytic means, scientists aim to represent its objective, quantitative features. Both

artists and scientists need lots of creativity!

The scientific enterprise requires abstraction from reality: retaining the aspects that

are relevant to a particular question or research, searching for universal patterns,

laws, and principles that can be reproduced and tested.

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http://science.nasa.gov/science-news/science-at-nasa/2004/13jul_solarblast/

Experiment and observation. Experiments allow scientists

to test their hypotheses or gather new information about

nature in a controlled setting. Changing the experimental

conditions allows to establish or disprove causal links.

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“Traditionally these are questions for philosophy,

but philosophy is dead. Philosophy has not

kept up with modern developments in

science, particularly physics. Scientists have

become the bearers of the torch of discovery

in our quest for knowledge. The purpose of

this book is to give the answers that are

suggested by recent discoveries and theoretical

advances. They lead us to a new picture of the

universe and our place in it that is very different

from the traditional one, and different even from

the picture we might have painted just a decade

or two ago. Still, the first sketches of the new

concept can be traced back almost a century.”

(The Grand Design).

Big Questions in Science, fall 2012. SdH, AUC

Science and philosophy:

a love-hate relationship

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Method does not guarantee full truth or even empirical adequacy.

Dogmatism about ‘method’ can kill creativity:

Rutehrford wouldn’t let Bohr publish his result.

Bohr wouldn’t Heisenberg publish his result.

Heisenberg said the Higgs was not the way the world works.

Methodologies change. Look at actual examples!

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14

Presu

pp

ositio

ns

Mathematics Logic

Axioms

Model

Presuppositions (ethical, epistemic, ontological)

Reality

Future reality

Past reality

Observation

Experiment

Technology

Big Questions in Science, fall 2012. SdH, AUC

• Science aims at representing reality in a model that allows to

explain the present and predict the future (retrodict or understand

the past). Technology, experiment, and observation play an

important role in connecting models with reality.

• The model itself rests on experimental data, a number of specific

axioms, as well as a broader set of assumptions. The particular

logic employed depends on the particular field.

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A brief history of the universe

http://planck.cf.ac.uk/science/timeline/universe

Turning points in the

history of the universe

organized around the

universe’s timeline.

Main era’s in the

evolution of the

universe.

Documentary film Powers of Ten (9 min)

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In groups of two: go to http://htwins.net/scale2 and look up, for ten different length scales (

, etc.), ten corresponding items in

the universe. Go also to the negative powers! Pay particular attention to earth science & biology.

Switch off the sound! We will make a (linear) map of the universe. You can cross-check your data with estimates

that you find on the internet. Big Questions in Science, fall 2012. SdH, AUC 17

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Metric prefixes

Prefix Symbol 1000m 10n Decimal Short scale Long scale Since[n 1]

yotta Y 10008 1024 1000000000000000

000000000 septillion quadrillion 1991

zetta Z 10007 1021 1000000000000000

000000 sextillion trilliard 1991

exa E 10006 1018 1000000000000000

000 quintillion trillion 1975

peta P 10005 1015 1000000000000000 quadrillion billiard 1975

tera T 10004 1012 1000000000000 trillion billion 1960

giga G 10003 109 1000000000 billion milliard 1960

mega M 10002 106 1000000 million 1960

kilo k 10001 103 1000 thousand 1795

hecto h 10002/3 102 100 hundred 1795

deca da 10001/3 101 10 ten 1795

10000 100 1 one –

deci d 1000−1/3 10−1 0.1 tenth 1795

centi c 1000−2/3 10−2 0.01 hundredth 1795

milli m 1000−1 10−3 0.001 thousandth 1795

micro μ 1000−2 10−6 0.000001 millionth 1960

nano n 1000−3 10−9 0.000000001 billionth milliardth 1960

pico p 1000−4 10−12 0.000000000001 trillionth billionth 1960

femto f 1000−5 10−15 0.000000000000001 quadrillionth billiardth 1964

atto a 1000−6 10−18 0.000000000000000001

quintillionth trillionth 1964

zepto z 1000−7 10−21 0.000000000000000000001

sextillionth trilliardth 1991

yocto y 1000−8 10−24 0.000000000000000000000001

septillionth quadrillionth 1991 Big Questions in Science, fall 2012. SdH, AUC

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The Big Questions Connecting Circle

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Different length scales

distributed on the Big

Questions Connecting

Circle.

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Examples of scientific theories distributed on

the Big Questions Connecting Circle.

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Examples of sciences distributed on the

Big Questions Connecting Circle.

Presocratic science: study of matter and astronomy

Atomism and Plato’s Timaeus: mathematics Greek science: First Theories of Everything

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Thales: water, predicted solar eclipse.

Anaximander: apeiron,

Earth cylindrical, suspended in void.

Anaximenes: air (rarefaction,

condensation).

Heraclitus: fire

Empedocles: four elements

Democritus and Leucippus: atoms,

Flat earth.

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585 BC Thales

of Miletus

Time and length scales Great adventure: curiosity Abstraction Methods:question, observation, knowledge,

innovation From mythos to logos Greek science: matter, geometry.

26 26 Big Questions in Science, fall 2012. SdH, AUC

Theaetetus via Plato and Euclides: the five Platonic solids

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Cube (rectangle) Tetrahedron, octahedron, icosahedron

(equilateral triangles)

No

!

Set minimal length to 1.

Use Pythagoras theorem

other lengths follow

The numbers (1,2,3) are given by musical octave and fifth. Generate the Dorian musical scale:

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1:2 octave

2:3 perfect fifth

3:4 perfect fourth

4:5 major third

5:6 minor third

6 8 9 12

1 2

D E F# G A B C# D

4/3

3/2 arithmetic mean

harmonic mean

Properties of elementary triangles linked with harmonies of music.

Platonic solids built up of such triangles. Properties of triangles give properties of solids and will ‘explain’ properties of matter.

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Big Questions in Science, fall 2012. SdH, AUC 31

Earth Fire Air Water

Symmetry among

these three: all share

same elementary

triangles

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Earth Fire Air Water

rarification, condensation

evaporation

condensation

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Largest volume when inscribed in sphere. Contains other Platonic solids.

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Numbers as universal language, at the root of all natural processes.

Symmetry leads to ‘conserved quantities’:

Stable earth: isosceles triangle symmetric.

Interchangeability fire, air, water.

Link between numbers, physiology, and arts: quantity and quality.

Adds concept of ‘measure’, ‘form’ to Ionian/atomistic ideas.

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Although speculative, basic principle is a chemistry of four elements.

Reactions explained from mathematical combinations allowed by geometry.

Problem of ‘asymmetry’ always present: ‘likely account’. Hypothesis open to critique.

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“Our illustrator of the atomic model [in a school text-book of physics] would have done well to make a careful study of Plato before producing his particular illustration” (Heisenberg, cited by Guthrie).

Heisenberg first thought about atoms while reading Plato’s Timaeus.

Pythagoras highly influential at dawn of two scientific revolutions: Kepler and Sommerfeld.

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38 Big Questions in Science, fall 2012. SdH, AUC

Rational explanation Logic, argumentation Empirical (though not ‘experimental’) Universe finite and knowable Important factors:

Development of culture

Overseas trading, different civilizations

Openness to intellectual innovation

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Periodic table: classification scheme of the chemical elements based on simple physical principles.

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Physical forces: seemingly distinct forces can be reduced to simpler forces and mathematical principles.