Solar System Astronomy

ASTR 111 – Summer 2010

Welcome to Astronomy Professor Jack Brockway

Reed 121 250-6941 brockway@radford.edu www.radford.edu/brockway

Office Hours: MWF 10-12

Welcome to Astronomy ASTR 111 – Solar System Astronomy

Lecture McGuffey 203 2:00 – 2:50 MWF

Laboratory Curie 145

7:00 – 9:00 Monday 9:00 – 11:00 Monday 8:00 – 10:00 Wednesday

Welcome to Astronomy

ALWAYS ASK QUESTIONS!

Welcome to Astronomy

There are problems to whose solution I would attach an infinitely greater importance than to those of mathematics, for example touching ethics, or our relation to God, or concerning our destiny and our future; but their solution lies wholly beyond us and completely outside the province of science.

— Carl Friedrich Gauss (1777-1855)

Why Science? I have a theory…

Water causes cancer Only water causes cancer

Not cigarettes… Not UV radiation… Not nothing else…

Who/how it affects cannot be predicted Now or ever

Why Science? I have a theory…

Water causes cancer Only water causes cancer Who/how it affects cannot be predicted

Evidence: Every single cancer victim has been exposed to

water Rebutting evidence to the contrary:

Not every lung cancer victim smokes Not every smoker gets lung cancer

Why Science?

Why Science?

What is Science? Science is a system of knowledge that is

based on empirical evidence and testable explanations Empirical – we can observe and measure Testable – we can support or disprove

A theory must be falsifiable A theory – of any sort – that cannot conceivably fail

any test is not science

What is Science? In science we do not teach…

What might be true What we believe to be true

Perhaps not even things that are true

We search for, find, and teach the best explanations for nature we can find

What is Science?

Science is NOT any conjecture chosen to justify belief –

not even popular or widely-held belief

What is Science? Science is an exploration

Guided by natural law Explanatory by reference to natural law Testable against the empirical world Conclusions are tentative It is falsifiable

Science vs Authority Authority often works by suppressing

inquiry favors (or even depends upon) the status quo

Science is subversive Old ideas can be falsified and rejected New ideas must be supported by evidence Scientific authority can be overthrown by new

or better evidence Nature is the arbiter of science. It decides

what ideas are good or bad

Science vs Authority Science provides tools

For separating truth from fiction Science can only suffer under ideological

requirements Galileo vs Church Scopes trial AIDS research Global Warming USSR/China – Lysenko

Accepting Science Many reject science

Astrology crystal healing

Hostility to Modern Medicine Vaccines cause autism… or kill Smoking

Rejection of climate change findings

Accepting Science Science is not “natural”

The brain is an ever-turning “belief engine” Full moons are dangerous 13 is unlucky Health insurance providers are our friends

Accepting Science Science is not “natural”

Science requires doubt and skepticism Society holds unshakeable faith to be a virtue People seek security and certainty

Faith delivers Science doesn’t

Science enables us to recognize (and turn away from) incorrect beliefs

To be fair, let’s not assume that scientists are without bias, nor are they always right…

Scientific World View Which of the following would be a

scientific way of viewing nature?

a) All ideas are equally valuable and should be equally respected

b) Well established ideas should never be checked or tested

c) Nature informs us about the usefulness of our ideas

Scientific Method Knowedge from Science

We think we understand empirical phenomena when a satisfactory theory

explains how the phenomena work, what regular patterns they follow, or why they appear to us as they do

Scientific explanations are in terms of natural phenomena rather than supernatural phenomena

science itself requires neither the acceptance nor the rejection of the supernatural

Scientific Method Scientific “facts” and theories

many scientific theories, initially, are often little more than guesses based on limited information

mature and well-developed scientific theories systematically organize knowledge and allow us to explain and predict wide ranges of empirical events

Scientific Method Science

Conclusions are a posteriori Theory follows observation Theories are conclusions

a position, opinion, or judgment reached after consideration

Measurable predictions Key to falsifiability

Falsifiable We can distinguish between accurate and inaccurate

predictions (Precambrian rabbits) Reproducible

Scientific Pretenders Pseudoscience

Set of ideas based on theories put forth as scientific when they are not scientific

They are missing one or more of the characteristics of scientific disciplines/theories

Scientific Pretenders Pseudoscience

Conclusions are a priori Observations made (often chosen) to confirm theory Theories are assumptions

Reached without consideration Conclusions are not conclusions!

Not Falsifiable Not reproducible No measurable predictions

Predictions allow competing theories to be compared

Scientific Method Science makes conclusions

Based on weight of evidence All the data must be considered

Pseudoscience makes assertions Not supported by most of the data

Though it might be supported by some of it

I’m being tendentious – look it up

Our Criteria A priori or a posteriori?

Did you conclude or did you assume? Falsifiability

Is it possible to collect contradicting evidence? Is contradicting evidence considered when

available? Reproducibility Observable predictions

Science is a tool, not a rationalization

Benefits of Science What benefit has science provided?

Vaccines Computers Anesthetics Spacecraft Hydrogen bombs Women surviving childbirth Greatly Increased life expectancy Social/economic prosperity…

Benefits of Science What benefit has science provided?

Cell Phones Toilets Books

Benefits of Rejecting Science Ignorance Gullibility

Benefits of Rejecting Science Astrology

“You’re not going to marry him because she’s a Taurus??”

“You’re quitting your job because Mercury is in Cancer??”

Intelligent Design ID is an attack against science

Gardisil Debate

Gardisil Debate Gardisil is a vaccine against HPV virus

HPV is believed to be a necessary factor in the development of nearly all cervical cancer cases

Fifth most deadly cancer in women Nearly 4000 will die from it this year in the US

Gardisil Debate Critics say it’s unnecessary or dangerous:

They say the body’s immune system is sufficient 90% of the time,

that it only protects against 4 of over 100 strains of HPV,

that there are serious side effects, that Gardisil has killed people, that HPV hasn’t been proven to cause cervical

cancer

Gardisil Debate Facts suggest otherwise:

the body’s immune system is sufficient 90% of the time

..and fails 10% of the time It protects against 4 (of over 100 strains) of

HPV there are side effects People have died that were taking Gardisil HPV hasn’t been proven to cause cervical

cancer

Gardisil Debate

Gardisil Debate Facts suggest otherwise:

the body’s immune system is sufficient 90% of the time

it protects against 4 (of over 100 strains) of HPV

there are side effects About half of the adverse effects that most drugs

have People have died that were taking Gardisil HPV hasn’t been proven to cause cervical

cancer

Gardisil Debate Facts suggest otherwise:

the body’s immune system is sufficient 90% of the time

it protects against 4 (of over 100 strains) of HPV there are side effects People have died that were taking Gardisil

People have also died that were taking Tylenol, were sleeping, or were sitting in chairs

No evidence has shown a link between the drug and the deaths (at least not yet)

About 40 people out of 40 million recipients have died HPV hasn’t been proven to cause cervical cancer

Gardisil Debate Facts suggest otherwise:

the body’s immune system is sufficient 90% of the time

it protects against 4 (of over 100 strains) of HPV there are side effects People have died that were taking Gardisil HPV hasn’t been proven to cause cervical cancer

But the link is far stronger than for smoking and lung cancer…

Each year in the US Nearly 4000 die from cervical cancer Gardisil can prevent over 3000 of those deaths

Benefits of Rejecting Science Astrology Intelligent Design Gardisil Debate

Population control

Fact vs theory

This textbook contains material on evolution. Evolution is a theory, not a fact, regarding the origin of living things. This material should be approached with an open mind, studied carefully, and critically considered.

– sticker in Cobb County GA

Fact vs Theory No real difference…

Theories are typically considered to be less developed/established

In science, “fact” can only mean “confirmed to such a degree that it would be perverse to withhold provisional assent.”

– Stephen Gould

Scientific “fact”

This textbook contains material on evolution. Evolution is a theory, not a fact, regarding the origin of living things. This material should be approached with an open mind, studied carefully, and critically considered.

– sticker in Cobb County GA

Scientific “fact”

This textbook contains material that states smoking can lead to cancer. That is a theory, not a fact, regarding the dangers of smoking. This material should be approached with an open mind, studied carefully, and critically considered.

– my sticker for Cobb County

Evolution & Natural Selection Scientific “facts” and theories

mature and well-developed scientific theories systematically organize knowledge and allow us to explain and predict wide ranges of empirical events

Science vs Ideology Trofim Lysenko

Director of Soviet biology under Stalin Rejected Mendelian genetics

Inheritability of acquired characteristics Plucking a plant’s leaves can reduce leaves on

offspring…

Genetics stigmatized ‘bourgeois science’ or ‘fascist science’ Stalin disliked fascist Germany’s embrace of

genetics Gregor Mendel himself was a priest

Religion considered backward and evil

Science vs Ideology Trofim Lysenko

Stalin insisted on applying Lysenkoismto human genetics

Geneticists were fired, sent to labor camps, or executed

‘Scientific’ arguments were made based on conformity to Marxist ideology

Serious, long-term harm to Soviet biology Massive crop failures, famine, millions of deaths Economic disintegration Crippled advances in biology and biochemistry

Science vs Ideology Soviet Sciences

While USSR invested heavily in science Strictly persecuted deviations from communist

ideology Introduced party control over sciences In general, ideologically-offensive disciplines and

scientists were suppressed Notable exception was nuclear physics

“Stalin was crazy, but he wasn’t stupid”

Science vs Ideology Where is science subordinated to

ideology? Nazi Germany USSR China American schools

What’s my point? Science is profoundly important in our

society Only effective tool for understanding nature

Biology Medicine Physics Fossil Fuel alternatives Chemistry Geology Engineering

Informed decisions are impossible without some understanding of science

What’s my point? Science is a way of evaluating

propositions It provides mechanisms for distinguishing

between true and false

Science and Mathematics

Science and Mathematics Science discovers patterns and rhythms in

nature. Most phenomena work regularly and

predictably. Mathematics is the language of patterns. Mathematics works when used to describe

nature and its patterns.

Back to Astronomy… Earth is a small planet…

Orbiting a medium-size star… In a galaxy of 100 billion stars… Which is one of billions of galaxies… In a universe that is 13.7 billion years old.

We’re going to measure EVERTHING!

Measurements – metric & more… Système International d'Unités (SI)

International System of Units mks system

meter kilogram second

cgs system centimeter gram second

Metric System meter

1/40,000,000th of the polar circumference of the Earth

length of a particular bar of platinum-iridium alloy

now defined as the distance traveled by light in a vacuum during 1/299,792,458 of a second

Metric System kilogram

Originally one liter of pure water at standard pressure and 3.98° Celsius definition was hard to realize accurately

density of water depends slightly on the pressure pressure units include mass as a factor circular dependency in the definition!

since 1889, equal to mass of the international prototype

made from an alloy of platinum and iridium 39 mm height and diameter

kept at the Bureau International des Poids et Mesures

Metric System second

currently defined as the duration of 9,192,631,770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the cesium-133 atom

cesium atom at rest at a temperature of 0 K

Metric System Temperature

Kelvin An absolute temperature scale

Absolute zero* (definition)

Water's freezing point

triple point of water*

Water’s boiling point

0 K

273.15 K

273.16 K

373.1339 K

–273.15 °C

0 °C

0.01 °C

99.9839 °C

−459.67 °F

32 °F

32.018 °F

211.9710 °F

Metric System

What parts of the world use (or don’t use) the metric system?

Units are for convenience Mass

Solar Mass Earth Mass

Distance Astronomical Unit

Time… Temperature

Kelvin

A Vast Universe We need to handle great distances and

long times We can do this through the travel time of

light Light travels 300,000 km every second

299,792,458 m/s 186,000 miles per second

We often use time to denote distance e.g. we may say a friend’s house is two hours away

A Vast Universe Travel time of light

300,000 km/s 1¼ seconds to arrive from the Moon. 8.3 minutes to arrive from the Sun. 5.5 hours to get to Pluto from the Sun. 4.3 years (yr) to get to the nearest star. 100,000 yr to cross the galaxy. 2.9 million yr to get to the nearest big galaxy. 10 billion yr to come from distant galaxies.

Nearby DistancesMoving outward through the Universe at the speed of light, Earth is like a snap of your fingers…

The Moon is a little more than a second away…

The Sun’s distance is like a quick meal…

Longer Distances…and the diameter of the Solar System is a long night’s sleep.

The distance to the nearest star is like the time you spend in college…

Hopefully

The Longest Distances

…and the distance between galaxies is like the time since earliest human ancestors walked on Earth.…

The radius of the Galaxy is like the age of our species…

The Longest Distances

The size of the universe is like three times the age of the Earth…

Comparing the size of the universe to the size of Earth is like comparing the age of the planet to a snap of your fingers – times three

Scales will be aconceptual handicap

Campus scene (16m × 16m)

16 meters across

City View

1 mile

Pennsylvania

100 miles

Earth

12,756 km

diameter

Earth & Moon

384,000 km

Earth & Sun

150 million km

= 1 AU or 1 ua

Solar System

100 AU

Empty Space

10,000 AU

Solar Neighborhood

17 light-years

Astronomical Scales – 1 billion Jupiter is about 1 billion kilometers away

~600 million miles How big is one billion?

What was happening 1 billion minutes ago? How much do 1 billion dollar bills weigh?

Our first day of Astronomy…

Applause