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Solar System Astronomy ASTR 111 – Summer 2010. Welcome to Astronomy. Professor Jack Brockway Reed 121 250-6941 [email protected] 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 - PowerPoint PPT Presentation
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Solar System Astronomy
ASTR 111 – Summer 2010
Welcome to Astronomy Professor Jack Brockway
Reed 121 250-6941 [email protected] 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