Good Science vs. Bad Science. Syllabus? Website? Slides from last class Questions? Assignment #1 posted

Transcription

1 Good Science vs. Bad Science Syllabus? Website? Slides from last class Questions? Assignment #1 posted

2 Pathological Science & Pseudoscience How not to and the baloney kit

3

4 Crop circles Theory 1: UFOs Theory 2: humans are responsible Theory 2 consistent with Occam s razor Be skeptical!

5 The virtue of simplicity Occam s Razor (William of Occam ):... entities must not be multiplied beyond what is necessary law of parsimony or Occam s razor Isaac Newton ( ): We are to admit no more causes of natural things than such as are both true and sufficient to explain their appearances. To this purpose the philosophers say that Nature does nothing in vain, and more is in vain when less will serve; for Nature is pleased with simplicity, and affects not the pomp of superfluous causes.

6 Sagan article Read article by the late Carl Sagan Comments? Questions?

7 Airplane crash dreams analysis of rare events Say there are 150,000,000 adults in US Say 1 in 3 have such a dream once in their lifetime 50,000,000 dreams Adult life span = 30 yrs x 365 days/yr = 10,000 days 5,000 dreams/day Say 10% are vivid, lurid, even accurate 500 new psychics every time there is a crash!

8 People cheat Shooting of President Reagan on 3/30/1981 was predicted Scientists are also people so some of them also cheat Lucent scientist fabricated data

9 Scientific Misconduct: Hendrik Schön : at Bell Labs, Schön authors or co-authors over 100 papers. Some of these papers claimed significant advances in a variety of fields: organic semiconductors, organic superconductors, inorganic superconductors, and fullerenes. Late 2001: researchers find obvious discrepancies in data. May 2002: Bell Labs convenes an inquiry committee, chaired by Malcolm R. Beasley (Stanford). September 24, 2002:, the committee of inquiry concludes that Schön had committed scientific misconduct by manipulating and misrepresenting data, substituting mathematical functions for data, and creating false data. Schön was immediately fired. Clean-up of the mess in the literature is continuing.

10 Bad Science Pathological Science: Irving Langmuir Chemistry Nobel Laureate These are cases where there is no dishonesty involved but where people are tricked into false results by a lack of understanding about what human beings can do to themselves in the way of being led astray by subjective effects, wishful thinking or threshold interactions. These are examples of pathological science. These are things that attracted a great deal of attention. Usually hundreds of papers have been published on them. Sometimes they have lasted for 15 or 20 years and then gradually have died away.

11 Characteristics of Pathological Science (Langmuir) The maximum effect that is observed is produced by a causative agent of barely detectable intensity, and the magnitude of the effect is substantially independent of the intensity of the cause The effect is of a magnitude that remains close to the limit of detectability or, many measurements are necessary because of very low statistical significance of the results There are claims of great accuracy Fantastic theories contrary to experience are suggested Criticisms are met by ad hoc excuses thought up on the spur of the moment The ratio of supporters to critics rises up to somewhere near 50% and then falls gradually to oblivion

12 Examples of Bad Science N rays Blondlot Quake predictions Browning Cold fusion Pons & Fleischman

13 N Rays & Blondlot Time of X-rays (1903) Hot wire in iron tube with aluminum window Rays come out through aluminum window (not iron) Rays fall on object and are barely visible sit in the dark for a long time Helped seeing in the dark Rays could be stored in bricks; if you kept the brick close to your head, the rays would help you see better Prism would split N rays and he could measure refractive indices to very high accuracy Enter Wood: observed him and saw that results were inconsistent with ordinary optical phenomena: They don t follow the ordinary laws of physics Wood asked him to repeat the experiment but put the prism in his pocket! Results came out as before! Then Wood published and the whole story collapsed

14 Iben Browning & the New Madrid Fault New Madrid Fault: 4 earthquakes in 1811 and 1812, estimated at 7 to 7.9 on the Richter scale. December 1989: Iben Browning predicts a 50% chance of a major earthquake around Dec. 3rd, Original theory based on tidal forces; specific prediction on unknown methodology. Browning had no credentials in seismology...

15 Cold Fusion 1989 Press conference by Pons & Fleischmann : fusion under normal lab conditions Implications potentially huge (this course would be very different if claim correct) No paper published (retracted) no reproducible results (in the end) Briefly pitted chemists against physicists Lawyers involved Some people still working on this (but no federal funding)

16 The paranormal, ESP etc. Claims that humans can exert or experience forces with varying degrees of conscious control that are not part of the known forces of nature Known forces depend on distance, psi phenomena apparently indifferent to it Parapsychological Lab at Duke 1927 (Rhine) Cards you guess at before being turned over (telepathy) Looking for extrasensory perception Or read the mind of the person turning the cards Rhine got significant results by eliminating the numbers from people who didn t like him

17 Carl Sagan s baloney kit tools for skeptical thinking Whenever possible there must be independent confirmation of the facts Encourage substantive debate on the evidence by knowledgeable proponents of all points of view Arguments from authority carry little weight (there are no authorities in science at most experts) Try different explanations Don t get attached to one hypothesis because it s yours Quantify In a chain of arguments every link including the premise must work Occam s razor: choose the simplest explanation that explains the data Ask if the hypothesis can be falsified. If not, it s not worth much Rely on carefully designed and controlled experiments

18 Pseudoscience A pseudoscience is a set of ideas based on theories put forth as scientific when they are not scientific Examples: Based on authoritative texts: Creationists make observations only to confirm infallible dogmas, not to discover the truth about the natural world static and no new scientific discoveries or improved understanding of the natural world Some pseudoscientific theories explain what non-believers cannot even observe Some can't be tested because they are consistent with every imaginable state of affairs in the empirical world

19 Books / articles Carl Sagan The demon-haunted world - science as a candle in the dark Robert Park Voodoo Science: the road from foolishness to fraud Michael Friedlander At the fringes of science Irving Langmuir Pathological Science Physics Today October 1989 p.36

20 Do a little science How do we know what we know? About the world? About the universe? Why is the Earth round? Earth s shadow on the moon is North Star Ships & the horizon

21 Measure the size of the Earth Suggestions for doing this 235 BCE? Consider A Earth is round Find angle α Measure AB α B Because: α 360 = AB circumference

22 Still measuring How to find α? Use the sun: assume light rays are straight & parallel shadows Note the equal angles Distance AB can be measured any time but should be large (why?) Measurement of shadows gives angles; but should be done at the same time!

23 Eratosthenes was smart: There are special times and places during the year when/where we know what the shadow will be: Tropic of Cancer, June 22 : sun directly overhead at noon no shadow Don t have to go there to measure; can stay at home! Eratosthenes ( BCE), head of the library in Alexandria figured out how to do it : Alexandria is due north of Syene (Aswan) which is on the TofC Measure on June 22 in Alexandria! Result: shadow 1/8 of pillar shadow α