The Nature of Science

1. The Nature of Science Intuition leads to the flat Earth society and bloodletting; experiments lead men to the moon and microsurgery. - Seth Mnookin

2. Basic Rules of Science • Science is the pursuit and application of the natural and social world through the collection and analysis of evidence. • There are four major concepts in the pursuit of science: • Facts are observations that we make about the world. • Hypotheses are proposed, testable explanations of observations that can serve as a basis for experimentation. • Theories are much broader explanations of various observations that have been tested and confirmed through observation and experimentation. • Laws describe a constant phenomenon of nature, but do not explain it.

3. Pseudoscience • A far different idea is pseudoscience – practices or beliefs that appear or claim to be scientific, but does not follow scientific principles. • The claim is not repeatable or reproducible. • The claim is not backed by evidence. • No alternative explanations for the claim have been tested. • There are many examples of pseudoscience throughout science, impacting the disciplines of biology, chemistry, and astronomy.

4. Spontaneous generation is a theory that life can arise from non-living matter. • This idea arose sometime in the 4th century B.C., and persisted through the mid-19th century. • This is based on observations, such as: • Beetles will appear in piles of animal dung. • Maggots will grow out of rotting meat. • Mice will generate from jars containing dirty garments and husks of wheat. • Fleas will arise from dust. • Spontaneous generation is considered pseudoscience, because: • No alternative explanations were considered. • No controlled experiments were conducted to test it.

5. Since the time of ancient Greece, many chemists believed that all matter was composed of four elements: earth, water, air, and fire. • Alchemy used this hypothesis to try to devise ways to transform common elements (like lead) into gold. • This led to many early discoveries in chemistry, such as Hennig Brand discovering phosphorous as he tried to isolate gold from his own urine! • Alchemists kept much of their research a secret, and this lack of knowledge sharing kept progress in the field of chemistry at a standstill for many centuries. The Alchemist in Search of the Philosophers Stone (1771) by Joseph Wright.

6. Astrology is the belief that the movements and positions of stars and planets affects the natural world. • This is partially based on the zodiac, a series of constellations that the sun crosses from the perspective of the Earth. • The original 12 zodiac signs were recorded by the ancient Babylonians in about the 5th century B.C., but are no longer accurate. • A “new” zodiac chart was created by the Minnesota Planetarium Society to reflect a shift in the Earth’s axis.

7. The Scientific Method • Scientists all follow the same basic set of steps when attempting to answer a question or explain an observation, called the scientific method. • The scientific method has been used to solve some of the greatest problems to face humanity, including the treatment of disease.

8. The First Vaccination • Up through the 20th century, one of the most serious diseases of mankind was smallpox. • The most common form of smallpox had a 30% fatality rate. • The only known “cure” was to contract the disease and recover. • Some inoculated themselveswith fluid and pus from the sick,hoping to contract a mild caseand survive.

9. The First Vaccination • A British physician named Edward Jenner observed that dairymaids living in his hometown often contracted cowpox, a nonlethal disease with similar symptoms to smallpox. • He decided to intentionally infect a young boy with cowpox, then expose him to smallpox. • Immunity was successfully conferred to the boy. • This discover serves as the basis forall vaccines used today, which haveprevented over 700,000 deaths inthe past 20 years alone. Edward Jenner vaccinating a child with cowpox from a dairymaid. Source: Bettman Archive / Corbis.

10. Scientific Method • The first step in the scientific method is making an observation, information gathered by noticing specific details of a phenomenon. • Dr. Edward Jenner observed that dairymaids who contracted cowpox seemed to be protected from the more deadly smallpox. The Dairy Maid, 1650s, by AelbertCuyp.

11. The goal is to be able to explain the observation. • A hypothesis, or testable explanation, will be made based on the scientist’s prior experience and research. • Hypotheses are preliminary explanations – they can and are often not supported by the resulting experiment. • Dr. Jenner’s hypothesis was that if a child was exposed to cowpox , they would become immune to smallpox.

12. The experiment tests the hypothesis under controlled conditions, with carefully defined variables. • The independent variable is the new factor or condition that is to be introduced and tested. • The dependent variable changes as a result of the independent variable, and will be measured and recorded as data. • Controlled variables are kept constant throughout the experiment. • Dr. Jenner’s experiment was to inoculate the 8 year-old son of his gardener with fluid from a cowpox pustule, allow the infection to pass, then repeat with a smallpox pustule. • The boy survived 20 inoculations without succumbing to smallpox! • The conclusion states whether or not the hypothesis is supported by the results of the experiment.

13. The final step is communication, where the results are published and reviewed by others to check for errors, bias, or other issues. • Dr. Jenner submitted his study to the Royal Society for Medicine, but was told he needed more data. “The Cow-Pock—or—the Wonderful Effects of the New Inoculation!—vide. the Publications of ye Anti-Vaccine Society.” - Satirical cartoon, 1802.

14. Margin of Error • Accounting for every single variable in a scientific study is nearly impossible; there will be variability in all data. • Margin of error is an estimate of the amount of random sampling error in a set of data due to errors in measurement, experimental design, or other factors. • The margin of error can be reduced by increasing sample size, or the number of observations used in an experiment or study.

15. Dr. Jenner was able to locate several other parents who were willing to volunteer their children. He even included his own 11 month-old son in the study. • The results were finally published. Jenner called his technique vaccination after the Latin word for cow “vacca”.

16. Experimental Design • Controlled experiments aren’t always possible or ideal. • Natural experiments are conducted in the field under normal circumstances. • The advantage is that these experiments take place in a more accurate, realistic environment. • The disadvantage is that natural phenomena are often very difficult to find.

17. Combating Bias • Another significant problem in science is bias; the preference for an experiment to turn out in a certain way. • Bias is not always intentional, but must be controlled by the experimental design. • A blind experiment is conducted so the experimental subjects do not know which is the control and which is the experimental group. • Eliminates the “placebo effect” • A double-blind experiment also prevents the actual scientists from knowing which is the control or experimental group.

18. Scientific Fraud • There are many examples of published studies or report that have been later found biased, flawed, or outright fraudulent. • These are always detected, eventually, due to the scientific method and peer review. • The net effect is loss of time, resources, and public mistrust. • In 1998, Dr. Andrew Wakefield published a study in the British journal The Lancet documenting a link between the MMR vaccine and autism in children.

19. Although the study was retracted, much of the public trust in vaccines was shaken, and vaccine rates dropped in many countries. • Pseudoscience books, articles, and speakers against the use of vaccines have become increasingly prevalent, even though there is no evidence to support their claims. • Similar movements can be seen opposing climate change and the use of genetically-modified organisms (GMOs). “Green our vaccines” was a rally held in 2008 to raise awareness of supposedly toxic substances in vaccines.

20. Energy and Matter “The sun, with all those planets revolving around it and dependent on it, can still ripen a bunch of grapes as if it had nothing else in the universe to do.” - Galileo Galilei

21. Lessons From Thin Air • In 1995, filmmakers from the Harvard Smithsonian Center for Astrophysics approached some new graduates from Harvard and the Massachusetts Institute of Technology. • One of the questions they posed: “Here’s a seed. Imagine I planted that seed in the ground, and a tree grew. …Where did all that weight come from?” “The President,” a giant 3,200 year-old sequoia in California with a height of 247 feet.

22. The Willow Tree Experiment • The basic knowledge that plants need water, sunlight, and soil has been around since ancient times. • The working hypothesis was that plants grew by “eating” soil through their roots. • Jean Baptiste von Helmont wanted to verify this – to isolate the exact source of the increased mass of trees as they grew.

23. The Willow Tree Experiment • Van Helmont planted a 5-pound willow tree in 200 pounds of dry, potted soil. • He massed the tree, grew it for 5 years, then massed it and the soil again. • The tree gained over 160 pounds of mass. • The soil only decreased in mass by about 2 ounces! • The old hypothesis was rejected in favor of a new one – the mass came from water!

24. The Building Blocks of Life • Life cannot exist without two basic inputs: matter and energy. • Matter is any physical substances that has mass and occupies space (volume). • Energy is the ability to do work.

25. BUILDING BLOCKS OF LIFE • All matter in the universe is made of atoms, the smallest particle that still exhibits the characteristics of its element. • The periodic table represents all the known types of atoms in the universe – called elements.

26. Priestley’s Experiment • Joseph Priestley, a British chemist, believed that air was not a single “elementary substance”, but a “composition” of gases. • During one experiment, he discovered that a candle placed in a sealed jar would extinguish very quickly. • He called the air “injured.” • Placing a mouse in the jar would have a similar effect, and it would die. • Priestley had discovered oxygen.

27. BUILDING BLOCKS OF LIFE • All atoms are made of a combination of the same three particles. • Protons - Positively charged, located in the nucleus. • Electrons - Negatively charged, orbits the nucleus. • Neutrons – Neutral, located in the nucleus. • Atoms have the ability to form chemical bonds with each other, making molecules. • Oxygen gas is actually made of two oxygen atoms bonded together, sharing electrons.

28. Air • Priestley’s hypothesis about the composition of air was correct. • Air is primarily made of: 78% 21% 0.03% 0.02%

29. Ingenhousz’s Experiment • A Dutch physician, Jan Ingenhousz, decided to repeat Priestley’s experiment, with a few changes. • Two sealed containers were studied – one exposed to sunlight, the other left in the shade. • Only when exposed to the energy of the sunlight did the plants produce oxygen.

30. Energy • There are many different forms of energy in the universe. • Potential energy is stored. • Potential energy can exist as a result of position or chemical structure. • Kinetic energy is in motion. Position. Position. Chemical Structure.

31. Electromagnetic Spectrum • Energy travels in the form of waves. Each type of energy has its own wavelength.

32. Energy and Life • Most of the energy that supports life on Earth originates from the sun. • Solar radiation actually contains three wavelengths of energy: • Ultraviolet • Able to penetrate living tissue; causes skin damage. • Visible • Range of wavelengths we can detect with our eyes. • Infrared • Heat energy.

33. Plants are able to use some wavelengths of visible light as a source of energy. • Everything but green. • What relationship does this process have with the mass plants gain as they grow?

34. Photosynthesis • The final piece of the puzzle was solved by a Swiss botanist named Nicolas de Saussure. • He enclosed the plants in a sealed container of carbon dioxide. • By weighing the plant and the carbon dioxide before and after growth, he was able to show that the increased mass was a combination of: • Water from the soil. • Carbon from the air. • The process was called photosynthesis. The overall equation was eventually discovered to be: 6 H2O + 6 CO2 + solar energy  C6H12O6 + 6 O2

35. Cell Respiration • Other organisms, such as animals and fungi, cannot directly absorb sunlight. • They rely on a process called cell respiration, which breaks down the complex molecules found in organisms they ingest as a source of energy. C6H12O6 + 6 O2 6 H2O + 6 CO2 + energy • Photosynthesis and cell respiration complement each other, forming the basis of the flow of energy and cycling of matter that makes up living ecosystems.

36. Energy Flows • As energy flows through an ecosystem, it obeys two Laws of Thermodynamics. • Energy cannot be created or destroyed, it only changes form. • This is also known as the Law of Conservation of Energy. • During each transformation, some energy is given off in the form of heat. • This energy is no longer available to do work.