- SCIENCE is a method of investigation based on the formulating and testing of falsifiable hypotheses.
Is this boy (Pasquale) suggesting a falsifiable hypothesis? Explain why or why not.
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SCIENTIFIC METHOD:
- Facts are gathered.
- A problem is stated.
- A tentative, testable explanation (hypothesis) is suggested.
- Hypotheses can originate from comparison (analogy) with something else, from a nonscientific belief,
or from pure imagination. Rutherford's 'planetary model' of the atom (with the electrons circling around the
central nucleus, "like a miniature solar system") arose from a comparison with the sun and the planets.
Einstein said that he arrived at his relativity theory by imagining what it would be like to ride
as a passenger on a beam of light. German chemist August Kekule said that his hypothesis for the
ringlike chemical structure of benzene came from a nightmare in which snakes had grasped their tails in their
mouths and were frightening him by rolling out towards him from his fireplace.
- The hypothesis must be rigorously tested.
- EXPERIMENTAL SCIENCES: In many fields of science (those in which the
questions are usually some version of "How does it work?"), the main method
of investigation is by EXPERIMENTATION. An experiment is an unnatural
situation, set up by a scientist in order to test some hypothesis. Good experiments
always compare "experimental" subjects (exposed to something that is being tested) to
"control" subjects (not exposed to the test material). In order to ensure unbiased results,
the experimental and control groups need to be treated the same way in all other ways, except
for the one variable being tested. Physics, chemistry, and cellular and molecular biology
rely mostly on experiments.
- NATURALISTIC SCIENCES: In some fields of science (like astronomy, geology,
paleontology, ecology, or evolutionary biology), the objects of interest do not allow experimental manipulation
because they are too big, too far away, or inaccessble in some other way. Also, scientists studying
behavior under natural conditions are reluctant to alter those natural conditions because they would
no longer be studying what they are interested in. These sciences usually conduct NATURALISTIC INVESTIGATIONS,
comparing situations in which some variable is present with situations in which it is not. Most of these
sciences are also HISTORICAL SCIENCES whose main questions take the form, "Why does it
work that way, and not some other way?", which often comes down to "How come?", meaning
"How did it come to work that way?"
- A hypothesis that has withstood repeated testing over time becomes accepted as a theory.
Most theories contain a cluster of related hypotheses, plus a vocabulary of special ("theoretical") terms.
Good (productive) theories help guide further research.
Is this girl (Danae) using the word "theory" correctly? Explain why or why not.
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SCIENTIFIC DISCOVERIES:
- Some examples of simultaneous discovery:
- Natural selection (1858-1859): Charles Darwin developed the theory of natural selection
during the 1830s and 1840s and wrote it down in some notebooks but did not publish his ideas. In 1858,
Alfred Russell Wallace developed the same ideas and wrote them down in the form of a long letter that he sent to Darwin.
Darwin showed the letter to Charles Lyell and Joseph Hooker, who arranged for the simultaneous publication (in 1858)
of Wallace's letter, excerpts from Darwin's unpublished writings, and an explanation that documented the
circumstances of independent discovery. In 1859, Darwin published his monumental book,
On the Origin of Species by Means of Natural Selection, in which he elaborated the full theory, with abundant evidence.
- Mendelian inheritance (1900): In the Spring of 1900, three scientists (Carl Correns in Germany, Erich von Tschermack in Austria,
and Hugo DeVries in Holland) all published the results of experiments they had conducted, confirming Mendel's earlier
work of 1865, which had gone unnoticed, and which they each discovered only after completing their own work.
- Chromosomal theory of inheritance (1931): In 1931, the American team of Harriet Creighton and Barbara McClintock
published a study showing that the crossing-over of chromosome material caused the rearrangement of genes, thus showing
that genes were located on chromosomes. Their experiments were conducted using corn (Zea mays), but a similar
experiment in fruit flies (Drosophila melanogaster) was also published that same year in Germany by Curt Stern.
- Human genome sequence (2003): In 2003, two independent groups (an international consortium of over 100 scientists,
and a private corporation, Celera) both published nearly complete sequences of all the information in the human genome,
the culmination of the Human Genome Project.
- Some examples of ideas published "ahead of their time" and not widely appreciated until later:
- Vaccination or innoculation against smallpox (1721): Colonial Massachusetts experienced a smallpox epidemic
in 1720-1721, during which an African American named Onesimus, house servant to Rev. Cotton Mather, suggested
rubbing fluid from pustules (skin sores) of the disease onto healthy people to protect them from the disease.
Onesimus said that this was a tradition among the Yoruba people in his African homeland (in present-day Nigeria).
Cotton Mather tested the innoculation method on his own family and various other people, none of whom
aquired smallpox even though hundreds of other people in the area got sick and many died. Cotton Mather
urged the medical community to adopt the practice, but the idea was ignored until Edward Jenner in England
reintroduced the idea in 1796. Jenner had observed that milkmaids hardly ever got smallpox, but that they
frequently rubbed the sores of cows infected with cowpox, a similar but nonfatal disease. Jenner innoculated
members of his own family and several others with fluid from the sores of cows infected with cowpox, and he
showed that they were now immune to the smallpox. Since he had obtained the fluid from cows (Vacca in Latin),
he called his fluid a vaccine and the process vaccination.
- Mendelian inheritance (1865): Gregor Mendel published his findings on the principles of inheritance in 1865, in a
journal that was not widely read. His ideas were ignored by the scientific community until 1900 (see above).
- The origin of life on Earth (1931): Alexandr Oparin, a Russian biochemist, developed his ideas on the origin of life
and published them in 1931, in Russian. Although his writings were translated into English in 1935, they were largely ignored until
1952, when an American biochemist, Stanley Miller, conducted experiments showing that Oparin's ideas could indeed
account for the evolution of many important organic compounds (including amino acids, the building blocks of proteins,
and also adenine and ribose sugar, two of the building blocks of nucleic acids) under abiotic conditions.
- DNA as the genetic material (1944): In 1928, Frederick Griffith showed that virulence (the ability to cause an
infectious disease) could be transmitted from one bacterial strain to another and would be inherited in the recipient strain.
In 1944, Avery, MacLeod, and McCarthy showed that this process required the transfer of a "transforming principle,"
which they carefully identified as DNA. Few people knew much about DNA at the time, and their findings made almost no
impact until 1952, when Hershey and Chase demonstrated that a bacteriophage virus that infected and killed bacteria
(and reproduced while doing this) did so
by injecting their DNA, not their protein, into the bacterial cells.
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THE METRIC SYSTEM:
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Scientists all over the world have used the Metric System as the basis of all measurements since it was first introduced
in the late 1700s by the chemist Antoine Lavoisier.
- The metric system uses the meter as the basic unit of length or distance, the gram as the basic unit of mass,
and the second as the basic unit of time. Other basic units include the ampere for electric current, the candela for light intensity,
the mole for chemical quantities, and the Kelvin for absolute temperature. Derived units include the liter, the basic unit of
volume, equivalent to the volume of a cube 0.1 m on each side.
- Larger and smaller units are designated by a consistent set of prefixes, as given in the following chart. These units are all
based on powers of ten, so that conversions between larger and smaller units only involve the moving of a decimal point.
- An inch is exactly 2.54 centimeters, and a meter is 39.37 inches. A pound is 454 grams. A liter is 1.08 quarts. A gallon is 3.632 liters.
| Prefix
| Abbrev.
| Multiply base unit by:
| Example: |
| Tera- | T | 1 trillion = 1012
| 1 Terameter (Tm) = 1012 m |
| Giga- | G | 1 billion = 109
| 1 Gigameter (Gm) = 109 m |
| Mega- | M | 1 million = 106
| 1 Megameter (Mm) = 106 m |
| Kilo- | K or k | 1000 = 103
| 1 Kilometer (km) = 103 m |
| | | 1 = 100
| 1 meter (base unit) = 1 m |
| deci- | d | 1/10 = .1 = 10-1
| 1 decimeter (dm) = 10-1 m |
| centi- | c | 1/100 = .01 = 10-2
| 1 centimeter (cm) = 10-2 m |
| milli- | m | 1/1000 = .001 = 10-3
| 1 millimeter (mm) = 10-3 m |
| micro- | μ ("mu") | 1/million = 10-6
| 1 micrometer (μm) = 10-6 m |
| nano- | n | 1/billion = 10-9
| 1 nanometer (nm) = 10-9 m |
| pico- | p | 1/trillion = 10-12
| 1 picometer (pm) = 10-12 m |
|