Natural Science

1. Natural Science How Science Works

2. The Scientific Method is traditionally presented in the first chapter of science textbooks as a simple recipe for performing scientific investigations.

4. The linear, stepwise representation of the process of science is simplified, but it does get at least one thing right. It captures the core logic of science: testing ideas with evidence. However, this version of the scientific method is so simplified and rigid that it fails to accurately show how real science works.

5. The Scientific Method, as presented in many textbooks, is oversimplified.

6. 2 The real process of science

7. The process of science is non-linear. http://undsci.berkeley.edu/article/howscienceworks_02

9. The process of science is iterative. Science circles back on itself so that useful ideas are built upon and used to learn even more about the natural world. This often means that successive investigations of a topic lead back to the same question, but at deeper and deeper levels.

10. Let's begin with the basic question of how biological inheritance works. In the mid-1800s, Gregor Mendel showed that inheritance is particulate — that information is passed along in discrete packets that cannot be diluted. In the early 1900s, Walter Sutton and Theodor Boveri (among others) helped show that those particles of inheritance, today known as genes, were located on chromosomes. 

11. Experiments by Frederick Griffith, Oswald Avery, and many others soon elaborated on this understanding by showing that it was the DNA in chromosomes which carries genetic information. And then in 1953, James Watson and Francis Crick, again aided by the work of many others, provided an even more detailed understanding of inheritance by outlining the molecular structure of DNA.

12. Still later in the 1960s, Marshall Nirenberg, Heinrich Matthaei, and others built upon this work to unravel the molecular code that allows DNA to encode proteins. Biologists have continued to deepen and extend our understanding of genes, how they are controlled, how patterns of control themselves are inherited, and how they produce the physical traits that pass from generation to generation.

14. The process of science is not predetermined. Any point in the process leads to many possible next steps, and where that next step leads could be a surprise.

15. For example, instead of leading to a conclusion about tectonic movement, testing an idea about plate tectonics could lead to an observation of an unexpected rock layer. And that rock layer could trigger an interest in marine extinctions, which could spark a question about the dinosaur extinction — which might take the investigator off in an entirely new direction.

17. The real process of science is complex, iterative, and can take many different paths.

18. 3 A blueprint for scientific investigations

19. The process of science involves many layers of complexity, but the key points of that process are straightforward.

20. There are many ways into the process: Serendipity, or making fortunate discoveries by accident. (e.g., being hit on the head by an apple). Personal motivation (e.g. your baby brother has an inherited disease and you want to find a cure) Surprising observation (e.g. you see that people who have one mild disease then don’t get a different dangerous disease)

21. There are many ways into the process: Concern over a practical problem (e.g., finding a new treatment for diabetes). A technological development (e.g., the launch of a more advanced telescope). Everyday curiosity (e.g., “I wonder how I can think?”).

22. Scientists often begin an investigation by playing around: • tinkering, • brainstorming, • trying to make some new observations, • talking with colleagues about an idea, or • doing some reading

23. These processes are grouped under Exploration and Discovery

25. Scientific testing is at the heart of the process. In science, all ideas are tested with evidence from the natural world, which may take many different forms. You can't move through the process of science without examining how that evidence reflects on your ideas about how the world works — even if that means giving up a favorite hypothesis.

27. The scientific community helps ensure science's accuracy. Members of the scientific community (i.e., researchers, technicians, educators, and students) play many roles in the process of science, but are especially important in generating ideas, scrutinizing ideas, and weighing the evidence for and against them. Through the action of this community, science is self-correcting.

28. For example, you have heard of global warming. in the 1990s, John Christy and Roy Spencer reported that temperature measurements taken by satellite, instead of from the Earth's surface, seemed to indicate that the Earth was cooling, not warming.

29. However, other researchers soon said that those measurements didn't correct for the satellites slowly losing altitude as they orbit and that once these corrections are made, the satellite measurements were much more consistent with the warming trend observed at the surface. Christy and Spencer immediately acknowledged the need for that correction.

31. The process of science is strongly linked with society. The process of science both influences society (e.g., investigations of X-rays leading to the development of CT scanners) and is influenced by society (e.g., a society's concern about the spread of HIV leading to studies of the molecular interactions within the immune system).

33. There are many routes into the process of science. • The process of science involves testing ideas with evidence, getting input from the scientific community, and interacting with the larger society.

34. Let’s look at an example. You can download the full color version of this study from http://undsci.berkeley.edu/lessons/pdfs/alvarez_wflow.pdf Or a simpler one from http://undsci.berkeley.edu/lessons/pdfs/alvarez_esl.pdf

35. Asteroids and dinosaurs. In the 1970s, plate tectonics was cutting-edge science. Walter Alvarez wanted to study plate tectonics, but an intriguing observation would eventually lead him and the rest of science on an intellectual journey across geology, chemistry, paleontology, and atmospheric science. The journey was to solve a great mystery: What happened to the dinosaurs ?

36. Luis and Walter Alvarez stand by the rock layers where unusually high traces of iridium were found at the Cretaceous-Tertiary boundary. Was this evidence that of an ancient supernova or an ancient asteroid impact? And what did it have to do with the dinosaur extinction?

37. This case highlights these aspects of the nature of science: • Science can test hypotheses about events that happened long ago. • Scientific ideas are tested with multiple lines of evidence. • Science relies on communication within a diverse scientific community. • The process of science is non-linear, unpredictable, and ongoing. • Science often investigates problems that require collaboration from those in many different disciplines

38. From plate tectonics to paleontology

39. One of the key pieces of evidence supporting plate tectonic theory was the discovery that rocks on the seafloor record ancient reversals of the Earth’s magnetic field: as rocks are formed where plates are moving away from one another, they record the current direction of the Earth’s magnetic field, which flip-flops irregularly over very long periods of time.

40. As new seafloor forms, the igneous rock records the Earth’s magnetic field. Sedimentary rock layers forming at the bottom of the ocean may also record these magnetic flip-flops as sediment layers slowly build up over time. Alvarez studied such sedimentary rocks that had been uplifted and are today found in the mountains of Italy.

41. In these “flip-flops,” the polarity of the magnetic field changes, so that a compass needle might point south for 200,000 years and then point north for the next 600,000 years.

42. Walter Alvarez and his collaborators were looking for independent verification of the timing of these magnetic flip-flops in the sedimentary rocks of the Italian Apennine mountains. Around 65 million years ago, those sediments lay undisturbed at the bottom of the ocean and also recorded reversals of the magnetic field as sediments filtered down and were slowly compressed over time.

43. As Alvarez explored the Apennines, collecting samples for magnetic analysis, he regularly found a distinct sequence of rock layers marking the 65 million year old boundary between the Cretaceous and Tertiary periods—the “KT” boundary. This boundary was made up of a lower layer of sedimentary rock rich with a wide variety of marine fossils, a centimeter-thick layer of claystone devoid of all fossils, and an upper layer of sedimentary rock containing a much reduced variety of marine fossils.

44. The Cretaceous-Tertiary boundary, as recorded in the rocks. At left, the later Tertiary rocks appear darker—almost orange—and the earlier Cretaceous rocks appear lighter. At right, there are a few different sorts of microfossils in the Tertiary layers, but a wide variety in the Cretaceous sample.

47. Alvarez began asking questions. Why the sudden reduction in marine fossils? What had caused this apparent extinction, which seemed to occur so suddenly in the fossil record, and was it related to the simultaneous extinction of dinosaurs on land?

49. False starts and a new lead At the time, most paleontologists viewed the dinosaur extinction as a gradual event with the final extinctions at the end of the Cretaceous. To Alvarez, however, the KT boundary certainly looked catastrophic and sudden—but the timing of the event was still a question: was the KT transition (represented by the clay layer in the stratigraphy) gradual or sudden?

50. To answer that question, he needed to know how long it had taken to deposit the clay layer—but how could he time an event that happened 65 million years ago? Walter’s father suggested using beryllium-10, which is laid down at a constant rate in sedimentary rocks and then radioactively decays. Perhaps beryllium could serve as a timer.