Transcript: Scientific reasoning is an important part of how science works. You may have your own beliefs or your own faith, and they are your own. They’re unchallengeable. But if you make an assertion in a scientific way, you have to be able to back up that assertion. So when scientists argue about theories and models and data they are using a formal way of arguing about things that can lead to advances in knowledge. A scientist can only make an assertion if it’s backed up by evidence. They can only make an assertion if some other scientist could go out and verify the assertion. That’s the way that science proceeds. Why then do scientists argue so much? Often because there are multiple theories or models to explain a given set of data. Equally data itself is never perfect, is often limited, and sometimes has errors attached. These uncertainties allow scientists to have room for doubt and lead to the fact that not all scientists agree on every issue.
12 Jul 2011
Scales of Mass
Transcript: The study of astronomy contains an enormous range in scales of mass. The lightest thing there is is an electron, 10-30 kilograms. The heaviest atom, Uranium atom, is 10-25 kilograms. The tiny living organisms, a bacterium or a virus, about 10-15 kilograms. Somewhere in the middle of the huge range are human beings with a typical mass of 100 or 102 kilograms. The entire Earth is 1025 kilograms. The sun, 1030 kilograms. And the entire mass of the observable universe, containing some 60 billion galaxies, amounts to 1052 kilograms. The entire range from the largest to the smallest is 82 orders of magnitude or powers of 10.
11 Jul 2011
Mass, Length and Time
Transcript: Scientists use a system of units based on mass, length, and time. Almost every physical quantity in the world can be reduced to some combination of units of mass, units of length, and units of time. For example area is length times length. Volume is length times length times length. Velocity is a distance or a length divided by a time. Momentum is a mass times a velocity. So many of the things you see in astronomy will be simply reducible to combinations of mass, length, and time. This is the way in which astronomers make sense of a complicated world, and in astronomy as in all science we measure mass, length, and time in units of the metric system: kilograms for mass, seconds for time, and meters for length.
11 Jul 2011
Transcript: Logic is a fundamental tool of the scientific method. In logic we can combine statements that are made in words or in mathematical symbols to produce concrete and predictable results. Logic is one of the ways that science moves forward. The first ideas of logic using words were put together by the Greek philosophers, especially Aristotle. The equivalent mathematical formalism for logic was put together about a hundred years ago by the philosopher Bertrand Russell. The word logic comes from a Greek root “logos” meaning logical, natural order. The Greeks believed that the universe was a rational place, and in fact the word cosmos, which we take today to mean the universe and everything in it, meant a little bit more to the Greeks. Cosmos meant natural and harmonious working of all the parts in the whole. The antithesis of cosmos is chaos, disorder and utter disorganization. So for the Greeks the universe was a balance between cosmos and chaos, and logic was their way of making sense of the natural world.
11 Jul 2011
Most Popular Podcasts
Transcript: The study of knowledge is called epistemology. There are two fundamental routes or paths for the study of knowledge. One is the idea of empiricism which dates back to Aristotle 25 hundred years ago. In the empirical approach to the method of science everything is based on observation or data. You start by gathering data or observations and then proceed to make a hypothesis which leads to a prediction of other observable phenomena. Then you make more observations to test your hypothesis and adjust it as needed. In this view of the universe and how science works everything is based on observations. The alternative view is called rationalism, and it probably dates back also 25 hundred years to the mathematician Pythagoras. In the rationalists view of how science works you start by conceiving mentally of models or ways that the world works. So you start with a mental framework, and then you proceed to derive observational tests of that mental framework and you go from there. Clearly science as it’s actually practiced by scientists imbeds elements of both ways of doing science. Science cannot proceed without observation, and clearly scientists have formulated important and sophisticated mathematical models of how the universe works. Both are required if science is to move forward.
11 Jul 2011
Causation and Correlation
Transcript: Science starts by looking for patterns in data. Therefore it’s important to understand the distinction between causation and correlation. Scientists believe in causation, the general idea that events have causes. However science starts by looking for patterns in observational data. Typically two quantities may be plotted on a graph against each other. If there’s a correlation, science tries to look for a cause. However it’s not always possible to find a cause, or it’s not correct to infer a cause. For example, it took 30 years of research before the government was sufficiently convinced of the correlation and the causation of smoking and cancer rates to put health warnings on all packets of cigarettes. So we must be careful of the distinction between two quantities that are correlated and whether one causes the other. Sometimes there may be an underlying variable or third quantity that relates to the causation. In astronomy we plot the Hertzsprung-Russell diagram where the luminosity and the effective temperature of main sequence stars are tightly correlated. However the underlying variable in this case is mass, a quantity not plotted at all. So scientists must be very careful not to make the jump from causation to correlation without a justified physical theory that makes predictions that can be confirmed.
11 Jul 2011
The Scientific Method
Transcript: The scientific method is a way of gaining knowledge about the world we live in. Science starts with curiosity about nature, observing the world, but there is a method to science, a way that distinguishes it from other modes of thought. Science is based upon evidence, upon observations. Scientists take the evidence, and from that they formulate ideas or hypotheses. And eventually when those have been sufficiently tested, the hypotheses become turned into theories about the natural world. It’s important to understand the scientific method because that’s the way we create knowledge. If I told you a fact it would be as if I gave you a fish to eat. You have that one fish. You have that one meal. But if I gave you a net you could catch many fish. The scientific method is the net that allows us to catch many fish, to learn many things about the world we live in.
13 Jul 2011
The Work of Scientists
Transcript: The bare bones of the scientific method does not encompass the fact that science is done by people. In the scientific method we have to have someplace for the ideas of luck, serendipity, being in the right place at the right time, persistence, inspiration. How did these fit into the scientific method? The stories of science are full of such ideas. Alexander Fleming, the discoverer of penicillin, itself an accidental discovery, once said “Fortune favors the prepared mind.” When a scientist makes what seems to be an accidental discovery it’s often because they are doing careful experiments and are noticing something that doesn’t fit a pattern or appears out of the norm. The discovery of vitamin-C dates back to a scientist noticing that citrus fruit never bruise and other fruit did and wondering why. The discovery of x-rays occurred because one scientist, Wilhelm Rontgen about one hundred years ago, noticed that certain photographic plates in his lab fogged in the presence of a radioactive source. It was an accident, but he was able to deduce that invisible rays were traveling from the radioactive source and fogging the photographic plate. The discovery of x-rays revolutionized modern medicine. When scientists make discoveries they cannot always tell where they are going to lead. When Thomas Edison first started using electricity he was asked what possible use is it. He said “What use is a new born baby?”
12 Jul 2011
The Evidence of Astronomy
Transcript: There’s very little direct evidence in astronomy. In a few cases we’ve been lucky enough to have meteorites falling from space. We’ve even had a few free samples of Mars. But most of the evidence of astronomy is gathered remotely. We’ve sent spacecrafts to most parts of the solar system, and they’ve sent back images and other information of radiation received. We’ve used telescopes to explore distant regions of space. We’ve extended our senses across the electromagnetic spectrum with detectors that can measure everything from x-rays and gamma rays to long wavelength radio waves. In astronomy we depend on the extension of our senses through technology but must of the evidence of astronomy is indeed indirect, the radiation that reaches us from throughout the universe.
12 Jul 2011
Steps of the Scientific Method
Transcript: There are several essential steps in the scientific method. They apply equally to astronomy and all other sciences. The first step is gathering data or observations. In astronomy this is usually not direct evidence. Usually it’s radiation gathered from space. The more observations or data the better. The second process is to analyze the data or look for patterns. Scientists look for patterns in the evidence or observations as a way of understanding how nature works. This leads to insights as in the example of the periodic table or the patterns in fossils that might tell how species evolved. Astronomers also look for patterns. In the third step astronomers take the patterns they have found and form a hypothesis to try and explain all the observations they have in hand. They hope this hypothesis will lead to predictions about new situations as yet untested. And if the hypothesis is successful, they form a theory of nature to try and describe what they’ve been observing. Science can never guarantee truth, but with sufficiently good observations it can guarantee good explanations of the natural world we live in.
12 Jul 2011