Part 1: Basic principles that underlie all of the scientific method and the discipline of astronomy.
These short videos were created in August 2007 by Dr. Christopher D. Impey, Professor of Astronomy at the University of Arizona, for his students. They cover a broad range of terms, concepts, and princples in astronomy and astrobiology. Dr. Impey is a University Distinguished Professor and Deputy Head of the Astonomy Department. All videos are intended solely for educational purposes and are licensed under a Creative Commons Attribution-NonCommercial-NoDerivs 3.0 Unported License. The full list of collections follows below:
01. Fundamentals of Science and Astronomy
02. Ancient Astronomy and Celestial Phenomena
03. Concepts and History of Astronomy and Physics
04. Chemistry and Physics
05. Quantum Theory and Radiation
06. Optics and Quantum Theory
07. Geology and Physics
08. Solar Neighborhood and Space Exploration
09. Outer Planets and Planetary Atmospheres
10. The Solar System
11. Interplanetary Bodies
12. Formation and Nature of Planetary Systems
13. Particle Physics and the Sun
14. Stars 1
15. Stars 2
16. Stars 3
17. Galactic Mass Distribtuion and Galaxy Structure
19. Galaxies 2
20. Galaxy Interaction and Motion
21. Deep Space and High-Energy Phenomena
22. The Big Bang, Inflation, and General Cosmology
23. The Big Bang, Inflation, and General Cosmology 2
24. Chemistry and Context for Life
25. Early Earth and Life Processes
26. Life on Earth
27. Life in the Universe
28. Interstellar Travel, SETI, and the Rarity of Life
29. Prospects of Nonhuman Intelligences
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.
Transcript: There is no science without evidence. When a scientist makes an assertion he must back it up with evidence. The evidence could be evidence that is physical evidence. It could be evidence gathered from telescopes, or microscopes, or other mechanisms we have to extend our senses. But a scientist must always back up what they say with real data. For instance, 200 years ago Jean Batiste Biot in France saw stones that fell from the sky. Nobody thought that stones could fall from the sky. But by gathering the eye witness accounts of many villagers and by gathering up fragments of stones that had no known terrestrial composition, he was able to prove that meteorites do exist, and they do indeed fall from the sky. Contrast this with the idea of UFOs, unidentified flying objects. Eye witness reports of UFOs have been piling up for decades, yet there has never been a single confirmed case where physical evidence has been evaluated independently by scientists leading to support for the idea of alien visitations. And so on through the whole edifice of science we can not understand anything without relying on evidence.
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.
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.
Transcript: People make many statements in everyday life. Some statements are quantitative and some are qualitative. You might say, “This piece of music is great,” or, “It was cold outside yesterday.” The first statement cannot be quantified. It may be true for you and not true for one of your friends. It’s a purely qualitative statement. The second statement can be quantified, but we need a system of units. Scientists only deal with quantitative statements. Every statement about science that involves a measurement has two parts. It has a quantity and a unit, and science always deals with these two things coupled together. So when I say, “It was cold yesterday,” I need a system of units and a measurement. And even if I say, “Fifteen degrees,” I have to tell you which measurement system I was using, Celsius or Fahrenheit. If I said, “The Dow fell fifty points yesterday,” that’s a quantitative statement, but you would have to know something about the units; which means you would have to know something about what goes into making a point on the Dow-Jones Industrial Average. So in general scientists always deal with quantitative measurements, and those measurements must have units attached.
Transcript: Astronomers have to deal with very large and very small numbers. As we deal with things as low density as the vastness of space and as high density as the center of a black hole, as hot as the first instant after the big band and as cold as intergalactic space, we are dealing with very large and very small numbers. Scientific notation is a short hand for writing very big and very small numbers. For instance, the nearest stars are about 4 or 5 trillion miles or kilometers away. 4 or 5 trillion is 4 or 5 followed by twelve zeros. So scientists use a shorthand form of writing this large number, 4*1012 or 4 times 10 with 12 as an exponent. If the number is very small the exponent has a negative sign in front of it. In science in general and in astronomy in particular we need scientific notation as a quick and efficient way of writing and manipulating large and small numbers.