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Fingerprints in the sky
| Our main concern in philosophy and in science should be the search
for the truth. Justification is not an aim; and brilliance and cleverness
as such are boring. We should seek to see or discover the most urgent problems,
and we should try to solve them by proposing true theories.
Carl Popper, Objective Knowledge, 1972.
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Assignments:Read Chapter 23 |
| Procedures: Plainspheres distributed
Observation labs start this week (if the weather is nice to us) Review: Light properties: Speed: 3 x 10^ 8 m/s Wave properties: Waves do not transfer matter, just energy. They produce "Junk Piles" after a "wave breaker" encounter. Same as light. Demo 1: Spectra of some stars, a black & white picture. Q1:Why not in color prints at the shown range?
Also: "Negative " spectrum. Both for stars & the sun. For the sun the picture IS colorful for non-UV wavelengths. Why? Because the sun is brighter. Why is it negative? Light passing through cold, tennous, gas excite electrons from low energy levels to higher levels. Q2: From which direction should I look at the light & see emission
spectrum? Answer: a direction such that the
Kirchoff laws: Liquids and solids when heated up give "rainbow" spectra.
(More on that on Wednesday).
The emission lines and absorption lines can tell us about the materials these gasses are made of. (See lab #2!!!) So by looking at the stars we learned how to identify materials remotely. This method is used not only in "fingerprinting" what the stars are made of - but also what every crime-seen material is made of here on earth!
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