2What is science? a) Finding the truth. b) A set of facts. c) Performing experiments and observations.d) All of the above.
3What is the difference between scientific laws and theories? Laws have been proven.Theories have not been proven.Theories become laws.Theories and laws are two different kinds of scientific information.a, b & c above.
4Some Aspects of NOS Scientific knowledge is tentative. Scientific knowledge has basis in empirical evidence.There is a difference between data and evidence.Scientific laws and theories are separate kinds of scientific knowledge.Scientific knowledge is based upon observations and inferences.
5Some Aspects of NOS Continued Scientific knowledge is created from human imagination and logical reasoning.Scientific knowledge can be obtained by a variety of scientific methods.Scientific observations are inherently subjective based on interpretations.Science is a human endeavor influenced by society and culture.
6Revolutionary Science and Normal Everyday Science Copernican revolution turned science upside down. Old theories are abandoned for new theories. These are rare scientific times.Everyday science is the normal development of science based on the revolutionary ideas.
7Charles Messier (1730-1817) French comet hunter Looking for Halley’s Comet to return as predicted.Complied catalog of annoying fuzzy things in the sky that were not comets.Most of these could not be resolved by telescope available at the time.
9Joseph von Fraunhofer (1787-1826) Studied dark lines in the Sun’s spectrum during the years
10Gustav Kirchhoff (1824-1887) Was from Prussia. Developed three laws of spectroscopy.These laws describe the condition that produce the three types of spectra observed.
11Kirchhoff 1st Law Continuous spectrum A luminous solid or liquid, or a sufficiently dense gas, emits light of all wavelengths (colors) and produces a continuous spectrum.
12Kirchhoff 2nd Law Emission line spectrum A low-density, hot gas emits light whose spectrum consists of a series of bright emission lines. These lines are characteristic of the chemical composition of the gas.
14Kirchhoff 3rd Law Absorption line spectrum A cool, thin gas absorbs certain wavelengths from a continuous spectrum, leaving dark absorption lines in their place. These lines are also characteristic of the chemical composition of the gas.
16Christian Doppler ( )Studied wavelength shift produced by moving objects.He stated this relationship in 1842 in Über das farbige Licht der Doppelsterne und einiger anderer Gestirne des Himmels (On the Coloured Light of Double Stars and Certain Other Stars of the Heavens) while working in Prague.
18Math of the Doppler Effect V = (Dl/l) SWhere:V = velocity of moving objectl = wavelength emittedDl = chance of wavelengthS = speed of the wave.For light waves this becomes,V = (Dl/l) cc = speed of light = 300,000 km/sec.Math of the Doppler Effect
19Lord Ross Giant Telescope (1850) It was (recently restored) a 6 foot (72 inch) diameter telescope, which made it largest in the world.Some of Messier’s nebulae were seen to have distinct spiral structure.
20Vesto Slipher ( )Discovered red shift in spectra of several spiral nebulae using Lowell 24-inch refractor.This later became the first evidence that the universe is expanding ( ).
21Henrietta Leavitt (1868-1921) Discovered 2400 variable stars. Observed Cepheid variable stars in LMC and SMC.In 1912 discovered Period-Luminosity Relation for CepheidsCepheids could be used to estimate distances.
25Shapley’s Observations In 1918 Shapley used the 60-inch telescope on Mt. Wilson to observe variable stars in globular clusters.
26Shapley’s Huge Discovery Found that Sun was 2/3 of the way out form the center.Center was located in direction of Sagittarius.This set off the Great Debate.
27The Shapley - Curtis Debate of 1920 They debated the size of the universe.Are the spiral nebulae close or are they far away and separate universes outside our universe, island universes.Shapely claimed they were close and within our universe.Curtis thought they were far away and outside for our universe. Shapley won debate but was wrong!!
28George Hale (1868-1938) Built 100-inch telescope on Mt. Wilson in 1917 Largest telescope in the world until 200inch was built in 1940’sNamed after John Hooker who paid for the mirror
29Albert Einstein (1879-1955) General Theory of Relativity Predicted an expanding universe.He rejected idea and introduced the cosmological constant to force a static universe. This removed the natural contraction caused by gravity.Mass is distributed evenly within the universe.
30Alexandra Friedmann (1888-1925) Russian meteorologistProposed an expanding universe model in 1925 based on Einstein’s theory.
31George Lemaitre (1894-1966) Roman Catholic clergyman at the Vatican. Independently proposed an expanding universe that had a moment of creation.Sent his idea to Einstein who rejected it claiming Lemaitre’s physics was bad.
33Mt Wilson ObservatoryIn 1923 used 100-inch to observe Cepheid’s in the Andromeda Spiral Nebula.It was one-hundred thousand times farther away than the nearest stars!!!!!!!THAT SETTLED THE ISLAND UNIVERSE DEBATE! Curtis was right, even though he lost.
34Hubble’s Image of Andromeda Galaxy In 1923, Edwin Hubble was examining photographic plates of the Andromeda Nebula taken with the 100-inch telescope in order to find novae -- stars that would suddenly increase in brightness. On this place from the night of October 5-6, 1923,Hubble located three novae, each marked with an ``N.'' One of these novae, however, turned out to be a Cepheid variable, a star that changes predictably in brightness, and the ``N'' was crossed out and the star was relabeled ``VAR!'' This Cepheid, and others subsequently discovered in the Andromeda Nebula, enabled Hubble to prove that the Nebula was not a star cluster within our own Milky Way, but a galaxy more than a million light years away.
35Hubble Discovers Expansion of Universe In late 1920’s hubble used 100-inch to observe spectra of many galaxies.They ALL had red shifts.This implied they were all moving away from Milky Way.
36Hubble’s LawHubble’s Law (1929) says that the farther away a galaxy is the faster it moves away from us.V = HDwhere V = velocityD = distanceH = Hubble’s constant (slope of the line)
37Interesting Big Questions Does this imply that the Milky Way is thecenter of the universe?Does this imply a creation event that formed the universe?
38The Raisin Cake ModelThe entire Universe is expanding similar to an expanding raisin cake.There is NO center to the expansion. Every raisin is getting fartheraway from every other raisin.No matter which raisin you live on, ALL other raisins appear to begoing away from you.
39The Expansion of the Universe The universe expands but the individual galaxies do not expand.The cosmological red shift is cause by the stretching of light waves as universe expands.
40Fred Hoyle (1915-2001) A Big Bang or a Steady State? Disliked the idea of a creation event and made fun of it by calling it “The Big Bang”Developed the Steady State theory (1948), which said that as the universe expanded new matter was formed to fill the void left by the expansion.
41George Gamow ( )Suggested a test to see which theory was most likely.If universe was created in an explosion the current temperature of that explosion should be about 3 Kelvin.Look for background radiation of the temperature.Where do you look?
42The Cosmic Black Body Curves As the universe expandsit should cool. Gamowpredicted the universeshould now have a blackbody curve following3 Kelvin, observable inmicrowaves.
43Robert Wilson (1936- ) Arno Penzias (1933- ) In 1965 they used a horn antenna to accidentally observe the 3 Kelvin microwave background radiation left over from the Big Bang.IS THE BIG BANG CONFIRMED?IS THE STEADY STATE THEORY DEAD?
44Cosmic Background Explorer COBE Launched November 18, 1989.Obtained black body curve for a temperature of 2.7 Kelvin!WAY COOL!!! (Pun intended).
45The Inflationary Universe The Horizon Problem Why does the early Universe look the same in all directions?Rapid expansion says that universe expanded so fast that it could remember how its neighbors looked.
46The Inflationary Universe The Flatness Problem The Universe appears to have formed with exactly the amount of mass necessary to make it flat. WHY?
47The Inflationary Universe The Flatness Problem Early in the formation of the Universe it expanded very rapidly, which makes it appear flat.It may not really be flat. It may only look flat.
48COBE Microwave Map 2 years of data. There are temperature variations. 2 years of data.There are temperature variations.Fluctuations maybe the seeds of galaxy formation.A PICTURE OF CREATION!
49The Fate of the Universe Two possible futures1) A low density universe will expand forever.2) A high density universe will collapse in the Big Crunch.
50The Fate of the Universe At the moment we cannottell the difference.Critical density is the density that isrequired to cause the universe stopexpanding in infinite time.
51The Fate of the Universe Type Ia supernovae all have about same actual brightness.They help us determine distances.Universe appears to be accelerating!!This is inconsistent with The Big Bang Model!!!!!!
52The Fate of the Universe Again it is very difficult to sort out how the universe will end!
53The Fate of the Universe Are distances to supernovae correct?Is there a dark repulsive force, Dark Energy?Do we need to rethink Einstein's cosmological constant?This is the fun of science and it is why humans DO science!
54ResourcesChaisson & McMillan, (2002, 2004). Astronomy Today (4th & 5th Ed.)Bennett et al. (2004) The Cosmic Perspective (3rd Ed.)Shipman, Wilson, and Todd, (2003). An Introduction toPhysical Science (10th Edition).