New version page

Munich-07Nov05-clean

This preview shows page 1-2-3-24-25-26-27-49-50-51 out of 51 pages.

View Full Document
View Full Document

End of preview. Want to read all 51 pages?

Upload your study docs or become a GradeBuddy member to access this document.

View Full Document
Unformatted text preview:

A Century of CosmologyA Big Media Splash in 1992:But really, what have we learned since 1905?Cosmology is an Observational ScienceNo special laws for the heavensNewton’s Apple & the MoonThe Universe is dominated by gravityTwo and a half FactsOnly One Fact in 1917General Relativity & CosmologyEffect of  term was unexpectedSource of Cosmological ConstantRepresent Force by SlopeTotal Energy implies ShapeEinstein’s Static UniverseNew Data Was Demoted CN non-discovery of the CMBFred Hoyle missed the Nobel PrizeCN followup after Penzias & WilsonDiscovery of the Cosmic Microwave BackgroundCMB Disproved the Steady StateTrue Contrast CMB SkyEnhanced Contrast:Inflation: Large  during an early phaseAnimated View of InflationCOBE DMR vs EPASAccelerating Universe: 1998We recently learned how to read the “wattage” label on supernovae:As a result, data on velocity vs distance is now much better! 1929As a result, data on velocity vs distance is now much better! 1995As a result, data on velocity vs distance is now much better! 2004Acceleration causes FaintnessWMAP QVW as RGBEffects on Peak Position: lpkResults With WMAPCDM is a Good FitSo is “super Sandage”Is the Universe Really Flat?One BOOMERanG Claim is WrongInfo from peak & trough heightsResults With WMAPIs  really a CONSTANT?JDEM in 10 years? NASA needs $$$Search for Two Numbers?Can we say anything about w?Same Laws of Physics? Confirmed by CMB & IR mapsConclusion: A Century of ProgressA Century of CosmologyEdward L. (Ned) WrightUCLA7 November 2005A Big Media Splash in 1992:Prof. Stephen Hawking of Cambridge University, not usually noted for overstatement, said: “It is the discovery of the century, if not of all time.”25 April 1992But really, what have we learned since 1905?• Expansion of the Universe in 1929• The Universe is homogeneous & isotropic.• Dark matter in 1932• Cosmic Microwave Background in 1964• Accelerating Expansion in 1998Cosmology is an Observational Science• We can’t do experiments on the Universe.• We can’t change the initial conditions and see what happens.• But we can observe what is the Universe is like.• And we can study what past, present and future conditions of the Universe are compatible with our observations and the same laws of physics that apply in our laboratories.No special laws for the heavensNewton’s Apple & the Moon• Newton did not invent gravity to explain the apple’s fall.• Instead he realized that the same force law applied to the apple and to the Moon, which is always falling toward the Earth.The Universe is dominated by gravity• Einstein developed general relativity in 1915• Gravity is the only long-range force without positive and negative charges, so it dominates the large scale structure of the Universe.• Naturally Einstein created a general relativistic model for the Universe, based on what was known in 1917: ALMOST NOTHINGTwo and a half FactsPeter Scheuer (1963): “There are only two & a half facts in cosmology:1) The sky is dark at night.2) The galaxies are receding from each other as expected in a uniform expansion.3) The contents of the Universe have probably changed as the Universe grows older.”Only One Fact in 19171) The sky is dark at night. And Einstein ignored it.General Relativity & Cosmology• General relativity allows a consistent calculation of the effects of gravity in a uniform distribution of galaxies that fills the entire Universe.• But Einstein thought the Universe was static, and a static uniform distribution of galaxies that filled the entire Universe would be unstable to collapsing into clumps.• So Einstein added a new constant to his equation for gravity: the cosmological constant, Λ.Effect of Λ term was unexpectedSource of Cosmological Constant• A vacuum energy density is equivalent to Einstein’s cosmological constant: Λ• Quantum fluctuations could lead to a vacuum energy density.Represent Force by Slope• This is quite a good analogy for cosmological models.Short range attraction Matter dominatedLong Range Repulsion Λ dominatedTotal Energy implies Shape• Total Energy > 0– Sum of angles < 180o– Negative curvature– Infinite• Total Energy = 0– Sum of angles = 180o– No curvature– Infinite• Total Energy < 0– Sum of angles > 180o– Positive curvature– FiniteEinstein’s Static Universe• Einstein made a static spherical model of the Universe.• The diagram is a space-time diagram with time running up and a 1-D version of the 3-D sphere [a circle] for space.In this space-time diagram there are two observers with different velocities. One observer sees the circumnavigating light rays return at the same time, while the otherdoes not.Velocity with respect to the Universe is easily measured.New DataΛ Was Demoted• Expanding models with or without matter and/or Λ are possible.• But matter is needed – we are here.• Λ was not needed so it was deprecated.CN non-discovery of the CMBPlate 3 of Adams (1941, ApJ, 93, 11-23) reporting McKellar’s workHerzberg (1950) in Spectra of Diatomic Molecules, p 496:“From the intensity ratio of the lines with K=0 and K=1 a rotational temperature of 2.3oK follows, which has of course only a very restricted meaning.”There went Herzberg’s [second] Nobel Prize.Fred Hoyle missed the Nobel Prize• Hoyle (1950, The Observatory, 70, 194), reviewing a book by Gamow & Critchfield: “[the Big Bang model] would lead to a temperature of the radiation at present maintained throughout the whole of space much greater than McKellar'sdetermination for some regions within the Galaxy.”• This book implied To= 11 K. Gamow in 1956 Scientific American implied 6 K. But Alpher & Herman explicitly gave 5 K or 1 K in the Physical Review.• Nobody followed this up!CN followup after Penzias & Wilson• Reworking and reobserving the CN lines gave 2.78±0.10 K at 2.64 mm. (Thaddeus, 1972, ARAA, 10, 305-334)• By 1993, 2.73±0.03 K (Roth, Meyer & Hawkins 1993)(UCLA PhD’s) (advisor was Meyer)Discovery of the Cosmic Microwave BackgroundCMB Disproved the Steady State• A blackbody spectrum comes from an opaque, isothermal source.• The Universe now is transparent, not opaque.• The Universe now has a wide range of temperatures.• Therefore, the Universe must have evolved from an opaque, isothermal state into its present condition, which contradicts the Steady State hypothesis.True Contrast CMB Sky33, 41


Loading Unlocking...
Login

Join to view Munich-07Nov05-clean and access 3M+ class-specific study document.

or
We will never post anything without your permission.
Don't have an account?
Sign Up

Join to view Munich-07Nov05-clean and access 3M+ class-specific study document.

or

By creating an account you agree to our Privacy Policy and Terms Of Use

Already a member?