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Cosmology and art |
New on the tutorial:
Cosmology is the study of the origin, current state, and future of our Universe. This field has been revolutionized by many discoveries made during the past century. My cosmology tutorial is an attempt to summarize these discoveries. It will be "under construction" for the foreseeable future as new discoveries are made. I will attempt to keep these pages up-to-date as a resource for the cosmology courses I teach at UCLA. The tutorial is completely non-commercial, but tax deductible donations to UCLA are always welcome.
Astronomy and cosmology are very much mathematical sciences, but I have attempted to avoid higher math in these pages. I do use high school algebra and geometry - courses required for admission to UCLA - but I have also included some animations [1, 2, 3, 4, 5, 6, 7], some Java applets [1, 2], and many illustrations in the tutorials, the ABC's of Distances, and the answers to some of the Frequently Asked Questions.
In addition to the cosmology tutorial, there is also a relativity tutorial and extensive discussions on the age, density and size of the Universe. There is also a bibliography of books at a range of levels, and a Javascript calculator of the many distances involved in cosmology.
Slides for recent talks:
The course notes (130 pages, 398 equations, 51 figures) for the upper division undergraduate Stellar Systems and Cosmology course, Astronomy 140, that I last taught in spring 2008 are available on the Web. And for a much more technical discussion of cosmology see my graduate course Astro 275 lecture notes (137 pages, 432 equations, 46 figures). This course was last taught in the spring of 2011 but will be taught again in the spring of 2013. If this course Web site gets closed, you can use a backup copy of the A275 notes.
23 July 2013 - Hanson et al. announce the first detection of the B-mode polarization signal in the CMB. B-modes have a swirling pattern like a pinwheel. The result is at very small angular scales using the South Pole Telescope, and the signal is produced by gravitational lensing distorting the polarization produced by electron scattering (the E-mode). A distorted E-mode pattern contains a B-mode component. So this is not the primordial B-mode signal from the era of inflation, but a foreground pattern whose shape and amplitude can be definitely predicted. That prediction is now confirmed.
14 July 2013 - The Gruber Prize in Cosmology goes to Viatcheslav Mukhanov and Alexei Starobinsky. Starobinsky was a pioneer in studying the inflationary scenario.
29 April 2013 - The European Space Agency's Herschel Space Observatory has run out of liquid helium coolant, nearly 4 years after its launch. This means that there are currently no space infrared telescopes operating at wavelengths longer than the 4.5 μm channel of the Spitzer Space Telescope.
31 March 2013 - Planck released its first cosmology results today. Technical preprints are available here. The 6 parameter Λ CDM model is an excellent fit to the Planck data, and also to the Planck plus ACT, SPT and WMAP polarization extended CMB data, and to the CMB plus supernovae, Hubble constant and baryon acoustic oscillation data.
The parameters of the 6-parameter ΛCDM model fit to Planck+WMAP polarization+SPT+ACT+BAO are ΩΛ = 0.692 ± 0.010; the baryon density = 0.416 ± 0.0045 yoctograms per cubic meter; the cold dark matter density = 2.23 ± 0.032 yoctograms per cubic meter; CDM:baryon density ratio = 5.36 ± 0.10; dark energy density = 3352 ± 125 eV/cc; H0 = 67.80 ± 0.77 km/sec/Mpc; and the age of the Universe = 13.798 ± 0.037 Gyr. The baryon density is known to 1.1% precision and the cold dark matter density is known to 1.4% precision.
The dark energy density is known to 3.7% precision. For theorists who set hbar and c to 1, it works out to (2.25 meV)4. We still have no good theory to explain this value.
Limits on 1 parameter extension to the 6 parameter model are
Planck data is available at the InfraRed Science Archive (IRSA).
21 Dec 2012 - Bennett et al. presents the basic results, while Hinshaw et al. presents the cosmological fits. The 6 parameter Λ CDM model is still an excellent fit to the WMAP data, and also to the WMAP plus ACT and SPT extended CMB data, and to the CMB plus supernovae, Hubble constant and baryon acoustic oscillation data. The data are available now at LAMBDA. This is the last version of WMAP results. The baton is now passed on to Europe's Planck.
The parameters of the 6-parameter ΛCDM model fit to WMAP+BAO+H0 are ΩΛ = 0.712 ± 0.010; the baryon density = 0.426 ± 0.008 yoctograms per cubic meter; the cold dark matter density = 2.17 ± 0.04 yoctograms per cubic meter; CDM:baryon density ratio = 5.11 ± 0.14; dark energy density = 3607 ± 144 eV/cc; H0 = 69.33 ± 0.88 km/sec/Mpc; and the age of the Universe = 13.75 ± 0.085 Gyr. Both the baryon density and the cold dark matter density are known to 2% precision.
The dark energy density is known to 4% precision. For theorists who set hbar and c to 1, it works out to (2.3 meV)4. We still have no good theory to explain this value.
Several extensions to the 6 parameter ΛCDM are considered, but none are necessary to fit the data. The non-flat model gives Ωtot = 1.0027 ± 0.0039. This is perfectly consistent with a flat Universe.
The sum of the neutrino masses is < 0.44 eV.
The number of neutrino species is Neff = 2.83 ± 0.38
which is consistent with the standard value of 3.04 for 3 neutrino species.
Update 30 Jan 2013: v2 of the papers are posted to
the preprint server. With the helium abundance fixed, the number of
neutrino species for the WMAP+eCMB+BAO+H0 dataset is 3.84 ± 0.40
which is consistent (at 2σ) with the standard value.
12/12/12 - The Hubble Ultra Deep Field has been reobserved to greater depth in new filters in the infrared. Here are some highlights from the abstract of Ellis et al.:
Update 04 Jan 2013: Brammer et al. report a tentative emission line in UDFj-39546284 at 1.599 μm, which they feel is probably [O III] at z=2.19.
29 Oct 2012 - The South Pole Telescope announced new data on the small angular scale anisotropy of the Cosmic Microwave Background. Notable conclusions are:
01 Aug 2012 - Inflation cosmology theorists Alan Guth and Andrei Linde are among the 9 winners of the first Milner Prizes to be awarded. This prize amounts to $3,000,000.
12 Jun 2012 - Rahmani et al. report that the ratio of the 21 cm line of hydrogen to optical line wavelengths has not changed since 9 Gyr ago. Their limit on the change in a combination of constants x = gp α2 me/ mp is -0.1+/-1.3 parts per million. This makes earlier claims unlikely, since the claimed 10 parts per million change in α would change x by 20 parts per million.
13 Jan 2012 - The BBC reports that the dilution refrigerator that cools the High Frequency Instrument on the European CMB satellite Planck to 0.1 K has run out of 3He. The Low Frequency Instrument continues to operate at 4 K. The first announcement of cosmological results from Planck is scheduled for Jan 2013.
04 Oct 2011 -
Saul Perlmutter, Adam Riess & Brian Schmidt have won the
2011 Nobel Prize in Physics
for their work showing the Universe is accelerating
by measuring the brightness of distant supernovae.
This is evidence for an energy density of the vacuum or a
cosmological constant.
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© 1996-2013 Edward L. Wright. Last modified 27 Jul 2013