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Topic: Scale factor (Universe)

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In the News (Wed 20 Mar 19)

  Hubble law and the expanding universe
Discussions about the expansion of the universe often refer to a density parameter Ω which is the density divided by the critical density, such that Ω = 1 represents the critical density condition.
Hubble's law is a statement of a direct correlation between the distance to a galaxy and its recessional velocity as determined by the red shift.
The Hubble parameter is the ratio of the rate of change of the scale factor to the current value of the scale factor R: The scale factor R for a given observed object in the expanding universe relative to R
hyperphysics.phy-astr.gsu.edu /hbase/astro/hubble.html   (840 words)

  Scale factor (Universe) - Wikipedia, the free encyclopedia
The scale factor, parameter of Friedmann-Lemaître-Robertson-Walker model, is a function of time which represents the relative expansion of the universe.
The scale factor could, in principle, have units of length or be dimensionless.
The evolution of the scale factor is a dynamical question, determined by the equations of general relativity, which are presented in the case of a locally isotropic, locally homogeneous universe by the Friedmann equations.
en.wikipedia.org /wiki/Scale_factor_(Universe)   (180 words)

 PA 765: Factor Analysis
Factor analysis is part of the multiple general linear hypothesis (MLGH) family of procedures and makes many of the same assumptions as multiple regression: linear relationships, interval or near-interval data, untruncated variables, proper specification (relevant variables included, extraneous ones excluded), lack of high multicollinearity, and multivariate normality for purposes of significance testing.
Factor analysis generates a table in which the rows are the observed raw indicator variables and the columns are the factors or latent variables which explain as much of the variance in these variables as possible.
Factor scores are coefficients of cases on the factors, whereas factor loadings are coefficients of variables on the factors.
www2.chass.ncsu.edu /garson/pa765/factor.htm   (8883 words)

 Scale - Wikipedia, the free encyclopedia
Scale or Balance (In Urdu:Mizan or ميزان) is a comprehensive treatise on the contents of Islam written by Javed Ahmed Ghamidi, a Pakistani Sunni Islamic scholar.
The Medvedev-Sponheuer-Karnik scale and the Mercalli scale are used to measure the intensity of earthquakes.
The Fujita scale estimates the intensity of tornadoes.
en.wikipedia.org /wiki/Scale   (363 words)

 Astronomy - New type of energy hypothesized - Provided by Michigan Technological University
Nemiroff noted that early in the universe, the nuclei of elements formed in a way that is understood without the dominating presence of ultralight.
The species of ultralight that dilutes as the fifth power of the universe scale factor would not only have a positive definite sound speed but that sound speed would be less than the speed of light.
Other unusual energy species include the "cosmological constant," a proposed interpretation of dark energy which does not dilute at all as the universe expands, domain walls, which dilute as a single factor of the universe scale factor, and cosmic strings, which dilute as the second power of the universe scale factor.
www.astronomy.com /asy/default.aspx?c=a&id=5096   (994 words)

 Structure of the Universe
The infinite universe was said to be the source of an infinity of worlds, of which ours was but one, that separated off and gathered its parts together by their rotary motion.
It was his belief that the universe was infinite and that the primary qualities of the universe were mathematical in nature.
Persuasive observational evidence that the universe is indeed expanding and changing in time was found by Hubble (1889-1953) in 1929 while employing the technique known as Doppler shift for measuring the red shift of colors in the spectrum of nebulae.
www.columbia.edu /~ah297/un-esa/universe/universe-chapter2.html   (2800 words)

 The Uncaused Beginning of the Universe (1988)
The issue of whether oscillating universes are finite or infinite in respect of the past lost much of its urgency in the middle and late 1960s, with the development of the Hawking-Penrose singularity theorems,[8] which entailed that an inexactly homogeneous and isotropic universe must have a singularity.
Tryon argues that the universe is able to be a fluctuation from a vacuum in a larger space in which the universe is embedded since it does have a zero net value for its conserved quantities.
The metric of a homogeneous and isotropic universe is
www.qsmithwmu.com /the_uncaused_beginning_of_the_universe_(1988).htm   (7386 words)

 Setting the Size or Luminosity of Particles | Partiview User's Guide | Digital Universe | Hayden Planetarium
Given the luminosity from either of the two lum commands, a scaling factor is multiplied to brighten all or a portion of particles in the data group.
This command is a global scale factor on the luminosity.
This is a scaling factor that is relative to a particular data variable.
www.haydenplanetarium.org /universe/partiviewguide/using_groups_lum.php   (1285 words)

 Scale factor in Robertson-Walker metric
As I understand it, the R-W metric allows BB theorists to model an ideal expanding universe that is homogeneous and isotropic, and that the scale factor's base values are set at 1 for present time and at 0 for the BB singularity.
If you believe that redshift is primarily due to cosmological expansion, the scale factor allows you to extrapolate the present separation of a distant galaxy based on the presumed cosmological expansion rate and the estimated time that has passed since the emission of the light that we just received.
Once we know what fraction of the total content of the universe is relativitic, non-relativistic, cosmological constant or dark energy etc., and the value of curvature constant k, (which says how the universe is curved; it depends on the total density of the universe) we get an expression for the scale factor.
www.physicsforums.com /showthread.php?t=53233   (2638 words)

 How does the cosmological constant affect the evolution of the Universe?
A negative cosmological constant adds to the attractive gravity of matter, therefore universes with a negative cosmological constant are invariably doomed to recollapse (1).
These universes are called "loitering" universes, and are located on the red line in the finding plot (10).
We are in the Department of Astrophysical and Planetary Sciences at the University of Colorado, Boulder.
super.colorado.edu /~michaele/Lambda/evol.html   (751 words)

 Research at KICP: Structures in the Universe   (Site not responding. Last check: 2007-10-30)
This acceleration is caused either by a mysterious new component of the Universe --- dark energy --- or by a breakdown of Einstein’s theory of gravity (General Relativity) at large scales.
One of the major research objectives of the Kavli Institute for Cosmological Physics is to use observations and simulations of structures in the Universe to measure the expansion history of the Universe and thereby probe the nature of the dark energy.
In 1998, two groups used measurements of Type Ia supernovae to demonstrate that the expansion of the Universe is accelerating, ushering in the current fascination and preoccupation with dark energy.
cfcp.uchicago.edu /research/structures/index.html   (1363 words)

 PES 105 Fall 2003 | In-Class Projects   (Site not responding. Last check: 2007-10-30)
To provide as sense of the immense scale of the universe by scaling down astronomical distances to distances more readily conceived.
In the second section, the local star group and the universe are scaled down such that the local star group is the size of a saucer.
The scaled value is entered into column S. Then the table of familiar objects and distances is consulted to find the entry that matches the scaled astronomical object.
www.uccs.edu /~rgist/PES/AstroProj/PES106/ScaleUniverse.htm   (169 words)

 Magnitude - a measure of brightness
Original Windows to the Universe artwork by Randy Russell, using a simulated view of Orion generated by Dennis Ward.
The magnitude scale for stars was invented by the ancient Greeks, possibly by Hipparchus around 150 B.C. The Greeks grouped the stars they could see into six brightness categories.
The magnitude scale was invented by the ancient Greeks around 150 B.C. The Greeks put the stars they could see into six groups.
www.windows.ucar.edu /the_universe/Stars/magnitude_scale.html   (1782 words)

 Dynamics of the Universe   (Site not responding. Last check: 2007-10-30)
The key factor that determines which history is correct is the amount of mass/gravity for the Universe as a whole.
Given all the range of values for the mean density of the Universe, it is strangely close to the density of a flat Universe.
In this equation, `R' represents the scale factor of the Universe (think of it as the radius of the Universe in 4D spacetime), and H is Hubble's constant, how fast the Universe is expanding.
zebu.uoregon.edu /~js/cosmo/lectures/lec16.html   (648 words)

 The Universe
In any case, oxygen is the third most abundant element in the Universe, ranked between the inert gases helium and neon.
All matter detected to date falls short of this critical value by a factor of about ten: as there is also ten times as much dark matter exerting its gravitational influence as there is matter in the form of bright stars, we conclude that the bright stars represent only 1% of the Universe.
Considering the future of water, it appears quite poor in the closed Universe scenario, when billions years from now the matter, space and time will collapse in a Big Crunch and the existing laws of physics will loose any meaning.
www.k26.com /witus/What_s_New/The_Universe/the_universe.html   (923 words)

 Planetarium Show
In our scale model with the Milky Way the size of a mini-basketball, the Local Supercluster is about 190 meters long and the entire observable universe is about 49.5 kilometers in diameter.
The scale model is called the ``cosmic calendar'' in which every second in the ``cosmic calendar'' called the ``cosmic calendar'' in which every second in the ``cosmic calendar'' corresponds to 475 real years (so 24 cosmic calendar days = 1 billion real years).
The universe starts in the early morning of January 1 at midnight in the cosmic calendar and our present time is at December 31 at 11:59:59.99999 PM in the cosmic calendar.
www.astro.washington.edu /planetarium/activities/Motions/post2.html   (1662 words)

 Position of Earth in the Universe
of the observable universe is rather reminiscent of the old practice of talking up demons, deities, spirits, sea-serpents, and dragons, or the new habit of speculating about bubble universes.
Although it does not require a universe of size bigger than we observe, it does allow for it just as naturally as a universe that is smaller.
If the universe had a topological scale around the size of our particle horizon, that would suggest that we are somehow special and the observable universe has stopped growing just in time for our appearance.
www.physicsforums.com /showthread.php?t=126255   (3239 words)

The basic idea is that the universe, which is expanding now with some time dependent scale factor a(t), starts expanding faster and faster.
When the universe isn't inflating, such as now, regions which are larger and larger come inside the horizon and become causally connected.
For example, the Cosmic Microwave background is homogeneous on scales which were not in causal contact when the signal was created, and thus suggests we need something like inflation to explain its homogeneity.
astro.berkeley.edu /~jcohn/inflation.html   (1147 words)

 A sense of scale
Although there are uncountable galaxies, each made of billions of stars, the extent of the universe is so vast that the matter of which it is made occupies only an infinitesimal fraction of its volume.
It is difficult to get a feeling for the scale of the solar system, much less the universe, but here is a model we can build which may help.
Again, we establish the scale by multiplying the astronomical unit (93 million miles) by our scale factor, after converting miles to inches.
members.tripod.com /w.g.seeley/astronew/scale.htm   (861 words)

 Universe Builder
Scale a select group of respondents to the total population (i.e., BuyingStyles respondents).
Press [Add] and enter the definition, label, and scale factor for each segment of the group.
The segments of the group should total 100% of the population, even if it means scaling one or more segments to 0%.
www.mediamark.com /memri/docs/Universe.htm   (470 words)

 Physics 110 Universe Age and Size
In the current, best model for the universe, the universe was created in the Big Bang event 12 to 15 billion years ago.
The universe is so old that all of recorded human history occupies only the last 13 seconds or so of the year.
A nice demonstration of the scale of the universe is to start with a view showing our galaxy and then zoom by a factor of ten once per second.
www.cs.csubak.edu /Physics/phys110/UniverseScale.html   (1035 words)

 Cosmology Tutorial - Part 3
The ages of the Universe in these five models are 13.8, 9.2, 7.9, 13.7 and infinity Gyr.
In fact, recent data from the HIPPARCOS satellite suggest that the Cepheid distance scale must be increased by 10%, and also that the age of globular clusters must be reduced by 20%.
Since the wavelengths in the CMB scale the same way that intergalaxy distances do during the expansion of the Universe, we know that a(t) had to be 0.0009 at recombination.
www.astro.ucla.edu /~wright/cosmo_03.htm   (1521 words)

 Is the Universe younger than we thought?
Maoz' research indicates the universe may be as young as 12 billion years, nearly the same age as its oldest stars.
This implied relatively low age of the universe could revive an old paradox in the field of astrophysics that the universe seems to be younger than some of the stars in it.
However, this measurement was different from another independent, highly accurate distance determination to that galaxy made using masers (the microwave equivalent of lasers), which are located at the galaxy center and orbiting a supermassive fl hole.
science.nasa.gov /newhome/headlines/ast27sep99_1.htm   (614 words)

 Why is the Universe accelerating?
One of the most important discoveries of the late 20th century was the evidence from Type Ia supernovae (SNe-Ia) that the expansion of the Universe is accelerating [1].
Assuming the scale invariant spectrum of initial adiabatic fluctuations and flat spatial geometry of inflationary models, a series of peaks are predicted to occur in the CMBF data.
Due to the mass scale, the non-perturbative effects are dynamically negligible in the early universe.
www.phys.lsu.edu /mog/mog17/node9.html   (992 words)

 Sepp Hasslberger: Scale Expanding Cosmos - A Universe of Variable Size
In his Scale Expanding Cosmos model, Masreliez postulates that the universe is constantly and incrementally changing scale, but the increase is imperceptible because the change in space metrics is accompanied by a corresponding change in the metric of time, so for us who are inhabiting the universe, things remain the same.
This model of the universe also gained support from the fact that a spatially expanding universe may be modelled by GR, which gave the model physical credibility.
Scale expansion means that the length of a fixed distance like a meter slowly expands and that the pace of time slowly decreases.
blog.hasslberger.com /2006/07/scale_expanding_cosmos_a_unive.html   (5327 words)

 Seeing the Universe
With such a large volume of the universe mapped, cosmologists will be able to make firm quantitative measurements about the nature of large scale structure which any successful model must reproduce.
A particularly important key program of the HST is the measurement of the Hubble constant, which is a key parameter in cosmological theories and presently unknown to within a factor of two.
A high resolution CMB image would be able to map the "seeds of structure" on length scales corresponding to clusters and superclusters of galaxies, and thus provide direct measurements of the primordial density fluctuations required as input to numerical models.
archive.ncsa.uiuc.edu /Cyberia/Cosmos/SeeUniverse.html   (802 words)

 Cosmology Tutorial - Part 3
The age of the Universe is 15, 10 and 8.6 Gyr in these three models.
The Universe was opaque before protons and electrons combined to form hydrogen atoms when the temperature fell to about 3,000 K at a redshift of 1+z = 1000.
Since the wavelengths in the CMB scale the same way that intergalaxy distances do during the expansion of the Universe, we know that a(t) had to be 0.001 at recombination.
cats.sao.ru /~satr/cosmo/cosmo_03.htm   (1408 words)

 directopedia : Directory : Recreation : Models : Scale
Architect's scale - (or draughtsman's scale) is a ruler-like device, which facilitates the production of technical drawings.
Kinsey scale, sexual orientation (Klein scale is superior but not yet as well known)
The Richter scale, the Mercalli scale, the Rossi-Forel scale and the Omori are all used to measure the intensity of earthquakes.
www.directopedia.org /directory/Recreation-Models/Scale.shtml   (1166 words)

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