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When we say the universe is accelerating, do we mean the expansion is speeding up or slowing down? ... If the density is less than the critical density the Universe will continue to expand forever and is known as an Open Universe. The critical case, where the density of the universe exactly equals that critical density,
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www.astro.lsa.umich.edu/undergrad/Labs/cosmo/worksheets...
www.astro.lsa.umich.edu/undergrad/Labs/cosmo/worksheets-cosmoShort.html
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Ask the experts your physics and astronomy questions, read answer archive, and more. ... When we compare the true density of the universe to the 'critical density', we determine whether we live in a 'closed,' 'flat,' or 'open' universe. What do these words mean?
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www.physlink.com/ae252.cfm
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C) A black hole is truly a hole in spacetime, through which we could leave the observable universe. ... 11) What do we mean by the singularity of a black hole? ... C) It is the center of the black hole, a place of infinite density where the known laws of physics cannot describe the conditions.
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www.physics.sfasu.edu/friedfeld/ast105/finalreview.htm
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What is the temperature of the universe and has it always been that temperature? What is the standard cosmological model? What is the future of the universe? What do we mean by the critical density of the universe?
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academic.udayton.edu/ToddSmith/SCI190/AC_handout.html
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We first consider the case of a critical density universe with a CDM power-spectrum (Davis et al. 1985), normalized to . We choose a baryonic density parameter and H0=60 kms-1/Mpc. ... 2 also allows us to build a model for Lyman- clouds, some of which are objects with a lower density than the mean density of the universe.
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www.aanda.org/articles/aa/full/2001/05/aa9559/node4.htm...
www.aanda.org/articles/aa/full/2001/05/aa9559/node4.html
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When talking about the distance of a moving object, we mean the spatial separation NOW, ... If the Universe does not have the critical density then the distance is different, and for the low densities that are more likely the distance NOW to the most distant object we can see is bigger than 3 times the speed of light times...
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www.astro.ucla.edu/~wright/cosmology_faq.html
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If the actual density of the universe is greater than the critical density, then the universe will someday stop expanding. ... What do scientists mean by the critical density of the universe? ... the minimum density that a universe needs in order to form galaxies...
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www.shari.com/2002/04/phys_1412_quiz_.html
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Question 51; If we learn that the universe is closed, it will mean that the universe is presently contracting, rather than expanding as generally believed. ... we live in a critical-density universe.
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www.shari.com/2002/04/phys_1412_quiz__1.html
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I conclude this section by describing what it would mean for the universe to be infinite or finite. ... The problem is that the measured density turns out to be pretty close to the critical density. Right now the evidence seems to favor an infinite universe, but it is not yet conclusive.
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www4.ncsu.edu/unity/lockers/users/f/felder/public/kenny...
www4.ncsu.edu/unity/lockers/users/f/felder/public/kenny/papers/cosmo.html
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