![]() It falls apart with the actual topography of the Universe. The Big Bang didn’t happen there, in the middle. Image credit: īefore I get onto the question, I need to remind you that is a bad model. ![]() Is this how the Universe ends, and then begins again, and then probably ends again? And you could build a forward only time machine that keeps looping into a totally new but identical universe over and over? The history of the universe starting the with the Big Bang. And maybe this leads to another Big Bang, and then another Big Crunch, and so on and so on. Will the Big Bang go in reverse, eventually smashing the entire Universe into a singularity again – the Big Crunch. Will the expansion go on forever? Will it keep coasting, and never quite come to a stop? Will it expand and come to a stop over the course of infinite time? Or will the mutual gravity of all these galaxies eventually overcome the momentum and pull everything back in again. The SNAP mission: a proposed satellite mission to study cosmology with supernovae.Here’s a big question.The High-Z Supernova Search: the multi-national program to measure the expansion history.The Supernova Cosmology Project: the LBL program to measure the expansion history.Other Interesting Sites: On cosmology with supernovae: Further study of the dark energy with future experiments and space missions is needed to understand its nature and effect on the rate of future expanison. The results suggest the geometry of the universe is flat and will expand forever. The WMAP satellite measures the basic parameters of the Big Bang theory including the fate of the universe. If this is true, then dark energy is the major driving force behind the fate of the universe and it will expand forever exponentially. Approximately 24% of this is in the form of a low pressure matter, most of which is thought to be non-baryonic dark matter, while the remaining 71% is thought to be in the form of a negative pressure dark energy, like the cosmological constant. There is a growing consensus among cosmologists that the total density of matter is equal to the critical density, so that the universe is spatially flat. If dark energy in fact plays a significant role in the evolution of the universe, then in all likelihood the universe will continue to expand forever. Unlike gravity which works to slow the expansion down, dark energy works to speed the expansion up. This strange form of matter is also sometimes referred to as the dark energy. Recent observations of distant supernova have suggested that the expansion of the universe is actually accelerating or speeding up, like the graph's red curve, which implies the existence of a form of matter with a strong negative pressure, such as the cosmological constant. In this universe, there is sufficient mass in the universe to slow the expansion to a stop, and then eventually reverse it. If the density of the universe is greater than the critical density, then gravity will eventually win and the universe will collapse back on itself, the so called “Big Crunch”, like the graph's orange curve. This is also known as the “Big Chill” or “Big Freeze” because the universe will slowly cool as it expands until eventually it is unable to sustain any life. Gravity might slow the expansion rate down over time, but for densities below the critical density, there isn’t enough gravitational pull from the material to ever stop or reverse the outward expansion. If the density of the universe is less than the critical density, then the universe will expand forever, like the green or blue curves in the graph above. If the pressure of the matter is low, as is the case with most forms of matter we know of, then the fate of the universe is governed by the density. The current rate of expansion is measured by the Hubble Constant, while the strength of gravity depends on the density and pressure of the matter in the universe. The evolution of the universe is determined by a struggle between the momentum of expansion and the pull (or push!) of gravity. Just as Robert Frost imagined two possible fates for the Earth in his poem, cosmologists envision two possible fates for the universe: What is the Ultimate Fate of the Universe?
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