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The local geometry of the universe is determined by whether the relative density Ω is less than, equal to or greater than 1. From top to bottom: a spherical universe with greater than critical density (Ω>1, k>0); a hyperbolic, underdense universe (Ω<1, k<0); and a flat universe with exactly the critical density (Ω=1, k=0).
The first one to address the problem of an infinite number of stars and the resulting heat in the Cosmos was Cosmas Indicopleustes, a 6th-century Greek monk from Alexandria, who states in his Topographia Christiana: "The crystal-made sky sustains the heat of the Sun, the moon, and the infinite number of stars; otherwise, it would have been full of fire, and it could melt or set on fire."
This is a different voyage than the one shown above, as both schemes take the same assumed total point-of-view time: T=12 (stay-at-home), resp τ=12 (ship), so the results of the calculated other-one's times must be different: τ=9.33 (ship), resp T=17.3 (stay at home). In the standard proper time formula
The density parameter is the average density of the universe divided by the critical energy density, that is, the mass energy needed for a universe to be flat. Put another way, If Ω = 1, the universe is flat. If Ω > 1, there is positive curvature. If Ω < 1, there is negative curvature.
In cosmology, a static universe (also referred to as stationary, infinite, static infinite or static eternal) is a cosmological model in which the universe is both spatially and temporally infinite, and space is neither expanding nor contracting. Such a universe does not have so-called spatial curvature; that is to say that it is 'flat' or ...
In short, the thought experiment is set up in such a way that one's intuitions will be pumped in the desired direction. John McDowell, in his paper "Putnam on Mind and Meaning", [4] criticised Putnam for still having in play a latent commitment to a picture of the mind as modelled on the brain and located in the head.
This is the principle behind what happened at the beginning of the universe. When the Big Bang produced a massive amount of positive energy, it simultaneously produced the same amount of negative energy. In this way, the positive and the negative add up to zero, always. It's another law of nature. So where is all this negative energy today?
In physics and cosmology, the mathematical universe hypothesis (MUH), also known as the ultimate ensemble theory, is a speculative "theory of everything" (TOE) proposed by cosmologist Max Tegmark. [ 1 ] [ 2 ] According to the hypothesis, the universe is a mathematical object in and of itself.