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The center of the Universe is a concept that lacks a coherent definition in modern astronomy; according to standard cosmological theories on the shape of the universe, it has no distinct spatial center. Historically, different people have suggested various locations as the center of the Universe.
Assuming a finite universe, the universe can either have an edge or no edge. Many finite mathematical spaces, e.g., a disc, have an edge or boundary. Spaces that have an edge are difficult to treat, both conceptually and mathematically. Namely, it is difficult to state what would happen at the edge of such a universe.
In physics, gravity (from Latin gravitas 'weight' [1]) is a fundamental interaction primarily observed as mutual attraction between all things that have mass.Gravity is, by far, the weakest of the four fundamental interactions, approximately 10 38 times weaker than the strong interaction, 10 36 times weaker than the electromagnetic force and 10 29 times weaker than the weak interaction.
Before Newton’s law of gravity, there were many theories explaining gravity. Philoshophers made observations about things falling down − and developed theories why they do – as early as Aristotle who thought that rocks fall to the ground because seeking the ground was an essential part of their nature.
[99] [100] However the theory of gravity itself was not accepted quickly. The theory of gravity faced two barriers. First scientists like Gottfried Wilhelm Leibniz complained that it relied on action at a distance, that the mechanism of gravity was "invisible, intangible, and not mechanical".
After Shapley and Hubble showed that the Sun is not the center of the universe, cosmology moved on from heliocentrism to galactocentrism, which states that the Milky Way is the center of the universe. [156] Hubble's observations of redshift in light from distant galaxies indicated that the universe was expanding and acentric. [158]
According to the Big Bang theory, the energy and matter initially present have become less dense as the universe expanded. After an initial accelerated expansion called the inflationary epoch at around 10 −32 seconds, and the separation of the four known fundamental forces , the universe gradually cooled and continued to expand, allowing the ...
Despite major efforts, no complete and consistent theory of quantum gravity is currently known, even though a number of promising candidates exist. [191] [192] Attempts to generalize ordinary quantum field theories, used in elementary particle physics to describe fundamental interactions, so as to include gravity have led to serious problems. [193]