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The mass of the observable universe is often quoted as 10 53 kg. [48] In this context, mass refers to ordinary (baryonic) matter and includes the interstellar medium (ISM) and the intergalactic medium (IGM). However, it excludes dark matter and dark energy. This quoted value for the mass of ordinary matter in the universe can be estimated based ...
Perhaps unsurprisingly, our universe has just the right mass–energy density, equivalent to about 5 protons per cubic meter, which has allowed it to expand for the last 13.8 billion years, giving time to form the universe as observed today. [65] [66] There are dynamical forces acting on the particles in the universe which affect the expansion ...
Historically, different people have suggested various locations as the center of the Universe. Many mythological cosmologies included an axis mundi, the central axis of a flat Earth that connects the Earth, heavens, and other realms together. In the 4th century BC Greece, philosophers developed the geocentric model, based on astronomical ...
Knowledge of the location of Earth has been shaped by 400 years of telescopic observations, and has expanded radically since the start of the 20th century. Initially, Earth was believed to be the center of the Universe, which consisted only of those planets visible with the naked eye and an outlying sphere of fixed stars. [1]
The Earth and Moon are much closer to being a binary planet; the center of mass around which they both rotate is still inside the Earth, but is about 4,624 km (2,873 miles) or 72.6% of the Earth's radius away from the centre of the Earth (thus closer to the surface than the center).
But the mass density of the universe can be measured from its gravitational clustering, and is found to have only about 30% of the critical density. [13] Since theory suggests that dark energy does not cluster in the usual way it is the best explanation for the "missing" energy density.
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If Jupiter had Mercury's orbit (57,900,000 km, 0.387 AU), the Sun–Jupiter barycenter would be approximately 55,000 km from the center of the Sun ( r 1 / R 1 ≈ 0.08). But even if the Earth had Eris's orbit (1.02 × 10 10 km, 68 AU), the Sun–Earth barycenter would still be within the Sun (just over 30,000 km from the center).