<Tr> <Th> Average temperature </Th> <Td> 2.72548 K </Td> </Tr> <Tr> <Th> Contents </Th> <Td> Ordinary (baryonic) matter (4.9%) Dark matter (26.8%) Dark energy (68.3%) </Td> </Tr> <P> The observable universe is a spherical region of the Universe comprising all matter that can be observed from Earth at the present time, because electromagnetic radiation from these objects has had time to reach Earth since the beginning of the cosmological expansion . There are at least 2 trillion galaxies in the observable universe . Assuming the Universe is isotropic, the distance to the edge of the observable universe is roughly the same in every direction . That is, the observable universe has a spherical volume (a ball) centered on the observer . Every location in the Universe has its own observable universe, which may or may not overlap with the one centered on Earth . </P> <P> The word observable in this sense does not refer to the capability of modern technology to detect light or other information from an object, or whether there is anything to be detected . It refers to the physical limit created by the speed of light itself . Because no signals can travel faster than light, any object farther away from us than light could travel in the age of the Universe (estimated as of 2015 around 7010137990000000000 ♠ 13.799 ± 0.021 billion years) simply cannot be detected, as they have not reached us yet . Sometimes astrophysicists distinguish between the visible universe, which includes only signals emitted since recombination--and the observable universe, which includes signals since the beginning of the cosmological expansion (the Big Bang in traditional physical cosmology, the end of the inflationary epoch in modern cosmology). </P>

What is at the center of the observable universe
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