The size of the universe is unknown.

The diameter of the observable (where "observable" refers to the universe that can theoretically be observed since the light coming from that area has had time to reach us since the Big Bang) universe is estimated to be about 93 billion lightyears (about 29 billion parsecs or about \(8.8 \times 10^{23}\) kilometers).[1] As nothing can exceed the speed of light, some nonastronomers and laymen assume that the observable universe is actually 13.8 billion light-years in size, as this is the scientifically hypothesized age of the universe in years. The curvature of the universe makes it much larger than this.[2]

The size of the observable universe is determined by how far light can travel given the total elapsed time since the Big Bang. There are most likely galaxies outside the observable universe that cannot be seen yet because they are too far away for their light to have traveled to Earth, and no conceivable technology by modern means can change that.

The diameter of the actual universe is unknown. One source estimates that the whole universe is at least 250 times larger (3,450 billion light-years) than the observable universe,[3] whereas other sources give lower bounds of \(3 \times 10^{23}\) (1.5 × \(3 \times 10^{34}\)) light-years) times[4] and \(10^{10^{10^{122}}}\) times.[5]

Cosmologist Andrei Linde estimates possible number of universes in the multiverse as \(10^{10^{10^7}}\).[6]

If the universe's geometry is flat (i.e. it has zero curvature), it will be infinite in size. A NASA study showed that the universe is flat with only a 0.4% margin of error.[7]

It is also unknown whether the universe is infinite in time. For googology, it is important that if the universe is eternal, then infinitely many googologisms will be invented during the eternity in somewhere in the universe.

Sources

Large numbers in science
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