Expanding Universe Before Telescopes

Currently, the observable universe is about 28 billion parsecs (91 billion light-years) in diameter. The size of the whole Universe is not known and may be either finite or infinite. Observations and the development of physical theories have led to inferences about the composition and evolution of the Universe.

There are many competing hypotheses about the ultimate fate of the Universe. Physicists and philosophers remain unsure about what, if anything, preceded the Big Bang. Many refuse to speculate, doubting that any information from any such prior state could ever be accessible.

Suppport AboutIslam.net

There are various multiverse hypotheses, in which some physicists have suggested that the Universe might be one among many universes that likewise exist.

The discovery in the early 20th century that galaxies are systematically redshifted suggested that the Universe is expanding, and the discovery of the cosmic microwave background radiation suggested that the Universe had a beginning.

Finally, observations in the late 1990s indicated the rate of the expansion of the Universe is increasing indicating that the majority of energy is most likely in an unknown form called dark energy. The majority of mass in the universe also appears to exist in an unknown form, called dark matter.

In principle, the expansion of the universe could be measured by taking a standard ruler and measuring the distance between two cosmologically distant points, waiting a certain time, and then measuring the distance again, but in practice, standard rulers aren’t easy to find on cosmological scales and the time scales over which a measurable expansion would be visible are too great to be observable even by multiple generations of humans. The expansion of space is measured indirectly.

This article is from Science’s archive and we’ve originally published it on an earlier date.