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Facts About The Universe for Kids


The universe is commonly defined as the totality of everything that exists, including planets, stars, galaxies, the contents of intergalactic space, and all matter and energy. Scientific observation of earlier stages in the development of the universe, which can be seen at great distances, suggests that the universe has been governed by the same physical laws and constants throughout most of its extent and history.

  • There are various multiverse theories, in which physicists have suggested that our universe might be one among many universes that likewise exist.
  • The earliest quantitative geocentric models were developed by the ancient Greek philosophers.
  • Discovery of the red shift and cosmic microwave background radiation revealed that the universe is expanding and apparently had a beginning.
  • According to the prevailing scientific model of the universe, known as the Big Bang, the universe expanded from an extremely hot, dense phase called the Planck epoch, in which all the matter and energy of the observable universe was concentrated.
  • Recent observations indicate that this expansion is accelerating because of dark energy, and that most of the matter in the universe may be in a form which cannot be detected by present instruments, called dark matter.
  • The common use of the “dark matter” and “dark energy” placeholder names for the unknown entities purported to account for about 95% of the mass-energy density of the universe demonstrates the present observational and conceptual shortcomings and uncertainties concerning the nature and ultimate fate of the universe.
  • According to general relativity, space can expand faster than the speed of light, although we can view only a small portion of the universe due to the limitation imposed by light speed.
  • Since we cannot observe space beyond the limitations of light (or any electromagnetic radiation), it is uncertain whether the size of the universe is finite or infinite.
  • Regarding Plato’s Metaphor of the sun, Aristotle suggests that the rotation of the sphere of fixed stars inspired by the prime mover, motivates, in turn, terrestrial change via the Sun.
  • Careful astronomical and physical measurements (such as the Foucault pendulum) are required to prove the Earth rotates on its axis.
  • According to our current understanding, the universe consists of three principles: spacetime, forms of energy, including momentum and matter, and the physical laws that relate them.
  • An easily visualized metaphor is a group of separate soap bubbles, in which observers living on one soap bubble cannot interact with those on other soap bubbles, even in principle.
  • According to one common terminology, each “soap bubble” of space-time is denoted as a universe, whereas our particular space-time is denoted as the universe, just as we call our moon the Moon.
  • For comparison, the diameter of a typical galaxy is only 30,000 light-years, and the typical distance between two neighboring galaxies is only 3 million light-years.
  • The hypothesis that the large-scale universe is homogeneous and isotropic is known as the cosmological principle, which is supported by astronomical observations.
  • On the average, space is observed to be very nearly flat (close to zero curvature), meaning that Euclidean geometry is experimentally true with high accuracy throughout most of the Universe.
  • Many models of the cosmos (cosmologies) and its origin (cosmogonies) have been proposed, based on the then-available data and conceptions of the universe.
  • Over the centuries, improvements in astronomical observations and theories of motion and gravitation led to ever more accurate descriptions of the universe.
  • According to the prevailing theory, a slight imbalance of matter over antimatter was present in the universe’s creation, or developed very shortly thereafter, possibly due to the CP violation that has been observed by particle physicists.