The Universe is all of time and space and its contents. It includes planets, moons, minor planets, stars, galaxies, the contents of intergalactic space, and all matter and energy. The observable universe is about 91 billion light-years in diameter, and this is just the portion of the Universe that we have observed so far.
In other words, it’s so big that it will take a light beam almost 182 billion years to make a round trip from one end to the end and then back at the starting point. This is of course based on theories which are based on lightwave and sound wave observations, but no one knows the exact dimension of our Universe for sure.
The Universe is composed almost entirely of dark energy, dark matter, and ordinary matter. Other contents are electromagnetic radiation and antimatter. The percent of individual types of matter and energy has changed over the history of the Universe. Today, ordinary matter, which includes atoms, stars, galaxies, and lifeforms, accounts for only 4.9% of the contents of the Universe.
The nature of both dark energy and dark matter is unknown. Dark matter, a mysterious form of matter yet to be understood, accounts for 26.8% of the contents. Dark energy, which is the energy of empty space, accounts for the remaining 68.3% of the contents. Hypothetically, it is dark energy that is responsible for the accelerated expansion of the Universe.
There are many hypotheses, but the actual size of the Universe is unknown. None of these theories are proven or can be confirmed at this time, so we won’t get into explaining them.
There is no firm boundary where outer space begins. However, the Kármán line, existing at an altitude of 100 km (62 mi) above sea level, conventionally marks the start of outer space in space treaties and for aerospace record keeping. Space is the void that exists between celestial bodies, including the Earth.
Space is not entirely empty but consists of a vacuum containing a low density of particles, predominantly hydrogen, plasma and helium as well as electromagnetic radiation, magnetic fields, neutrinos, dust and cosmic rays.
The baseline temperature, as set by the background radiation from the Big Bang, is 2.7 Kelvins or −270 °C or −455.81 °F.
August 3, 2016 12:00 am 2 Comments