Universe

Big Bang 13.7 Billion Years (1) The very early Universe was opaque due to the constant interchange of energy between matter and radiation.
300,000 years: The Universe then cooled to a temperature of ∼ 4,000 K through its expansion about 300,000 years after the Big Bang. At this stage, the matter does not have sufficient energy to remain ionised. The electrons combine with the protons to form atoms.

About 3,000 stars are visable from earth with the naked eye. The andromeda gallexy can be seen with the naked eye in ideal conditions (low light and clear skies).

There are at least one hundred billion (10¹¹)galaxies in our Universe. There are 70 sextillion (7x10²²)stars in the visible universe

    Mostly H with some He
   -> Hyper Novi
   Creats 
1 Billion Yrs
Stars (Initially H fused to create He)
   As a star starts to use up He it starts to shrink and gets hotter
   so it can burn He.
   3 He -> C
   Creates more elements up to Fe (Iron) but can
   Creats super Nova which creates heavier elements

see http://www.pbs.org/wgbh/nova/origins/univ-nf.html 4.5 Billion - Our Sun

Bibliography:
Cosmology: A Short Bibilography. at NCSA U. Ill Urbana-Champaign
Our Cosmic Habitat, Martin Rees

(1) Until the mid-1990s the data on the rate cosmic expansion were so uncertain that the best estimates of the age the universe stood at between 10 and 20 billion years. New calculations have zeroed in on 13.7 B years.

In 2004 Astronomers announced that "The Universe is is at least 156 Billion light years across."
The cosmos is 13.7bn years old but the stretching of space with its expansion after the Big Bang means that simple distance measurements do not apply. Astronomers realise the Universe is more complex. It has been expanding ever since the Big Bang when energy, space and time itself began. To get the picture try to imagine the Universe a million years after the Big Bang. Light travels for a year, covering one light-year. But at that time, the Universe was about a thousand times smaller than it is today meaning that one light-year has now become stretched to about a thousand light-years.

History > Universe

last updated 8 Jan 2005