Download Beginning With a Bang

Theories of how the Universe
Began
BEGINNING WITH A BANG
Big Bang Theory
 Scientists believe Universe started with a big
explosion
 15 billion years ago
 Matter, gravity, and electromagnetism were
created by the blast
 Universe expanded
Edwin Hubble
 First to discover Universe expanding
 Distant galaxies moving away from Earth
faster than close ones
 Discovery of cosmic background radiation
supported Hubble’s theory
 Four basic forces control the Universe:
gravity, electromagnetism, strong nuclear
forces, weak nuclear forces
Hubble Cont.
 As Universe expanded, it began to cool
 One billionth years old, started condensing
into galaxies, stars and planets
Oscillating (Big Squeeze
Theory)
 Expansion of the Universe (Big Bang) will be
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followed by a contraction or a squeezing of
the Universe
This is caused by gravity
Farther planets will slow down and stop, then
fall toward the center
Planets will collide
A new Big Bang will occur
Steady State Theory
 Challenged Big Bang Theory in 1940
 Scientists believe that Universe did not begin
with an explosion
 Believe Universe will exist forever (steady
state)
 Theory discarded after discovery of cosmic
background radiation
Today
 Scientist believe a fraction of a second after
Big Bang explosion, gravity emerged
 At birth, Universe was 180 billion degrees
Fahrenheit
 60 seconds later it cooled to 18 billion
degrees Fahrenheit
 Today average temperature of Universe is 454 degrees Fahrenheit
Measuring Vast Universe
 Basic unit of distance: light year
 Light year – the distance light travels in one
year or about 6 trillion miles.