Download Astronomical Unit (AU)

Big Bang Theory
Investigative Science
What is a Theory?
• Well-established idea that is supported
by scientific evidence.
• Theory statements can be refuted, but
not verified, no matter how strongly we
believe in the truth of a theory. It is
always possible for it to be falsified.
How do we measure distances
in space?
• Astronomical Unit (AU) – average
distance between the Earth and the Sun
• About 93 million miles
• Light-year – the distance that light
travels in a year
• Used to measure distance to stars and
galaxies
• Nearest stars are several light-years away
What is the size scale in
space?
• Put the following in order from smallest
to largest:
•
•
•
•
•
•
•
Galaxy
Universe
Planet
Star
Comet
Solar system
Asteroid
What is the size scale in
space?
• Put the following in order from smallest
to largest:
•
•
•
•
•
•
•
Comet
Asteroid
Planet
Star
Solar system
Galaxy
Universe
What is Hubble’s Law?
• Hubble then noticed a correlation
between the distance of the galaxies
and the speed at which they are moving
away from us
• The farther away the galaxy,
the faster it is receding
(moving away) from the Earth.
So if the universe is expanding, then it
must have had a beginning.
What is the Big Bang Theory?
• Universe formed 12 to 14 billion years ago
• At “time zero” universe was an explosion of a
primeval atom.
• Temperatures extremely high at beginning
• Expanded rapidly, temperatures dropped
• Matter formed from original energy
What evidence is there for the
Big Bang Theory?
• Cosmic background radiation: radiation left
over from the initial moments of Big Bang
spread evenly around the universe.
• Red Shifted galaxies indicating that they are
moving away from our galaxy.
• Galaxies and stars formed from cooling
energy.
• Leftover heat from the original explosion
• Big Bang model describes our current
understanding of the universe.
• New discoveries, such as dark matter and
accelerating expansion (Dark Energy), lead
us to refine our model, but there is no crisis in
our understanding (yet).
• Science is an ongoing process - forcing us to
test our model through prediction and
observation. The more tests it passes, the
greater is our confidence in it.