Download Hypothesis vs. Theory ~The Big Bang

HYPOTHESIS VS. THEORY
Unit 1 – Spaceship Earth
Theory vs. Hypothesis
Hypothesis
 What is a hypothesis:
 Is a guess as to why something happens
 A creative idea as to how a scientific event or
entity came to be, based on a number of logical
assumptions.
 There is no scientific basis for a hypothesis,
but the idea comes from logical assumptions.
 In attempting to answer a question about the
nature of the world, a scientist will form a
hypothesis (or a guess) regarding the
question's answer.
Theory
 What is a theory?
Definition:
 An idea that results when a hypothesis is
supported by observation and scientific
inquiry.
The Big Bang!
 A widely held scientific theory that contends
the creation of the universe, the Milky Way,
and our solar system resulted from a violent
explosion of matter.
 Let’s look at how it went from hypothesis to
theory.
Hubble Telescope
1922 Edwin Hubble
 Observed the universe was expanding
 Calculated that the universe is expanding at
40,000 km/s
 Picture of the M32 Galaxy
Hubble’s Law
 The velocity at which a galaxy is moving away
from us is proportional to the distance of the
galaxy from us.
 If galaxy B is twice as far away as galaxy A, then it
is receding twice as fast as galaxy A.
 Basically, if the universe is expanding, then it
is logical to assume that it was once infinitely
smaller.
Georges Lemaitre
Cosmic Egg
Belgian Astronomer
Albert Einstein
 Hypothesized that this
cosmic egg exploded
with such violence that
its fragments are still
flying out from the
centre of the explosion
billions of years later
Hair stylist
George Gamow
1940s coined “Big Bang”
 He hypothesized that the
radiation that accompanied
the explosion would still exist.
Radio-wave radiation comes
from all parts of the universe.
Russian Physicist
Arno Penzias & Robert Wilson
1964 Arno Penzias & Robert
Wilson
 Found the radio wave background radiation.
Most astronomers believe that this is
sufficient evidence to move the big bang
from the category of hypothesis to that of a
theory.
 This occurred 15-20 billion years ago
*Most astronomers accept that this is sufficient evidence to
move big bang from the category of hypothesis to that of a
theory!
Galaxies
 Formed from giant eddies in the swirling
cloud of dust after the explosion.
Solar Systems
 Formed from smaller sub-eddies that
formed in the bigger eddies
Sun
 Was formed as the gravitational pull of denser material
at the centre of each sub-eddy drew matter inward until
radioactive elements began to produce huge amounts
of energy through thermonuclear fusion.
Planets
 Formed from the 5% of the swirling cloud
that was left after the stars were created.
Asteroids
 Leftover chunks of material that were too
small to form into planets
Our Place in the Universe
Our study of Astronomy requires us to look UP and not
DOWN. Humans today are not used to looking UP, we
are not used to observing the sky – it appears to be of
little use – and city living with its extensive light
pollution often prevents us from seeing, and hence
exploring, the “heavens”.
Most of us have some awareness that we are part of a
system of planets encircling a star we call the Sun, and
that we are part of a galaxy called the Milky Way, but
beyond that our knowledge is often sketchy, cloudy,
or even just plain wrong.
The next picture slide summarizes our location within the
Universe, something that can be briefly summarized
as:
 Earth – we all live somewhere on the surface of this
spherical body we call Earth
 Solar System – Earth is part of a system of different
planets (in fact, Earth is the third planet out from the
Sun) which all orbit a star (the Sun) in the same
direction and almost all in the same plane in space
 Milky Way Galaxy – our Solar System is part of a
huge collection of stars (and dust and gas) known as
a galaxy, which we humans have named the Milky
Way
 Local Group – galaxies (and there are billions in the
Universe) tend to congregate in groups or clusters
and our group is known as the local group
 Local Supercluster – groups of galaxies
congregate in larger groups known as
superclusters; thus, our local group belongs
to the local supercluster
 Universe – finally, all the superclusters
comprise the Universe; as far as we know
there are no other universes (we can’t even
“see” to the edge of our own universe)
although some science fiction writers have
speculated about this notion