Big Bang TheoryBig Bang Theory

Investigative ScienceInvestigative Science

What is a Theory?What is a Theory?• Well-established idea that is Well-established idea that is

supported by scientific evidence. supported by scientific evidence. • Theory statements can be refuted, Theory statements can be refuted,

but not verified, no matter how but not verified, no matter how strongly we believe in the truth of strongly we believe in the truth of a theory. It is always possible for it a theory. It is always possible for it to be falsified.to be falsified.

How do we measure How do we measure distances in space?distances in space?

• Astronomical Unit (AU) Astronomical Unit (AU) – average – average distance between the Earth and the distance between the Earth and the SunSun• About 93 million milesAbout 93 million miles

• Light-yearLight-year – the distance that light – the distance that light travels in a yeartravels in a year• Used to measure distance to stars and Used to measure distance to stars and

galaxiesgalaxies• Nearest stars are several light-years awayNearest stars are several light-years away

What is the size scale in What is the size scale in space?space?

• Put the following in order from smallest Put the following in order from smallest to largest:to largest:• GalaxyGalaxy• UniverseUniverse• PlanetPlanet• StarStar• CometComet• Solar systemSolar system• AsteroidAsteroid

What is the size scale in What is the size scale in space?space?

• Put the following in order from smallest Put the following in order from smallest to largest:to largest:• CometComet• AsteroidAsteroid• PlanetPlanet• StarStar• Solar systemSolar system• GalaxyGalaxy• UniverseUniverse

What is Hubble’s Law?What is Hubble’s Law?• Hubble then noticed a correlation Hubble then noticed a correlation

between the between the distancedistance of the of the galaxies and the galaxies and the speedspeed at which at which they are moving away from usthey are moving away from us

• The farther away the galaxy,The farther away the galaxy,the faster it is receding the faster it is receding (moving away) from the Earth.(moving away) from the Earth.

So if the universe is expanding, then So if the universe is expanding, then it must have had a beginning.it must have had a beginning.

What is the Big Bang What is the Big Bang Theory?Theory?

• Universe formed 12 to 14 billion years Universe formed 12 to 14 billion years agoago

• At “time zero” universe was an At “time zero” universe was an explosion of a primeval atom.explosion of a primeval atom.

• Temperatures extremely high at Temperatures extremely high at beginningbeginning

• Expanded rapidly, temperatures Expanded rapidly, temperatures droppeddropped

• Matter formed from original energyMatter formed from original energy

What evidence is there for What evidence is there for the Big Bang Theory?the Big Bang Theory?

• Cosmic background radiation: radiation left Cosmic background radiation: radiation left over from the initial moments of Big Bang over from the initial moments of Big Bang spread evenly around the universe.spread evenly around the universe.

• Red Shifted galaxies indicating that they Red Shifted galaxies indicating that they are moving away from our galaxy.are moving away from our galaxy.

• Galaxies and stars formed from cooling Galaxies and stars formed from cooling energy.energy.

• Leftover heat from the original explosionLeftover heat from the original explosion

• Big Bang model describes our current Big Bang model describes our current understanding of the universe.understanding of the universe.

• New discoveries, such as dark matter and New discoveries, such as dark matter and accelerating expansion (Dark Energy), accelerating expansion (Dark Energy), lead us to refine our model, but there is lead us to refine our model, but there is no crisis in our understanding (yet).no crisis in our understanding (yet).

• Science is an ongoing process - forcing us Science is an ongoing process - forcing us to test our model through prediction and to test our model through prediction and observation. The more tests it passes, observation. The more tests it passes, the greater is our confidence in it.the greater is our confidence in it.