D.3.1: Big Bang Theory

The Big Bang theory states that both space and time originated with the expansion from a singularity. The hot big bang model is a theory that describes the origin and expansion of the universe and is supported by extensive experimental evidence.

Start here for a more stylistic view of the beginnings of the universe.

Some additional ideas and the beginnings of some IB terminology.

Lots of review of some major concepts and some deep ideas about the origins of the universe.

Big Bang Model Evidence

The universe began at one point at a particular time. It was incredibly hot and has been expanding and cooling ever since.
It is important to realize that the Big Bang was the creation of everything, including both space and time.
Light from galaxies show red shift
- This indicates that the universe is expanding
Working backward, it is predicted that the universe should have started with a tiny volume of extremely dense matter
Big Bang - NOT AN EXPLOSION - just an expansion of the Universe from an extremely tiny and dense state to what it is today (Instanton)
Space and time started with Big Bang
Before Big Bang, nothing existed !
- Asking what happened before the Big Bang is contriditory to the theory.
- We cannot answer what happened before the big bang.
Universe does not expand into a VOID
- Likewise, we cannot answer what is beyond the universe?
- What does the universe expand into?

This illustration summarises the almost 14-billion-year long history of our Universe. It shows the main events that occurred between the initial phase of the cosmos, where its properties were almost uniform and punctuated only by tiny fluctuations, to the rich variety of cosmic structure that we observe today: stars and galaxies.

The series of panels on the right side of the illustration zooms into the cosmic large-scale structure to reveal first a cluster of galaxies, then a spiral galaxy similar to our own Milky Way Galaxy, and finally, the Solar System.

Big Bang Evidence and Reasoning

Cephied Variable Stars

The distance of galaxies from Earth can be determined by using Cepheid variables as 'standard candles' (Cepheid Variable Stars). The recession speeds can then be compared to the distances.

Cosmological Red Shift

Light from galaxies show red shift
- This indicates that the universe is expanding

Recession Speed:

We can see from the graph, that the recession speed of a galaxy is

proportional to its distance from Earth.

Backward Thru Time:

Moving backwards in time, the conclusion must be that all the galaxies were together at the same place at some point in time. This is the (hot) Big Bang model of the universe.

Apparent Movement of Galaxies

The galaxies are not moving from a central position into a pre-existing space,

rather space itself is expanding.

Before the Big Bang model of the universe became fully accepted, it was widely believed that the universe was uniform and static (and infinite). This is sometimes called the Newtonian model of the universe.

Cosmic Scale Factor

The Cosmic Scale Factor represents how the universe has changed in size over time. In the figure to the right, the 'before' time is 0.55 of 'now'. Likewise, 'later' is 1.45 of 'now'.

The pattern of the stars is the same, it has 'simply' expanded in its scale.

Using the Geogebra Transformations- Enlargements simulation below, you can change the shape of the green polygon by dragging each point to a new location. You can then scale the figure by dragging the slider bar to either a positive or negative value.

Page updated

Google Sites

Report abuse