Cosmology and Cosmogony

Many (most?) humans are fascinated with the concepts of our "place in the universe" and of the origins of all things. Knowing where something comes from helps us understand that thing better, whether it's the universe or just ourselves. Understanding nature (and human nature) is valuable at both practical and emotional levels.

Some Definitions

Let's make sure we know what we are talking about.


Types of Cosmology

There are:


(Physical) cosmology is sometimes considered to have arrived as an experimental science during the 20th century.

Exercise: What discoveries helped physical cosmology to be recognized as an experimental science?

The SEP has an article on the relationship between physcial and religious cosmology.

Exercise: Read the SEP article. How do the various cosmologies mentioned in the article seem to simultaneously support theistic and atheistic viewpoints?

The Big Bang Cosmology

The Big Bang Theory (BBT) is today's most accepted cosmology. It accounts for how the universe is thought to have developed after something triggered an expansion from some massively hot and dense gravitational singularity, whose size was smaller than an atom.

What it is not

The BBT does not say:

The History of Universe according to the BBT

First, a little of the evidence for the theory. I'm not sure who the author of this video is, but it is a nice introduction....

If you'd like to start with external sources...

The following timeline is summarized from Neil deGrasse Tyson's article The Greatest Story Ever Told:

0 to 10-43s, 1050K: All speculative physics. General relativistic and quantum mechanical phenomena indistinguishable. All forces unified.
Gravity splits from the other three forces.
The strong force splits from the electroweak, triggering inflation, universe grows by a factor of 1050. Matter/energy density get smoothed, but not perfectly so.
Photons can now create matter-antimatter pairs, but somehow slightly more matter remains after annihilation.
Cooling continues. Electoweak force splits into electromagnetic and weak forces. Universe is now too cool for spontaneous matter-antimatter creation.
Protons, neutrons start to form (from quarks). Electrons are still free, scattering photons back and forth.
At about 380,000 years, the universe cools below a few thousand K. Electrons get snatched up by the proton-neutron things to make atoms: predominately hydrogen and helium, with a tiny bit of lithium. Photons are now free! The universe lights up. This is the CBR.
Over the next few billion years, gravity starts creating large structures which will be come galactic filaments, sheets and clusters. Galaxies form. Stars are born.

Understanding the Expansion of Space

Why do most of the galaxies appear to be moving away from us? Are we at the center? Actually no—every point in the universe sees the same thing: galaxies flying away from itself; there's no center. How can this be? It's because space is expanding. Huh?

Imagine raisins in bread as it expands while baking. Or people sitting on a huge rubber sheet being expanded. In the following diagram:


From the point
of view of
At time t1At time t2
Red Green is 5.385 units away
Blue is 2.828 units away
Green is 10.77 units away
Blue is 5.657 units away
Green Red is 5.385 units away
Blue is 5 units away
Red is 10.77 units away
Blue is 10 units away
Blue Red is 2.828 units away
Green is 5 units away
Red is 5.657 units away
Green is 10 units away

Note how the farther away something is to begin with, the farther away it flies in a fixed time period!

Play with the following interactive. Here the green galaxies represent the universe at time t1, and the red galaxies at some time t2 later than t1. Move the reds so that they overlay any green galaxy you choose, to see how the expanding universe looks like from its point of view.

Alternatives to the Big Bang Cosmology

You can find "alternatives" to the BBT, some serious, some bordering on or squarely in the realm of, really bad science, here and here.

Exercise: Research the cosmological principle. Does the BBT require the cosmological principle to hold?
Exercise: Research the discovery of the Huge-LQC in January 2013. Why does this challenge the cosmological principle?

Religious Cosmology

Wikipedia is a good place to start:

Exercise: Classify the various religious cosmologies as describing the universe as created out of nothing, or formed out of an eternal formless matter, or via some other means.

Social scientists and historians often study these cosmologies and relate them to the historical and social context in which they were written. For example, consider the two origin stories in the Tanakh. They each describe an order of creation events:

Genesis 1-2:4aGenesis 2:4b-24
Heaven and a formless Earth (but with water)Heaven and earth
LightWater, flowing out of the ground
Firmament (sky dome)A man (Adam), made from the soil
Dry land, vegetationA garden (Eden), vegetation, lots of trees, one special "knowledge" tree, and four rivers
Sun, moon, stars
Fish, sea-monsters, birdsLand animals, birds
Land animals (cattle, creeping things, and wild animals), humansA woman (Eve)

How might we explain the structure and content of these stories? Here are two explanations:

Exercise: Is there any evidence to back up the above explanations? Can you think of other explanations?

More on Cosmology

Here are some excellent sources for more information:

Some related works (mostly on spacetime, etc.):

Here's a TED talk by Sean Carroll:

For more videos like this, see this TED playlist.


While it's difficult (impossible?) to test theories about the origin of everything, people have certainly given opinions (often backed up by appeals to related experimental data). For example, big bang could be explained in different ways:

Cosmogony is a scientific field, but one can't help bring in Philosophy when talking about origins. Immanuel Kant's First Antinomy, on Space and Time, is worth reading.

Exercise: Discuss Kant's First Antinomy.

More on Origins

Origin of Structure

Why isn't the universe perfectly uniform and "smooth"? On enormous scales, it is homogeneous and isotropic, but yet there are structures.

Origin of Stars and Planets

We know that stars are born, live, and die. They are born from the gravitational collapse of pockets of gas clouds. During their lives they manufacture new elements through fusion. In death the really big stars explode in a supernova creating the elements that make us. You've undoubtably heard: "A star died so that you can live." *Sniff*.

Origin of Life

What is life? Here's a definition from Tyson and Goldsmith's Origins:

A property of matter characterized by the abilities to reproduce and evolve

A definition from Wikipedia:

A characteristic that distinguishes objects that have signaling and self-sustaining processes from those that do not

So do the processes we call life originate? We know living organisms come from other living organisms, but can life processes arise from inanimate sources? Good question! That's the idea of abiogenesis. Why not start with the Wikipedia article on abiogenesis, or Part V in the Tyson and Goldsmith book.

Origin of Sentience

Let me know if you know anything about this.


If cosmogony deals with the ultimate beginning and cosmology deals with what happens just after the beginning, then maybe we can talk about "physical eschatology" as dealing with the ultimate end. Just a thought....

Exercise: What is eschatology, anyway? Is anyone using the term in the context of addressing the possible fate of the universe, or is that still under the umbrella of physical cosmology?
Exercise: Research the following: The Big Crunch, The Big Freeze, and The Big Rip. Which one is most in vogue today?