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.
Let's make sure we know what we are talking about.
Cosmology is the study of the universe at its largest scales, including theories of its origins,
its dynamics and evolution, and its future.
Cosmogony is the (scientific) study of the origin of the cosmos (or of reality itself).
Cosmography deals with mapping the universe.
Cosmetology is the art or profession that deals with beauty product application and
Astronomy deals with celestial objects (rather than the universe as a whole).
Types of Cosmology
Physical cosmology (Wikipedia), incorporating physics, astrophysics, and astronomy;
Religious cosmology (Wikipedia), involving
origin stories and mythologies from religious traditions;
Metaphysical cosmology, dealing with questions "beyond science," such as the cause of the origin
of the universe, whether its existence is necessary, whether it has a purpose, its ultimate composition,
and even the nature of consciousness, without requiring a religious tradition; and
Esoteric cosmology (Wikipedia), which
deals, with, well, start with the Wikipedia article....
(Physical) cosmology is sometimes considered to have arrived as an experimental science during the
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:
where the supposed singularity came from
what caused the initial expansion, or how or why it occurred
that something actually exploded
anything about the origin of life (though origins of matter, energy, and structure are considered)
that an external creator is required (though this is embraced by many theists)
that an external creator is ruled out
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....
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 t1
At time t2
Green is 5.385 units away Blue is 2.828 units away
Green is 10.77 units away Blue is 5.657 units away
Red is 5.385 units away Blue is 5 units away
Red is 10.77 units away Blue is 10 units away
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,
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?
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:
A garden (Eden), vegetation, lots of trees, one special "knowledge" tree, and four rivers
Sun, moon, stars
Fish, sea-monsters, birds
Land animals, birds
Land animals (cattle, creeping things, and wild animals), humans
A woman (Eve)
How might we explain the structure and content of these stories? Here are two explanations:
Story 1 was written by farmers and city dwellers, living in river basins worried about
floods (hence the fish); the story talks of humans being created in the image
of God, taking "dominion over the earth" and shaping it to their needs, celebrating
civilization and progress.
Story 2 was written by sheperds and camel drivers, living in semi-arid
areas (hence NO fish); the story tells of humans who are servants of the garden
and cast out because they tried to be godlike, and of the virtues of the simple
The two stories complement each other by talking about two sides
of human nature: our power over nature but the need to, perhaps, not get carried away.
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:
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:
Time is eternal, but at some point a gravitational singluarity underwent a phase transition
into the (expanding) universe we know today; or
The big bang event created the very idea of time itself.
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.
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*.
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?