Where Cosmology Meets Philosophy

We continue our series of excerpts (and discussion) from the outstanding survey paper by George F. R. Ellis, Issues in the Philosophy of Cosmology.

The physical explanatory power of inflation in terms of structure formation, supported by the observational data on the fluctuation spectra, is spectacular.  For most physicists, this trumps the lack of identification and experimental verification of the underlying physics.  Inflation provides a causal model that brings a wider range of phenomena into what can be explained by cosmology, rather than just assuming the initial data had a specific restricted form.  Explaining flatness (Ω0 ≅ 1 as predicted by inflation) and homogeneity reinforces the case, even though these are philosophical rather than physical problems (they do not contradict any physical law; things could just have been that way).  However claims on the basis of this model as to what happens very far outside the visual horizon (as in the chaotic inflationary theory) results from prioritizing theory over the possibility of observational and experimental testing.  It will never be possible to prove these claims are correct.

Inflation is one compelling approach to explaining the structure we see in the universe today.  It is not necessarily the only one, but it currently has the most support.  Basically, a tiny fraction of a second after the Big Bang, the universe expanded dramatically.  Around 10-36 seconds after the Big Bang the universe had a diameter on the order of 1.2 × 10-27 meters.  To put that size in perspective, the diameter of a proton is between 0.84-0.87 × 10−15 meters.  So, when inflation began, the entire universe had a diameter almost a trillion times smaller than a single proton!  10-34 seconds later when the inflationary period was coming to an end, the size of the universe was a little over half the distance to Alpha Centauri!

The basic underlying cosmological questions are:
(1)  Why do the laws of physics have the form they do?  Issues arise such as what makes particular laws work?  For example, what guarantees the behaviour of a proton, the pull of gravity?  What makes one set of physical laws ‘fly’ rather than another?  If for example one bases a theory of cosmology on string theory, then who or what decided that quantum gravity would have a nature well described by string theory?  If one considers all possibilities, considering string theory alone amounts to a considerable restriction.
(2)  Why do boundary conditions have the form they do?  The key point here is, how are specific contingent choices made between the various possibilities, for example whether there was an origin to the universe or not.
(3)  Why do any laws of physics at all exist?  This relates to unsolved issues concerning the nature of the laws of physics: are they descriptive or prescriptive?  Is the nature of matter really mathematically based in some sense, or does it just happen that its behaviour can be described in a mathematical way?
(4)  Why does anything exist?  This profound existential question is a mystery whatever approach we take.

The answer to such questions may be beyond the limits of experimental science, or even beyond the limits of our intellect.  Maybe, even, these questions are as meaningless as “What lies north of the north pole?1because of our limited intellect.  Many would claim that because there appears to be limits to what science or human intellect can presently explain, that this constitutes evidence for the existence of God.  It does not.  Let’s just leave it as we don’t know.

Finally, the adventurous also include in these questions the more profound forms of the contentious Anthropic question:
(5)  Why does the universe allow the existence of intelligent life?
This is of somewhat different character than the others and largely rests on them but is important enough to generate considerable debate in its own right.

Well, a seemingly flippant answer to this question is we wouldn’t be here if it didn’t, but that begs the question.  Perhaps intelligent life is the mechanism by which the universe becomes self-aware, or is this just wishful thinking?  In the end, I am willing to admit that there may be some higher power in the universe—in the scientific pantheist and humanist sense—but I will stop short of calling that “God” in any usual sense of the term.

The status of all these questions is philosophical rather than scientific, for they cannot be resolved purely scientifically.  How many of them—if any—should we consider in our construction of and assessments of cosmological theories?

Perhaps the limitations of science (and, therefore, cosmology) is more a manifestation of the limitations of our human intellect than any constraint on the universe itself.

One option is to decide to treat cosmology in a strictly scientific way, excluding all the above questions, because they cannot be solved scientifically.  One ends up with a solid technical subject that by definition excludes such philosophical issues.  This is a consistent and logically viable option.  This logically unassailable position however has little explanatory power; thus most tend to reject it.

Let’s call this physical cosmology.

The second option is to decide that these questions are of such interest and importance that one will tackle some or all of them, even if that leads one outside the strictly scientific arena.  If we try to explain the origin of the universe itself, these philosophical choices become dominant precisely because the experimental and observational limits on the theory are weak; this can be seen by viewing the variety of such proposals that are at present on the market.

And let’s call this metaphysical cosmology.

1Attributed to Stephen Hawking

References
Ellis, G. F. R. 2006, Issues in the Philosophy of Cosmology, Philosophy of Physics (Handbook of the Philosophy of Science), Ed. J. Butterfield and J. Earman (Elsevier, 2006), 1183-1285.
[http://arxiv.org/abs/astro-ph/0602280]

Ryden, Barbara. 2003.  Introduction to Cosmology. San Francisco: Addison Wesley.

What Is and What Might Have Been

We continue our series of excerpts (and discussion) from the outstanding survey paper by George F. R. Ellis, Issues in the Philosophy of Cosmology.

Thesis E2: We cannot take the nature of the laws of physics for granted.
One cannot take the existence and nature of the laws of physics (and hence of chemistry) as unquestionable in cosmology—which seems to be the usual habit in biological discussions on the origin and evolution of life.  This is in stark contrast to the rest of science, where we are content to take the existence and nature of the laws describing the fundamental behaviour of matter as given and unchangeable.  Cosmological investigation is interested in the properties of hypothetical universes with different physical behaviour.  Consideration of ‘what might have been’ is a useful cosmological speculation that may help throw light on what actually is; this is a statement of the usefulness of ‘Gedanken experiments‘ in cosmology.

Practical science, engineering, and technology are prescriptive.  If we do a, we know from experience that b will occur.  Using the laws of physics, we can predict the location of the Moon as a function of time, put a spacecraft in orbit around Saturn, or build a light bulb that will illuminate.  Though we may be curious, we are not required to know why or how these laws exist—or how they might have been different—only that they do work, time and time again.

Cosmology, though firmly rooted in science, is different.  We are passive observers in a very large and very old universe, and there is no absolute guarantee that the laws of physics that work for us so well in the here and now apply to all places and at all times.  We must attempt to understand the laws of physics in a larger context that does involve some well-reasoned and reasonable speculation.

“Not only does God … play dice, but He sometimes confuses us by throwing them where they can’t be seen.” – Stephen Hawking

“Sometimes attaining the deepest familiarity with a question is our best substitute for actually having the answer.” – Brian Greene

In politics, governance, sociology, and philosophy, too, I would submit to you that consideration of “what might have been” is useful in helping us to understand what actually is.  Such reflection, en masse, might even lead to substantive change.

“Why is it that here in the United States we have such difficulty even imagining a different sort of society from the one whose dysfunctions and inequalities trouble us so?  We appear to have lost the capacity to question the present, much less offer alternatives to it.  Why is it so beyond us to conceive of a different set of arrangements to our common advantage?” – Tony Judt

Getting back to cosmology, however, for the moment…

Indeed if one wants to investigate issues such as why life exists in the universe, consideration of this larger framework—in essence, a hypothetical ensemble of universes with many varied properties—is essential (this is of course not the same as assuming an ensemble of such universes actually exists).  However, we need to be very cautious about using any claimed statistics of universes in such a hypothetical ensemble of all possible or all conceivable universes.  This is usually not well defined, and in any case is only relevant to physical processes if either the ensemble actually exists, rather than being a hypothetical one, or if it is the outcome of processes that produce well-defined probabilities—an untestable proposal.  We can learn from such considerations the nature of possible alternatives, but not necessarily the probability with which they might occur (if that concept has any real meaning).

It is easy to imagine a universe without life.  But we obviously do not live in such a universe.  There may be other universes devoid of life.

For the more thoughtful among us, it is easy to imagine a civilization without war, guns, violence, extrinsic suffering1 caused by others, or deprivation.  Obviously, we do not live in such a society.  But how can we say it is impossible, or even improbable?  It would be easy to find many millions of people in the world even today that would never fight in a war, would never own or use a gun, who would never resort to violence, who would never cause others to suffer, and who would make eliminating deprivation and poverty a top priority.  The question for the scientists is: what is wrong with the rest of us?

1Extrinsic suffering is suffering caused by others or circumstances completely outside of one’s control.  Intrinsic suffering, on the other hand, is self-inflicted—through our own failings, poor judgement, or mistakes that we make.

Growing Older

As we grow older,
That which is older grows upon us.
Time accelerates,
And the world seems a smaller place.

The years go by like months,
The months go by like weeks,
The weeks go by like days,
The days go by like hours,
And the hours go by like minutes.

And our world which in our youth was all that we knew
Slowly reveals itself to be a surprisingly alien place,
Full of centuries of hard work, unlikely events, and compromise:
The world could be a very different (and better) place,
Even within the confines of human nature.

Taken to its natural conclusion
Were we each to live for millennia, perhaps longer
We would find eternity in an instant
And infinity at the door.

David Oesper

References
Ellis, G. F. R. 2006, Issues in the Philosophy of Cosmology, Philosophy of Physics (Handbook of the Philosophy of Science), Ed. J. Butterfield and J. Earman (Elsevier, 2006), 1183-1285.
[http://arxiv.org/abs/astro-ph/0602280]