Monday, August 26, 2013

Far, far away

These are not stars!

These are galaxies; about 10,000 of them.  This is a view of just a small portion of the sky; it's what you could see if you looked through a soda straw that was about 8 feet long.

This is the deepest visible-light image of the cosmos. Called the Hubble Ultra Deep Field, this galaxy-studded view represents a "deep" core sample of the universe, cutting across billions of light-years.

In ground-based photographs, the patch of sky in which these galaxies reside looks largely empty.  The image required 800 exposures taken over the course of 400 Hubble orbits around Earth. The total amount of exposure time was 11.3 days, taken between Sept. 24, 2003 and Jan. 16, 2004.

Stars gather in galaxies, galaxies gather in local groups, groups gather in clusters, and clusters gather in super-clusters which align in strands that make up the universe.  The strands look not unlike the interior structure of a sponge, strangely enough.  The number of stars is incomprehensible, yet what we see is not even a tenth of what's there.

Astronomers now recognize that the universe is held in place by dark energy and dark matter. The current cosmological model describes a universe that is 68 % dark energy, 27% dark matter, and only 5% normal matter.  That 5% includes everything you can see in this and other pictures of the visible sky.

We don't know what dark energy is, or why it exists. On the other hand, particle theory tells us that, at the microscopic level, even a perfect vacuum is filled with quantum particles that are perhaps the natural source of dark energy. Beyond that, troublingly,  a naïve calculation of the dark energy generated from the vacuum yields a value 10120 times larger than the amount we think the universe consumes. Some further and unknown physical process is required to make use of most, but not all, of that energy, leaving enough behind to drive the accelerating expansion of the Universe.  Wonder what that energy might be doing?

Dark energy is theoretical and of course undetectable except perhaps by inference.  Dark matter, which makes up most of the universe is equally invisible, unknowable, imperceptible, and between the two of them, they make up about 95% of what is.  Our physical reality is 95% unknown.  We suspect that both dark energy and dark matter pass by us continually without our awareness.  We have based all our science and conclusions on that visible and perceptible 5%.  Having grasped the elephant by the tail, we speak confidently yet we have no no grasp whatsoever of 95% of what is real; we can't even point at it or talk about it except by ... faith?

Our sun is one of thousands of billions of trillions of stars which make up perhaps 5% of what actually comprises the universe.  We know so little and live so confidently on that basis.  We hope we're right, but can we support our conclusions with comprehensive science?

Our Milky Way is an average spiral galaxy, perhaps 120,000 light-years across with maybe 400 billion stars.
So how many stars and galaxies are there?

According to astronomers, there are probably more than 170 billion galaxies in the observable universe alone, stretching out into a region of space 13.8 billion light-years away from us in all directions.  That's what we can 'see' with our speed-of-light limited methods.
That's just the minimum; the universe is perhaps much larger, but we can't see those farther places because they're beyond the light-speed boundary.  It’s possible that the universe is infinite after all.

We have a difficult enough time developing a personal worldview that isn't uninformed.  It's perhaps even more difficult to have a coherent view of 'the universe' and what it might mean.  Whether your faith rests in our '5% science' community and their interpretation of it all, or in something more, the best we have at the moment is as though we were seeing through a glass darkly.
Sweet friends from the 'real' world most of us have never seen ...

There’s a lot of stars in the universe.
And a lot of unanswered questions.  

(The confident fundamentalists in every community could benefit from a breath-taking moment facing the reality of what no one yet knows.  Perhaps we all might.)