26 August 2014

Darkness invisible

The tenth cosmic myth, according to Marcus Chown [1], is that the stuff that science has been studying for 350 years is the important stuff.  Because only 4.9% of the universe is made of atoms:
About six times as much - that is, 26.8 per cent - is invisible, or "dark" matter [which] reveals itself by tugging with its gravity on the visible stars and galaxies.  No one knows what the dark matter is made of, though speculation ranges from hitherto undiscovered subatomic particles to fridge-sized black holes the mass of Jupiter.
But even the dark matter is trumped by the final component of the universe. About 68.3 per cent is dark energy. It is invisible, it fills all of space and it has repulsive gravity [which] is speeding up the expansion of the universe...
What all this tell us is that the stuff science has been studying for the past 350 years is not the most important stuff. In fact it is but a minor component of the universe...
But proportion is not necessarily the same as importance. Iron, for example, constitutes just 0.00067 per cent of the elemental composition of the human body yet it is essential to life.  Further, the existence of dark matter and dark energy are still disputed. All the same, Chown's point is worth attention. [2] As Paul Broks put it:
We may, as a species, be suffering the cosmic equivalent of Anton’s syndrome, the neurological condition in which patients rendered totally blind by damage to the visual cortex believe they can see perfectly well. 
Sometimes, an overlooked absence contains clues to something amazing.  In 1814 Joseph Fraunhofer discovered that the apparent continuity of a rainbow is an illusion:
There are tiny gaps, dim or black arcs of missing colors, too narrow for us to see in the glare of natural rainbows...Fraunhofer eventually cataloged 576 of these gaps, or "absorption lines"...Today tens of thousands are known. [3]
Analysis of the "gaps" in the light from stars has taught us what they are made of, and that star-stuff is the same as Earth-stuff.

Image: the Trifid nebula, or nothing very much at all really, by R. Jay GaBany via Cosmotography


[1]  Autumn 2014 edition of New Humanist on the occasion of the publication of the paperback of What a Wonderful World
[2] "Our worldview has at times been trapped in a rut because some of the most important clues are buried in the details of what we see around us." Caleb Scharf, The Copernicus Complex (2014).
[3] Longing for the Harmonies, Frank Wilczek and Betsy Devine (1987)

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