Our
scientists are often giving us visual displays designed to impress us
with their grasp of nature. Such visuals should sometimes be taken with a large
grain of salt, as they are often examples of dubious dogma. An
example is the type of “composition of the universe” pie graph
that shows the universe as about 71% dark energy, 24% dark matter and
5% regular matter. But as I discussed in my previous post “A
Second Bullet in the Chest of Dark Matter?” the case for dark
matter is wobbly, and two recent findings are hard to reconcile with
standard accounts of dark matter. Commenting on one of these
findings, an astrophysicist has said, “Nothing in the
standard cosmological model predicts this and it is almost impossible
to imagine how that model could be modified to explain it, without
discarding the dark matter hypothesis completely.”
In
my previous post I suggested that we should replace the dogmatic
“composition of the universe” pie chart with a table listing the
universe's contents as ? % dark matter, ? % dark energy, ? % atoms,
and ? % unknown. Coincidentally, a few days after making this post,
there appeared a news science story that seems to further shatter all
confidence that we understand the composition of the universe.
The
new science story dealt not with dark matter but dark energy. No one
has any idea what dark energy is, but there is a vague idea that the
vacuum of space may be filled with dark energy. The case for dark
energy seemed to solidify when scientists announced that the
expansion of the universe is accelerating. Scientists said that only
dark energy in the vacuum of space could account for this
acceleration. We were told that dark energy has a kind of expansive
pressure, rather like the gas pressure that keeps a helium balloon
from collapsing, and that this is causing the universe's expansion to
accelerate.
But
now dark energy may have taken its own bullet in the chest. It comes
from this paper dealing with supernova explosions. The conclusion
that the universe's expansion is accelerating was based largely on an
analysis of the star explosions called supernova explosions. The new
paper also analyzes supernova explosions, but uses a more
sophisticated technique and a larger database. The new paper says,
“We find, rather surprisingly, that the data are still quite
consistent with a constant rate of expansion.”
As
discussed here, the new paper casts doubt on the claim that the
expansion of the universe is accelerating. In doing so, it seems to
undermine the main evidence for dark energy.
Ouch!
It looks like our swaggering, strutting cosmologists may have little
idea about what they are talking about when they pontificate about
the composition of the universe. But we shouldn't be surprised by
such dogmatic overconfidence, seeing how extremely common it is in
the fields of physics, biology and neuroscience. Should we tear out
those pages of the astronomy textbooks that have dogmatic
“composition of the universe” pie charts? Perhaps instead we can
print up some candid stickers resembling the visual below, and paste
them over such “composition of the universe” pie charts. The
figure in the white coat represents a scientist with the proper
degree of intellectual humility.
Postscript: Some news reports said that the authors of the new paper on supernova explosions had said that the expansion of the universe is not accelerating. But their paper was actually entitled "Marginal evidence for cosmic acceleration from Type Ia supernovae." They merely claimed that the evidence for an accelerating universe was marginal. Their paper is rebutted by this paper from today, entitled "Is the expansion of the universe accelerating? All signs point to yes."
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