by Patrick Appel
A reader writes:
As a cosmologist who works on dark matter and dark energy, I emphatically object to the description of the Universe that Zoe quoted:
"The Big Bang merely separated out a uniform state of chargelessness into many individual instances of charge, positive and negative. The same goes for matter and energy generally: the total amount of matter and energy in the universe seems to be balanced out by huge amounts of "dark matter" and "dark energy," which express themselves in terms of gravitational attraction. The Big Bang didn't create all that energy, as such. Instead, it seems to have turned an initial Nothingness into a "much more interesting and potent" Nothingness — a "Nothing that has been separated into opposites to give, thereby, the appearance of something.""
The part about charge is true: the Universe seems to be electrically neutral, and charge can only be created if it accompanies the creation of equal and opposite charge. There are also conservation laws for matter and energy, but the Universe is by no means "energy neutral." According to current estimates, the universe is made of about 5% ordinary matter (atoms), 25% dark matter and 70% dark energy. Dark matter is a hypothetical particle needed to explain the excess gravitational forces observed in large bound objects like galaxies. Dark energy is very mysterious – it doesn't seem to make interesting structures, rather its strange hallmark is that it is gravitationally repulsive instead of attractive, causing the Universe to expand faster.
All of these components have "positive" energy. They are not "opposites" of each other in any meaningful sense, and they do not balance out in the same way that the total charge in the Universe balances to zero. Yes, the dark energy is gravitationally repulsive while the other components are attractive, but there is no balance here either. The net repulsion of dark energy is greater than the net attraction of matter. Dark energy also doesn't dilute as fast as matter, so as the Universe expands, we may ultimately be left with a Universe made almost exclusively of dark energy (but not for several billion years)!
My point is that our Universe is not "Nothing" in the sense that the quote is claiming. I do not see any cosmic balance of things as Atkins does. In fact, it is the imbalance in the Universe which makes it interesting. For instance, you'll notice that the non-dark part of the Universe is made almost entirely of matter and not anti-matter (matter's true opposite). In the super-hot moments of the early Universe, matter and anti-matter would have been present in equal amounts, but the fact that one eventually dominated over the other implies that there is some subtle yet crucial asymmetry in how they behave.
Frankly, the idea that the Universe is a type of Nothing sounds to me like a deepity.
Disclosure: I have not read Atkins' book, and I realize he may have been misrepresented in Rothman's summary.
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