Swing And A Miss

big dark cloud

And this isn’t it.

I’m going to tell you what is so beautifully ironic about this meme, but first let’s talk about that (maybe) huge gaping hole in the Universe. This demands a little historical background, so stick with me.

When scientists were trying to piece together the history of the Universe, several things became clear. First, the Universe is expanding, and there is no reason to think that it ever didn’t expand. Ergo, the Universe was much, much smaller in the past, and it must have also been much, much hotter. As space expanded, the intense energy of the Big Bang dissipated and cooled, but it’s not entirely gone. It’s still there in the form of microwave radiation permeating the Universe.

The cosmic microwave background, or CMB, has a temperature of 2.73 kelvins, or about -455 degrees Fahrenheit. That’s not far above absolute zero, so the radiation is pretty puny. Nevertheless, it can be detected by sufficiently sensitive radiotelescopes as a faint microwave “glow” that seems to come from every point in the sky and which isn’t connected to any known stars or galaxies.

Although the CMB is fairly uniform, there are minor variations across the sky, owing to the fact that the Universe isn’t empty. Distant galaxies add to, subtract from, and generally play with the microwave radiation as it zips around the cosmos, causing minor peaks and valleys in the intensity of the radiation. Regions where galaxies are a dime a dozen show up as slightly “hotter” – not because the galaxies themselves are hot, but because they tend to intensify the CMB radiation as it passes through their space. Galaxy-poor regions – often called voids – appear colder.

In the direction of the constellation Eridanus, in southern hemisphere skies, there is an anomalously wide cold spot in the CMB often called – wait for it – the CMB cold spot. If the cold spot represents a void, then the size of this void is staggering, and that’s saying a lot when you’re talking about intergalactic space. This supervoid would be centered between six and ten billion light years from Earth and would be about one billion light years across. That’s roughly 1000 times greater in volume than “normal-sized” voids, and while it’s not impossible for such a huge void to have formed in the Universe, it is statistically unlikely.

That’s one of the reasons why many scientists do not accept that the Eridanus cold spot is a supervoid. While some astronomers claim to have found a suspicious dip in the number of galaxies in the direction of the cold spot, others have used different sampling techniques and more conservative statistical calculations to show that the correlation between the supposed galaxy shortage and the cold spot is weak to non-existent. In other words, the existence of a supervoid is not established fact in the cosmological community. Although hypotheses abound, nobody actually knows what caused the CMB cold spot.

So that’s strike one for the meme: like many other gee-whiz scientific memes, it presents a disputed hypothesis as revealed truth.

Then there’s the image. That’s not the CMB cold spot; that’s Barnard 68. Barnard 68 is a molecular cloud, and it’s just about as different from an intergalactic supervoid as anything can possibly be. For one, it’s not intergalactic; at a distance of 500 light years, Barney (It told me to call it Barney) is well inside the boundaries of our own Milky Way galaxy. Secondly, it isn’t a void; in fact, it’s full of dust that blocks out the visible light from stars behind it, which is why it appears so dark. And it isn’t one billion light years across; it’s barely half a light year wide. Okay, half a light year is still huge by human standards, but it’s no supervoid.

So strike two for using the wrong image – either by accident or because the author assumed nobody would know the difference – and strike three for picking an image that is pretty much the opposite of what the author was talking about. If the author of this meme reads my blog and decides to remake the meme, here’s a false-color image of the CMB cold spot.


You’re welcome.


2 thoughts on “Swing And A Miss

  1. I would assert the Great Red Circle is, inarguable, the Largest Structure in the Known Universe.
    I effing hate circles around obvious things. The bastardization of pretty pictures is the bane of the visible spectrum.

    • Ha ha…the Great Red Circle really sounds like something that would exist in deepest space. Also, I share your sentiment about pointing out the obvious. Thank you for reading and for commenting.

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