I suppose most people have seen the picture of a black hole that made headlines around the world on 11 April. I’ve copied it from a news item and reproduced it above. A few different teams from various parts of the globe all collected data on what was thought to be a black hole. They then used a special algorithm to stitch together the data to produce the world’s first ever picture of one.
And while it looks kind of blurry and low-resolution it also fits the common popular image of what a black hole should look like. It’s bright stuff surrounding a circular patch of blackness.
To which I say: hmm.
This is going to make me sound like a demented conspiracy theorist. I’m well aware that the people involved in the project are a lot smarter than me, and a lot better educated. I also doubt that there is any kind of international conspiracy to fake a picture of a black hole because let’s face it, why would you?
And yet, the way that picture has been explained in the media doesn’t seem right.
Let me explain. As is commonly understood, a black hole is a star that has collapsed under the weight of its own gravity. It pulls in material and the mass eventually becomes so great that the escape velocity is greater than the speed of light. As nothing in the universe travels faster than light, light itself cannot escape and so the term “black hole” is a literal and fitting description.
A black hole has something called an “event horizon” that is effectively the point of no return. That’s the edge, so to speak. Go beyond that and you are in the bit that light can’t ever escape from.
The Theory of Relativity has some physics associated with this and I won’t pretend to understand it. From what little I know, anything that approaches the event horizon would seem to an outside observer to get closer and closer to the horizon without ever crossing it; whereas the object itself would rapidly cross it and never be able to return. It’s all to do with who can observe what.
There’s also a phenomenon whereby matter being dragged into a black hole, but not yet at the event horizon, is subject to great friction and lets out a lot of radiation. Some is in the visible spectrum and that’s the glowing stuff you see around the edges of the blackness in the picture above.
I’ve read about a phenomenon called “Hawking Radiation” where radiation can actually escape from a black hole. This sounds impossible but is something to do with a pair of particles existing on either side of the event horizon. In other words, the laws of physics seem to have a kind of loophole. Stephen Hawking figured this one out.
But here’s the thing. Getting back to that description of how matter that is close to the event horizon heats up and emits a lot of light, unless I understand it wrongly this should happen in all directions. That is, a black hole is a three-dimensional object and some of that emitted light that comes to us should come from matter directly in front of the black hole, but outside of the event horizon. In other words, between us and the blackness.
Stand in front of something black and shine a light in my direction and I don’t see the blackness. I see the light.
In other words, where there’s a black hole I would expect to see bright, glowing gas. The picture above doesn’t show that. It shows what I would expect to see if I could look at the cross-section of a black hole. So the question is, if you could position yourself to the left or to the right of the black hole in this image, and looked towards the black hole itself, would you expect to see a black circle surrounded by glowing gas? Or would you just see the glowing gas that you can see to the left and to the right?
A lot of data and a lot of computing power went into producing the image. Like I said, I don’t actually believe there’s an international conspiracy to produce a fake black hole picture. Rather, I think it’s more of a computer-generated image than an actual photograph.
Of course, the alternative is that it’s accurate and I’m simply ignorant of the science involved. I’ll fully admit that that is a strong possibility.
I’m curious as to which one it is, though.