Thursday, 25 September 2014

Science facts and black holes

Chandra image of the black hole (or not)
at the centre of spiral galaxy M81
As any regular readers will know, I have a habit of banging on about the nature of science - that it isn't about establishing the 'truth' about reality, but rather about developing models that produce as close as possible results to what is observed, and that these models are inevitably provisional and could always be thrown out as new data becomes available.

This not saying 'anything goes' or 'all theories have equal value.' We will typically have a best theory of the moment, and the only sensible thing is to use that until something is established to have better credibility. But it does mean we shouldn't treat our models as certainties.

Sometimes when the model suffers a defeat it is patched up - as in the introduction of inflation to the big bang model. This isn't always a good thing as it can lead to epicycles - effectively taking a bad model and making it more and more complex and obscure to match observation. Other times the old model is genuinely thrown away.

Different areas of science have to be more or less loose with the models they accept. Cosmology, for instance, suffers hugely from the fact you can't do experiments in the lab and there is no opportunity for repetition. Inevitably, then, cosmological models are particularly at risk of revision or rejection as new data emerges. This is why I have always been very uncomfortable with saying that the universe began with* the big bang 13.7 billion years ago, something you will generally hear stated as fact by pretty well anyone doing science presentation on TV. (Naming no names.) I understand why they do this - there is a huge temptation to over-simply under media pressure. I've done it myself. But what they really should say at least once is 'when I say this happened, please take this as having an unsaid proviso "this is our best current theory, but it may well change in the future."'

A recent paper suggests that one of the keystones of modern cosmology, black holes, don't exist. There have been mutterings about black holes in the past, but this a mathematical proof that they can't form. The paper hasn't been peer reviewed yet, so there's a big proviso to this, but it's entirely possible it's true. If so, in some ways it's a relief. We would still have near black holes, doing all the things currently ascribed to black holes by astrophysicists and cosmologists. We would still have spaghettification. But we wouldn't have all the uncomfortable weirdness and breakdown of theory provided by the event horizon and the singularity.

However, my point here isn't so much the implications of the proof, if true. Rather it's that here again is something that we all knew was speculative, but have spoken about far too often and too long as if we were dealing with fact. It's time scientists and science presenters were rather more, erm, scientific about the way they presented what we know - and don't know.

* Technically just before (this is inserted to keep John Gribbin happy)

Image Credit: X-ray: NASA/CXC/Wisconsin/D.Pooley & CfA/A.Zezas; Optical: NASA/ESA/CfA/A.Zezas; UV: NASA/JPL-Caltech/CfA/J.Huchra et al.; IR: NASA/JPL-Caltech/CfA

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