Physicists say there is now good evidence that a legion of floating space brains are not spontaneously bursting into existence throughout the universe.
For about a decade there has been a theory (really a thought experiment) that so-called Boltzmann brains - self-aware conscious entities with no external physical presence - might exist in space.
The idea roughly goes - and we'd suggest further reading - that given a suitably dramatic timescale, energy and matter, it's possible that a consciousness could form into a working mind, of its own accord, in space.
Consciousness is commonly thought by scientists to be essentially an illusion, created by the interaction of a vast number of simple 'actors'. In the human brain these are neurons, of which we each have about 86 billion.
Just as a computer is able to use simple calculations to build up complex systems, so too our brains build memories and actions by the interaction of neurons. And so the fanciful idea of a Boltzmann brain is that the same thing might be possible by chance. The idea is really more of a thought experiment, designed to question our assumptions about the organisation of the universe. And like most experiments that involve the vast infinity of space, if such a thing were possible then it's almost certainly happening all the time, everywhere.
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For if the universe is as massive as we think it is, and Boltzmann brains are real, then they're forming at such a rate they will eventually - depending on the fate of the universe - outnumber every human being who has ever lived.
A similar, arguably testable hypothesis suggests that the universe is probably a computer simulation - since if such a simulation is possible then every civilisation formed within one will eventually end up creating its own simulation. (It's turtles all the way down, for computer models.)
If the maths pointed to Boltzmann brains outnumbering humans, our theories of space and time could be compromised. That's because we would no longer be 'typical' observers, and might not have the ability to see reality from the 'correct' perspective. But according to a new report by New Scientist, new understandings of string theory and the theory of multiple universes might just give us an escape clause.
Physicists Claire Zukowski and Raphael Buosso at Berkely say that the key to this balance (of us, versus the superbrains) is whether or not universes expand forever and linger - full of Boltzmann brains - for much longer than creatures like humans would be able to survive.
But according to New Scientist, their work suggests this won't be the case after all. A new mathematical analysis says that by comparing two models of the universe - an older one proposed by Stephen Hawking and James Hartle, and one based on new models of string theory - it now seems less likely that reality as we know it is dominated by space superbrains.
It's worth reading the full report at New Scientist - or tackling the real report itself, if you fancy a challenge.
But don't get too cocky even if you understand it all. Chances are a space brain has got there first.