IT ISN鈥橳 easy to predict where the next leap in scientific understanding will come from. Indeed, ideas that, in hindsight, mark obvious paradigm shifts can first make you feel quite unsteady on your intellectual feet. So, as scientists poke around for new ways to understand the universe, how seriously should we take these embryonic revolutions?
In this week鈥檚 cover feature (see 鈥淗ow to wrap your head around the most mind-bending theories of reality鈥�), philosopher Eric Schwitzgebel provides a handy guide to 鈥渨eighing competing implausibilities鈥�. Much of his advice boils down to whether you prioritise conceptual simplicity over adherence to empiricism.
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Take supersymmetry, the much-beloved (by physicists, at least) notion that every fundamental particle we know of has a much heavier partner that we are yet to discover. Its mathematical elegance sends proponents into rapture, but it is let down by the small matter of us not having a shred of evidence it is true.
Dark matter at first appears on firmer ground. Under our current best understanding of gravity, Albert Einstein鈥檚 general theory of relativity, various lines of evidence point us towards the idea that 85 per cent of the mass within the universe is invisible. We see its gravitational effects throughout the cosmos. And yet, dark matter feels a bit too convenient. Yes, it explains a bunch of otherwise unexplainable phenomena, but given that we are yet to directly detect a particle of dark matter, that explanation feels uncomfortably like writing 鈥渉ere be dragons鈥� in the margins of cosmology.
That is why alternative approaches must be welcomed and judged on their relative merits, no matter how outlandish they may seem. As we report on page 10, a 鈥減ost-quantum鈥� theory of gravity is making waves by revisiting Einstein鈥檚 assumptions about the nature of space and time. Crucially, it can explain a key observation without needing to invoke the existence of dark matter. Much work is needed, but judged using Schwitzgebel鈥檚 tools, you may find this development is worth taking seriously, even if the current paradigm stands firm for now.
