Despite remarkable accomplishments (and despite any claims to the contrary), we are in many, many respects still profoundly ignorant about the nature of the universe and its contents. That might seem depressing, but I think it's wonderfully exciting - there are so many things for the human intellect to study and attempt to understand, so much fun to be had and so much awe to explore!
For a little northern-hemisphere summer stimulation I've picked a triplet of puzzles spread across this and two other posts. These certainly aren't the only big conundrums for science - but they're good fodder for sun-dazed pondering.
#2 Origins of Life:
As seemingly rationale beings (well, mostly, if you exclude politicians, celebrities, and make-believe orange real-estate moguls) we are in a quite peculiar position when it comes to the origins of the very phenomenon that we're a part of.
Put simply, we don't have a really good answer for the origins of life on Earth or anywhere else.
Although it's true that we've come a long way since the conflation of spontaneous generation with heterogenesis (mice come from cheese, butterflies from flowers, toads from mud, and so on), we're still very far from reaching a scientific consensus on how, why, and where life starts up.
That doesn't mean that we don't have a lot of ideas. I think most researchers would agree that some of the most promising avenues currently include:
(1) Laboratory and computational work on chemical networks of simple organic molecules that - in the right circumstances, with the right catalysts - can build more complex molecules that have the potential to continue up the chain of complexity (e.g. eventually making polymers carrying information).
(2) Studying the first metabolic drivers - including chemical potentials and chemical reactions that can operate within auto-catalytic cycles (e.g. the Formose reaction). Anywhere electrons and protons can get shuttled around there is the possibility of a system exploiting that energy flow to drive other, less 'easy' chemistry.
(3) Exploring natural environments, like hydrothermal systems in the deep oceans, where a whole bunch of useful stuff comes together. From raw chemical potential energy to ionic gradients and potential templates for cell membranes and the like - hydrothermal environments seem to fit the bill as life incubators and should have been around a very long time.
(4) A step slightly beyond the precise moment of abiogenesis could be an RNA-world, a less constrained, more chaotic pre-biological milieu that could have offered a vast network of rapid molecular experimentation and evolution. Figure this out and you might figure out what had to be in place right before.
But tying all the threads together to build a coherent and testable hypothesis for both the origins of life on Earth and the potential origins of life elsewhere still seems a way off. I've written about elements of this problem a few times in recent months, and it makes the field of origins of life both exciting and extremely challenging.
This continued uncertainty also throws a spanner in the works for the search for life elsewhere. Astronomers and astrobiologists are getting closer and closer to the moment where a terrestrial-type planet around a nearby star may reveal some of its chemical secrets. Those clues - perhaps a spectral fingerprint of water and oxygen in a temperate atmosphere, could be construed as a life detection. Except, without good insight to whether a planet could have ever given rise to life in the first place we might be waiting a long time to convince ourselves that we've actually got an inhabited world in our sights.
And for me, perhaps the biggest mystery about life is the very fact that it appears so difficult for us to figure out. Is it because living systems are necessarily so complex, and the details so layered and obscured by eons of evolution? Is it because life only occurs in very, very specific and peculiar circumstances in the universe? Or are we simply missing something, overlooking a key point that would allow all the bits to fall into place - a critical insight about chemistry, computation, or complexity?
It sure would be nice to know.