Cosmologist Squirms at Thought of Fine-Tuning
Lawrence Krauss (Case Western Reserve U, Ohio) meant to talk about prospects for distinguishing between sources of so-called dark energy, the mysterious force that appears to be accelerating the expansion of the universe. But in the process, he opened his soul and revealed feelings, dreams, and nightmares. First, he states the problem:
Dark energy is perplexing. Physical theory currently has no explanation of why the energy of empty space should be precisely zero (quantum-mechanical effects combined with relativity in fact predict quite the opposite). But it also gives no explanation of why that energy should not instead be so huge that it would dwarf all of the energy in anything else (making galaxy formation impossible). (Emphasis added in all quotes.)
The measured value for the cosmological constant hovers around exactly -1. That is far from huge, but not zero. Sounds like we a fine-tuning problem here. Krauss would rather find a theory that predicts why the universe has to be the way it is. If dark energy, whatever it is, appears to be due to a finely tuned value for the cosmological constant, we are stuck with explaining how we became so lucky to have another precisely fixed cosmic parameter that, if changed, would rule out life, because it would rule out galaxy formation. He takes some comfort in the work of Kunz et al. who are looking for other sources for the dark energy. If he fails, the thought of this “ big problem in cosmology lurking on the horizon” gives Krauss nightmares:
Thus, some of us wake up in the middle of the night worrying that the discovery of dark energy may put cosmology on the same footing as particle physics, with all of the data that have come in over the years pointing consistently to exactly the same set of cosmic parameters, but without revealing any smoking-guns that could direct us to a fundamental theoretical rationale for why the data take these values. I have even made a bet with physicists Stephen Hawking and Frank Wilczek that this will happen (then, even if my worst nightmare turns out to be true, I will at least get a few bottles of wine out of the bargain). On the other hand, perhaps the cross-comparison of present and future cosmological observations, along the lines proposed by Kunz et al., will yield some new handle on this slippery problem. In that case, I might lose my bet, but the ‘golden age’ of cosmology would persist.
1Lawrence M. Krauss, “Cosmology: What is dark energy?”, Nature 431, 519 – 520 (30 September 2004); doi:10.1038/431519b.
Atheists would rather get drunk than face the prospect that they live in a finely-tuned universe, created on purpose by an all-wise, caring, intelligent Creator. Fear not, Dr. Krauss; the sober life brings more ultimate satisfaction.