{"id":184100,"date":"2010-01-15T11:43:11","date_gmt":"2010-01-15T16:43:11","guid":{"rendered":"http:\/\/blogs.discovermagazine.com\/cosmicvariance\/?p=3776"},"modified":"2010-01-15T11:43:11","modified_gmt":"2010-01-15T16:43:11","slug":"24-questions-for-elementary-physics-cosmic-variance","status":"publish","type":"post","link":"https:\/\/mereja.media\/index\/184100","title":{"rendered":"24 Questions for Elementary Physics | Cosmic Variance"},"content":{"rendered":"

This weekend at Caltech we had a small but very fun conference: the “Physics of the Universe Summit,” or POTUS for short. (The acronym is just an accident, I’m assured.) The subject matter was pretty conventional — particle physics, the LHC, dark matter — but the organization was a little more free-flowing and responsive than the usual parade of dusty talks. <\/p>\n

One of the motivating ideas that was mentioned more than once was the famous list of important problems proposed by David Hilbert in 1900<\/a>. These were Hilbert’s personal idea of what math problems were important but solvable over the next 100 years, and his ideas turned out to be relatively influential within twentieth-century mathematics. Our conference, 110 years later and in physics rather than math, was encouraged to think along similarly grandiose lines.<\/p>\n

And indeed people had done exactly that, especially ten years ago when the century turned: see representative lists here<\/a> and here<\/a>. I asked the organizers if anyone was taking a swing at it this time, and was answered in the negative. I was scheduled to give one of the closing summaries, and this sounded more interesting than what I actually had planned, so naturally I had to step up.<\/p>\n

Here are the slides from my presentation<\/a>, where you can find some elaboration on my choices. <\/p>\n

\"hilbert1\"<\/a><\/p>\n

And here’s the actual list:
\n<\/span><\/p>\n

    \n
  1. What breaks electroweak symmetry?\n<\/li>\n
  2. What is the ultraviolet extrapolation of the Standard Model?\n<\/li>\n
  3. Why is there a large hierarchy between the Planck scale, the weak scale, and the vaccum energy?\n<\/li>\n
  4. How do strongly-interacting degrees of freedom resolve into weakly-interacting ones?\n<\/li>\n
  5. Is there a pattern\/explanation behind the family structure and parameters of the Standard Model?\n<\/li>\n
  6. What is the phenomenology of the dark sector?\n<\/li>\n
  7. What symmetries appear in useful descriptions of nature?\n<\/li>\n
  8. Are there surprises at low masses\/energies?\n<\/li>\n
  9. How does the observable universe evolve?\n<\/li>\n
  10. How does gravity work on macroscopic scales?\n<\/li>\n
  11. What is the topology and geometry of spacetime and dynamical degrees of freedom on small scales?\n<\/li>\n
  12. How does quantum gravity work in the real world?\n<\/li>\n
  13. Why was the early universe hot, dense, and very smooth but not perfectly smooth?\n<\/li>\n
  14. What is beyond the observable universe?\n<\/li>\n
  15. Why is there a low-entropy boundary condition in the past but not the future?\n<\/li>\n
  16. Why aren’t we fluctuations in de Sitter space?\n<\/li>\n
  17. How do we compare probabilities for different classes of observers?\n<\/li>\n
  18. What rules govern the evolution of complex structures?\n<\/li>\n
  19. Is quantum mechanics correct?\n<\/li>\n
  20. What happens when wave functions collapse?\n<\/li>\n
  21. How do we go from the quantum Hamiltonian to a quasiclassical configuration space?\n<\/li>\n
  22. Is physics deterministic?\n<\/li>\n
  23. How many bits are required to describe the universe?\n<\/li>\n
  24. Will “elementary physics” ultimately be finished?<\/li>\n<\/ol>\n

    Clearly I cheated somewhat by squeezing multiple questions into single problems. But the real challenge was thinking sufficiently big to come up with problems that people a century from now would agree are interesting. And I stuck to “elementary physics” — particle physics, gravitation, cosmology — just because I’m not competent to pick out the important problems in any other fields. Twenty-four, of course, because Hilbert had 23, and we had to go one better. There was certainly no shortage of candidates; I was coming up with more good problems and throwing out old ones right up until the last minute. Any obvious ones I missed?<\/p>\n

    <\/p>\n","protected":false},"excerpt":{"rendered":"

    This weekend at Caltech we had a small but very fun conference: the “Physics of the Universe Summit,” or POTUS for short. (The acronym is just an accident, I’m assured.) The subject matter was pretty conventional — particle physics, the LHC, dark matter — but the organization was a little more free-flowing and responsive than […]<\/p>\n","protected":false},"author":641,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[7],"tags":[],"class_list":["post-184100","post","type-post","status-publish","format-standard","hentry","category-news"],"_links":{"self":[{"href":"https:\/\/mereja.media\/index\/wp-json\/wp\/v2\/posts\/184100","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/mereja.media\/index\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/mereja.media\/index\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/mereja.media\/index\/wp-json\/wp\/v2\/users\/641"}],"replies":[{"embeddable":true,"href":"https:\/\/mereja.media\/index\/wp-json\/wp\/v2\/comments?post=184100"}],"version-history":[{"count":0,"href":"https:\/\/mereja.media\/index\/wp-json\/wp\/v2\/posts\/184100\/revisions"}],"wp:attachment":[{"href":"https:\/\/mereja.media\/index\/wp-json\/wp\/v2\/media?parent=184100"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/mereja.media\/index\/wp-json\/wp\/v2\/categories?post=184100"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/mereja.media\/index\/wp-json\/wp\/v2\/tags?post=184100"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}