物理定律会改变吗?
Kenneth Taylor

13 August 2017

What if gravity suddenlystopped working? Or what if e gradually came to equal mc3rather than mc2? Could the fundamentals of physics really change? Or Is this just the stuff of science fiction? That’s the question we’re addressing this week on Philosophy Talk.

Now I must admit that part of me wonders whether this idea even makes sense. I admit, though, that we can surely imagine such a thing. Early in the history of the cosmos, the fundamental constants have one set of values. Later, they have a different set. No doubt that would be surprising, but the idea itself isn’t incoherent, I suppose—which is what saying it doesn’t make any sense would seem to imply.
But surprising also doesn’t do it justice. The Cubs winning the World Series—that was surprising. The strength of gravity changing? That would be more than merely surprising. I’m not exactly sure what the right word is. Mystifying, perhaps? Whatever word you want to use, it would need some explaining.
But that’s precisely the problem. It is hard to imagine what the explanation could possibly be. We can’t appeal to even more fundamental laws to do the explaining. That would mean that the original laws weren’t fundamental after all. The only other possibility that I can see off the top of my head is that the fundamental laws could somehow explain their own evolution. But that seems… paradoxical.
But perhaps we’re thinking of it the wrong way. So far, we suppose that the universe is this very big and ever evolving totality. We also assume that the evolution of the universe simply must be governed by a ground floor of fixed unchangeable laws that hold everywhere and every-when. It’s a lovely and elegant picture. And it’s one that we inherited from the incomparable Newton. Moreover, it’s worked awfully well, at least up until now. And though I’m not really suggesting we should abandon this Newtonian picture, it has left us with questions that we can’t answer. For example, it can’t really hope to explain why we have just the laws we have, rather than some other laws. Indeed, the Newtonian picture assumes that the basic laws themselves need not explanation—at least no explanation from within physics. From the point of view of physics, the fundamental laws just are. That’s just part of what it means for laws to be fundamental.
But the laws governing our universe aren’t just any old laws. They’re really very special laws. To appreciate just how special just look around you! The laws have produced an amazingly complex and delightful universe. It’s like it was designed by an architect with an incredibly rich imagination. Now I’m not suggesting that we should accept intelligent design. But the advocates of that approach are addressing a real, so far unanswered question. And it's not just that it hasn’t been answered yet. It may well be in principle unanswerable within our broadly Newtonian framework.
To fully appreciate how special our laws are, you allow yourself to be amazed by the mere fact of our universe. There are many, many ways that our universe might have turned out. And it wouldn’t have taken very much at all for it to be completely different than it is. If the masses of the different elementary particles, or the strengths of the fundamental forces had differed ever so slightly, the universe would be more like a puddle than like a vast and varied menagerie. Now it’s a darned good thing that we don’t live in a puddle-verse. The million dollar question is WHY we don’t. Of all the universes that there could have been, how and why did it happen that the universe turned out just the way and it did and not some other of the myriad of ways it might have turned out. Why are the laws, constants and parameters tuned just enough to avoid a puddle-verse and to yield a menagerie instead?
Some are tempted to say even here that there is no explanation needed. But that reduces the universe to something like a lucky accident. Another, increasingly popular explanation is the idea of a multiverse. And that may be a start of insight. But if every possible universe is simultaneously actual, then NONE of them is special in the right way.
但如果多元宇宙是连续的而不是同时的呢?也就是说，假设这些定律、参数和常数随着时间的推移而演变。想象一个自组织的宇宙，随着时间的推移，尝试各种不同的配置。随着时间的推移，通过一个宇宙选择的过程，一个拥有刚刚好的法则，刚刚好的参数和常数，以及刚刚好的值的宇宙逐渐出现了。
这与生物进化的相似之处应该是显而易见的。不过，我们学的不是生物学，而是宇宙学——进化宇宙学。进化宇宙学涉及到宇宙选择而不是自然选择。宇宙选择逐渐设计宇宙，就像自然选择逐渐设计生物世界一样。它保留了有趣的宇宙，丢弃了水坑的诗句。我们有适者生存的宇宙。现在，这个想法的美妙之处在于，它不需要吸引外部设计师，它回答了一个问题——“为什么只有这些法律，而不是其他一些?”回答:“由它们统治的宇宙更适合宇宙!”
The physicist Lee Smolin has proposed a rather more sophisticated theory of something like the approach just outlines. And I gather many take the idea seriously, as a hypothesis worth thinking about, even if they don’t quite endorse it. I myself can’t quite get my head around even the spirit of his approach—let alone the details, which are way beyond my depth. My problem is that it seems like cosmic selection would itself have to be governed by… well… laws. And wouldn’t those laws be the truly fundamental ones? And it just doesn’t seem likely that the a law governed process could explain the evolution of the laws that do the governing. In the end, I guess I’m just stuck on Newton, aren’t you? That’s not surprising. He’s hard to get over.
Still, it should be an interesting discussion—a truly mind-bending one. We’ve got a great guest and a great guest host—both of whom know a lot a more about this topic than I do. Maybe they can help me get my head around the idea that the fundamental laws of physics might possibly be the sorts of things that change and evolve.

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