"A different set of physical laws may apply in other galaxies/universes"

I’ve heard cosmologists and science popularizers make this assertion, but haven’t heard how these different physical laws might play out elsewhere in our cosmos. The insinuation is that these differences might go well beyond silicon-based life forms, but what are the possibilities in terms of physics, chemistry, biology, mathematics, etc?

[Yes, I know. Since no one knows just how “outside the box” these differences might be, speculating on them gets more than a little iffy. That said, can someone provide even the wildest sketch?]

Well, pretty much everyone expects mathematics to be the same everywhere, since at its root mathematics is nothing but a logical construct. An extremely useful logical construct, mind you, but a construct nonetheless.

What you may have heard cosmologists and science popularizers blathering on about in recent years is the so-called “string theory landscape”. This is the idea that there are other regions of the Universe, causally disconnected from ours, in which the laws of physics are completely different. In such a region you could have different ratios of the gravitational to the electromagnetic constant, different strengths of the nuclear forces, different particle masses, even fundamentally different forces and particles that don’t map neatly on to the fundamental particles that we see here in our vicinity.

This isn’t quite as absurd as it might sound. There’s a phenomenon in solid-state physics called the “Curie temperature”: if you heat up a block of iron, and then let it cool back down below a certain temperature, you’ll find that on a microscopic level the iron has thousands of little regions (called “domains”) which act like little magnets. The “poles” of each domain are pointing in a different direction, and so there’s no net magnetic field for the whole block, but within each domain there’s a preferred direction to the magnetic field.

The analog, then, is that the Big Bang “heated up” the Universe, and as it cooled down there were certain “domains” that were created. Instead of having different magnetic fields in the different domains, though, you have different fundamental constants. If, like the string theorists, you believe that all of the fundamental constants (or at least most of them) and other stuff like the particle content of the Universe are determined via some “higher-energy” theory that we can’t easily investigate, then pretty much anything is fair game.

Oh, and once you start tinkering with the fundamental constants of physics, anything goes as far as chemistry and biology are concerned. Tweak the fundamental constants so that the neutron no longer exists, and all of a sudden you can’t have any atoms heavier than hydrogen — so no chemistry and probably no biology either. Tweak them slightly differently, and the periodic table could look completely different. Evolution via natural selection would still apply to any Universe with imperfectly self-replicating systems, but other than that all bets are off.

You might find The Anthropic Cosmological Principle, by John Barrow & Frank Tipler, interesting reading in this regard. While their conclusions are still very much a matter of debate, there are many, many, many calculations therein that show that “life as we know it” would not exist if the fundamental constants of the Universe were tweaked very much at all.

See, I always wonder about this when people start saying there’s no evidence of life elsewhere in the universe. I figure they’re looking for something specific, but if they’re looking for a carbon-based life form and life forms elsewhere just don’t happen to be carbon-based, how would we even know what we were seeing if we saw it?

(Do not attempt to answer this, it’s not actually a question, just the random neuron-firings of an overtired and overcaffeinated brainstem.)

Just to nitpick, we know damn well that the same physical laws apply in other galaxies, because the stars there act just like the stars in ours. For other universes, if there are any, the jury is still out.

I dunno… geometry could be different if the universe had different properties - maybe a different number of spatial dimensions, or some kind of exotic built-in curvature to those dimensions…

That’s not different mathematics. It just provides different input for the equations, which will in turn provide different output (for the sum of the angles of a triangle, for example). But the equations themselves are still the same.

I agree, but a poster here (?) several weeks ago made a passing remark that mathematics might not “be the same everywhere.” Maybe he was talking about the Office of Management and Budget.

If your talking about what see can see and measure within our own universe then we can certainly say that the same laws apply everywhere. We can see light spectra from different stars and calculate their age and speed. We can measure the paths of stars and galaxies and determine that the same gravitational forces apply everywhere.
If your talking about some other universe that is totally disconnected from ours and into which we can never enter then, in my opinion, you are talking science fiction and fantasy and there is no answer to your question.

In my mind, the immutability of physical laws is a base of science. If we cannot assume that things behave there (whether in a different galaxy, outside the oort cloud, or just on a different continent) the same way they behave here (say in my labratory), then all science falls apart.

What is it that would define the domain boundaries? If you cannot see or detect them, then there is no way to know if any science is correct because the laws might be different down the block…

There was actually an article about this sort of thing in the search for life on Mars that I read earlier this week.

Next time I will preview…

Actually there is an interesting essay in January’s Physics Today that touches on why immutability of physical laws is important…

Belief and knowledge—a plea about language

The immutability of fundamental physical laws, sure. But which laws are truly fundamental and which are caused by your environment are up for debate. For example, if we had somehow lived 10[sup]-12[/sup] seconds after the Big Bang, we would have thought that there were three “fundamental forces” in the Universe: the strong, the gravitational, and the electroweak. Now that things have cooled off a little more, we see four “fundamental forces”. It’s only because of the environment at those particular moments in time that the number of “different” forces varies; the fundamental laws underlying them are always the same. But figuring out what, exactly, is “fundamental” is the name of the game. In the extreme versions of what the string theorists are saying these days, pretty much everything is up for grabs, since a string-theoretical description can underlie a whole bunch of different physical theories.

But physics (on some level) does vary with position. Water boils differently at sea level than at the top of Everest. Sure, we know why and we can account for it, but there is still a difference in the way things interact at different positions in space.

No, that’s not an example of the what the OP is talking about any more than saying that the Gravitational foroce of the earth is less at higher altitudes, too. It’s not “physics” that is varying, but measurable qunatities like pressure-- quantities which are predicted by physics to vary as they do.

GAH! I am so weirded out when I say something stupid, idly off the top of my head and it turns out to have some basis in fact.

The point of the string-theory-landscape advocates is that a whole lot of what we think of as “fundamental constants” — the mass of the electron, the fundamental unit of charge, the strength of the nuclear binding force, the number of generations of quarks & leptons — aren’t really fundamental, but are merely “local effects” and could vary. If the Universe had cooled off from the Big Bang in a slightly different way, the “low-energy” laws of physics might be totally different, just like there’s no particular reason that the magnetic field in a particular domain of a bar of iron had to point in that precise direction. And once you’ve accepted that analogy, then there’s no reason to question that there couldn’t be other “domains” out there with different low-energy laws of physics.

Or that’s what the advocates of the landscape say. Personally, it sounds a little like they’re grasping at straws, and even within the string theory community the “landscape gardeners” are something of a minority.

I wasn’t responding to the OP, but to Eyer8 and the call for the immutability of physical laws. I was under the impression that on a quantum scale there is a vast difference on how things behave than on a macroscopic scale and the search is on to find the unifying theory between them. This, in itself, doesn’t postulate there is any reason to suspect quantum physics is different 10 billion light years from here, but it does argue against the notion that all physical laws are the same everywhere.

What laws are you referring to? Objects at rest tend to stay at rest, et al? There are concepts like entropy. Then there are theories like relativity and chaos. Then there are equations like kinetic energy and velocity. I think the laws are pretty ‘universal’. Theories stand on shaky ground. Concepts and equations are somewhat in between. These were developed in order to predict outcomes. We learn in physics that nothing can go faster than the speed of light because it’s mass approaches infinity. Frankly, nothing can go faster than the speed of light because the equations that man developed tells us that nothing can. If God wanted to move something faster than light, I think God could. There’s probably way more out there that we haven’t discovered and probably even more that we can’t even mentally conceive. Therefore I think it’s pretty safe to say that the entire universe(s) does not conform to our laws of physics.