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by pmoriarty 1852 days ago
"We know the answer to why uniform radiation propagates due to an inverse square law."

This is an answer to a "how" question rephrased (incorrectly) as an answer to a "why" question.

First, the "inverse square law" isn't a law in the colloquial sense (like a maximum speed limit law) where the universe is forced to obey it. Instead, "law" is just a conventional phrase indicating what the consensus among scientists is regarding certain observations.

So it's really an answer to the question of "how does [our current observations of how] radiation propagate?": "according to the inverse square law".

Future observations of radiation propagation might run completely contrary to those we've had up to now, and it is scientific explanations that will have to be modified to accommodate those observations.

But the inverse square law does not explain why radiation has been observed to propagate in this way.

For such an answer you'd have to resort to a much grander explanation of the universe, involving all sorts of other theories involving many other observations, back to the big bang, which is not yet fully understood and may never be (even if we assume that the big bang theory itself won't be replaced by some other origin theory in the future, and not to mention what happened "before" the big bang, which may be even more impenetrable still).

But even were there to be some comprehensive "theory of everything" (in the larger sense), that doesn't mean the why of it has been explained, as there'll still be open questions like: "why something rather than nothing?" or "why this universe and not another?"

"But," some may object, "I just wanted to know why radiation propagates as it does, not why there's something instead of nothing." Well, I'm afraid that science can't answer your little question without answering the big questions. Religion or philosophy might, but they're also seen as unsatisfactory to many, so such why questions might never be answerable to everyone's satisfaction.

Harder questions, like those about consciousness, are even less likely to be satisfactorily answered, as touching them immediately lands one in to the morass of assumptions, definitions, points of view, and perspectives.

Half the time people are completely speaking past each other because they've never agreed on or even stated what their definitions or assumptions are, so are going off about two or more completely different things. Consciousness itself is notoriously difficult to define, so when two or more people are talking about something that they "know it when they see it," they're bound to talk past each other half the time, whether they agree or disagree.

Some philosophers are better at setting the ground rules and making their fundamental assumptions and defintions explicit, but they're usually pretty balkanized, and you'll find plenty of other philosophers disagreeing with their assumptions and definitions.

I personally see little hope of this thorny problem ever being resolved to everyone's satisfaction, but there'll surely be plenty of arguing about it until the end of time.

1 comments

> First, the "inverse square law" isn't a law in the colloquial sense (like a maximum speed limit law) where the universe is forced to obey it. Instead, "law" is just a conventional phrase indicating what the consensus among scientists is regarding certain observations.

That's incorrect in this case. It's a hard requirement that can easily be mathematically derived, so easily that I'll do it here:

1. The surface area of a 3D sphere, 4πr^2, is proportional to the square of the radius.

2. Radiation from a point source that is evenly radiating outward is therefore spread out over an area that increases in proportion to the square of the distance from the source.

3. Therefore, such radiation must obey an inverse square law, in any universe in which the preconditions -even radiation from a point source through 3D space - are true.

> Future observations of radiation propagation might run completely contrary to those we've had up to now

That's provably not the case, and I've just proved it beyond doubt. From this proof, we know what kind of situations are subject to this law, and can even determine what kinds of situations might not be subject to it.

A similar point applies to conservation laws, such as conservation of energy and conservation of momentum. Noether's theorem shows us that such conservation laws must hold, again in any universe where the preconditions around differentiable symmetries hold.

With that in mind, I don't think the rest of your comment makes much sense. Not only does science answer "why" questions in many cases, it can answer them so definitively that we can apply that knowledge to other universes.

You just shifted the question from "Why do we have an inverse square law for radiation" to "Why do we live in a 3d universe".

Same goes for the Noether theorem. It shifts the question from "why do we have certain conservation laws" to "why do we have certain symmetries".

> You just shifted the question from "Why do we have an inverse square law for radiation" to "Why do we live in a 3d universe".

That's not "shifting the question", that's a different question.

The point is that there is a meaningful sense, discovered by scientific study, in which we understand why there is an inverse square law for radiation.

If the examples I've given are not answers to "why" questions, how would you characterize them?

In any case, the idea that we can never know the answer to any "why" question because there's a causal chain that goes back to the creation of the universe is silly. We can understand the connection between parts of a chain without knowing where the chain came from, and that's exactly what science has done, so successfully that some people are now complaining that we don't know how the universe began.

Besides, the question of why we live in a 3D universe has a similar answer - see Max Tegmark's "On the dimensionality of spacetime": https://space.mit.edu/home/tegmark/dimensions.pdf

Given that, where do you think "I've shifted the question" now? At some point, do you not recognize that the question being asked really has no meaningful relevance to the original question?

In fact, examples like these go beyond just answering "why" questions - they tell us that this universe, and even other universes with similar properties, couldn't be any other way!