Actually, she's completely right. I suspect you're just not capable of comprehending her point. Whatever the explanation, you owe her an apology.
Science V.S. Philosophy
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You would correct to 1 part in 150 (er, well, more or less).
The next step, hypothesizing Venus' orbit to be "nearly circular" no matter when or how observations were taken would be induction.
BTW, your spacetime invariance thought is the way I understand things too, dammit.
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epepke
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Because it might work.
On the other hand, it might not work. Practically, there's at least a 1 in 2 chance that it doesn't work.
When it does, it does. And we can tell when it does, because it does.
epepke
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Sure. The most obvious example is interpreting QM in terms of classical events.
epepke
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No, and you're wrong, too. Wrong McWrongerson.
epepke
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My view of induction? Isn't that begging the question?
My scientific view of induction is that it is like a hand plane in carpentry, unless it's like a saw.
epepke
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Much, much earlier, I made the distinction between an assumption and a job description. I guess it didn't have any effect.
I'm not suggesting that your view isn't the correct one, I just want to understand it. I understand that you seem exasperated that your explanations so far don't seem to be taking. I thought that if you defined induction it would help me understand, and maybe others as well.
From what I can make out of PM's point, he's saying that induction doesn't work if you don't know that what works now will tend to work in the future, or at other places. And he's also saying that science is based on induction. I'm not sure, but I think you disagree with both of those things.
I don't see how science can reach any conclusions about the way things will work without induction. And if it can't do that, there's very little reason to engage in science.
I'm not sure if you think that it can reach conclusions (about the future), or if those conclusions aren't a part of science, but are a part of something else, or if your point is something else that I'm just too dumb to get. I can certainly buy the last explanation, but I am trying.
In order to try to construct a model of how the universe works, we need to assume that the precise location and precise time-coordinates of our observations aren't relevant. If they were - if a thing that happened at X would happen differently at Y, even if all other factors were the same, we could never establish any model, because we'd never be able to control for place-and-time.
The idea that the laws of physics must be space-time invariant was key to Einstein's understanding of Relativity, as well.
You're wrong. And you still owe that apology.
epepke
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No, that's fair enough, and I don't take it as hostile. The "begging the question" aspect is about holding induction up to be something basic. This is begging the question to me, because I don't see it as so basic. I see it as a tool; that's all.
OK, I'm going to try to explain. Induction is a tool. It's like a saw, or an awl, or a plane, or something like that. It works sometimes. Sometimes, it doesn't.
I don't think that people stop doing science when a particular tool doesn't work.
Now, I might do something in science in the hopes that it will tend to work in the future or in other places. But this is by no means an axiom. If it works, great! If it doesn't, maybe I can find something else that works.
Well, as I see it (which seems to be difficult to convey), if it reaches a conclusion, then it's reached a conclusion, and this can be evaluated by other means. And if it doesn't, well, then it doesn't.
As for "why do science," well, most people don't. Doing science takes a particular kind of attitude, and most people don't have that attidude. It takes a kind of humility that seems rather hard to achieve, and most people can't. They want things to follow from analytic propositions, and they aren't happy when they don't. Well, that's fine. They can make shoes or do construction or work at Walmart.
In order to do science, one has to become comfortable with a certain level of ignorance and a certain lack of security, which a lot of people can't manage. And if science is not something that they are particularly able to do, that's fine. I don't look down on them.
Horse manure.
I have a very good model of how the universe works, and it's not at all space-time invariant. This was obvious to my primitive ancestors. Planting corn in the spring produces a radically different result than planting it in the autumn, and the people who weren't aware of that distinction tended to either live in areas with much less seasonal variation -- or simply starved to death. The grapes on the south face of the hill are doing much better than the grapes on the north face of the hill... and because this is has been a rainier spring, I need to adjust my planting.
And if I learned that I do better planting grapes on the south side of my hill, I don't assume that you will also do better planting grapes on the south side of yours. Even the observations that I make -- and the rules I draw from those observations --are not space-time invariant.
The task of much of science is to try to find a model that accounts for the space and time variance of what we observe. Now, it appears to happen that if we push the rules hard enough, we've recently been able to find that a lot of apparently variant things can be described in terms of space-time invariant things. But that's a new development, applies only to a relatively small amount of "science," and only works for describing simple things.
Try telling a doctor that medicine doesn't vary with "place and time" and watch him laugh at you. Two words : "flu season." How can something be seasonal, and yet time-invariant?
drkitten: "time-invariant" does not mean what you think it does.
It does not mean that a flu virus cannot change over time, or that the attributes of a population cannot change over time. What it means is that, if all other things were identical, the past would not be fundamentally different merely because it was the past. There are general principles that hold no matter when and where they are applied, and the specific circumstances that hold in a particular case are just a subset of those rules. Those rules are time- and space-invariant.
It does not mean that a flu virus cannot change over time, or that the attributes of a population cannot change over time. What it means is that, if all other things were identical, the past would not be fundamentally different merely because it was the past. There are general principles that hold no matter when and where they are applied, and the specific circumstances that hold in a particular case are just a subset of those rules. Those rules are time- and space-invariant.
epepke
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The problem with this is that time is something about the universe that we study. It's not an assumption. And there are also good reasons to think that, if all other things were identical, we might see something different.
Sorry for the lack of response of late - been having trouble getting on the forums.
I think I get the point about induction being a tool.
Here's my interpretation of what epepke and drk are saying. Until now, we've always observed that what works at one time works later on. Experiements have been repeatable, and when they haven't there's been some reason for that. So we conclude (provisionally) that we can continue the expect this to be true.
It may not be. If it isn't, well, we'll make allowances for that in the future, and try to understand why it isn't. It's not the end of the world.
We didn't start out our scientific endevour knowing that we could trust this to be true, and we still don't know it.
Which is no different from anything in science. We don't know that natural selection is one of the main forces that produced the biological diversity we see in the world, but we have concluded that it is based on the evidence. So when we see a new species, we work within that framework. But if new evidence came to light that showed natural selection to be useless in describing what really shaped the biology of the earth, we wouldn't be forced to stop doing biology. We'd form new theories, and try to understand.
And space-time invarience as a conclusion isn't circular (we don't require it to be able to look at the evidence in order to conclude it). If things always have been this way, the simplest explanation (not necessarily the right one, but the best conclusion based on what we know) is that they will go on that way. And that is our conclusion until new evidence comes in.
That's the argument as I see it. Please correct me if I've misunderstood. Or those who disagree, a heavy thrashing may be in order.
I think I get the point about induction being a tool.
Here's my interpretation of what epepke and drk are saying. Until now, we've always observed that what works at one time works later on. Experiements have been repeatable, and when they haven't there's been some reason for that. So we conclude (provisionally) that we can continue the expect this to be true.
It may not be. If it isn't, well, we'll make allowances for that in the future, and try to understand why it isn't. It's not the end of the world.
We didn't start out our scientific endevour knowing that we could trust this to be true, and we still don't know it.
Which is no different from anything in science. We don't know that natural selection is one of the main forces that produced the biological diversity we see in the world, but we have concluded that it is based on the evidence. So when we see a new species, we work within that framework. But if new evidence came to light that showed natural selection to be useless in describing what really shaped the biology of the earth, we wouldn't be forced to stop doing biology. We'd form new theories, and try to understand.
And space-time invarience as a conclusion isn't circular (we don't require it to be able to look at the evidence in order to conclude it). If things always have been this way, the simplest explanation (not necessarily the right one, but the best conclusion based on what we know) is that they will go on that way. And that is our conclusion until new evidence comes in.
That's the argument as I see it. Please correct me if I've misunderstood. Or those who disagree, a heavy thrashing may be in order.
Time is not "a thing that we study" in the sense you mean.
Even probablistic outcomes which cannot be truly predicted ahead of time are time-invariant, because it doesn't matter at what time they're determined. If time were a relevant variable, there would be no way to repeat any experiment, even in theory.
epepke
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Yes it is. At least since 1905, it has been.
You have it all backward. That experiments are repeatable shows weak support for time symmetry. It's weak because it could show that time symmetry exists or that time is sufficiently close to symmetric that it would not show up to the precision of the experiment. Time symmetry and the other symmetries were not put on an even remotely solid foundation until the work of Emmy Noether in the 1910s and 1920s.
I note once again that this work ties time symmetry to conservation of energy (which was only possible since relativity was settled), and that Newton himself did not think that energy was conserved. Actually, even more than that: energy itself as a unifying concept did not even take significant importance until the middle of the 19th century.
In any event, time symmetry, which is what you mean by time invariance, is hardly an axiom.
epepke
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I'm translating between the language used by philosophers (or whoever) and the language used by physicists.
What I get is that you are referring to the property of the universe such that the laws of physics will be the same after some time has passed as they are now. Physicists call this "time symmetry."
However, if you really mean "time invariance," according to the way physicists use the word "invariant," then I have news for you: time isn't invariant.