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I'd like to ask if the dating " saying something has existed for XXXX years " is scientific ?

When i try to apply the criterion of being falsifiable i find that the dating fails to satisfy that condition , since anything i will say can't be falsified by experiments for example if i said the universe has existed for billion years while you said two billions years ? we can't run an experiment to know who is right? one may argue that the consequences of your models can be observed but what if the two models can contain the observations ? my point is how to know if the dating is right or wrong while it is impossible to run the events from the past.

  • K-Ar dating is a very well-understood technique. I don't understand why you're characterizing it as unscientific. – Kevin Apr 19 '15 at 21:56
  • I mean how you know if it is valid in the past while you can't simulate the past events , idk how you know if it good technique if you can't test it in the past and you did not answer how to make it falsifiable ? – Mohamed Osama Apr 19 '15 at 22:16
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    We've got no evidence the K-40 decay rate changes over time, and if it did change, that would be significantly at odds with established physics and nuclear chemistry. I have a question for you: How do you measure the length of an object? You put a ruler next to it and count hash marks. But how do you know the ruler didn't magically change since the last time you picked it up? – Kevin Apr 19 '15 at 22:24
  • You say it's not falsifiable but that depends on how specific you are about what you are testing. As you say, we can't actually test things like K-Ar dating. However, we can test stuff like C-14 dates. We have calibrated C-14 dates against fixed calendars like tree rings. – Loren Pechtel Apr 20 '15 at 2:38
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Let's ask a different question: how do you know you're not twenty minutes old? That is, "you" didn't actually write the question, you just think you did because things were different in the past such that, well, somehow or other you exist now and have memories of writing a post, but there are parameters which changed and somehow spoiled stuff.

Pretty silly, right? But, frustrating, you can't completely rule this out with logic or science or anything else. It's just a variant of Descartes' evil demon, albeit possibly a non-intelligent demon (maybe there's just some process that generates pretend histories, and a flag flipped saying, "okay, stop generating pretend histories now, plug them into beings and start doing stuff for real").

So if you really want to know absolutely for sure, it is logically possible that we could be almost arbitrarily badly confused about almost everything. This does an absolutely terrible job of explaining all the regularities we see, but it can't completely be ruled out.

But if you're "just" doing science, you don't need absolute certainty. You ask: can we construct hypotheses that make predictions about what we observe, and do those hypotheses work on both observations we've already made and ones we haven't made yet? Can we find better hypotheses?

And here, of course we can do science on stuff that's already past because it doesn't matter why you failed to make the observation before. It doesn't need to have not happened; you just need to have not cheated by plugging the answer into the hypothesis before "testing" it. You could get new observations by making new things happen, or looking at consequences of what has happened previously. Doesn't matter at all, as long as it's honestly independent from the generation of the hypothesis.

Then the question is whether parameters can change in the past in a way that will confuse us. Possibly! The length of the day has, we think, changed throughout Earth's history. Based on physical effects we can observe now, it looks like the rotation of the earth is slowing slightly, and if we extrapolate the day should have been about 22 hours long during the Cambrian. If we check, by measuring relative changes in sedimentary patterns that occur on yearly, daily, and lunar-monthly cycles, it seems pretty much spot-on.

Now, note what we did: we took multiple different predictions and they agreed with each other. We didn't take one and trust it, we checked. If some parameter changed in the past, it would somehow have to have affected these different factors by the same amount, so that they'd agree.

Dating via radioisotopes is done much the same way. There are all sorts of radiogenic decay processes (for over a dozen, see Radiogenic Isotope Geology by Alan P. Dickin, Cambridge University Press (1995)) that agree with each other. So any "parameter change" would have to affect all radioactive decay the same way. Since decay of U235 and U238 is responsible for much of the internal heating of earth, if it had happened much much faster, the earth would have been a sphere of boiling lava unless thermal conductivity were also different. (And the sun wouldn't work properly either.) Furthermore, these methods agree with completely non-radioactive methods of relative time such as sediment accumulation, coral reef growth, sea-floor spreading, and so on. So not only can we perform scientific studies in the past, when it comes specifically to radioisotope dating, we can check and cross-check and cross-cross-check, and everything checks out. (To be perfectly clear: these are tests of the hypothesis!) Now, all measurements have some associated error, so if you want to tell to 0.1% how old something is, it can be quite a challenge. But if you want to tell if something is 5 million or 500 million years old it's really easy, and really robust (if you follow proper procedures and measure or avoid sources of error, as you will if you e.g. read Radiogenic Isotope Geology).

So, in conclusion: while it is logically possible for evil demons to trick us, or for multiple models to give similar answers, in practice with radioisotope dating there are no competing models which make any sense at all, and tons of hypothesis-testing has been performed and the standard hypothesis has done really, really well.

  • But if i can't prove that i have existed for twenty minutes through science , it is ok with me because i see science as not the source of knowledge only so i do not expect science to prove everything and it must have strict conditions , other question , if someone said i will only believe in experiments in science and not from any inductive statement about the past , Do you know a school that hold that thinking ? am i against science if i did so ? – Mohamed Osama Apr 20 '15 at 21:44
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    @MohamedOsama - Science doesn't prove anything. (But neither does essentially anything else: see Descartes' evil demon.) Whether or not you're against science if you say it can't tell you about the past, you're certainly against logic. Science just formalizes the process of coming to know things, and at any instant, science is always about stuff in the past even if you plan to do more experiments in the future. Also, science doesn't care what is OK with you and what is not. It's not like it'll say, "Ungrateful person! You don't believe in me! No iPhone for you!" – Rex Kerr Apr 20 '15 at 22:18
  • But maybe i have different difinition for science than for you , that's why i asked you about a school holding that definition – Mohamed Osama Apr 21 '15 at 9:11
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    @MohamedOsama - I am not aware of any significant school of thought among either philosophers of science or practicing scientists that holds that science is limited in the way you suggest, probably because, as I explained, it's illogical to hold such a view. In particular, the Popperian view is generally the most conservative in what it calls science, and it easily admits scientific examination of certain kinds of historical events (including dating things). – Rex Kerr Apr 21 '15 at 18:06
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There are many things that are unclear or uncertain in this question. What does it mean to be "scientific?" Since you use the phrase falsifiable, I will assume you refer to the idea of science as put forward by Karl Popper. In particular, the scientific method is about testing ideas through empirical falsifiability. A theory cannot be proven right, but it can be falsified.

In this context, the act of declaring any one thing or another is not the pertinent question. You ask if "saying something has existed" is falsifiable. This is broad and depends on many things. Let's say I claim that I have existed for 200 years. To better ignore metaphysical questions about what it means to exist, let's rephrase this as I have been alive for 200 years. Sure, this is a lousy theory. My parents and governmental records could easily say that I wasn't. In that sense, it is falsifiable - but it's mostly an uninteresting theory. Whether or not one calls it scientific, it is utterly irrelevant.

But it may be that you are asking about whether the actual techniques that scientists use to date events in the past are scientific. And here, the answer is yes.

There are very many interrelated theories about dating. Some can be found on the Wikipedia page Absolute Dating. The important aspect is that we have theories involving dating from carbon-14, or potassium-argon, or argon-argon, or thermoluminescence, or relatively simpler tasks like counting tree rings or cross-examining found fossils or the like. The Earth's magnetic field changes from time to time, and we believe we understand how this affects rocks. So some rocks can be roughly dated through paleomagnetism. Or we can use volcanic ash.

We build up larger cohesive theories about dating from these smaller, individual theories. Counting tree rings is a particularly easy to imagine theory with clear testing mechanisms. Grow some trees, take core samples, and count the rings. We can get a little more involved by noting that particularly large rings occur during seasons of particularly favorable weather. Matching these up across many trees (and fossilized or otherwise preserved trees from the past) might allow one to get even deeper. Now someone might come along and start to compare carbon-14 dating to tree ring dating. If there was disagreement, then something is wrong. Ideas must be adjusted or thrown away.

And so it goes, each part tested and honed against each other. I haven't even mentioned that each technique is interrelated with areas of science. Nuclear physicists and geologists have a lot to say about the science going into their respective techniques. The fact that we now have a rather large and interconnected set of resources for dating suggests that dating is highly scientific.

As a final reference, you might consider reading about the Problem of induction, which is a related concern.

  • Let me tell you what i understand from a thing being falsifiable and scientific : is that the experiments must be done on it and the results are ok , you said we tested the Dating in our time and hence it works , but maybe there were effects which distorts the results of dating? – Mohamed Osama Apr 20 '15 at 18:14
  • Another question , if someone said i will only believe in experiments in science and not from any inductive statement about the past , Do you know a school that hold that thinking ? – Mohamed Osama Apr 20 '15 at 18:18
  • @MohamedOsama "there were effects which distorts the results of dating" -- that's why different methods are used and validated against each other. If these effects were real, it'd mean most of the involved branches of knowledge would have to revise their foundations. It is not impossible, but highly unlikely. As for not believing in inductive statements about the past, wouldn't that exclude the same experiments you mentioned, since they happened in the past too? If this school of thought would hold that the past could have been an exception to the rule, where's the limit? Was it yesterday? – Alpha Apr 25 '15 at 13:33
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This is a bizarre contention. Experiments do not have to be things we contrive in a lab. They just have to be predictions of measures not yet taken. When we looked at Mercury coming around the Sun and found what General Relativity predicted, that was an opportunity for the theory to be falsified. We do not have to create the Sun and Mercury from scratch to call that an experiment, we just have to do something we have not done before about which the theory makes new and specific predictions.

Noting that living things continually take in carbon affected by radiation, and that once dead they stop doing so, and noting that carbon becomes less radioactive over time at a given rate, I can run an experiment that measures the radioactive content in a fiber.

If I am guessing the fiber is X years old, and there is more radioactivity than those observations would indicate, my guess is falsified, or the entire notion of carbon-dating, and thus all of nuclear physics is falsified.

Every other form of dating has the same construction. Knowing X process happens Y fast, I expect it to be a degree Y * A complete after A years, and if I guess something is A years old and find the process is less complete than expected, the guess is falsified or the whole theory that supports the measured speed of the process is falsified.

Either way, dating is one of the things most consistently done in science in a falsifiable manner.

  • But the problem is you connected the results in the future with the past? maybe there are parameters which simply spoiled the dating results – Mohamed Osama Apr 20 '15 at 18:17
  • @MohamedOsama That falls into the case of 'ceteris paribus'. Every evaluation can be wrong for unforeseen reasons. That is why good scientists use p-values. – jobermark Apr 20 '15 at 20:04
  • What is p value ? – Mohamed Osama Apr 20 '15 at 21:40
  • A p-value is the statistic that indicates how likely you are to be wrong, more properly, it is the percentage of those repeating your experiment who can expect to get contradictory results if the model is actually good. In general scientists allow for a 5% chance of failure, and they expect others to be able to repeat similar experiments, and fail 5% of the time. Choosing the rate of failure and handling it responsibly whenever the statistics are strong enough for you to compute it, acknowledges that control is limited -- that stuff goes wrong in experiments and they should be re-checked. – jobermark Apr 20 '15 at 22:36
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I think there are a couple important points:

First, you are right when you say that we can't use an experiment to see how old this universe is, but I think that misses the point, because we can run experiments on the consequences of that event instead, and falsify hypotheses of the universe backwards from that.

Second, we know that to run such experiments or to deduce logically from them the consequences of those experiments makes sense because matter is intelligible. Matter isn't magical. It doesn't behave unpredictably. It is governed by rules. Many philosophers throughout the ages have held this. In terms of contemporary thinkers, you can see this idea in works as diverse as those of Richard Dawkins and of Pope Benedict.

  • The problem is alot of theories can contain the results ? how you will judge then ? i did not say magic occurs i simply mean i do not know maybe there is some parameters that affected the carbon – Mohamed Osama Apr 20 '15 at 18:16
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There is a non-philosophical answer, which I believe dodges many of the more quirky issues associated with the question "what is scientific." Instead, it is a linguistic one.

The vast majority of science is backed by statistical rigor. Scientists talk of dating because the techniques used in dating have been backed scientifically using statistics. There are plenty of questions about whether those dating schemes are valid, but they have at least chosen to expose themselves to the brutality of statistics: if the statistics start to suggest the hypothesis is false, people will abandon the hypothesis.

A single measurement, however, cannot claim such statistical rigor. Even multiple consistent measurements by the same or related techniques may not be sufficient to claim statistical rigor. However, what can be claimed is that the method has been tested statistically.

I think that if you treat "saying something is XXX years is scientific" as though it had been "saying something has been measured at XXX years old using scientifically rigorous techniques" might have been more what was intended by the statement in the first place. This wording recognizes an individual measurement of age as a process with error, but argues that the error is bound by the methodology.

  • Is this approach described/based on published work? – Dave Apr 20 '15 at 22:57
  • Yes and no. No, I did not draw it directly from a published work. It is a natural result of statistics. My terminology may be flawed, because I come from a simulation background not a philosophical one, but in our terms, this is called "drawing" from a random variable. You can draw a "heads" from a coin toss, and it says nothing about the statistical behavior of a coin. It is the predictive part of science which extends science out from the realm of cheap-to-repeat experiments into the real world of engineering. – Cort Ammon Apr 20 '15 at 23:11
  • Individual measurements can, nonetheless, invalidate hypotheses. For example, "all crows are black" is a hypothesis; upon seeing a white crow, you reject the "all crows are black" hypothesis. No statistics needed. – Rex Kerr Apr 20 '15 at 23:15
  • @Rex Kerr: Yes they, can as long as you use logical terms like "all" or "none" and don't have any statistical behaviors built into the model. once you get into hypotheses phrased statistically (which all dating methods that I know of are), a single data point cannot invalidate the hypothesis. At worst it can draw a great deal of negative attention to the hypothesis. – Cort Ammon Apr 20 '15 at 23:16
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    If you come up with "hypothesis invalid because it is inconsistent with expected variation, p < 1e-40", why does it matter how many data points went into the calculation, as long as the calculation is right? – Rex Kerr Apr 21 '15 at 0:24

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