Discussion in 'Earth Science' started by Mind Over Matter, Aug 16, 2011.
i presented a link from cornell that suggests it isn't.
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He can't even spell!
We give all members, including ourselves, quite a bit of leeway regarding the rule about insults, so long as the target is either a religionist or an antiscientist. Leopold appears to be both, so feel free to bring out the big guns.
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completely off topic, opinionated, flaming, and trolling post.
i guess i am asking too much when i ask for the posts that prove your unsubstantiated claim i am anti science and/or "religious" ( whatever the hell "religious" means ).
must be nice to be able to say shit like what you have just said about me without fear of reprisal.
you would have me to actually call james "der fuhrer" fraggle?
Hmmm... can't tell much from the link. Probably don't have the background to understand the implications anyway.
How significant is this variance? What would the effects be... ie. would things appear older than they actually are, younger, no way of telling?
Can we minimize the effect by using several samples and other dating methods?
And since you don't seem to trust anything you weren't there to review, how can you trust these guys?
i asked james what he thought about the link hoping to get his viewpoint.
all he said was "nice link. well done" or something along those lines.
From the abstract:
For a start off, Solar activity is unrelated to the Earth-sun distance, other wise it would be a 12 month cycle, not an 11 year one.
Has that article been published in any peer-reviewed journal?
I found their graphs interesting. They point to regions that seem to show lower than expected decay rates, while ignoring regions that appear to show higher than expected decay rates. What I see is the usual kinds of random fluctuations you'd expect.
Page 2, Para 2&3, there's something in there that doesn't quite sound right to me, but I can't quite finger it.
No control group.
If they were serious, they should have done a simultaneous run with a 'blank' sample that was in an otherwise identical setup.
That would give their results a greater degree of robustness, and nipped a whole bunch of questions in the bud.
how would you set up a control group for this type of experiment?
what do you mean by "blank sample"?
i am trying to picture what you mean but it eludes me for some reason.
i don't know.
i was only aware of the article because it was posted here on the forums.
The answer is no, there is nothing on the Arxiv website to indicate that the article has been accepted for publication in any journal.
Yes, some scientists "assumes" that if we find a 3 million year old piece of native rock then the Earth is at least three million years old.
We do indeed use some indirect methods, for example meteorites. Astronomy tells us that the whole planetary system formed at about the same time from an accretion disc round the Sun. Dating a meteorite gives us a date for the accretion disc. Indirectly that dates the Earth, since the Earth is also a part of the same accretion disc.
PS: Be careful of using the word "proof" in a science discussion. Strictly speaking, science does not do "proof", since in principle every scientific theory can be replaced with a better theory and every measurement comes with error limits on it.
this isn't necessarily true.
the retrograde orbits of the moons of jupiter and saturn could not have come from the same "cloud" as the planets themselves.
but i will have to admit earths orbit follows the progression of planetary orbits in general.
thanks, but i'm not exactly a noob.
all of the radiometric dating methods except one rely on the following assumptions:
1. beginning conditions are known
2. beginning parent/ daughter ratio is known.
3. constant decay rate.
4. no leaching or additions to parent/ daughter isotopes.
5. all assumptions are valid over the course of billions of years.
6. not really an assumption but the ability to measure extremely minute amounts of isotope.
the exception is "isochron" dating.
it relies on the following assumptions:
1. all areas of a given specimen formed at the same time.
2. the specimen was completely homogenous when formed.
3. limited contamination.
4. isochrons that are based on intra-specimen crystals can be exprapolated to the entire specimen.
the main advantage of isochron dating is that the initial parent/daughter ratio does not need to be known.
any comments on the above?
How is (1) different from (2)? What "conditions" are you talking about in (1)?
As for (2), the process of formation of many radioactive nuclides is well understood, and these processes have been directly confirmed in experiments. For example, take C14 dating. From memory, C14 is formed by cosmic ray bombardment in the atmosphere. The rate at which plants absorb atmospheric C14 is testable. And we know for sure that once a plant dies it no longer absorbs carbon from the atmosphere.
There is no good evidence that radioactive decay rates are not constant, so this is a perfectly reasonable assumption until such time as contrary evidence comes to light.
Mechanisms of leaching and addition are similarly well-understood. These are taken into account when scientists determine dates, and in particular the scientists always say when a given date might be unreliable due to such factors.
Not all radioisotopes are useful over billions of years. For example, C14 has a half life of only about 5700 years. Radioactive dating is not really useful once you get beyond a few multiples of the half life, due to the small amounts of radioisotope remaining. Therefore, no scientist would ever use C14 dating (for example) to try to date something that is millions of years old (let alone billions).
The difficulty in measuring extremely minute amounts is exactly why short half-life radioisotopes are never used to determine vast ages (as explained immediately above).
i'm learning as i go james.
i have no idea how they are different.
rereading the post i got the same question coming to mind.
i would assume they meant parent/ daughter ratio.
c14 is not used to date fossils and very old rocks
agreed, but the possibility exists.
if the universe did indeed start off with a bang then it's reasonable to expect some "very strange physics", at least in the earlier stages.
how leaching occurs isn't the question.
the question is "did it happen?"
the only exception would be a sample that was immediately isolated when formed.
from what i've read radiometric dating can be considered reliable upto 8 times the half life.
whether that is true or not i do not know.
i would assume that this isn't really a problem due to advances in measuring methods.
They did the experiment using a detector isolated by lead bricks, and that detector has a window (I forget what kind just off the top of my head) that detects specific kinds of radiation and quantifies their energies.
What I am proposing is that a more robust methodology would have been to run two experiments at the same time. You run, on the one hand, the isolated detector with the lead bricks, and the sample of Manganese 54 that you want to measure the activity of. And on the other hand, at the same time, you run an identical detector (for most purposes, a detector of the same model and year will suffice, but the closer to being identical, the better), with the same kind of window, and isolate it as well, also using lead bricks (again, the closer to being identical, the better), and run it for the same duration, and at the same time, but without the sample of manganese 54 - effectively, you're measuring the background rate. Ideally, you can do a blank run with both detectors before beginning the experiment, and prove a correlation, then subtract the background signal from the experimental signal, and see what you have left.
Finally, a smart experimentalist would also have used multiple radionuclides, and perhaps a variety of decay paths to give a truely robust result.
Yes, because its half-life is too short.
The big bang theory, like evolution and radioactive dating, is very well established science. Are you now adding the big bang to your science-denial list? Oh wait, don't tell me. You weren't there to witness it personally, so there's no way to know if it happened or not. Right?
That's the only exception, is it? So leaching is what normally happens, then? What's your source for that claim?
After 8 half lives you have 1/256th of the original radioactive material left, compared to what you started with. Whether you can reliably measure that or not depends on a number of factors.
You do know the basics of half life and radioactive decay, I assume. I'd hate to think you haven't done the bare minimum research to inform yourself about how radioactive dating actually works.
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