I was just wondering if anyone wants to explain radiometric dating and why the scientists trust it.

First, welcome nishaun, and it's great to see you're reading through the forum and adding life to a whole bunch of old threads, as well as starting some new ones.

We've been through the issue here a few times before, so a Search of the forum may turn up some useful posts, but here's a very quick rundown.

Chemical elements tend to have some isotopes (kinds of atoms of the same element) that are radioactive. Normal carbon is carbon-12, for example, and is not radioactive, but there is another isotope called carbon-14 that is radioactive.

Radioactive atoms (at least, the nucleus of each radioactive atom) breaks down in a way that is very predictable, and that is not effected at all by outside conditions like temperature, pressure, pH and so on. For each radioactive isotope there is a specific amount of time that will pass before half of the atoms in any given sample will have broken down. That period is called the 'half-life' for that isotope. The half-life of carbon-14 is about 5700 years.

If you know how much carbon-14 was in something at the start, and then figure out how much is in it now, you can use that plus the half-life to calculate how old the thing is. There is a certain, fairly stable amount of carbon-14 in the air that we breathe and the food that we eat. As long as we're alive we are taking it in and excreting it, and have a fairly constant amount in our bodies. Once we die we stop taking in new carbon-14, and what is there breaks down in a predictable way according to the half-life.

This means that carbon-14 is only useful for dating things that were formerly living, both plants and animals. It is not used for dating rocks. The half-life also means that at some point, after maybe 3 or 4 half-lifes (so about 20,000 years for carbon-14) there won't be enough left to make an accurate reading, so carbon-14 can only date things back a few tens of thousands of years.

There are other isotopes, found in rocks, that have half-lives of hundreds of thousands of years, or millions of years. These are used to date rocks, but certain assumptions have to be made about the amounts of the different isotopes that were in the rocks in the first place. There are a number of such methods, though, and they are to some extent used to 'calibrate' each other.

The science is pretty clear, and there are no real scientific challenges to the methods. Some creationists have claimed that the rate of radioactive decay might have been much faster in the past, but if they also say the earth is only about 6000 years old that amount of radioactive decay would have killed all living things on earth with radiation poisoning.

Hope this is useful/interesting.

The creationists that suggest the decay rate was faster at some time in the past suggest it occurred during the Flood and God protected those in the ark from the radiation. The other possibility is that rocks had daughter elements in them at their formation. Thus counting the ratio of parent and daughter elements in a given rock would give an inaccurate age of the rock.

"Build an ark of shittim wood and 15 feet of lead shielding..."

(just joking around, not making any kind of serious point at all)

The Bible doesn't really claim that the earth is any specific age but I was really talking about the methods used to date fossils like uranium lead dating. My main question is how is the age of rocks relevant to the age of fossils.

Good question! The plant or animal died when it was covered by the material that became a rock, or shortly before. We have actually found some animals fossils being eaten by other fossils so we know the fossil being eaten was dead before it was covered. If we can date the rock we can than date the fossil that is in it. Uranium-lead dating goes on the assumption that when the rock was formed there was no lead in it. Since uranium turns into lead when it decays, we can calculate the age of the rock by how much lead is in it and presto, we know the age of the fossil. Of course, if there was lead in the rock when it was formed, then we have no way to calculate the age. However science has more than one way to test rocks. Different testing techniques have given similar dates thus "proving" the ages to be reliable.

The RATE Group has published a study that offers a plausible explanation for what we observe in the rocks. Here we see a big difference between Natural Science and Creation Science. Natural Science looks for probable answers and Creation Science looks for plausible answers. Basically natural scientists are trying to figure out what likely happened based on the observable evidence around us. Creation scientists are looking for how things could have happened in light of God's Word and the evidence around us. That means the threshold is much lower for Creation Science and as a result many natural scientists reject or baulk at creation science.

nishaun said:

A good question, which Shane has done a good job of answering above (with one reservation which I'll discuss below). Can I just ask you, though, if you have a specific question, to ask it directly? Might have saved me spending half an hour or so writing the general account of radioactive dating above, on a day when I had a grant application to write, if I'd known you already roughly understood dating methods and had a specific question about a specific issue.

Shane said:

It's only a minor correction, but the assumption is not that there was no lead, but that there was a 'normal' amount of lead for that particular kind of rock at formation.

But yeah, Shane explained it well. Due to the nature of how fossils form, the age of the rock in which they form is the age of the fossils.

Probably worth noting that there are issues in dating besides the proportions of the various isotopes - as some elements decay they create 'halos' in the rock around them as the particles split off from the nucleus. These halos show that the radioactive decay happened in that piece of rock, rather than earlier and elsewhere, or rather than the daughter element already being present in the rock.

Interesting explanation I believe there are certain weak points in this explanation. I believe radiometric dating is a weak science because there is still a gap. What you said Shane is what I expected you to say. Your explanation does not show a strong connection between the age of rocks and the age of fossils. My problem with evolution is that it is built on so many weak sciences. Science needs strong connections, an example of a strong connection would be the way airplane engineers connect the shape of a wing to causing lift.
Evolution is a weak science, when compared to other more provable sciences would you agree?

It is a science in which more inferences have to be made, true. The same is true of subatomic particle physics, as we discussed here recently, but I'm not sure anyone would call that a 'weak science'.

Perhaps part of the problem is that you are judging evolution without fully understanding it, as your posts in the 'Monsters' thread illustrate. Would you agree that in order to make a good judgement about the claims of a science it is necessary to have a good understanding of that science?

(just a side note - Shane is a creationist, so arguably on the same 'side' as you in this discussion. He described fossil formation from that perspective, so I'm not sure it makes sense to be snarky to him)

You've claimed that the link between rock age and fossil age is weak: would you be willing to share some evidence for that position?

I don't like the term 'evolution' because often times the meanings people attach to it are so different. Bravus is the scientist in this discussion. I consider myself more of a philosopher although my degree is in business so I am more of a self-educated philosopher than a formally trained one. I approach the discipline of Origins from a philosophical perspective and have often made the claim that it shouldn't be considered a science.

Many creationists consider the science of origins a "weak" science because it is not something that is observable, measurable and repeatable. Natural science approaches the study of origins from a uniformatarian perspective. That means they assume that the processes we observe today have always been the same. That seems like a safe assumption. They assume the speed of light has always been the same. They assume gravity has always been the same. And... they assume the rate of radioactive decay has always been the same. Creationists bring a big question mark to the table.

I think most creationists will concede that the age of rocks and fossils are the biggest challenges we (creationists) face in understanding the world around us in light of God's Word. Creationists have only plausible explanations, not probable explanations.