The oldest trees in the dendro time scale for various regions go back over 10,000 years. The trees don’t need to be alive, they just need to be the appropriate species, then linked to later ones and eventually living ones.

The C14 calibration curves are somewhat context dependent (both environment and materials used because there are fractionation, context, and reservoir effects). They initially were based on trees, but that is not the only way to do it.

There is no pragmatic limit on how far back C14 can be calibrated. Using trees, somewhat over 10K, but varves, speleothems, etc. can be linked into that as well. There is no theoretical reason that the entire time range of C14 can’t be calibrated.

Currently, it is calibrated to somewhere between 25K and 30K. (see Reimer et al 2004 in Radiocarbon)

The oldest tree known is a bit over 5,000 years old. And if you want dates within the past 100 years, Pb-210 is a much more reliable method. The bomb signature is great, but as you said, the other radioisotopes are there too, to establish a check against other dating methods. The key to using a method is establishing its limitations, and C-14 is useful for some purposes; however, it’s not the be-all-and-end-all of our arsenal, and the creationists would do well to recognise that the knowledge of the past scientists have assembled goes far beyond what we have learned with C-14.

So the bombs converted Nitrogen to Carbon, and then scientists have converted the Carbon to Silver, as in Silver Lining.

Can a creationist even consider a period of time as long as 150 My?

It’s a combination of blissful denial, ignorance of the evidence against their beliefs, and the demonizing of scientists as representatives of the devil. At least, that’s how I remember it being at the evangelical/pentacostal churches I used to frequent.

That was the original machine, with which the technique was invented, of course. The thing was COVERED with dust.

Now uranium dating, or potassium-argon dating, those have error bars, sure, but the samples are hundreds of millions of years old! What’s a few million years, plus or minus, when the number’s that large! Here’s where young-earth Creationism meets its ultimate destruction…there’s no getting around those zircons man, they absolutely slay any chance that the Earth is less than 4 billion years old, and the fact that they had to crystallise from a molten state adds half-a-billion to the tally. Is it that creationists don’t understand the damning evidence, or do they just live in blissful denial? Observation 1: Uranium turns into lead at a known half-life. Observation 2: If uranium is trapped in a crystal, the ratio between it and the particular radiogenic lead isotope it produces change according to the half-life, so you can calculate how long it took to produce the observed ratio.

I oversimplify, but…duh?