[youtube_video Lnqb_5JOpP8](This post has been updated to add new information and — hopefully — to simplify it.)
This tiny, almost microscopic sliver of zircon, just the length that four human hairs are wide and said to be just slightly larger than a dust mite, is literally older than the hills. Older than any of the hills on earth, that is. At 4.374 billion years — yup, that’s Billion with a B — it’s almost as old as the planet itself. Earth is only estimated to be approximately 4.5 billion years old. (Only??? Only 4.5 billion years???)
Next time you hear somebody opine that the world and the universe were created in six literal 24-hour days about six or nine thousand years ago, you’ll remember how incredibly carefully these scientists studied a few tiny zircon shards and found them to be many, many times older. 750,000 times older!
When I was in high school almost 60 years ago, it was believed we’d NEVER be able to see atoms with any kind of microscope. Atoms were said to be just too incredibly tiny to ever be seen. Now you can see them right here. (No, I haven’t changed the subject. I’m still telling the same story, but with a slight diversion.)
Only 30 or so years later, IBM showed they could not only see atoms but move them around on a contrasting surface to form a message.
It must have been fun, because they didn’t stop there. They went ahead and made the world’s tiniest video by moving individual atoms, frame by frame, and then magnifying them a hundred million times. Here it is for your viewing pleasure.
A competing group of scientists — No, not competing with IBM. Competing with the ones studying the rocks. — Anyway, the competing scientists said “No, these rocks are only 3.8 billion years old.” You might think, “So what? That’s still older than God.” But it does matter, because the world and the whole solar system only formed about 4.5 billion years ago; so these rocks were formed less than two hundred million years after that. I know, two hundred million years is still a long time. But it’s a lot less than the seven hundred million years implied by the other group of scientists. It matters. It matters a lot to science.
So what did the original discoverers do? They chose another one of the hundred or so methods of testing the age of rocks, and they did the whole thing again the hard way. These methods are not quick or easy. They are time consuming, tedious, expensive, and complicated. But they work.
Now these scientists have actually counted every single individual atom of the lead contaminating one of these zircon slivers so they could date it with one of the many OTHER radioactive half-life methods available for dating rocks. The lead was an impurity, because pure zircons don’t contain any lead; so every single atom of it had to be accounted for before the testing could be done. They used a technology similar to IBM’s to count the atoms.
This second dating method confirmed the first and improved on it. The first had dated the formation of the rocks at 4.4 billion years ago. The second was more accurate, and provided the better formation date at 4.374 billion years ago. Well “within tolerances” of the first, but far more precise.
The original zircon had been destroyed in the original testing, but they used another one from the same place to test again. And came up with the same result, only more precise. 4.374 instead of the earlier 4.4.
You can’t get much more careful about your procedures than that. This is science at its best, and it is exactly how science is supposed to work. A cynic will say, “See? They were wrong. They can’t even date the rocks twice and come up with the same answer.” The truth is they did. It was the same answer, but more precise. Science seldom works by overthrowing what has already been learned. It progresses by making the answers even more accurate.
Side note: It turns out the competing scientists were right, too. Their rocks from the same area were just 3.8 billion years old. An ancient volcano in the area had erupted at least 50 times in the distant past and formed that many layers of rock of different ages in the same general location.
The two groups of scientists were working so close together that they assumed originally they were working with the same age of rocks, but they were not. With that understanding, it all makes sense. Once again, it’s great science.