What evidence of the vast age of the Earth could an ancient Greek or medieval natural philosopher point to, given that the conclusive evidence we point to now (supernovae, isotope abundance, fossil record, continental drift etc.) all require some extra steps (constant light speed in vacuo, accurate coastline maps etc.) which were unaccessible to them? Just as they figured out the sphericity and size of the Earth, is there anything which a genius could point to demonstrating its age?
For example, petrified trees might present them with something of a quandary, since trees becoming rocks would not seem to be something which could happen over mere millennia. Water dripping from stalactite to stalagmite would also perhaps imply great age given nearby columns of various proximity to being “joined up”. Are there any other geographical/astronomical features which show, with a minimal leap of inference, the results of a process taking millions of years?
To get a really old age for the Earth, you need modern science, but there are a few places where you might get some idea of the magnitudes involved. The first step in the process would be realise that things we see today can, in fact, be related to things that occured in the past. A flood can cover a city in a layer of mud. One hundred floods can leave a thick pile of mud and a lot of layers. Mud turns into rock.
Let’s suppose our Ancient Greek philosopher climbs on a plane and flies out to Colorado. Then he looks at the walls of the Grand Canyon (possibly in his Ancient Greek helicopter). Layer on layer on layer of rock, alot of it stratified sandstone. It’s a massive jump to make, but if one flood = one layer of rock, then there’s a lot of time involved.
Providing an accurate estimate of the actual age would have been beyond them, I’m pretty sure. On the other hand that the world was truly ancient would not have been beyond them if a much earlier Steno (or Hutton, Werner, Smith, or Cuvier) had taken the same notes and drawn the same inferences. There is a lot of stratified rock visible throuhout the MENA region, Greece, and Italy. (Steno, working in the mid-17th century, began in Tuscany.) It did not take special tools to recognize that stratification was the result of deposition and erosion, just an insight that had not occurred, before.
… I’m not sure that they would have had any idea how stactites/stalagmites form. So, merely watching a drip of water from the end wouldn’t tell them that’s how the thing is built up (down).
I don’t think you can get to a very aged earth without some fairly modern geology (1700s, say) at a minimum. MHO.
Incidentally, Leonardo da Vinci studied stratifications in Northern Italian mountains, and hypothesized that the earth was much older than traditionally assumed. He based much of his observations on fossilized mollusks, which had puzzled many people before Leonardo–the fossils appeared to be seashells, but they were located in high mountains at quite some distance from the sea.
Previous interpretations had held that these shells were deposited on the mountains during the Biblical Flood (some Creationists repeat similar arguments to this day). Leonardo, on the other hand, deduced that the fossils were evidence that the entire region had once been underwater (not just submerged during one catastrophic flood), and that this must have been many, many ages ago.
Leonardo made his observations at the end of the fifteenth century–one can speculate that an earlier observer, with the same insight as Leonardo, could have looked at similar fossils and similarly realized that the earth’s age was much more ancient than previously believed.
I’ve seen stalagmites and stalagtites which have started to form in an abandoned subway station, which is about 50 years old. Couple that with watching icicles form, and measuring the height of a stalag of known (very short) age, and one could estimate the length of time needed to produce a very large cave feature.