World's Oldest Rocks???
Posted 04 December 2002 - 10:15 AM
Found this on CNN just now. How can the rocks on earth be "old" or "new"? Do rocks just appear out of nowhere every once in a while? The matter that makes up the rock is most likely just as old as the universe itself. Maybe they are referring to the rocks that have been unchanged for the longest time?
Posted 07 December 2002 - 07:59 PM
So, finding a rock that is almost 4 billion years old tells us (at least) two things:
1) There has been solid material around for at least that much time (which sets a definitive minimum age for our planet)
2) If solid matter has survived for that long, there is also a potential for inorganic lifeforms to have survived as well, although this is of course highly speculative.
It doesn't have anything to do with the age of the basic constituents of matter, which you point out to be as old as the Universe itself. But as an astronomer you also know that stars are born and die, and in the process they create new forms of matter out of these basic constituents.
I'm neither an astronomer nor a geologist, but I still think it's quite cool to know there is material on Earth that has existed for nearly a third of the age of the Universe...
Posted 07 December 2002 - 10:10 PM
Posted 10 December 2002 - 01:37 PM
how can be a rock older than other? All the matter wasn`t made at the same time?
Posted 10 December 2002 - 01:55 PM
Rocks are even formed today - consider lava flowing from an active volcano. This becomes rock when it cools.
That's why some rocks are older than others.
Posted 11 December 2002 - 04:59 AM
...cant we think that way?
Posted 11 December 2002 - 05:08 AM
In the early days, only a few elements were produced, like hydrogen and helium. The heavier elements (like carbon, oxygen, iron) have been produced in the stars. Marcus Chown wrote a great book on this topic, titled "The Magic Furnace". So over time, the fundamental particles become part of more and more advanced molecules. These molecules constantly change because of cosmic radiation. Earth is bombarded by cosmic radiation every day - as you read this sentence, trillions of neutrinos from the Sun pass through the spaces in your body without even touching you!
Over time the particles decay and eventually become energy again. If the Universe does not stop expanding, the energy will be so dispersed that it will, for all practical purposes, disappear.
For more on this, read my review of The Five Ages of the Universe, a great albeit speculative book.