[–] SaneGoatiSwear 0 points 2 points 2 points (+2|-0) ago
no one can fucking break this truth: rocks are fucking cool.
[–] darkhunt333 2 points 0 points 2 points (+2|-2) ago (edited ago)
What. All matter is the age of the universe. More accurate to say that this rock formed 4b years ago.
[–] TexasVet 0 points 1 point 1 point (+1|-0) ago
So you are saying that when a hydrogen atom gets fusioned into a helium atom inside a star that it is not considered new material? I get it that the quarks and gluons inside the protons are still the same particles, but surely there has to be somewhere that we draw the line when we say that all matter has existed since the big bang.
[–] oedipusaurus_rex 0 points 2 points 2 points (+2|-0) ago
OP's post was accurate even assuming that your complaint is valid.
Saying a rock is 4 billion years old is the same as saying that it formed 4 billion years ago.
A rock is a rock as long as it doesn't weather into aggregate (some of it will, but the aggregate part becomes sand/dirt), and as long as it doesn't melt. Gneiss is incredibly hard. It's basically tempered granite/schist.
[–] Myrv 0 points 1 point 1 point (+1|-0) ago
If we take the definition that matter is any particle with a non-zero rest mass then no, not all matter is the age of the universe. Matter can be created from photons (which given the non-zero rest mass condition are not matter). That said, what percentage of the the universe is new matter? I'm not sure but I guessing an infinitesimal small amount.
[–] [deleted] 1 point 0 points 1 point (+1|-1) ago
[–] Diamond_Deluge 0 points 2 points 2 points (+2|-0) ago
and how do we know its 4b years old?
[–] rwbj 0 points 4 points 4 points (+4|-0) ago
Some minerals are the product of the radioactive decay of other minerals. For instance in really old rocks it's probably going to be uranium turning into lead. In a mineral where you can safely assume that any trace of one element is a product of the radioactive decay of another element you can simply take a sample of it, measure the ratio of the elements and determine its age to a phenomenally high degree of accuracy. For uranium lead dating - the accuracy is higher than 99%. And it doesn't have to be anything like pure uranium. Various minerals contain trace amounts of radioactive elements. Zircon and Uranium for instance. But that trace is far more than enough for dating.
[–] DiscontentedMajority 0 points 12 points 12 points (+12|-0) ago
So for the entire time that life has exited on this planet with entire species rising and dying out, this thing has just sat there unchanging, being a rock.
Kind of cool.
[–] oedipusaurus_rex 0 points 4 points 4 points (+4|-0) ago
It's been changing. Gneiss is the most heavily metamorphosed rock. It's been buried deep enough and heated enough that it started flowing as a solid.
I'm jealous of OP. Gneiss is one of my favorite rocks, and I've been wanting a piece of the Acasta for a while now.