Isn't everything on the earth this old? The dirt in our backyard has been around for 4.4 billion years too. Or is it that this crystal hasn't been changed in that long?
We get new material thrown on us by space every day.
4.4 billion-year-old crystal is oldest confirmed piece of Earth
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Re: 4.4 billion-year-old crystal is oldest confirmed piece of Earth
#22Isn't everything on the earth this old? The dirt in our backyard has been around for 4.4 billion years too. Or is it that this crystal hasn't been changed in that long?
It solidified from the melt 4.4 billion years ago and hasn't remelted since.
Re: 4.4 billion-year-old crystal is oldest confirmed piece of Earth
#23In reference to the comments on this article, it really is quite a sad day when creationism is reduced to the single "6500 years" theory by those who beg for people to have a more comprehensive approach to the subject (Read: those on the "side of science".)
It's somewhat of a double-standard critique.
Can we all agree that there are a massive number of views on this, and the range between the views is quite a bit closer to continuous than absolute?
For instance, there are those of us creationists who believe in the story of creation as somewhat allegorical, a cultural way of explaining a complex series of events that originated from an intelligent design, possibly including a singularity, evolution, and whatever else might be considered the "anti-creationist" view.
Re: 4.4 billion-year-old crystal is oldest confirmed piece of Earth
#24Dumb question, would finding this just be pot luck, or did they have an idea of what they were looking at before they decided to subject it to the battery of tests?
Zircons are industrially useful as the primary ore for zirconium metal. If you keep it reasonably cool, like under red hot, it makes a great nuclear fuel rod protective cladding, assuming you refine out the hafnium which does little good in a fuel rod. Its also good for high temp ceramics, although too expensive for your fireplace, probably. If you get the metal red hot and dip it in water it does a fair impersonatio…
Actually, there's a lot of research on zircons because they're useful for other research.
There are cases ("heavy mineral sands") where zircon is used as an ore, but essentially none of the research on zircons has anything to do with this.
Zircons have a number of nice properties:
1) They contain trace amounts of uranium and (initially) no trace amounts of lead. This allows them to be dated through U/Pb dating, which is relatively precise and is still accurate over _very_ long timescales.
2) They can undergo heating to very high temperatures without allowing lead to escape from the crystal lattice, resulting in the date being "reset". This allows dating of the original zircon grain even after the rock hosting it has gone metamorphism.
3) They're very durable physically and chemically. For this reason, they show up in sedimentary rocks and preserve a record of what was being eroded to produce the sedimentary rocks in question. Even when the sedimentary rocks have been changed into metamorphic rocks, the zircons are often preserved.
4) They're not very rare. Zircon isn't "main" rock forming mineral, but it's a not-too-uncommon accessory mineral in many igneous rocks (mostly in felsic magmas). Because zircons are so durable, they show up in sedimentary and metamorphic rocks sourced from the original igneous rock.
All of these reasons is why you'll see a lot of dating of zircons. They're somewhat common, durable, easy to date, and yield accurate results.
This leads to a lot of uses that you might not think of at first.
For example, if you want to know where (geographically) a given sedimentary rock was sourced from (i.e. what was eroded to form it), the most accurate way is to use the "age spectra" of the zircons within it. You basically disaggregate the rock, sort out the zircons (they're very dense), and date every single grain of zircon (and sometimes many zones on every grain). You take the distribution of ages that you get and compare it to the know ages of large igneous bodies that were likely to be exposed and eroding at the time. By matching the distributions (i.e. mixing models, etc), you can get an estimate of where sediment was being sourced from.
This may sound esoteric, but it's very useful for things like oil exploration.
Re: 4.4 billion-year-old crystal is oldest confirmed piece of Earth
#25I just search a bit about Jack Hills. http://en.wikipedia.org/wiki/Jack_Hills The last modified was last December. The actual paper http://www.nature.com/ngeo/journal/vaop/ncurrent/full/ngeo20... was received last July but published on Fed 23, 2014. So it took a while to confirm and accept by the reviewers using the new technique. And Jack Hills seems to have caught a lot of attention as early as 2006. http://earthob…
The almost incomprehensible age of the Earth was famously summarized thus: “The reſult, therefore, of our preſent enquiry is, that we find no veſtige of a beginning,–no proſpect of an end.” — Theory of the Earth , James Hutton, 1788
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Re: 4.4 billion-year-old crystal is oldest confirmed piece of Earth
#26Isn't everything on the earth this old? The dirt in our backyard has been around for 4.4 billion years too. Or is it that this crystal hasn't been changed in that long?
breaking news: scientist claims to have found quarks which existed since the big bang.
Re: 4.4 billion-year-old crystal is oldest confirmed piece of Earth
#27The article does not seem to touch upon the possibility that the crystal was of extra-terrestrial origin.
The CNN article doesn't but it's a detrital zircon. It essentially has to be of terrestrial origin.
In other words, the zircon grain was found in what was at one point a sedimentary rock (now metamorphosed).
It formed in an igneous rock, was eroded, transported, deposited, lithified, buried, heated up, converted to a metamorphic rock, and then exhumed (actually all of this multiple times).
The zircon survived through all of that. (Which is why there's so much interest in making sure that the U/Pb ratio hasn't been altered by all of the rounds of deformation.)
However, extraterrestrial zircons have been found, and date back even farther.
This is the oldest piece of anything found that we know with reasonable certainty had to come from Earth.
Re: 4.4 billion-year-old crystal is oldest confirmed piece of Earth
#28Earlier quoted context omitted.
See my edit https://news.ycombinator.com/item?id=7299294 It has been found a long time ago on Jack Hills. But you are right, somehow, someone, a long time ago, walked on Jack Hills and found a crystal pretty old and started calling for interest.
It seems like it's a pretty small crystal (largest dimension is about the width of 4 human hairs - if I understand correctly). I'm curious as to how they actually found it...
Basically, they took chunks of what they already knew was a very old (~3.6 billion years old) rock, ground them up, separated out the zircon grains, and dated many (100's to 1000's) of individual zircon grains.
Re: 4.4 billion-year-old crystal is oldest confirmed piece of Earth
#29Isn't everything on the earth this old? The dirt in our backyard has been around for 4.4 billion years too. Or is it that this crystal hasn't been changed in that long?
It solidified from the melt 4.4 billion years ago and hasn't remelted since.
Or otherwise changed. Metamorphism doesn't involve melting.
Re: 4.4 billion-year-old crystal is oldest confirmed piece of Earth
#30Isn't everything on the earth this old? The dirt in our backyard has been around for 4.4 billion years too. Or is it that this crystal hasn't been changed in that long?
The dirt in your back yard hasn't been around for 4.4b years. Topsoil (decayed organic material and newly eroded rocks mostly) is usually pretty 'young' on geological timescales.