Billion-year-old air reveals surprise about oxygen on ancient Earth
cbc.ca
cbc.ca
A chemistry professor once told my class that due to the rate of diffusion, that we had just learned, the test of the "old air" would be wrong.
I don't know chemistry well. My question is if the salt completely stopped all diffusion over the last billion years. Maybe somebody here can answer.
Of course, they also said they used the same method with modern salt, and the O2 levels were lower than atmosphere by 9.2% for one of those samples.
It seems fairly legit but it would be great if they could test salt from the same period but from a different mine.
The air, which has been preserved, undisturbed, in tiny pockets in the crystals for about 815 million years, appears to contain 10.9 per cent oxygen — just half the amount in the atmosphere today.
But it's about five times more than scientists expected for that time period, which is about 200 million years before the first known multicellular fossils."
This is a weird angle for the article to pursue. We have a monocellular fossil record that dates back 4.1 billion years, and I don't think anyone is proposing that we assumed up to this point oxygen levels took off because of multicellular life. A high oxygen level is probably one of many prerequisites for complex life, but that doesn't mean the genetic machinery was available as soon as it reached a certain concentration.
I might just be imagining that factoid though.
The lifeforms that oxygenated the atmosphere were rather more primitive than trees. Generally cyanobacteria. Technically, yes, plants.
I can understand why not 90% since it's so reactive but 21% seems so high. Even more so now in modern times with seven billion people and billions of other animals plus industrialization I'd expect atmospheric oxygen to be falling rapidly.
We humans are pretty lucky to be able to breath, thank you ocean algae! Honorable mention to trees, good job.
A human uses about 0.84 kilograms O2 per day. There is about 5e18 kg O2 in the atmosphere.
Excluding all other sources of O2 consumption and replenishment, it would take about 500000 years for the current population of humans to "use up" all the current O2.
"The researchers also compared salt samples from other halite deposits of different ages — including the modern day — when oxygen concentrations were known and found their results matched up with known concentrations. That gave them confidence in their result, they said."
OK, so you take a recent sample and it matches up. Great.
But this seems to assume there is some sort of barrier at the atomic level that "traps" the atmosphere at the time the salt crystals were formed and that time and pressure will never have an impact on what components of the atmosphere remain in the salt crystal.
It is highly unlikely that oxygen could have been injected into halite inclusions without evidence of morphochemical disruption, and we must conclude that Cretaceous atmospheric oxygen was most likely higher than present-day levels. The tests performed on the modern, Messinian, and Cretaceous halites support halite’s robustness as an atmospheric oxygen archive.
http://geology.gsapubs.org/content/early/2016/07/08/G37937.1...
The paper discusses the type of crystal they studied and how they formed (and cites further work on those topics).
If what you say is correct then there's most likely a paper that's been widely cited and remains unfalsified that shows there aren't any changes in the ratios of gases in these crystal interstices (or the changes are well known and quantifiable). Such a citation would be a suitable rebuff.
It's tiresome to always see comments assuming that such-and-such science is flawed because a mainstream news article doesn't spell out every single detail.
If it were phrased more neutrally, like "I'm amazed that this stuff can be contained without any contamination for hundreds of millions of years, how do they know that it works that way?" I wouldn't have a problem with it. Start assuming that you've missed something, not the scientist who does this for a living. Maybe the scientist has missed something, they're certainly not perfect, but to me it's ridiculous and counterproductive to be "worried" about the results of years of professional work based on one popular article and five minutes of thought (if that).
You can have a healthy skepticism while still showing professional respect.
If an expert makes an argument that is invalid (i.e. doesn't logically demonstrate the conclusion), we may still hold some faith in the argument, because perhaps the expert made some omissions or mistakes in presenting the argument. But we still ought to recognize that the conclusion has not actually been demonstrated as the logical implication of the premises.
Obviously the language I'm using in the previous paragraphs applies to formal logic. As with all formal fallacies, they are not so easy to discuss with precision when we're talking about informal arguments (like scientific papers and studies).
Relevant part from the comment you linked: "My question is if the salt completely stopped all diffusion over the last billion years. Maybe somebody here can answer."
If you don't understand something and say so, you sound far less arrogant and condescending.
My message is that you, the reader, should consider that this "obvious problem" is a substantial one and that the entire premise of this measurement is based on a particular understanding of the ageing process of air in a salt crystal over time.
I don't have a problem with skepticism or questioning competency. I do have a problem with the attitude that a few minutes of thought and an obvious objection is sufficient to start questioning competency.
I won't apologize for requesting someone to show me how they are right about a topic I know little or nothing about because the simple fact that I know little or nothing of the topic doesn't let me understand they know what they are talking about. Lots of experts get things wrong all the time. If we just accept the results of experts without questioning then how do we know they are wrong? Wait for another expert to take notice and bother to care to check?
I am not saying that experts are infallible or that we should consider them as such. I'm just saying that when you've spent five minutes coming up with a problem in a scientific paper that has years of work behind it, your quest for information should reflect the likely possibility that the wrongness is on your end.
Edit: note that there is no question in the original post I object to. I'm definitely not criticizing questions. If anything, I'm criticizing not asking questions.
mikeash has already answered that. He's fine with questions.
You're arguing against a straw man of blind obedience to authority figures that (as far as I can see) nobody has made.
It should be fun!
EDIT: actually, I'm exaggerating here. I don't get them every day literally, but I encounter them quite a bit.
Asking question straight-up (for information, assuming competency) is different from asking hostile questions. You get better results if you can manage to avoid triggering defensiveness.
There is a huge difference between that simple question and assuming they didn't make sure of that and the research has to be flawed or the researchers incompetent because of it.
If there isn't a good answer to a simple genuine question, you can still go that step further and start questioning competency.
This method AND the prior method can't BOTH be right.
That means at least one of them is WRONG. Had I questioned the prior method's claims and techniques yesterday I would have had the same response from the same people.
Science (to some) is still about questioning everything. It scares me how many people on HN have lost sight of that.
> "They're using an indirect method," he said. "We're using a direct measurement and we're measuring from a mineral that has actually trapped atmosphere. It's a huge step forward, really."
The previous number was an estimate derived from other, indirect findings. In other words, "given what we know, 2.x% O₂ seems most likely and plausible" versus "we dug up some salt with air from the time trapped in it, and measured 10.9% O₂". So they did exactly what you're referring to: questioning previous results and giving evidence to support their claims. And yet you question their results without providing any evidence. Your criticism boils down to "well this isn't what we used to believe". How else could science progress if not by surpassing what was previously known or accepted as the best answer to date?
Science is about questioning stuff, coming up with new ideas and backing them up with evidence, not about making dismissive comments on the internet.
Wrong. See, this is the type of thing I'm talking about. There is only one way to make a direct measurement and it involves a time machine.
I'm not saying that to be pedantic. That is only way to prove this technique and/or others like it are absolutely correct. While I applaud this man's effort and his approach, I'm skeptical of the results given the difficulty of problem at hand and methodology used.
Let's make sure to call it what it is. Another method of estimation.
Oh and if you weren't so focused on absolute truth, you might have noticed that natural sciences concern themselves with models of reality, because nature is freakishly complex and if one doesn't settle for some approximation of reality. Otherwise one wouldn't get anywhere trying to solve the simplest problem.
Models in natural since need to be cross verified by multiple findings using various methodologies. Each model and method adding to the evidence of our understanding and the probability that we got it right.
In this case, the new methodology refutes the prior one. So, instead of adding the evidence that current models are right, this creates a new hypothesis, for which currently only this one model seems to agree with.
So, I get what you're saying about there will never be an absolute truth, but I hope you get what I'm saying about how this one finding alone means little in terms of being conclusive.
If you had questioned the prior method's claims and techniques yesterday based on this same sort of "what about this obvious problem?" then you would have had the same response and deservedly so.
If I declare that the Earth is round because I drew a circle on a piece of paper, I can't wave away criticism of my method just because the result is correct.
All extrapolations of this type are difficult to prove out. They are based on a lot of assumptions. Those assumptions may not all be right and some critical components might be missing. The model being used to compute slippage over time might be overfit to the parameters.
If I declared the world to be flat then proved it by going to a truly flat field to provide parameters to a mathematical model that showed I was correct, it wouldn't make me correct no matter how convincing my credentials or my paper.
Virtually all science is wrong in some respect. You can get a great batting average by just saying "no, wrong" to everything you see. That doesn't make it useful, nor does it make your reasons for saying "wrong" correct.
After that, you can ask a specific question about what was done and what was not done. Generally with an eye toward a useful mechanism that might explain things.
Then, you need to come up with a prediction based upon that question that can be tested.
At that point, you are contributing to the discussion.
"Could invisible sky fairies could have contaminated the results?" is not a useful question. "Is it possible that nuclear decay could have transmuted something into oxygen trapped in NaCl? (answer, no, for various reasons)" is at least in the vein of a useful question.
On the other side, if saltwater becoming brine releases gradually its oxygen, maybe the oxygen in an unknow mass X of water, could be trapped and slowly accumulate in a bubble under tons of silt.
Nice article to matchup with this http://www.scientificamerican.com/article/timeline-of-photos...