If I remember correctly, NaCl atoms are packed pretty closely together in crystallized form. They seem to be only looking at large crystalline structures, which do not have evidence of disruption.
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.
"What they found may have implications for the origin of complex life.
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."
> 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.
That was my understanding as well. The idea being that there is a lot of volume in the first few meters of ocean surface area churn. It's not hard to imagine that does better in surface area than (even a lot) of plants.
Not forgetting the fact that it seems like it would be substantially easier for a faintly mobile fluid filled bag(s) of DNA to survive and reproduce in an aqueous environment!
If my college biology understanding of evolution is at all accurate, a functional oxygen pathway would provide an edge in the ecosystem (read: high rates of population growth) and may have, in fact, been a catalyst for multi-cellular growth.
The most recent discussion I heard seemed to be the theory that a functional oxygen pathway enabled multicellular life by providing enough surplus energy to power the entire organism in an evolutionarily efficient manner. (Add in the fact that by that point the planet was also teeming with single celled biomass to consume)
What I find so interesting is why is the oxygen on Earth 21% why not 5%.
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.
Would be interesting to hear a discussion about how this impacts the timeline of the Great Oxygenation Event [1], and where there's conflict with what's proposed. If there's somebody a little more familiar with the geological evidence it would be great to know a little more.
Here's what worries me about this type of extrapolation:
"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.
Not a bad question, and they attempt to address it in the paper with their multi-sample calibration:
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.
I don't know who downvotes this because parent does have a point: there are extensive chemical transfers involved in the creation of minerals and crystals, it's not obvious at all that the atmospheric bubbles where chemically isolated from the encasing crystal afaict
I didn't down vote the above comment, but when the paper is available, complaints should usually be about something specific in the paper, not hand wavy concerns about methodology.
I don't even need to read the article or paper to see that the commenter didn't think through what he was saying. He specifically uses a quote that says "different ages - including the modern day" were used, but then suggests that the researches only used one "recent" sample.
I suppose that's the kind of question Prof Blamey might have considered when he was a first year student back around 1975. He probably knows what he's doing by now though.
Oh great an appeal to authority that'll set it right. /s
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.
IMO an appeal to authority is a perfectly reasonable response to an assumption of incompetence.
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).
I read what mikeash is saying as a sort of extension of one of the guiding principles behind the moderation of HN: default to assuming that others have good intentions. The extension being, let's not immediately assume that these researchers have made a basic error, especially on the basis of a brief article.
You can have a healthy skepticism while still showing professional respect.
Yes, exactly. I'm not saying they're right, I just find it crazy to come up with an obvious objection and present it as "this is wrong" rather than "how did they overcome this?"
The reason that an appeal to authority is a fallacy is that the deliverer of an argument is irrelevant to the validity of that argument.
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).
That's fair. To the point, this person [0] doesn't seem to be having any issues with downvotes, even though the comment raises the same basic issue -- the reliability of the crystalline entrapment.
In fairness, that comment was phrased as "I don't understand this, I'd like to know more" rather than "These guys are clearly making a mistake".
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.
When you say that this understanding "seems to assume" this, you're pretty strongly implying that there aren't any good reasons to think it's true. Maybe you just meant to say that it's based on that idea, rather than assuming it?
I reserve the right to question the competency of anyone at any time concerning any topic, whether they are considered an expert or not. I'd rather that have that attitude than having "he knows what he's doing so he must be right" way of thinking.
And I'd rather have "I know way less about this stuff than they do, so until I see evidence otherwise I'll assume problems I see are due to my lack of understanding, not theirs" than either of those.
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.
At what point would you start asking questions then? Because questioning anyone about their work is us asking for them to show us how they are right. That is questioning their competency on the topic at hand instead of just accepting what they say at face value.
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?
Start asking questions right away. Just do it from a perspective of "I don't understand this" rather than "you didn't think of this."
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.
Well, you said you're going to question their competency, which is different.
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.
No, it's just that I feel that asking someone questions about their work has an element of questioning their competency. I encounter it all the time with my work and it doesn't bother me. I expect it. I see it as a way for both sides to learn.
You could simply ask how you make sure that no oxygen could enter, leave or react with the crystal. That's a simple and obvious question that nobody will fault you for asking.
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.
In "Random Guy from the Internet -vs- Professor on the Subject", you can't really blame anyone for giving the scientists the benefit of the doubt. The paper is open access, btw, maybe they addressed your question or provided a citation? You can read it at http://geology.gsapubs.org/content/early/2016/07/08/G37937.1...
I'm surprised (but not really) at the amount of resistance to to questioning these results, when at the very least you have to agree with the following:
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.
Your comment didn't read like an ode on the scientific method to me. Instead, I saw a cheap dismissal of the research in it. And the article even addresses your concerns:
> "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.
We can never reach absolute certainty. Improving existing approximations of the truth is the best we can hope to achieve. If you only accept absolute unquestionable truth then I recommend you have a look at the history of science. Lots of what was the state of research in the past is now known not to have been entirely correct, sometimes even outright false. But we need to make incremental progress towards the goal of understanding the world, even if we sometimes get it wrong. That is the moly thing that opens the path for new discoveries. Following your reasoning, these surpassed results are worthless and were no good even when they were found. But in the grand scheme of things they are what enabled later researchers to uncover better and more accurate results.
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.
Being right for the wrong reasons doesn't win you any points.
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.
You have no idea if you're right or if this conclusion is actually correct. If the conclusion is wrong, you have no idea if it's wrong because of the problem you posted, or if it's wrong because of something completely different.
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.
First, you need to go read the actual paper, rather than some journalistic paraphrase, and them come back.
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.
But how do we know that those crystals were formed during "normal" conditions? ie. why is it valid to interpolate the air structure for the whole "ancient Earth"? I'm just curious how is it done?
Dissolved oxygen in water decrease when temperature and salts increase. Sea water have two hydrogen by each oxygen, and contains also atoms of sodium, chloride, magnesium, sulphur, among other. Therefore, saltwater will not have a 21% of oxygen normally, and a 10% of oxygen in salt should not be translated as: "wow, in that time there was only the half of the current oxygen in the air, how animals could live?". Aquatic organisms are adapted to the normal rate of between 6 and 12 mg of dissolved oxygen for each L of saltwater.
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 to measure it but wasn't there already proof of larger amounts of oxygen in the past and the earliest life (one of from what we know) was a bacteria that produced the first oxygen in abundance and explains the higher levels and is indeed thought why, or least factor in why early mammals were larger and during the dinosaur days (sorry but easier to call it that for many) the oxygen levels were higher than today by far.
Well this is talking about 200,000 years before the explosive emergence of life on Earth. Before this discovery it was thought that there was much less oxygen at that time (the Neoproterozoic era according to the article). And that life had to wait until more oxygen came along before it could happen. Now they are basically saying the oldest fossils we have found are probably not the oldest we could find. Time to look for older signs of life!
There were lots of anaerobic bacteria, however. And photosynthetic ones produced the oxygen. What oxygen enabled was evolution of complex multicellular life.
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.