Mars rocks have been found in Antarctica. Because if a big enough rock slams into Mars hard enough, little bits of Mars fly into space and eventually land on Earth. There are probably little bits of Earth on Mars, too.
I think it’s all isotope ratios. How do we know if water came from comets or formed terrestrially? Isotope ratios. How do we know that CO2 in the atmosphere is from burning fossil fuels? Isotope ratios. How do we know that meteorites are from Mars? Isotope ratios. How do we know how old some rocks are? Isotope ratios. How do we know the Moon is made of Earth? Isotope ratios. Why do some of my shirts need to be washed on normal and others on gentle? Isotope ratios.
I’m pretty sure I’m right on some of those things, anyway.
Of course that leads to the next question: why does comet water and terrestrial water have different isotope ratios? I don’t know, but space hydrologists probably do know.
The bottom line being, the scientists who study this stuff might know, even if you don’t. And, as said by others, the unsatisfying answer might be: first step, get a PhD in the relevant field.
To be fair, sometimes there is scientific storytelling. To me, this is when explanations are given that don’t contradict the evidence, but for which there isn’t any specific support. When done well, these are told in a way where they are testable, but data is not available. “The relationship between these two variables can be explained by…and therefore studies should be conducted to ascertain…”
Often the boogieman “popular media” or groups with an agenda will latch onto the story, causing people with some knowledge to say, “how can they know?” and the answer is, the actual scientists don’t know, but would like to find out.
And very often the real answer to that “How do they know?” is “We don’t, for certain, but so far nothing has falsified the working hypothesis. So, tentatively (and everything in science is only tentative) it’s the best answer that fits the available data.”
There are also lots (for extremely limited meanings of “lots”) of known meteorites from the moon and from a large differentiated body that is almost certainly the asteroid 4 Vesta. There are meteorites that are speculated to be from Mercury but there isn’t enough data from Mercury to be certain of that origin. Meteorites from Venus would probably be a tricky accomplishment.
The real answer to “how do they know” lies between the covers of thousands of scientific journals. Most people outside academia never encounter journals. Maybe they see in a newspaper article that the news first appeared in something called Science. All that does is give the impression that was satirized in the comedy troupe Duck’s Breath Mystery Theater’s radio show called Ask Dr. Science.
The show’s motto is “He knows more than you do.” The sketch always concludes with the disclaimer that he is “not a real doctor,” although Dr. Science insists he has “a Master’s Degree… in science!”
Scientists, of course, do not get Master’s Degrees in Science. They get them and their Ph.D.s in increasingly small and specialized topics. Then they publish many, many articles in incredibly small, specialized journals, mostly using very advanced math and very few English words. Journals are often so specialized that scientists in closely allied fields can’t understand them fully. Put together, though, these tens of thousands of articles in thousands of journals provide detailed insight into how and when and where (and why for non philosophic versions of why).
Telling non-scientists that they need to read tens of thousands of articles that no one mind could cope with is hardly a scheme for success. Telling non-scientists that they just need to have faith in the process fails far more often than it used to. Yet that’s the truth. Scientists do know many, many, many small things about the universe. Their bigger pictures do put these together into explanations that appear to work well. Experiment and theory are circular, building on one another constantly (and tearing down sometimes when needed). Who says this? Tens of thousands of working scientists in every country in every form of government of every faith or lack of it. No other form of human endeavor has such a wide and deep agreement factor.
The details keep getting argued about, true. These arguments take place in public and are monitored by every other scientist in the world with knowledge about the subject. Reputations are made by properly refuting or one-upping another scientist’s finding. This is the exact opposite of a conspiracy to invent scenarios for the unwashed plebes.
Moreover, science in its many forms gets used daily in many, many, many, many applications that touch every human being on the planet directly or indirectly. The equations of spherical geometry are used to fly planes and build bridges because if a flat earth were assumed people would die. Die dead deaths. Science keeps us aliver than any alternative. That alone is good reason to believe in it.
Indeed, but there is a twist to that: We, that is: the scientists, don’t just come up with theories. We start with data. We see this and that, measure, weigh, whatever. This leads us to theories. Theories are “just” mental methods to explain what we see, because they make us feel we “understand” better with the framework of a theory.
Then, after the theory, we make controlled observations, i.e. experiments, to check if the theories hold true. Of course they don’t, because we could not think of everything that plays a role at the first attempt. So we have to refine the theory, adjust it, make it more complicated, mostly. Or we discover that it is flat out wrong. Then we have to start anew from scratch. And again. And again.
But everything starts with data. First primary, elemental observations. Like: The sun rises everyday in the east. Theory: The sun revolves around the earth every day on a charriot of fire. Easy, that explains it. That was Greek mythology: not really scientific, but it is a start. But what would that entail? What logical consequences would that have? How would that chariot of fire illuminate the other celestial bodies we see that are not stars, for instance the moon, venus, mars? So people make preciser observations of those, with the help of optical devices, for instance. And see: the chariot of fire does not work as an explanation. Galileo did that, among others. And the next explanation is proposed: the non stars (i.e. planets) actually revolve around the sun. In circular orbits, because circles are cool, natural, perfect in their form and easy to calculate. Copernicus showed that. Then come new observations, this is getting closer and closer to our modern understanding of the scientific method. This observations are experiments that disprove that the orbits are circular, because if they were, the planet that is today here would be there after some time, but it is somewhere different. Close, but not were we thought. Fine, so Kepler postulates that the orbits are actually elliptical. That works much better. And Newton realized that elliptical orbits are very closely explained with an inverse quadratic law for a force (whatever a force is and how it acts and propagates) that attracts masses to masses. And so on.
Same for what we know about atoms, matter, electricity, mechanics, you name it. It is all based on observations, experiments to gather more observational data, and discussions about the meaning within a theoretical framework of those data.
But all those steps were rooted in observations. There is no such thing as “pure theory” in science, or very seldom. In maths, yes, there may be: Gödel’s incompletedness theorem comes to mind, or Cantor’s ideas about infinite numbers. And in philosophy and theology too, but those are almost always wrong.
Yes, this is a very simplified version of this process. But I believe it is a close approximation to the process that leads us to believe, with good reason, that we know something about the world.
You can do things like spectral analysis extra terrestrial rock or compare the gene structure of two different creatures but I would class that as “observing” it is determining what they they are like now, anything that says what it was like in the past is theory and can not be tested.
You can not have an experiment where you have 100 big bangs and observe what happens in each case in a sample of solar systems to “observe” when and how water arrives at those planets that have do have water. In particular those that are most like earth (in terms of things like size distance from the sun and size of sun) .
Water is constantly being formed from the combustion of any hydrocarbon material. There is probably a calculation somewhere as to how much as been produced over time. And I think it includes decay which is a slow combustion.
Of course it can. You can replicate things like rock compositions today, run them through some melt and pressure tests, if they match what you predicted for the past, that confirms your hypothesis until a better theory and confirmation comes along.
Of course theories can be tested.
Good thing those absurdities aren’t the only kind of experiments that can confirm this theory.
Which is why I clearly stated that
watching YouTube videos isn’t necessarily a good way to get accurate information.
Maybe you missed those 2 words “isn’t necessarily”.
If a person such as the OP describes herself isn’t going to bother checking cites or background information on what she watches on Youtube videos, then yes, she is better off finding websites that clearly offer these.
The origin of terrestrial water is a curious choice since it’s an area where there remains a lot of uncertainty. Sure, some qualitative aspects are pinned down, but significant uncertainties remain about how much water comes from where and when, and even how much water there even is on earth locked up in the crust and mantle.
Since whatever you heard was probably from some general audience article, keep in mind the tongue-in-cheek Knoll’s Law: “Everything you read in the newspapers is absolutely true except for the rare story of which you happen to have firsthand knowledge.”
More generally, as has been said, just ask in Factual Questions about any topic and a deep discussion can happen, although one must be willing to go on a long walk in many cases or be willing to accept brevity as a fair substitute if not.
Science is like one giant logic puzzle, with a battle against uncertainty being a core element of the puzzle. But this single puzzle has been under study by innumerable scientists for donkey’s years, so when a new insight comes to light (or even to understand an older insight), a good amount of background knowledge is needed to fully understand what’s being claimed and why. In the case of water on earth specifically, a very wide range of topical areas play a direct part.
Even as a working scientist, when I want to deeply understand some new result from a field of study just “a few blocks over” from my own field, I will need to either spend time digging through references to understand more background on the methods or past results or I will need to be satisfied to take certain building blocks as acceptable (leaning on intuition about what pieces are worthy of further digging or instead are quite plausible at face value, especially given that the work will have been vetted through some layers of review.) For those rare claims that seemingly upend some well-established piece of knowledge, deeper digging is always in the cards.
One thing I will never do is read the popular science article and call it a day. If it’s an interesting claim, I go immediately to the original scientific paper and see what is actually being claimed. Nine times out of ten it is something much less “big” or “certain” than the pop-sci article suggests. Not everyone is in a position to do this second layer of investigation, but Knoll’s Law remains of import all the same.
I did not know it was called Knoll’s Law, but I would like to point out that from my personal experience it holds true in non scientific contexts too.
Fortunately for cosmologists and astrophysicists, all observations outside the solar system are from the past. The nearest star system is four light years away, so observations reveal information about how the system was four years ago. The JWST telescope reveals conditions as they were up to 13.6 billion years ago. Therefore we can from Earth potentially speak about any time in between.
You can and that will tell you what happens to that rock composition when put under the melt and pressure tests you subjected it to, if doesn’t tell you what happened millions of years ago.
The point of what I am saying is for things like how water got to be on earth science does not have all the answers.
For example theories of the Missoula Floods have changes significantly over the last 100 years and who is to say our understanding will not change in the next 100 years.
There is still lots questions about evolution, in the 1950s natural selection or mutation was “settled” on the side of natural selection but there are many questions which it fails to answers such as “Why are their gaps in the fossil record of how things changed? Does this Implying evolution takes place in spurts rather than the concensus view of gradual change”, let alone specifics such as how the eye was formed (this requires the appearance of a light sensitive cells, lenses and iris to form when there is little benefit of having 1 and for them to mesh together to form a single organ) Do we need a new theory of evolution? | Evolution | The Guardian (warning long article)
Indeed, it refers to media accounts in general. Knoll was a journalist.
I didn’t know it was called Knoll’s Law, either, but I agree that it holds true in most contexts. Named after the American journalist Erwin Knoll, it’s formally “Knoll’s Law of Media Accuracy” and was intended in general non-scientific contexts. However, IMHO it’s even more true in scientific and technical contexts, because here journalists not only have the opportunity to get basic facts wrong, they have the additional opportunity to misunderstand and distort the science, too!
There are several “science” correspondents on CNN, for instance, who drive me to distraction with their terrible, ill-informed science reporting. I suppose if they knew anything they’d be doing science, not writing about it. To be fair, there are some really good science journalists, just not many. Bob McDonald, for example, who mainly does CBC Radio, is a good example of a journalist and non-scientist who takes pride in understanding science issues and serving his audience well.
I work with science writers from time to time, and on the whole they are keen to get the science facts absolutely correct, are willing to spend time learning what they need, and are skillful in crafting language that distills the ideas for a general audience without becoming “wrong”.
Do these folks work for the big news networks? No, because those corporate beasts are just interested in eyeballs and ad dollars. The writers that “know anything” about science (as you say) are either working closer to the science (e.g., university or laboratory communications offices) or for more honest popular science outfits. That’s why they seem rare: the loudest and largest news sources are providing much more noise than signal.
(This isn’t to detract from your general take but rather just a note that there are many good science journalists, but their work is just not on the nightly news.)
I don’t think so. In scientific matters it is easier to debunk wrong claims, because science is understandable and explainable: you can check an asseveration. But I work as an interpreter, so that I occasionally attend meetings about which the press sometimes reports. That kind of meetings usually consist of a part that is held behind closed doors and a public statement or a press conference afterwards. What the press writes about the part behind closed doors is wrong in a complicated way and for all kind of reasons. That is normal, people try to influence the discourse, even with flat out lies. But even the public part I witness is often relayed wrongly. Makes me wonder every time about the truth content of the other news I read about the events of the same kind where I was not present.
Which makes me understand a bit the attitude of the OP. But it is a category mistake: the doubt about a scientific assertion and the doubt about a political declaration are two different levels of doubt. But the feeling can be related, I think I have experienced that.
Actually, in political contexts the wrong reporting is the norm. In political contexts – and everything is political in the public discourse – it is the realitity that is distorted. For a reason, with an agenda.
Not always successfully, of course. But we all try to do it or to stop others from doing it.
\hijack.