EDIT: changed encryption / decryption to signing / veryfing. Thanks for the corrections
Not an expert, those who know more please correct me.
From what I understand, what they post is not a PGP key, but the same content published in clear text signed with their private key. That way anyone can verify it with the author’s public key to check it has been generated with the private one (that only one person should have).
In a digital signature system, a sender can use a private key together with a message to create a signature. Anyone with the corresponding public key can verify whether the signature matches the message, but a forger who does not know the private key cannot find any message/signature pair that will pass verification with the public key
You’re not though. You said encryption occurs with the public key and decryption occurs with the private. That’s the opposite of what happens and what the quoted text says.
From the same source:
In a public-key encryption system, anyone with a public key can encrypt a message, yielding a ciphertext, but only those who know the corresponding private key can decrypt
Funny story: you didn’t change the wrong info. The sad part is that you’re spreading misinformation and unwilling to hear otherwise. This is more dangerous than helpful.
How is Crul wrong in anything other than the terminology? You sign a document with your private key - generating basically a hash of the document entangled with your key information. Anyone holding the public key can then verify that hash with the public key - that the document contents are intact and unchanged (from the hash), and generated by the person holding the private key (entangled key information)
To help you with the terminology, the names for the two operations are “signing” and “verifying”. That’s it.
What can you do with…
public keyprivate keyEncryption:encryptdecryptSignature:verifysign“Signing” is not at all the same as “encrypting” with the keys swapped. It is a separate specific sequence of mathematical operations you perform to combine two numbers (the private key and the message) to produce a third - the signature. Signing is not called “hashing”. A hash may be involved as part of the signature process, but it is not strictly necessary. It makes the “message” number smaller, but the algorithm can sign the full message without hashing it first, will just require computation for longer time. “Hash-verifying” isn’t a thing in this context, you made that name up, just use “verify”.
@dohpaz42 is mad because you messed up your terminology originally, and thought you were trying to say that you “encrypt” a message with the private key, which is totally backwards and wrong. He didn’t know that in your mind you thought you were talking about “signing” the message. Because honestly no one could have known that.
Look at the words you used, encryption is not the same as a signature, with a signature you can prove that a person with access to the private key wrote the message.
What you’re talking about in your message is encryption, and you have it the wrong way around, messages gets encrypted with the public key, and can only be read with the private key.
what they post is not a PGP key, but the same content published in clear text encrypted with their private key.
So they are not excrypting it, but do we agree that with signatures the author uses their private key + the clear message to generate “something”?
That way anyone can decrypt it with the author’s public key to check it has been encrypted with the private one (that only one person should have).
… so then anyone can use the author’s public key to check that “something” against the clear mesage to confirm the author’s identity?
If that’s the case, then my error is that the operation to generate the signature is not an encryption. So, may I ask… what is it? A special type of hash?
Thanks again. I will edit my original comment with the corrections once I understand it correctly.
So they are not excrypting it, but do we agree that with signatures the author uses their private key + the clear message to generate “something”?
Yeah sure, and I think the person you are arguing with is saying as much as well, it’s just that this is not encrypting it, when you encrypt something you obfuscate it in a way that is possible to deobfuscate, think the caesar cipher as a simple encryption, a hash/signature on the other hand is something that is generated from the clear text using your private key, which is not possible to decrypt, think very simplified that the person would just put the amount of each letter of the alphabet used in in the text, then add the length of the thread, and then multiplied by your private key. This way it’s proven that the holder of the private key is the person writing the text, and that the text hasn’t changed since the signature was generated.
… so then anyone can use the author’s public key to check that “something” against the clear mesage to confirm the author’s identity?
They can confirm that the person holding the private key (not identity, just that they have the key) and also that nobody changed it since they signed it (like the person adminning the forum or a moderator or something)
If that’s the case, then my error is that the operation to generate the signature is not an encryption. So, may I ask… what is it? A special type of hash?
For signing, it’s backwards - you encrypt with the private key, and then everyone else can decrypt with the public key. If that doesn’t work, they know that the message wasn’t signed by the private key paired with the public key they have, and therefore is invalid and is not to be trusted.
Signing proves authenticity (only the private key holder can sign), encryption provides privacy (only the private key holder can read)
You are behind the times on physics advancements buddy! Thanks to the recently discovered concept of relativistic time dilation, a 5000 light year trip at the speed of light will take literally 0 seconds of your lifespan. More practically, travelling in a starship that accelerates at 1G to the halfway point, turns around and decelerates to the destination, you can reach ridiculous distances within a single human lifetime:
shipboard timedistanceearth time1 year.263 LY1.05 Y2 years1.13 LY2.37 Y3 years2.82 LY4.35 Y4 years5.80 LY7.50 Y5 years10.9 LY12.7 Y10 years166 LY168 Y15 years2199 LY2201 Y20 years28.8 kLY28.8 kY25 years380 kLY380 kY50 years149 GLy149 GY100 years22.8 ZLy22.8 ZYThis is the formula to calculate the distance and time:
Nah, it’s actually super hard to maintain that acceleration. Not to mention all the fun of radiation, avoiding random obstacles and I assume the interstellar medium will become more dense to an accelerated observer.
We have idea on how to do it, but the engineering is far from it yet.
But what about the bit about not hitting anything whilst travelling at that speed? Even a speck of space dust would do massive damage at those speeds, right?
Oh yeah, it’s like flying the wrong way down the tube of the Large Hadron Collider. The tougher challenge though is like @MuThyme said maintaining 1G acceleration. Following the rocket equation, which is logarithmic, a 50 year multi-stage rocket will be bigger than the universe itself, even if you use some kind of nuclear propulsion 10000 times more efficient than our chemical rockets.
It’s kind of interesting to think of society like a videogame. Like we put our stats in oil and tech. But not much in biotech. The different style of civilisation advancement we are missing out on could be wild. But we can’t go back and play the game from the start again, so we’ll never see what that’s like.
Could be computers built off of nerves instead of wires. Computers that grow and multiply. I wonder if it could lead to a new understanding of the nature around us and how we all fit and play a role in the galaxy.
Maybe our desire to explore space is immature. There may be whole other types of space that we can’t see because we don’t have the tech.
We already have a lot of biotech and even some biocomputers. The main issue is that bio structures are fragile for our common use cases.
We also have self replicating machines, 3D printers for example. They are as much as alive as viruses as both require some input from the hosts for full replication cycle. It’s just that most people don’t think about 3D printers as alive and self replicating beings.
I’ve wondered why no one seems to be seriously putting effort into a genealogical ship. I’d be okay with being the first generation; I can’t possibly be the only one.
I guess there’s a place to be conserned that eventually a society might emerge within the genealogical ship that might cause them to loose their allegiance to the rest of humanity and go their seperate way. We saw this when european colonists came to the new world, they didn’t stay loyal to their home governements because of the difficulty to communicate across the ocean and the difficulty the home government would experience projecting their authority. Communication would be just as difficult with a genealogical ship and they might leave us forever, like we’ll never see any benefits from the genealogical ship.
And when you think about it that would make the most sense, because even when the final decendants of the genealogical ship find a new home world they’ll never come back to earth, their will be no travel. That world would become a different world for people who might not even consider themselves as human.
Conclusion: there’s no way to space travel unless a person can travel between worlds and still have enough of their lifespans ahead of themselves to do stuff to contribute to the wider galactic human soceity. Unless you want to live in the cowboy bebop world where the government is too weak to do anything so they have to hire bounty hunters to suppress criminal organizations competing governments, and you don’t know who has your better intrest and who’s going to protect you from who, be my guest, fracture human soceity before we’re truly ready to go out into space. It sure worked out well 100 years ago.
Built a machine that can repair itself. Send it to a nearby planet. Give it the ability to manufacture human embryos from our genetic code using only inorganic material. Make at least 2 ; let’s call them Adam and Eve. Keep this machine somewhere hidden and near them so to guide them and their offsprings for a few milleniums. Someday, if they are mature enough, tell them what happened.
Ha, thanks … not available freely online yet it is : en.m.wikipedia.org/wiki/James_S._A._Corey
James S. A. Corey (June 27, 2023). How It Unfolds. The Far Reaches. Vol. 1. Amazon. ASIN B0C4R4V6KN
Essentially the issue with this question is that the usual ways you’d answer that question all seem unsatisfactory, and the key to “answering” the question is to understand not magnetism, but why magnetism seems mysterious and all the answers seem unsatisfactory. Like, actually understanding magnetism in the sense of having read and understood the Feynman lectures definitely helps but that’s no good to a layperson.
And the answer to that as I understand it is that we always understand things in terms of other things we understand. When you see a process you don’t understand and learn how it’s caused by a process you do understand, you will feel satisfied, like you understand the process. If you don’t understand a very weird thing but you find a good analogy to something you are familiar with, you will feel like you understand the thing. The thing is, that’s all a feeling. Hopefully the feeling correlates to having an internal model of the thing that’s closer to its nature than your previous internal model, and to being able to make better predictions about the thing’s interactions, and it usually does because the brain is well-made, but it’s still two different things and you can have a feeling of understanding without an improved model or predictions and vice-versa.
And the issue with magnetism is that unlike most other physical things we run into in daily life, it’s a fundamental force that has macroscopic effects our brain didn’t really evolve to be familiar with, and the best explanations for those effects require going directly to the fundamental force, and the fundamental forces is something that’s very very unfamiliar to anyone who hasn’t done university-level physics. If I say “electromagnetism explains how solid objects don’t just go through each other” your response won’t be “but I don’t understand electromagnetism!”, it will be “wait, did we need an explanation for why solid objects don’t go through each other?”. We have an innate sense of how solid objects interact at our scales that feels like it requires no extra explanation. And any behavior of solid objects that does require extra explanation usually involves explanations just one level deeper in the causal chain, which is close enough to what we are familiar with that we can understand it. And as explanations go deeper the causal chain things become weirder and weirder, but as a student of physics you go gradually, get used to each step and when a step becomes familiar enough it helps you “understand” the next one. So at some point you may end up feeling like you understand electromagnetism as a fundamental force, but it took a lot of work to get there (and that feeling my be fairly fleeing and changeable).
We don’t have an innate sense of how magnetism works, and the actual explanations for how it works aren’t just one step removed from things we do have an innate sense of. It’s legitimately the case that the answer to “Why do magnets work like that” is “electromagnetism”, and if you don’t understand electromagnetism (which, as a layperson, you don’t) you’re screwed. There is no phenomenon or analogy that you have an innate sense of that’s enough like magnetism to provide understanding. You straight-up have to do university-level physics until the concepts in question start becoming familiar.
In a way your question is even worse, because look:
What does it mean for them to be composed of “lines of force”? What is the mechanism of that force? What is actually going on in a magnetic field that the space outside of a magnetic field lacks?
You’re kind of asking “what component parts is the fundamental force of magnetism made of and how to they interact to make it behave that way”, aren’t you. And the issue with this is that in the current standard model, there are no such component parts and causes; that’s what “fundamental” means. Now, we know physics isn’t a solved field so in practice there may indeed be extra explanatory steps out there to be found. But 1) they’ll be even weirder than the current thing you’re asking about is. They won’t help you understand, they’ll just confuse you further and seem like worse ad-hoc gobbledlygook than “fields” and “force” do. They’d only help you understand if you’d studied enough quantum physics for it to feel familiar and maybe almost-understood. And 2) at some point we kind of do have to hit an explanation that has no further explanation, something that’s not made of something else. Maybe it’s worth it for you to think about what that might be like. You’ll probably still feel the urge to ask “but what is that basic thing made of, what explains that explanation?” but you’ll have to accept that this question is that of a brain that evolved in an environment where everything is made of something else and things have nigh-infinite causal chains explaining that they are what they are. It just might not be very good at thinking about a situation where that’s not the case.
You might be interested in Tomasello’s “The Evolution of Agency” where he kind of addresses this very question. It really depends on how you define “making decisions” and “purely chemical reactions” doesn’t it - all life is chemical reactions, including when we make decisions, and it’s easy for us to apply decision-making language even to systems that are simple enough that we can see them as “purely chemical reactions”.
Tomasello defines the notion of “agents” as “feedback-control systems” that he distinguishes from pure stimulus-response systems. In his examples a nematode for example is “stimulus-response”; its behavior is very directly related to its immediate environment. If it runs into food it eats, otherwise it doesn’t, and there isn’t really a notion of it seeking out food when it’s hungry and not when it’s not. In contrast and “agent” is a feedback-control system with goals, a perceptual system that checks whether the goal is accomplished at any given time and a behavioral repertoire aimed at accomplishing the goal. In our lineage he sets the appearance of this agency around the evolution of vertebrates, and uses lizards as an example of the most basic level. (he doesn’t address other lineages other than to say that various levels of agency clearly evolved convergently a few times; so octopuses and social insects for example would also have these systems). So where a nematode has feeding behavior that’s triggered by running into food and other behaviors when food isn’t present, a lizard’s behavior depends not only on the immediate stimulus but on more abstract goals - in a given environment it might be currently hungry and looking for food, or sated and looking for shade or sun to rest or hide or thermoregulate, or looking to reproduce, etc, and its behavior will depend on and be directed towards accomplishing that goal.
It’s interesting that you say “thinks through and makes decisions” as if they’re on the same level but the book actually claims that human agency is actually the result of the evolution of several successive layers of feedback-control mechanisms that each allow more flexibility and responsiveness - so for example lizards have a feedback systems that adjusts behavior to achieve goals, and mammals have that and also a higher-level feedback system above that to adjust the goal-seeking behavior itself, mentally “playing out” different ways of accomplishing the goal in order to pick the best one. He describes four such levels for humans and it suggests a variety of ways we could define “think through and make decisions”, with different species qualifying or not depending on which we choose.
Roche limit is not really relevant here. That’s for orbiting bodies, like a satellite around a Jupiter-like planet whose orbit spirals inward due to tidal forces, and eventually crosses the Roche limit, whereby the moon disintegrates into a cloud of rocks that spreads out and forms a ring. Yes, the hyperbolic orbit of the collision trajectory here is a “type” of orbit, but really the video is about the collision itself. There is not enough time for the planet to meaningfully disintegrate under the neutron star’s gravity. “What’s that? The ground is kinda shaking. Could that be the tidal force from that neutron st-ACK!!!”.
In the video you can see the surface of the Earth bulge out towards the star under its gravity in the last second, but most of the kinetic energy of the explosion is imparted by direct physical interaction (i.e. electromagnetic) between the matter of the earth and the matter of the star, and in particular between the matter of the earth that has already been accelerated and the matter of the earth lying farther out.
Or at least it would be if the impactor really was just a chunk of iron with the density slider cranked up. This fluid simulator can’t imagine anything else of course, but you are right that it remains a question of whether a neutron star or a black hole could impart any kinetic energy onto the greater earth at all. Maybe it will just pass through and leave a circular hole, sweeping the material in front of it onto itself. The tunnel would immediately collapse, and the crust would be messed up from tidal sloshing, but maybe the ball of the earth itself will remain intact.
The hard x-rays I believe is a reference to thermal radiation of infalling matter. Just like a bullet that hits a wall while staying intact is hot to the touch because its kinetic energy got 100% converted into heat, or a meteoroid that hits the Moon creates a flash of light visible from Earth because for a second the cloud of collision debris is as hot as the filament of a lamp, the earth material impacting the surface of the star gets really hot. The impact velocity is at minimum the escape velocity of the star, which is thousands of km/s, which means the peak of thermal radiation is in the x-ray range.
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Say we imagine that the entire kinetic energy of bulk material from Earth (let’s say iron) impacting the star at 10000km/s is converted into thermal kinetic energy of individual iron atoms (atomic weight 56).
Never heard of this channel, but either of those two claims would be a huge advancement in multiple fields, so the fact that it’s not being reported or published anywhere else is a pretty big indication that his claims are bunk.
Like I said, I don’t know that for sure and I haven’t watched the videos, but I do keep current on most big advancements and I’ve heard nothing about either of these.
If you have pieces of metal that you can filter out. Metals in water are usually in ionic form, they are “chelated” by water in solutions. Unless some salt is created and precipitate, solved metals distribuite over the solution to avoid concentration gradients.
So the answer is: what metal are you talking about? What is its form and concentration? Most likely, if you couldn’t see depositions before boiling it, metal ions will likely stay in solution.
Boiling water is used to kill biological organisms. If you want to get “pure” water you need to distillate it or filter it with material that can capture ions
They stay in the water when you boil it, what you need is a good filter. Most filters you find in the shop don’t do much tbf, but I cannot suggest anything, I am not an expert on commercial products.
I don’t think that is how it works. You could buy an air still, but you really don’t want to drink distilled water unless you add some minerals to it like calcium or fluoride. Water in nature always has dissolved minerals in it, and your body is designed with the assumption that those minerals are there.
Where did you read this? Unfortunately it doesn’t work like that, unless you have concentration so high that a deposit is created. But, in that case, I wouldn’t absolutely drink that water
Having done some pilot scale experiments (60 l barrels), I’ve noticed that mixers are absolutely essential. At that scale, metals really do form notable concentration gradients.
solid metals are a separate phase, they create a deposit
salts over a certain concentration, part create a deposit, so they slowly create a powder at the bottom, part stay in solution as ions
Ionic metal in solutions spreads all over, as any concentration difference (gradient) generates an excess of free energy that the system naturally releases. You need to add external energy to maintain the gradient, such as a external electric potential gradient (an anode and a cathode)
Generally speaking, the experiments should follow the third category, but the system didn’t have enough time to reach equilibrium.
If you have infinite time at your disposal, you can rely on diffusion to do its job. Unfortunately, the project had a finite amount of time allocated to it, and 60 l barrels are large enough that significant concentration gradients can exist. Found that out the hard way.
LPT: Don’t start your experiments until all the mixers have arrived.
You don’t have to wait for it to cool. As water evaporates the dissolved solids in it reach a higher concentration. If the concentration becomes greater than the molecule’s solubility it will precipitate and fall to the bottom.
The rule of thumb among paleontologists says that fossilization takes about 10.000 years, so that would be your youngest age. It should be noted, however, that there are many different mechanisms that lead to fossilization. The Lloyds Bank coprolite, for example, is generally described as a fossilized Viking poop despite being ‘only’ about 1200 years old.
Continental drift or just the idea that the continents move. And it makes sense, looking at a map of the earth, you can clearly see that some landmasses look like they fit together like puzzle pieces. Combined with the fossil record with also supported this, it seems obvious to us now, the continents were once all one landmass. However, back then, the issue was Alfred Wegener, who came up with continental drift, didn’t have an adequate mechanism for how it worked. The question on everyone’s mind was, if the continents moved, HOW did they move? There wasn’t a good answer. It was suggested at one point that the continents maybe just plowed through the ocean crust. But that idea doesn’t work because the ocean crust is too rigid. So without any mechanism to get it to work, many geologists simply dismissed the idea. And to be fair to them, most of what Wegener claimed was indeed wrong.
Further advancements in geology and technology allowed for a better understanding of the earth. A key finding was paleomagnetic stripes on the ocean floor which proved that the earth’s crust, and the continents must be moving. This, combined with other evidence helped construct the modern theory of plate tectonics.
The youngest at any given time is probably a diatom, I’d think. They just exist in such great numbers, that’s all. They’re even harvested up and sold as diatomaceous earth.
Oldest bone is a 400 million year old fishbone, apparently. I had to google it.
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