Strange

It isn't meant to hurt. I don't understand why it would. If someone hates broccoli, would it hurt them to say they are a "broccoli hater"? If someone hates some ethnic group, why would they care if that is pointed out? Wouldn't they be quietly pleased that their beliefs have been acknowledged? And is "white supremacist" an insult? It seems to be used pretty freely, even by respectable media. And I thought it was a label people used to identify themselves and their beliefs. But "white supremacist" == "racist". By definition. Would it be rational if someone said "I am a white supremacist but don't you dare call me a racist" Ahh. Bless. 🙂

"MCNP is an export-controlled code" https://laws.lanl.gov/vhosts/mcnp.lanl.gov/mcnp_how_to_get_to_mcnp.shtml I'm not sure who in the US is going to be knocking on the door of a university in Iran to complain about export violations! But it sounds like it was a collaborative project

Nope. Anyone who has someone come round and do some plumbing (or, less frequently, some physics) can call that person a plumber. You just have to see them engaged in the act of plumbing. They can then be called a plumber. There are certainly edge cases. It is not always, if you'll excuse the phrase, back and white. I would be suspicious of someone's motives who voted against something like this if the RCMP is systemically racist (and I have no idea if they are or not). However, that is not the sort of possibly implied racism we are discussing here. So both your analogy and your example fail to hit the spot, I'm afraid.

Tick. A useful blend of tap and click (Or tack? clap?)

! Moderator Note Your claims sound implausible (to say the least). As this information is so well known, it should not be difficult for you to confirm them.

But whatever reference you use, the speed of the solar system is less than the speed of light (because nothing is moving faster than light relative to us). Because the speed of light is not relative to the observer (all observers will see light move at the same speed, regardless of their relative motion) it turns out that the maximum relative speed is the speed of light. 🤣

I don't think you mean trade secret. (A "trade secret" has a very specific definition in IP law.) For one thing, the source code is available (with restrictions) so it is not secret. For another, it is produced by a government agency and so (I believe) it has to be made publicly available. But the simple answer to your question is, basically, smuggling. It is a restricted export item (effectively classified as an armament). But software is notoriously easy to copy and hide so trying to prevent the illegal export is almost impossible. Maybe a student at a university took a copy. Or a visiting academic. Or the cleaner. Who knows. (Maybe the CIA or the NSA knows.) Or maybe there was a time when Iran was not on the list of banned states. (But I doubt that. I'm fairly sure it was back in the 90s when I had to deal with these sorts of export restrictions.)

One problem is that you seem to be using a "common sense" concept of location when you talk about where the black hole used to be. That location (in formal terms) is not the same as the the location when the black hole was there. They are described by different coordinates. Also, (spatial) locations are not the issue. It is an event horizon. So you need to consider events. No event inside the black hole is accessible even if the black hole evaporates. The black hole does. The interior of the black hole doesn't.

I think there are a few different things going on here. One is that if you plant the sends from, say, a cherry you bought in the shop then that is probably going to grow 'true"; i.e. produce a plant that is similar to the parent, with similar fruit. The exception could be if the bees cross-pollinated it with a wild-cherry or some other compatible variant. Then you might get something rather different. But some fruit just don't work that way. (I have no idea why.) So if you plant seeds from a delicious variety of apple, you might get something completely different. (I mean, it will still be an apple, but possibly nothing like the cultivar you just ate.) So, successful apple varieties are propagated by cloning (e.g. from cuttings). And then grafting a particular variety or species onto a different rootstock can change the characteristics. Mainly, I think, in terms of how hardy they are, or how large they grow. I don't think it will significantly change the fruit. Except as side effect of the plants ability to thrive. (I know see that CharonY has posted. I might regret this relatively uninformed post!)

That is a pretty enormous straw man you have constructed there. Possibly the biggest I have ever seen. Do you need a hand with it? 🙂 You are (I think) Canadian/Italian. I have grey hair. He is a racist. It is just a statement of fact. I'm not sure why it is considered offensive or problematic to say that someone who plainly and openly espouses racist opinions is a racist. (Bizarrely, the BBC's code of conduct seems to say that it is OK to say that the British PM or US President "deliberately said something untrue" or "made a racist statement" but it is not OK to call them a liar or a racist. That makes zero sense. That is like insisting that I must be described as "a man who has been known to have some hairs that are of the greyish persuasion".) I'm sure you are right that it is not going to change their opinions. But I'm not sure what is. Certainly not rational argument. Maybe accidentally falling in love with someone of the race they despise? But outside of rom-coms, I don't see much hope for people like that.

! Moderator Note As this is a science forum, you need to provide some references to support these claims.

Of course it is important. How can anyone answer your nonsensical questions if we don't understand the reasons behind them. You have been told the ionisation energy of argon. What more do you need to know? This happens to all your threads: you ask some fairly meaningless questions, we try to explain some basic physics related to what you ask, you respond by posting even more nonsense. As this thread is apparently just a joke, I will request it is closed.

You can't make stars from argon.

This is the sort of question that might be better for StackOverflow or similar, where you might find more people who have actually used the tool. https://stackoverflow.com/questions/tagged/wireshark

I'm not sure what this "island" is. The spacetime inside the black hole is not in your past light cone. And never will be, even if the black hole evaporates. It is not points that are not in your past light cone, it is events. The difference is crucial. It would take someone with far more knowledge than me (e.g. Markus or Mordred) to say how the spatial coordinates inside the black hole relate to those after it has evaporated. You seem to think of it like a bubble shrinking and exposing the space that was inside. But it is much more complicated than that because of the space-time curvature. For example, inside the event horizon, the radial space dimension becomes the time dimension. So it isn't clear how, or even if, you can map the spatial coordinates inside the event horizon to those where the the event horizon used to be. For example, in Gullstrand-Painleve coordinates (which are one of the coordinate systems which are continuous over the event horizon) the spatial coordinates are effectively flowing towards the centre of the black hole. This means that as the black hole evaporates, the spatial coordinates that used to exist inside the black hole, no longer exist and have been replaced by other spatial coordinates "flowing in" from outside. So you cannot relate a "location" inside the event horizon with one in the space after the black hole has evaporated. (Which back relates to the point about a bubble earlier: in that case you can apply the same global, cartesian coordinates to describe the situation before and afterwards. You can't do that here. When you talk about a location where the black hole used to be, that isn't the same location as when the black hole was there.) As black holes, including the event horizon, are described by GR which requires a differentiable manifold that is obviously not the case. The point at which the manifold is no longer differentiable is at the centre of the black hole. That is why it is called a singularity: GR no longer applies there.

If it were to be confirmed, yes. But we are still a long way from that. I posted a couple of links to this as well: https://www.scienceforums.net/topic/122381-interesting-signal-at-dark-matter-detector/

https://www.forbes.com/sites/startswithabang/2020/06/17/is-it-dark-matter-mystery-signal-goes-bump-in-worlds-most-sensitive-detector/ Another article here: https://www.quantamagazine.org/dark-matter-experiment-finds-unexplained-signal-20200617/ And a Twitter thread from one of the physicists involved:

A somewhat sceptical analysis of this here: https://www.forbes.com/sites/startswithabang/2020/06/16/36-alien-civilizations-in-the-milky-way-the-science-behind-a-ridiculous-headline/#4f582fe079c5

If there is no fusion what is the point? You are just pouring vast amounts of energy in to maintain a plasma. For what?

! Moderator Note It is one page of text. Post that here, not in a document.

! Moderator Note Moved. A simple reminder to all: this is the "Homework Help" forum, not the "Homework Answers" forum. We will not do your work for you, only point you in the right direction. Posts that do give the answers may be removed. So @sam2209, would you explain where you have got to in solving this problem and what has stopped your progress - hopefully members can then help you to overcome your difficulties yourself.

No it doesn't. It would only contradict it if something from that event could affect you. For example, if a photon were released at that time and space; you would never be able to detect it because it could never leave the the black hole. Even if the black hole evaporates. So when I said it was in your past, I did not mean it is in you past light cone. (I probably should not have said that, it is misleading and arguably wrong.) They are only incompatible with your understanding of what an event horizon means. In the case of an evaporating black hole, any photon that happens to inside the black hole before evaporation cannot escape before the black hole evaporates. It will reach the singularity and disappear before the collapsing event horizon could reach it and allow it to escape. Changes to the event horizon are limited to occur at the speed of light. A photon inside the event horizon is heading towards the singularity at the speed of light. So the event horizon can never "overtake" the photon and leave it outside the event horizon. However, more generally, there may be some truth to what you say. We don't yet know what effect adding quantum theory to GR will have on our understanding of the event horizon. Hawking did some work that suggested the event horizon may be less well defined, possibly porous (from my limited understanding of the work). There also things like the firewall paradox, that show we don't yet know the full story. But none of that is enough to assert "event horizons don't exist" when the evidence (including a photograph of the accused) implies they do.

Is this homework?

I don't fully understand the argument you are making. But I think the key point is that it is the inside of the black hole that is not causally connected to the outside. It is not the event horizon or even the (past) existence of the black hole. In the case of an evaporating black hole, any photon inside the black hole before evaporation will not escape before the black hole evaporates. It will reach the singularity and disappear before the collapsing event horizon could reach it and allow it to escape. (This assumes that black holes can evaporate completely, which is no clear but might be off topic.) It is not reaching those locations that is the issue (there are problems with defining what "reaching that location" means, but that doesn't matter for the moment. It is an event horizon not a location horizon. An "event" is position in 4D space-time coordinates. So by the time the event horizon evaporates, that "event" is no longer accessible (it is in your past). One you pass beyond the event horizon, then every direction towards the "outside" is in your past and every direction towards the singularity is your future. That is why there is no escape, and no causal communication outwards. Edit: I see md65536 made the same point more succinctly. If you are happy to use GR to explain the orbits of the stars around a compact massive body at Sagittarius A* then you can't refuse to use GR when it predicts an event horizon. Picking which bits of a theory you use because you don't like the results is just not rational. The "we don't know everything therefore we don't know anything" is weak at the best of times. It fails spectacularly when there is a lot of direct evidence for the existence of black holes.

As noted, this works in principle (just isn’t very effective in practice - although light sails may be). But I am curious why you think it would require space to have drag for it to work? Are you thinking that the light would need to push against something? But that is not how propulsion works - otherwise rockets would not work in space! It is enough that the light pushes against the spacecraft (as it leaves). Physics 🙂