My boomerang I built will only turn just a bit back towards me, but that's it, but why? Is it my design, I incorporated the recommended dimensions from the website I used, such as an 107 degree concave, an 80 mm chord length near the center, and a 60mm chord length near the tips.Or is it what I i...
I just noticed a new "diamond" moderator. Welcome Jaydles!
Would you mind telling us a bit about yourself? It doesn't appear that you have been active on physics.SE before; we'd like to know a bit more about you than is shown in your profile. How did you become a moderator on this site?
A couple of questions here on meta.physics (namely this one and this one that I could find) already asked for how to use tags on Phys.SE. The answers to these questions seemed to imply that it is not possible to automatically number the equations, like what happens in standard Latex for example w...
@DavidZ or @dmckee or @ManishEarth can someone help me? A user posted a question about Bogolyubov transformation. I checked the problem and sent him a comment that it seems that there is a mistake. The user checked again in the book and says that he copied correctly from the book. I would like to reply to him but his post disappeared absolutely. It's not migrated, neither closed or put on hold. How can I find him? Please help me.
@Danu and @infinitesimal , thank you. Oh, I tried to help, I am so sorry. His name was greg, but there are so many greg. I checked all these greg, the question appears at none of them. Anyway, thank you.
@infinitesimal @Sofia @Danu @alarge @KyleKanos @Jiminion Based on the size of a black hole, how far away do you have to be in order for a black hole's gravity to start pulling you in?
Far enough away, you can treat a black hole is a massive object, so formally you could say (in the absence of all other matter), you're being attracted always.
However, once you cross the event horizon, you will not be able to cross back from it and will (eventually) get pulled into the black hole
Lots of really basic SR questions this week. Happens several times a year, so I'm going to refer to it as "Relative September".
Any one have any ideas how we might short-circuit new users who are coming to ask yet another version of the five or so questions that every one asks and get them to read an authoritative link instead?
All we need now is the "moving .51c relative something already moving .51c"; "push a very long pole"; and a twin paradox question and we'll have the full set.
@KyleKanos and @dmckee I am glad that you are here. I'd appreciate advice. There is a question, purely mathematical. I am going to vote for closing, but there is some technique that I would much prefer to leave it open, for the benefit of the users. I don't know to post things on Internet, otherwise I would do it, and just leave a comment to the user before the question is closed.
@KyleKanos I don't need points there. I only need the possibility to refer to some tricks that I'd like to put there, for referring to them here whenever needed.
@KyleKanos yes, thank you, I know. The issue is that sometimes I see people working hard on calculi, or being unable to solve, while simple tricks would solve the issue. Well, I'll try to register there.
@KyleKanos just a minute, when you migrate a question which is mathematics, where to do you migrate it? I see two sites, one is "mathematics", the other is "mathematica"? To which one do you migrate questions?
@KyleKanos aha! But I see that it doesn't require registration. A question please, you know that it does require. So, isn't a mistake, I mean this is the site where to you migrate question with mathematical character?
Mathematica is the program developed by the greatest scientist ever, Stephen Wolfram. (Don't believe me? Just ask Stephen Wolfram....) [It's actually a NEW BRANCH of Science.] <Massive tongue in cheek here>
"Wolfram's conclusion is that the universe is digital in its nature...." Really? So the universe is built using a base-10 number system? How convenient!!
@Jiminion sarcasm? You mean from me? No, no! I told you what I know. Who is the greatest scientist recognized by the whole world? Einstein! This is what I know. But, I won't be able to have a talk with you on this, I have some family troubles to settle.
I don't mean to be bashing Stephen Wolfram. But it makes me wonder if arrogance (useful to repel the fools so you don't suffer them) at some point becomes counterproductive. Like the Laffer curve there is some optimal arrogance btwn 0 and 100% that would make SW optimally productive.
@Sofia No, my initial comment about SW being the greatest scientist was me being sarcastic.
@KyleKanos could it be that you are on Internet? I see a very nice question, and I think that it is a bit engineering. But it would be regrettable to migrate or close it. There is no option to vote in advance against closing or migrating it. How bad!
Assuming no one can travel faster than say, 0.5C, isn't there a pretty limited range of places that could ever reach us? (Due to Hubble expansion). So the risk of invasion is limited unless they have warp capabilities.
@Danu what you mean by self-centered? A time will come when we will be interested to populate other places besides the Earth. (if no atomic war will be until then)
Maybe one can wiggle out of most non-physical solutions like Gödels closed time-like curves, but why should we accept such space-times in the first place?
Even in quantum-mechanics, there are super-selection rules. Even so these not allowed quantum systems don't feel as unphysical than some general solutions of GR, but they might be just as unphysical, if one only had the right intuition.
But I just write this, because quantum mechanics now feels more physical than GR to me...
And even so dark matter and dark energy don't contradict GR, they are also not something comparable to the great predictive power of quantum mechanics and the standard model.
@Sofia Sry. It's a term from Star Trek (a TV show). They would talk about travelling FTL with term Warp Factor 2, Warp Factor 3. (It presumably refers to the warping of space to get from one place to another faster than light). In the book 'Dune', they talk about 'folding' space.
I guess it's hard to explain. One could describe it as follows: "Moving through spacetime in a non-standard fashion that allows one to go from one place to a very distantly removed one almost instantaneously, while respecting the laws of general relativity"
This is only possible in some very specific solutions to Einstein's equations
If a brane folded back onto itself, then possibly you could go from one part to another without having to travel all the distance between them. (If you believe in the brane stuff, I guess).
@HDE226868 Could it be logical to think whether from stars close to our Sun, civilizations similar to ours but more advanced, could send those flying saucers to collect information?
@HDE226868 it's hard to believe that those objects are only atmospheric phenomena. There are too many reports of such phenomena, and all of them report that the object, after standing for a while in the atmosphere, flies away at a terrible velocity.
@HDE226868 it inspires the thought that these objects come, take pictures, and fly away after completing their missions.
BTW @alarge the link you sent me wasn't really helpful.. you see, there is two observables in one system.. therefore, we need to use tensor product and so forth, but that link is too simplistic and doesn't introduce those stuff..
@HDE226868 my last comment wasn't a question, just a thought. My small nephew told me some time ago that she saw a flying saucer, and she was terribly interested in the topic.
@Sofia UFOs are not really alien ships.. people see things and interpret what they are incorrectly...usually "UFOs" are balloons, drones, etc. not aliens
I just noticed a new "diamond" moderator. Welcome Jaydles!
Would you mind telling us a bit about yourself? It doesn't appear that you have been active on physics.SE before; we'd like to know a bit more about you than is shown in your profile. How did you become a moderator on this site?
