I just saw this thread: Parallel tangents and curves and there were discussions in it on whether or not it was appropriate to downvote an answer which was fully worked out for a questioner who seemed to do no more than post a homework question without thought/etc.
I'm new here and don't have a h...
@KyleKanos I think the greatest regret I had growing up in NJ was that anything remotely resembling gunpowder was banned. Everyone I knew in other states got to grow up with fireworks and rockets.
Hello void! Talk about a delayed response (to the chat 3 days ago), here I go...
@Danu said near the end of the last chat: "Really? You don't believe in things like Hawking radiation, etc?"
Yes, I most certainly do believe in Hawking radiation, though I think his last almost-paper puts some pretty weird twists on exactly how it works.
But why would you think Hawking radiation to be a long-range quantum effect anyway?
The whole point of Hawking's mass-temperature relationship is that the event horizon has to be very, very thin for the radiation event to take place.
Dirac's point was something else entirely, which I'll presume to summarize this absurdly oversimplified way: The more curved the space, the more compact the wave function.
So, what I was asserting is this: Entanglement in practice, as it plays out in real experiments using real classical events as the bookmarkers that make it detectable and subject to analysis, is a phenomenon of flat space.
Entanglement of course still exists in curved space, but the probability of decoherence versus the interval increases dramatically as the space becomes more highly curved.
Hi @Omen... I'm busy talking to the past here... :)
sheesh advertisers remind me of a rabies filled mongrel dog getting dementedly excited about rubbish - if an ad gets my attention, i refuse to buy the product they are slobbering about
Heh! Well, apart from sudden unexpected images of advertisers as rabid mongrel dogs (been there, thought that, especially when marketeers won't let me do obvious things like delete something just so they can plug their wares), I'm fine!
Hi @Danu, didn't really expect to see you, just didn't want to ignore your final point. (Or more likely I just wanted to yap more, this time to an empty stage... :)
Well, to be honest I think that classical is just an interestingly simplified limit of an underlying reality that is entirely quantum. So as long as you recognize classical as inherently an oversimplification of reality, I'm fine with mixing.
Sort of from the other direction: I've been tracking the extreme UV debate in semiconductor lithography for years, and the challenges there both in generating and handling the EUV are... interesting to say the least. The current mantra is "this really is the end of Moore's Law (of semiconductor density going up exponentially).
I have a different computer at home and at work (like most people). The one at work it's always open on, so that not a problem
It's the one at home. I'll try to keep the browser open to it, but power outages, updates, etc are terrible. All it takes is one busy Saturday or one weekend away from home and all those days are wasted
Sure, I also have one really close to getting populist
Well, six votes off. But all I need to do is get the question re-opened. It was closed as a duplicate (pretty close to being one too), but it differed in a key way that I only care about because it's so close to populist.
We all know that mostly stars are at the center of planetary systems, but is it possible that instead of star there was a rocky planet in the center with stars (and other planets and moons) orbiting it?
To be more concrete: Is it possible for a star to have the same mass and radius as e.g. the M...
This guy on twitch is going to stream for about 32 hours straight. He's in the middle of Final Fantasy 7 100% (runs it in about 15 hours, currently at 4.5 hour mark) and then will play Final Fantasy 8 100%
One of the problems with homework questions is that they often get an answer before the question can be closed. So the vile perpetrator gets the answer they want, and the subsequent downvotes don't hurt them because their rep is probably already just 1 and they may not be planning to come back an...
@Omen, yes, let's talk more later. Real stretch of physics, EUV for lithography, the method is more than a bit like sort of like surfing a very prickly wave to get max height. I think everyone's sort of given up on soft X-ray, though, so there are not many options left to keep those cell phones on their path to become smarter than their users... :)
@ACuriousMind, back on the Wed chat you said: "Why would you say such a thing? Entanglement is a direct consequence of the fact that the Cartesian product embeds into the tensor product, but that this embedding is not surjective, i.e. that there are states in the product space that do not come from a tuple of one-particle states."
I absolutely love that one! It is so precise and well-stated, and resolves the issue in such a firm and clear fashion.
Alas, because my day job these days is all about cognitive science and how to make computers really think like people, what I instead see when I read that is a very precise simulation program -- math truly being the ultimate form of programming if not executed too sloppily and informally in often very self-forgiving wetware -- whose links to external (experimental) reality have become a bit too subtle to recognize immediately from within the context of the program itself.
Things are not empty space. Our classical intuition fails at the quantum level.
Matter does not pass through other matter mainly due to the Pauli exclusion principle and due to the electromagnetic repulsion of the electrons. The closer you bring two atoms, i.e. the more the areas of non-zero exp...
The problem is what Konstantin Tsiolkovsky discovered 100 years ago: as speed increases, the mass required (in fuel) increases exponentially. This relation, specifically, is
$$
\Delta v=v_e\ln\left(\frac{m_i}{m_f}\right)
$$
where $v_e$ is the exhaust velocity, $m_i$ the initial mass and $m_f$ the...
The truth is we don't know. But when you think about it, how can we know? If we knew what technology would eventually come out of experiments like this, why would we not build that technology now?
Large expensive machines like the CERN super-collider help us to further understand that laws of na...
TL;DR: This answer arrives at roughly the same conclusion as Kyle Kanos', i.e. in addition to payload considerations, the difficulty lies in stuffing a small rocket with a mass of fuel exceeding to the mass of the rocket itself. This answer, however, is more rigorous in how the $\Delta v$ budget ...
@Jim, you got my +1 on that for the Faraday history and context remark. It is almost a rule of science history that anticipation of future impacts is insanely incorrect. I had never though of CERN quite that way; you made me rethink it a bit, hmm...
@TerryBollinger You can create a room, for example, by going to the chat profile of the user you want to talk with - there's a button "Start a room with this user" there. Or you go to chat.stackexchanged.com and click "Create a new room"
The electromagnetic spectrum covers a wide range of values:
(source)
What we see is visible light (just right of the middle of the page), which is a very small section of the spectrum. If the light source emits brightly in the infrared, our eyes will not be able to see it. As an example, consi...
Wait, make that 8 votes. The accepted answer needs 10 and currently has 7
Before my current AI-ish work (which is a lot more fun, and my last job was already hugely enjoyable), I worked with some top venture capitalists on future technology anticipation issues. Good VCs understand like no one else how incredibly hard estimation of future impacts are beyond, say, a year or two out.
My gaining the populist badge is already only dependent on the accepted answer in the question getting two (three if it needs 11) more votes here. (And yes, I've already voted for it myself, it's not a bad answer at all)
I noticed there are quite a few questions about the Populist badge. Some people are confused about its purpose, or upset about its existence, yet others simply wonder why they didn't get theirs.
I just want to change the Populist Badge's description from:
Highest scoring answer that outscore...
"not really allowed" makes me think of looks of stern disapproval. "forbidden" makes me think of being banned
So, yeah, you might argue that the two words mean the same on a purely logical level, but the implied degree of severity of the transgression is quite different (to me, at least)
Nice talking to everyone, must get going. Final thought for the day: What if both math and physics are ultimately just rules that approximate limits that don't actually exist? You know, you can postulate point particles, but not see them "for real".
@TerryBollinger Of physics, I've always thought that way. But math is not approximate, it is the only discipline that actually has undoubtedly true and false statements.
I still feel that there is someway to express the difference between mathematical truth and other "ways of knowing", but need to work a bit harder to exclude the tautologies.
And yet, there is something to showing that two differently defined objects A and B are really the same that feels different from the trivial tautologies you may encounter anywhere else
You grab an equation and define RHS=LHS. Then you do the same things to both sides of the equation, maybe sub in another tautology, but essentially you define something then say "and if I do the same thing to each side, they still equal" <-- tautology. But it's more understandable in the end
For example, you define the prime ideal in a ring without any reference to what will happen if you take the quotient. And what you find is that the quotient ring will not have zero divisors. Of course, the proof proceeds essentially by applying one tautology after the other.
so you define something, apply tautologies, and find an understandable result. In other words, you've used tautologies to change one tautology into another
I think I just now understand what the lecturer always meant when he said all we were doing was "unpacking the definitions". I always thought he only meant the style in which such proofs usually proceed, but it is also an apt statement about mathematics as such
I was reviewing First Posts just now, and I received the following message after my 20th vote:
Thank you for reviewing 20 First Posts today; come back in 8 hours to continue reviewing.
I see other users, with far lower reputation than me, voting up to 40 times per day.
Why is it I only hav...
So I did what I thought was my 40 reviews in the Close Vote Review Queue today. However, when I went to see about reviewing other queues, I noticed the message for the Close Votes said, "Thank you for reviewing 20 close votes today" instead of saying the normal 40. I went and counted my close vot...