Search found 196 matches

by drachefly
Thu Jul 10, 2014 1:52 am UTC
Forum: Science
Topic: FTL communication and time travel
Replies: 51
Views: 15360

Re: FTL communication and time travel

That's what I meant, but looking back I see I didn't emphasize the universality of this reference frame adequately. Thanks.
by drachefly
Mon Jul 07, 2014 9:14 pm UTC
Forum: Science
Topic: Toffo Talks about Trains
Replies: 128
Views: 19309

Re: Energy of transition in accelerating transportation

I'm guessing that light hitting the inside surface of the front of the train will in fact, donate some kinetic energy, as it does in the operation of a solar sail. Photons do not have mass, but they do carry momentum (the maths and physics of this is slighty above my pay grade)... Photons do have m...
by drachefly
Mon Jul 07, 2014 9:02 pm UTC
Forum: Science
Topic: FTL communication and time travel
Replies: 51
Views: 15360

Re: FTL communication and time travel

This looks like a pretty good resource, although it always makes my head ache when I try to get a handle on this one: http://www.theculture.org/rich/sharpblue/archives/000089.html I think the bottom line is that ansibles can work as long as they can only transmit between two points occupying the sa...
by drachefly
Mon Jul 07, 2014 12:54 pm UTC
Forum: Science
Topic: Is a "Slow-Motion" Wavefunction Collapse Possible?
Replies: 19
Views: 4267

Re: Is a "Slow-Motion" Wavefunction Collapse Possible?

Changing from constructive to destructive interference is limited by group velocity, and must be strictly less than c, and must have a probability flux proceed along some path between the endpoints. Collapse is not limited in this fashion. First time I hear about probability flux, but: Collapse mus...
by drachefly
Fri Jul 04, 2014 2:10 pm UTC
Forum: Science
Topic: Is a "Slow-Motion" Wavefunction Collapse Possible?
Replies: 19
Views: 4267

Re: Is a "Slow-Motion" Wavefunction Collapse Possible?

When some box containing a quantum wave is measured and found to be empty, then a wave is emitted into the box that cancels the wave that is in the box. That isn't necessarily how an absence detection would work. Do you mean this as an implementation detail or a central part of the interpretation? ...
by drachefly
Thu Jul 03, 2014 10:33 am UTC
Forum: Science
Topic: Is a "Slow-Motion" Wavefunction Collapse Possible?
Replies: 19
Views: 4267

Re: Is a "Slow-Motion" Wavefunction Collapse Possible?

In Copenhagen, we collapse the wavefunction so it doesn't include the excluded region, and the part we don't observe just vanishes. ... and the wavefunctions in the other cups react in some way, don't they? Spookily. EPR-entanglement of one particle in two cup arrays: When probability of finding th...
by drachefly
Wed Jul 02, 2014 7:57 pm UTC
Forum: Science
Topic: Is a "Slow-Motion" Wavefunction Collapse Possible?
Replies: 19
Views: 4267

Re: Is a "Slow-Motion" Wavefunction Collapse Possible?

I don't know, the OP's problem seemed to mostly be contained in the word "arbitrary" at the end. I.e. the apparent ability to confine into an arbitrarily small region for any given well. He has clarified his question to be about that, but his only use of the notion of doing this an arbitr...
by drachefly
Fri Jun 27, 2014 1:29 pm UTC
Forum: Science
Topic: Is a "Slow-Motion" Wavefunction Collapse Possible?
Replies: 19
Views: 4267

Re: Is a "Slow-Motion" Wavefunction Collapse Possible?

That only works until you confine the particle to a single well, from then on you run into the same problems as before. But by that point you've answered the question - can you gradually collapse a wavefunction? At no point did the OP ask if you can break the HUP or anything like that (you can't), ...
by drachefly
Thu Jun 26, 2014 6:20 pm UTC
Forum: Science
Topic: Is a "Slow-Motion" Wavefunction Collapse Possible?
Replies: 19
Views: 4267

Re: Is a "Slow-Motion" Wavefunction Collapse Possible?

As this is a quantum system we're talking about, you can't actually quite measure it continuously. In the gaps between measurements, the wavefunction will try to spread out. The more you confine it, the faster it will spread out. This is true, but you can provoke the same question without this dodg...
by drachefly
Mon Jun 16, 2014 4:54 pm UTC
Forum: Individual XKCD Comic Threads
Topic: 1379: "4.5 Degrees"
Replies: 879
Views: 155346

Re: 1379: "4.5 Degrees"

Dyno wrote:
gmalivuk wrote:"Is evolution really happening?" - perfectly acceptable questioning of science
"No, it's not." - science denial


So what you are saying is that the only acceptable answer to the question is in the affirmative?


Since it occurs that evolution actually is really happening, yes.
by drachefly
Fri Jun 13, 2014 12:18 pm UTC
Forum: Individual XKCD Comic Threads
Topic: 1379: "4.5 Degrees"
Replies: 879
Views: 155346

Re: 1379: "4.5 Degrees"

The wide WIDE fan of climate predictions isn't only due to inherent uncertainty from the models themselves. These models were also run with a variety of different conditions, including differing human CO2 emission levels , something entirely outside of their scope. Imagine modeling a skydiver's fall...
by drachefly
Thu Jun 12, 2014 9:59 pm UTC
Forum: Individual XKCD Comic Threads
Topic: 1380: "Manual for Civilization"
Replies: 107
Views: 21323

Re: 1380: "Manual for Civilization"

Principia Mathematica? Oh hell no. Modern intro physics textbooks would be way better. Unless you meant Bertrand Russell's Principia instead of Isaac Newton's, in which case, uh, oh-kay? We can dump that in there too I guess, but I can't see it as a high priority.
by drachefly
Mon Jun 09, 2014 10:42 am UTC
Forum: Individual XKCD Comic Threads
Topic: 1379: "4.5 Degrees"
Replies: 879
Views: 155346

Re: 1379: "4.5 Degrees"

Delta Temperature = d(Glacier) /dt
not
Delta Temperature = Delta Glacier
on the time scale of a century. Glacial accumulation and melt are far from instantaneous.
by drachefly
Fri Mar 14, 2014 1:08 pm UTC
Forum: Individual XKCD Comic Threads
Topic: 1342: "Ancient Stars"
Replies: 76
Views: 18114

Re: 1342: "Ancient Stars"

Taking the 1400 systems within 50 LY figure and extrapolating up to 1000 LY, that gives 8000 times as many systems, or about 10 000 000 stars. So the million brightest (by apparent magnitude) stars in the sky are probably mostly within 1000 LY Does not follow. Red dwarfs are so much commoner and di...
by drachefly
Fri Jan 24, 2014 2:02 pm UTC
Forum: Individual XKCD Comic Threads
Topic: 1321: "Cold"
Replies: 517
Views: 94381

Re: 1321: "Cold"

P.S. Fahrenheit is incredibly more useful than Celsius for measuring weather. 0 degrees: fucking cold. 100 degrees: fucking hot. "It's in the 20s" = bundle up. "It's in the 70s" = it's pleasant. You can give a ten degree range of temperature and people know what that means and w...
by drachefly
Fri Jan 17, 2014 1:14 pm UTC
Forum: Individual XKCD Comic Threads
Topic: 1318: "Actually"
Replies: 76
Views: 16685

Re: 1318: "Actually"

Actually, I want to make a literally/figuratively joke. but I literally just can't come up with anything. You read Basic Instructions, don't you? I do wonder though - if something looks like a sphere but it's in a part of space curved by its own gravity, what would it look like in a perfectly flat ...
by drachefly
Fri Nov 15, 2013 12:30 pm UTC
Forum: Individual XKCD Comic Threads
Topic: 1291: "Shoot for the Moon"
Replies: 67
Views: 17232

Re: 1291: "Shoot for the Moon"

If you miss, you'll have picked up 25 points. Make absolutely sure you get that last heart.
by drachefly
Mon Oct 28, 2013 2:14 pm UTC
Forum: Individual XKCD Comic Threads
Topic: 1283: "Headlines"
Replies: 58
Views: 19133

Re: 1283: "Headlines"

Eebster the Great wrote:1968 - Assassinations of Nguyễn Văn Lém, Dr. Martin Luther King Jr., and President of the United States Robert Francis Kennedy


RFK was never president of the USA.
by drachefly
Wed Oct 09, 2013 1:14 pm UTC
Forum: Individual XKCD Comic Threads
Topic: 1275: "int(pi)"
Replies: 95
Views: 29486

Re: 1275: "int(pi)"

orthogon wrote:This reminded me of the techniques used on the ZX81 and ZX Spectrum...


I can't quite decide whether that makes this better or worse.
by drachefly
Wed Jun 26, 2013 1:19 pm UTC
Forum: Individual XKCD Comic Threads
Topic: 1230: "Polar/Cartesian"
Replies: 36
Views: 16901

Re: 1230: "Polar/Cartesian"

The alt text is false. A circle does not describe such a motion unless the axes do not extend past the circle (what, did two ants suddenly materialize on your screen and then disappear later?). You can however say 'plot of the X and Y positions occupied by the ants on my screen'.
by drachefly
Fri Jun 14, 2013 1:00 pm UTC
Forum: Individual XKCD Comic Threads
Topic: 1225: "Ice Sheets"
Replies: 68
Views: 13553

Re: 1225: "Ice Sheets"

jgh wrote:All four pictures imply all four locations are the same height above datum sea level.


No, they don't.
by drachefly
Fri May 31, 2013 11:36 am UTC
Forum: Individual XKCD Comic Threads
Topic: 1219: "Reports"
Replies: 30
Views: 7415

Re: 1219: "Reports"

It is a quantity. You can rescale it if it ends up funnier. In this case, though, it just maintains the meaning of the scaled-up version, so I'm not sure that helps.
by drachefly
Sat Apr 20, 2013 3:07 pm UTC
Forum: Individual XKCD Comic Threads
Topic: 1201: "Integration by parts"
Replies: 81
Views: 26524

Re: 1201: "Integration by parts"

Integration by parts is a lot easier if you're a physicist: \int{dx f'(x) g(x)} = -\int{dx f(x) g'(x)} Well, assuming the value along the boundary is zero (e.g. you're integrating an interaction cross-section), yes. It still makes me cringe to see that done w...
by drachefly
Fri Apr 19, 2013 2:06 pm UTC
Forum: Individual XKCD Comic Threads
Topic: 1201: "Integration by parts"
Replies: 81
Views: 26524

Re: 1201: "Integration by parts"

Integration by parts is a lot easier if you're a physicist: \int{dx f'(x) g(x)} = -\int{dx f(x) g'(x)} Well, assuming the value along the boundary is zero (e.g. you're integrating an interaction cross-section), yes. It still makes me cringe to see that done w...
by drachefly
Fri Apr 12, 2013 10:48 am UTC
Forum: Individual XKCD Comic Threads
Topic: 1198: "Geologist"
Replies: 44
Views: 11744

Re: 1198: "Geologist"

SO, for those of you who are feeling lost, I'm surprised no one's explained yet - sometimes, geologists set up listening equipment along the ground, then shoot the earth with a gun to create a time-localized sound wave. It is the ping in underground sonar. The joke relies on your already being aware...
by drachefly
Wed Mar 20, 2013 8:37 am UTC
Forum: Individual XKCD Comic Threads
Topic: 1188: "Bonding"
Replies: 108
Views: 26537

Re: 1188: "Bonding"

Man, I loved this. I'm up coding and took a break to read xkcd. Wonderful. I wrote the program up for the hell of it. Aside from the obvious boilerplate ( like wrap in class{ } ), the only change I needed was that 'throw Ball' has to be 'throw new Ball()'. This is sort of funny in and of itself, si...
by drachefly
Thu Feb 28, 2013 1:59 pm UTC
Forum: Individual XKCD Comic Threads
Topic: 1179: "ISO 8601"
Replies: 379
Views: 102459

Re: 1179: "ISO 8601"

Today is clearly 2013-chaos-58. Nice try, but it would be 847-chaos-58. You are both wrong. Today is Pungenday, the 58th day of Chaos in the YOLD 3179 according to the Discordian calendar, which I would assume would be written 3179-1-58 if you would follow the guidelines in ISO 8601. Unfortunately ...
by drachefly
Wed Feb 27, 2013 4:38 pm UTC
Forum: Individual XKCD Comic Threads
Topic: 1179: "ISO 8601"
Replies: 379
Views: 102459

Re: 1179: "ISO 8601"

Today is clearly 2013-chaos-58.
by drachefly
Mon Apr 30, 2012 1:42 pm UTC
Forum: Individual XKCD Comic Threads
Topic: 1047: "Approximations"
Replies: 159
Views: 71000

Re: 1047: "Approximations"

houseofadams wrote:For all the chemists out there, Avagadro's Constant is about 25!/26 to 1 part in 106.


I prefer (4!)! It's not as accurate, but much more compact.
by drachefly
Fri Dec 02, 2011 4:09 pm UTC
Forum: Individual XKCD Comic Threads
Topic: 0985: "Percentage Points"
Replies: 85
Views: 25682

Re: 0985: "Percentage Points"

Senator Grayton called for repeal of the 10th amendment.

When Nate Silver's model predicted Senator Grayton had a 10^-150 chance of winning, he replaced it as it was obviously too lenient.
by drachefly
Fri Oct 21, 2011 7:38 pm UTC
Forum: Individual XKCD Comic Threads
Topic: 0967: Prairie
Replies: 117
Views: 29863

Re: 0967: Prairie

Ooooooh. I'd always wondered what a "graser" was. Now I know. I heard Kansas was trying to weaponise their remaining bison, though, into a sort of counter-grazer. I suspect that this involves careful interbreeding with dairy cows, in an attempt to produce a Bise-Holstein condensate. As an...
by drachefly
Fri Oct 21, 2011 2:41 pm UTC
Forum: Individual XKCD Comic Threads
Topic: 0967: Prairie
Replies: 117
Views: 29863

Re: 0967: Prairie

I recently read, and now cannot find, a rather amusing bit of fiction about an alternate universe where the Everett (many-worlds) interpretation became dominant before the Copenhagen (waveform-collapse) interpretation did, and the latter is now (in said alternate universe) considered a crazy crackp...
by drachefly
Fri Sep 09, 2011 1:55 pm UTC
Forum: Individual XKCD Comic Threads
Topic: 0949: "File Transfer"
Replies: 194
Views: 86120

Re: 0949: "File Transfer"

AIM direct connect is my usual method. It's especially simple since I normally get the file requests via aim! We had this problem a lot in the lab - you were not allowed to stick USB devices in the microscope computers because of viruses. The microscope computers were also on a totally firewalled st...
by drachefly
Mon Aug 29, 2011 7:44 pm UTC
Forum: Individual XKCD Comic Threads
Topic: 0944: "Hurricane Names"
Replies: 101
Views: 27815

Re: 0944: "Hurricane Names"

Well, if there's a hurricane at every point on Earth, then everyone's in the eyes of the local set of hurricanes, so it's actually pretty good weather.
by drachefly
Fri Jul 01, 2011 2:06 pm UTC
Forum: Language/Linguistics
Topic: Annoying words, and Words You Hate
Replies: 1994
Views: 494908

Re: Annoying words, and Words You Hate

The word Optics has also been used for hundreds of years to mean the study of light. You'd think that people would know that . :lol: I find the political usage no more offensive than calling optical devices 'optics'. Anyway... my latin teacher in high school hated the word 'breast'. She made us tran...
by drachefly
Wed Nov 11, 2009 3:40 pm UTC
Forum: Individual XKCD Comic Threads
Topic: 0661: "Two-Party System"
Replies: 102
Views: 16743

Re: "Two-Party System" Discussion

As for the problem with our system, it's the institutionalized plunder: a lot of politicians couldn't make it in the real world, so they live off the taxpayers(our current president, for example, has never held a real job I know of). So being an attorney and professor for 12 years is not a real job...

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