Search found 23 matches

by DavidSh
Fri Dec 02, 2016 11:43 am UTC
Forum: Individual XKCD Comic Threads
Topic: 1767: "US State Names"
Replies: 59
Views: 8967

Re: 1767: "US State Names"

thunk wrote:So what about Portwine Rocky?

It goes an a separate page, along with Gum and the Northern Marinara Islands.
by DavidSh
Sat Nov 26, 2016 2:42 pm UTC
Forum: News & Articles
Topic: Where Aren't They Now (Obituaries)
Replies: 156
Views: 21270

Re: Where Aren't They Now (Obituaries)

Angua wrote:Zoboomafoo

But the lemur died two years ago.
by DavidSh
Sat Nov 12, 2016 3:51 pm UTC
Forum: Mathematics
Topic: Three externally tangent circles sharing a single point of tangency
Replies: 19
Views: 4064

Re: Three externally tangent circles sharing a single point of tangency

Not exactly answering the last question, but as long as you can say things like: (1) If B is on a shortest path from A to C, and B is also on a shortest path from A to D, then either C is on the shortest path from A to D, or D is on the shortest path from A to C; and (2) If the distance from A to B ...
by DavidSh
Fri Oct 28, 2016 4:50 pm UTC
Forum: Mathematics
Topic: Finding a Quadrilateral for N Points
Replies: 20
Views: 3860

Re: Finding a Quadrilateral for N Points

For N=5, I think it works if we divide into cases based on the number S of sides of the convex hull of the points. For S=5 you should always be able to remove one side and extend two adjacent sides to meet, forming a quadrilateral. A detailed argument could involve the total exterior angles of a pen...
by DavidSh
Fri Jul 29, 2016 3:53 pm UTC
Forum: Individual XKCD Comic Threads
Topic: 1713: "50 ccs"
Replies: 46
Views: 5837

Re: 1713: "50 ccs"

I was figuring carbon copies.
by DavidSh
Thu Jul 28, 2016 4:27 pm UTC
Forum: Movies and TV Shows
Topic: Wander Woman
Replies: 71
Views: 7970

Re: Wonder Woman

Lawrence of Arabia and The African Queen are both WWI movies, although that may not be obvious to everybody. And there must be a slew of WWI aviation movies, going as far back as the 1927 Wings.
by DavidSh
Wed Jul 27, 2016 1:23 pm UTC
Forum: Science
Topic: Is the Hyperloop remotely possible?
Replies: 62
Views: 6398

Re: Is the Hyperloop remotely possible?

If you don't want passenger fatalities in event of cabin pressure loss, and you don't want your passengers to be wearing pressure suits, and you want the tube to be at 1 millibar, you will need to be able to repressurize the tube swiftly and safely. Or at least the segment containing your vehicle. I...
by DavidSh
Tue Jul 26, 2016 2:50 pm UTC
Forum: Individual XKCD Comic Threads
Topic: 1708: "Dehydration"
Replies: 109
Views: 10941

Re: 1708: "Dehydration"

Do I figure things correctly that nilane looks a lot like molecular hydrogen, that is, H2?
by DavidSh
Fri Jul 22, 2016 11:54 pm UTC
Forum: Individual XKCD Comic Threads
Topic: 1710: "Walking Into Things"
Replies: 22
Views: 3753

Re: 1710: "Walking Into Things"

I do like the addition of "sky" to Randall's list: a useful reminder that one doesn't need devices (or collections of paper) to be distracted. I was certainly at risk a few days ago when we had a pretty impressive rai nb ow . Only a double rainbow, not any of the extreme forms mentioned i...
by DavidSh
Wed Jul 20, 2016 5:00 pm UTC
Forum: Individual XKCD Comic Threads
Topic: 1708: "Dehydration"
Replies: 109
Views: 10941

Re: 1708: "Dehydration"

HES wrote:What tree has a bowl?

A lava tree?

Spoiler:
lavatory, pronounced lavat'ry
by DavidSh
Mon Jul 18, 2016 4:17 am UTC
Forum: Science
Topic: How do satellites not crash into each other?
Replies: 94
Views: 11922

Re: How do satellites not crash into each other?

Right, but is that also the median in some sense? Let's see. The distance from the Earth on an elliptical orbit increases monotonically from perigee to apogee, and then decreases again. Half of the ellipse is on the Earth side of the minor axis, half on the other side, so the median points should b...
by DavidSh
Sat Jul 16, 2016 1:10 pm UTC
Forum: Science
Topic: How do satellites not crash into each other?
Replies: 94
Views: 11922

Re: How do satellites not crash into each other?

But all those orbits will pass through the same (comparatively small) volume occupied by geostationary satellites every day, right? An inclined, eccentric geosynchronous orbit has to pass through the same altitude as the geostationary satellites, but it doesn't have to do so anywhere near the equat...
by DavidSh
Wed Jul 13, 2016 8:13 pm UTC
Forum: Mathematics
Topic: Trisecting an angle
Replies: 63
Views: 8926

Re: Trisecting an angle

You mean that formula enumerates all constructible angles. A nonconstructible angle can be trisectable. For example 3*pi/7 is not constructible, but if we were presented with it, we could take its supplement 4*pi/7, and then bisect to get 2*pi/7, and then again to get pi/7.
by DavidSh
Wed Jul 13, 2016 7:37 pm UTC
Forum: Mathematics
Topic: Trisecting an angle
Replies: 63
Views: 8926

Re: Trisecting an angle

Maybe it is that if an angle x is constructable, but x/3 is not constructible, then x is not trisectable, and that this formula implies that there are many such constructable but not trisectable angles, for example whenever a is not a multiple of 3 and b1 is one in the given formula.
by DavidSh
Wed Jul 13, 2016 3:37 pm UTC
Forum: Science
Topic: How do satellites not crash into each other?
Replies: 94
Views: 11922

Re: How do satellites not crash into each other?

Geostationary orbits, written as GEO, should fit in the torus. Geosynchronous orbits, written as GSO, don't need to be equatorial, which is probably why the shell was proposed. But they don't need to be circular, either. Wikipedia mentions an Infrared Space Observatory at a geosynchronous orbit with...
by DavidSh
Mon Jun 20, 2016 12:48 pm UTC
Forum: Individual XKCD Comic Threads
Topic: 1696: "AI Research"
Replies: 12
Views: 3119

Re: 1696: "AI Research"

What's "updog"?



(Is it anything like updoc?)
by DavidSh
Thu Apr 14, 2016 4:29 pm UTC
Forum: The Help Desk
Topic: Diagnosing a Dead Dell Inspiron Touchpad
Replies: 9
Views: 5418

Re: Diagnosing a Dead Dell Inspiron Touchpad

Have you looked in the BIOS? Sometimes hardware can be enabled/disabled there.
by DavidSh
Wed Mar 16, 2016 3:34 pm UTC
Forum: Individual XKCD Comic Threads
Topic: 1655: "Doomsday Clock"
Replies: 63
Views: 9233

Re: 1655: "Doomsday Clock"

Before the advent of mechanical clocks, one option taken was to start the reckoning of hours at dawn, and divide the day into twelve hours, and the night also into twelve hours. An hour of day would equal an hour of night only at the equinoxes. It wasn't too hard to make sundials for these hours. Wi...
by DavidSh
Sat Mar 12, 2016 11:51 pm UTC
Forum: Mathematics
Topic: does every unit length curve lie inside the semicircle?
Replies: 12
Views: 2972

Re: does every unit length curve lie inside the semicircle?

If you use that argument, you can't add the lengths from the two sectors together. Consider the path e-f-g-h defined as follows. Let theta be some small positive angle. Let e = (sin(theta), cos(theta)), f = (-sin(theta),cos(theta)), g = (-sin(theta),0), h = (sin(theta),0). This has a point on each o...
by DavidSh
Sat Mar 12, 2016 7:43 pm UTC
Forum: Mathematics
Topic: does every unit length curve lie inside the semicircle?
Replies: 12
Views: 2972

Re: does every unit length curve lie inside the semicircle?

I think the reasoning for Cradarc 's Claim 3 is faulty. Yes, the curve has to connect P, Q, and R, but you haven't shown that it has to do it within the sector. I think the following approach works, extending measure 's idea. Let S be a curve of length x. Let a and b be the two endpoints of S. Let R...
by DavidSh
Tue Mar 01, 2016 8:46 pm UTC
Forum: General
Topic: ITT: We make xkcd slightly worse.
Replies: 8617
Views: 1392075

Re: ITT: We make xkcd slightly worse.

I think Sableagle is off by six orders of magnitude, converting 6 x 106 g to 4.6 x 1012 cm3 can't be right for something with a density only slightly greater than water.
by DavidSh
Fri Feb 26, 2016 6:23 pm UTC
Forum: Mathematics
Topic: looking for a probability theorem
Replies: 3
Views: 1572

Re: looking for a probability theorem

Let x_1 and x_2 be independent standard normal random variables (mean 0, variance 1). Let y_1 be another normal random variable, with mean -0.1, variance 1, and y_2 = y_1. Then for all i,k, P(x_i > k) > P(y_i > k). But X = x_1+x_2 is a normal random variable with mean 0, variance 2, while Y = y_1+y_...
by DavidSh
Thu Feb 25, 2016 6:12 pm UTC
Forum: Mathematics
Topic: looking for a probability theorem
Replies: 3
Views: 1572

Re: looking for a probability theorem

I don't know of a general theorem, but you do need to state that the individual x_i are independent, and the individual y_i are independent. Otherwise there are counterexamples.

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