# ­xkcd thread **URL:** \ **Category:** Cafe Society\ **Tags:** comic-strips\ **Created:** [May 28, 2020, 12:57am UTC](https://boards.straightdope.com/t/xkcd-thread/854574 "2020-05-28T00:57:03Z")\ **Posts on this page:** 20\ **Page:** 130
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [December 9, 2023, 1:44am UTC](https://boards.straightdope.com/t/xkcd-thread/854574/2583 "2023-12-09T01:44:20Z")
What was wrong with Project Habakkuk? ---
**Author:** ![LSLGuy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lslguy/32/5813_2.png) [@LSLGuy](https://boards.straightdope.com/u/LSLGuy)\ **Post date:** [December 9, 2023, 2:01pm UTC](https://boards.straightdope.com/t/xkcd-thread/854574/2584 "2023-12-09T14:01:20Z")
I always loved that idea. It was epic Rule of Cool. Had it not been constrained by wartime resource limitations it might have gone somewhere. OTOH, had it not been a situation of wartime desperation, it probably would not have gotten a hearing; instead it’d have been laughed out of the room. ---
**Author:** ![Andy\_L](https://avatars.discourse-cdn.com/v4/letter/a/c67d28/32.png) [@Andy\_L](https://boards.straightdope.com/u/Andy_L)\ **Post date:** [December 9, 2023, 10:28pm UTC](https://boards.straightdope.com/t/xkcd-thread/854574/2585 "2023-12-09T22:28:49Z")
The idea is also used in a terrific SF novel. PS: Rule of Cool - argh ---
**Author:** ![hogarth](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/hogarth/32/1773_2.png) [@hogarth](https://boards.straightdope.com/u/hogarth)\ **Post date:** [December 10, 2023, 6:01am UTC](https://boards.straightdope.com/t/xkcd-thread/854574/2586 "2023-12-10T06:01:50Z")
> [@Chronos](#): > > What was wrong with Project Habakkuk? I think Mythbusters and other teams have tried building pykrete boats with little success. ---
**Author:** ![dtilque](https://avatars.discourse-cdn.com/v4/letter/d/d6d6ee/32.png) [@dtilque](https://boards.straightdope.com/u/dtilque)\ **Post date:** [December 12, 2023, 8:04pm UTC](https://boards.straightdope.com/t/xkcd-thread/854574/2587 "2023-12-12T20:04:49Z")
> **[Snow](https://xkcd.com/2866/)** > > For someone who has ostensibly outgrown staying up late waiting for Santa, I do spend an awful lot of time refreshing websites to see if packages are here yet. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [December 14, 2023, 3:15am UTC](https://boards.straightdope.com/t/xkcd-thread/854574/2588 "2023-12-14T03:15:39Z")
> **[DateTime](https://xkcd.com/2867/)** > > It's not just time zones and leap seconds. SI seconds on Earth are slower because of relativity, so there are time standards for space stuff (TCB, TGC) that use faster SI seconds than UTC/Unix time. T2 - T1 = \[God doesn't know and the Devil isn't telling.\] At first glance, I thought this was going to be about relativity. ---
**Author:** ![Dr.Strangelove](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dr.strangelove/32/6613_2.png) [@Dr.Strangelove](https://boards.straightdope.com/u/Dr.Strangelove)\ **Post date:** [December 14, 2023, 3:21am UTC](https://boards.straightdope.com/t/xkcd-thread/854574/2589 "2023-12-14T03:21:49Z")
Well, the tooltip is about general relativity. I had no idea these alternate time standards existed. > **[Barycentric Coordinate Time](https://en.wikipedia.org/wiki/Barycentric_Coordinate_Time)** > > Barycentric Coordinate Time (TCB, from the French Temps-coordonnée barycentrique) is a coordinate time standard intended to be used as the independent variable of time for all calculations pertaining to orbits of planets, asteroids, comets, and interplanetary spacecraft in the Solar System. It is equivalent to the proper time experienced by a clock at rest in a coordinate frame co-moving with the barycenter (center of mass) of the Solar System\[citation needed\]: that is, a clock that performs exa... > **[Geocentric Coordinate Time](https://en.wikipedia.org/wiki/Geocentric_Coordinate_Time)** > > Geocentric Coordinate Time (TCG - Temps-coordonnée géocentrique) is a coordinate time standard intended to be used as the independent variable of time for all calculations pertaining to precession, nutation, the Moon, and artificial satellites of the Earth. It is equivalent to the proper time experienced by a clock at rest in a coordinate frame co-moving with the center of the Earth\[citation needed\]: that is, a clock that performs exactly the same movements as the Earth but is outside the Earth'... > TCB ticks faster than clocks on the surface of the Earth by 1.550505 × 10^−8 (about 490 milliseconds per year). > TCG ticks faster than clocks on the surface of the Earth by a factor of about 7.0 × 10^−10 (about 22 milliseconds per year) Neat. ---
**Author:** ![Riemann](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/riemann/32/3133_2.png) [@Riemann](https://boards.straightdope.com/u/Riemann)\ **Post date:** [December 14, 2023, 3:18pm UTC](https://boards.straightdope.com/t/xkcd-thread/854574/2590 "2023-12-14T15:18:51Z")
> [@Dr.Strangelove](#): > > [Barycentric Coordinate Time - Wikipedia](https://en.wikipedia.org/wiki/Barycentric_Coordinate_Time) Apparently the barycenter is sometimes outside the surface of the sun. I guess that’s when they wind up the barycentric clock. ---
**Author:** ![LSLGuy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lslguy/32/5813_2.png) [@LSLGuy](https://boards.straightdope.com/u/LSLGuy)\ **Post date:** [December 14, 2023, 11:37pm UTC](https://boards.straightdope.com/t/xkcd-thread/854574/2591 "2023-12-14T23:37:02Z")
Gotta pull out on the Sun’s stem before you can twist it. Just don’t overwind and break it. Assuming I understand what’s being compared to what, it’s interesting and a bit surprising to me that the difference between TCB and SI time is a half-second a year. Gravity-based distortion is kinda bigger than my highly naïve intuition would have had it. ---
**Author:** ![Dr.Strangelove](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dr.strangelove/32/6613_2.png) [@Dr.Strangelove](https://boards.straightdope.com/u/Dr.Strangelove)\ **Post date:** [December 14, 2023, 11:50pm UTC](https://boards.straightdope.com/t/xkcd-thread/854574/2592 "2023-12-14T23:50:13Z")
It’s more than I’d have guessed also, but we’re pretty deep in the Sun’s gravity well. Escape velocity is ~42 km/s. You can ballpark the correction factor by just computing the Lorentz factor for escape velocity. \frac{1}{1 - \frac{v^2}{c^2}} = \frac{1}{1 - \frac{42^2}{300000}} \approx 0.9999999902 \approx 1 - 9.8 \cdot 10^{-9} \approx 1 - 10^{-8}. Which isn’t far from the given 1.550505 \cdot 10^{-8} correction. ---
**Author:** ![John\_DiFool](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/john_difool/32/19543_2.png) [@John\_DiFool](https://boards.straightdope.com/u/John_DiFool)\ **Post date:** [December 15, 2023, 12:04am UTC](https://boards.straightdope.com/t/xkcd-thread/854574/2593 "2023-12-15T00:04:45Z")
The time thing reminds me of a joke: a man who has one watch always knows what time it is. A man with two watches never knows. ---
**Author:** ![kaylasdad99](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/kaylasdad99/32/3398_2.png) [@kaylasdad99](https://boards.straightdope.com/u/kaylasdad99)\ **Post date:** [December 15, 2023, 1:05am UTC](https://boards.straightdope.com/t/xkcd-thread/854574/2594 "2023-12-15T01:05:55Z")
> [@LSLGuy](#): > > Gotta pull out on the Sun’s stem before you can twist it. Just don’t overwind and break it. Been a while since you’ve worn an analog mechanical wristwatch, has it? Pulling the stem out is how you enable charging the time setting. If we DID do it to the sun, would that resolve the whole DST clock-changing thing so we didn’t have to bother remembering to do it twice a year? It probably would. HEY! Scientists! Get off your asses and do something useful, why don’tcha? ---
**Author:** ![DesertDog](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/desertdog/32/11503_2.png) [@DesertDog](https://boards.straightdope.com/u/DesertDog)\ **Post date:** [December 15, 2023, 1:40am UTC](https://boards.straightdope.com/t/xkcd-thread/854574/2595 "2023-12-15T01:40:22Z")
> [@LSLGuy](#): > > Gravity-based distortion is kinda bigger than my highly naïve intuition would have had it. It has to be [taken into account](https://en.wikipedia.org/wiki/Error_analysis_for_the_Global_Positioning_System#Relativity) for GPS clocks or the system would not work. The curious thing is the velocity redshift error and gravitational error are in opposite directions but don’t cancel each other, the net being 11.4 km per day. ---
**Author:** ![TroutMan](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/troutman/32/6721_2.png) [@TroutMan](https://boards.straightdope.com/u/TroutMan)\ **Post date:** [December 15, 2023, 6:25pm UTC](https://boards.straightdope.com/t/xkcd-thread/854574/2596 "2023-12-15T18:25:29Z")
> **[Label the States](https://xkcd.com/2868/)** > > Even with a blank map, a lot of people can only name 45-50 of the 64 states. Oooh! I can do this! Wait a minute… ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [December 15, 2023, 6:34pm UTC](https://boards.straightdope.com/t/xkcd-thread/854574/2597 "2023-12-15T18:34:39Z")
As soon as I saw it, I had a hunch of what he’d done… but it took me three or four cycles worth of “No, wait, that’s actually right, so what’s the joke?”. Didn’t he also once do the opposite of this, with a bunch of states missing? ---
**Author:** ![TroutMan](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/troutman/32/6721_2.png) [@TroutMan](https://boards.straightdope.com/u/TroutMan)\ **Post date:** [December 15, 2023, 6:43pm UTC](https://boards.straightdope.com/t/xkcd-thread/854574/2598 "2023-12-15T18:43:03Z")
[Yup.](https://xkcd.com/2394/) ---
**Author:** ![smithsb](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/smithsb/32/12107_2.png) [@smithsb](https://boards.straightdope.com/u/smithsb)\ **Post date:** [December 15, 2023, 7:05pm UTC](https://boards.straightdope.com/t/xkcd-thread/854574/2599 "2023-12-15T19:05:28Z")
Seems there’s even more than 57 states. Thanks, Obama. ---
**Author:** ![echoreply](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/echoreply/32/3641_2.png) [@echoreply](https://boards.straightdope.com/u/echoreply)\ **Post date:** [December 15, 2023, 7:51pm UTC](https://boards.straightdope.com/t/xkcd-thread/854574/2600 "2023-12-15T19:51:36Z")
What times of year are best to visit Mid Carolina and West Wyoming? I’m also pleased that we now have a North Dakota, South Dakota, and just plain Dakota. ---
**Author:** ![abcdefghij](https://avatars.discourse-cdn.com/v4/letter/a/43a26b/32.png) [@abcdefghij](https://boards.straightdope.com/u/abcdefghij)\ **Post date:** [December 15, 2023, 8:01pm UTC](https://boards.straightdope.com/t/xkcd-thread/854574/2601 "2023-12-15T20:01:29Z")
> [@Chronos](#): > > Didn’t he also once do the opposite of this, with a bunch of states missing? > > > [@TroutMan](#): > > > > Yup. Well, at least we’re getting an idea of Randall’s measurement uncertainty. ---
**Author:** ![dtilque](https://avatars.discourse-cdn.com/v4/letter/d/d6d6ee/32.png) [@dtilque](https://boards.straightdope.com/u/dtilque)\ **Post date:** [December 15, 2023, 8:11pm UTC](https://boards.straightdope.com/t/xkcd-thread/854574/2602 "2023-12-15T20:11:06Z")
> [@echoreply](#): > > I’m also pleased that we now have a North Dakota, South Dakota, and just plain Dakota. Which one is North Takoma? [Previous page](https://boards.straightdope.com/t/xkcd-thread/854574.md?page=129) [Next page](https://boards.straightdope.com/t/xkcd-thread/854574.md?page=131)