# ­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:** 246
**Author:** ![markn\_1](https://avatars.discourse-cdn.com/v4/letter/m/f9ae1b/32.png) [@markn\_1](https://boards.straightdope.com/u/markn_1)\ **Post date:** [August 21, 2025, 12:31am UTC](https://boards.straightdope.com/t/xkcd-thread/854574/4903 "2025-08-21T00:31:28Z")
Sorry, you can’t afford it. It costs 2.9.00. ---
**Author:** ![BigT](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bigt/32/12044_2.png) [@BigT](https://boards.straightdope.com/u/BigT)\ **Post date:** [August 22, 2025, 8:41am UTC](https://boards.straightdope.com/t/xkcd-thread/854574/4904 "2025-08-22T08:41:34Z")
> [@LSLGuy](#): > > The written version of that one is great. And one of the earliest what-ifs (#4): **[What if? - A mole of moles](https://what-if.xkcd.com/4/)**. The video is actually an updated version, as it specifically specifies the value of a mole has changed. ---
**Author:** ![Lumpy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lumpy/32/446_2.png) [@Lumpy](https://boards.straightdope.com/u/Lumpy)\ **Post date:** [August 22, 2025, 4:31pm UTC](https://boards.straightdope.com/t/xkcd-thread/854574/4905 "2025-08-22T16:31:58Z")
So what is the big deal about moles anyway? I guess, but am not sure, that it allows chemists to know that reacting a weight measured in grams of two chemicals with known empirical formulas will produce a complete reaction with little or no residue of the precursor chemicals. I don’t see much use for knowing what the actual value of Avogadro’s number is. ---
**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:** [August 22, 2025, 5:49pm UTC](https://boards.straightdope.com/t/xkcd-thread/854574/4906 "2025-08-22T17:49:29Z")
It’s basically just the inverse of the mass of a proton in grams, with a small correction factor. One mole of carbon 12 weighs 12 grams because a single nucleon weighs about 1/mol grams. ---
**Author:** ![markn\_1](https://avatars.discourse-cdn.com/v4/letter/m/f9ae1b/32.png) [@markn\_1](https://boards.straightdope.com/u/markn_1)\ **Post date:** [August 22, 2025, 5:50pm UTC](https://boards.straightdope.com/t/xkcd-thread/854574/4907 "2025-08-22T17:50:51Z")
> [@BigT](#): > > value of a mole has changed. I think that the value of a mole has always been negative, at least for the ones in my garden. ---
**Author:** ![dtilque](https://avatars.discourse-cdn.com/v4/letter/d/d6d6ee/32.png) [@dtilque](https://boards.straightdope.com/u/dtilque)\ **Post date:** [August 22, 2025, 6:02pm UTC](https://boards.straightdope.com/t/xkcd-thread/854574/4908 "2025-08-22T18:02:29Z")
> **[Coastline Similarity](https://xkcd.com/3132/)** [![](https://imgs.xkcd.com/comics/coastline_similarity.png) ](https://imgs.xkcd.com/comics/coastline_similarity.png) “Hey! A bunch of the early Cretaceous fossils on each coast seem to have been plagiarized, too!” ---
**Author:** ![Lumpy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lumpy/32/446_2.png) [@Lumpy](https://boards.straightdope.com/u/Lumpy)\ **Post date:** [August 22, 2025, 8:34pm UTC](https://boards.straightdope.com/t/xkcd-thread/854574/4909 "2025-08-22T20:34:14Z")
My understanding is that the fit is even better if you take the ~~cited references~~ submerged continental shelf into account. ---
**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:** [August 22, 2025, 11:29pm UTC](https://boards.straightdope.com/t/xkcd-thread/854574/4910 "2025-08-22T23:29:39Z")
Yes, that is true ---
**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:** [August 23, 2025, 12:43am UTC](https://boards.straightdope.com/t/xkcd-thread/854574/4911 "2025-08-23T00:43:11Z")
> [@Lumpy](#): > > So what is the big deal about moles anyway? Two big things. One, it lets you do calculations involving number of particles, without needing to use inconveniently-large numbers. Two and more importantly, you can do calculations involving moles without needing to know what Avogadro’s Constant is, which was very relevant before that measurement was made, and still somewhat relevant so long as there was some uncertainty in the value. It’s difficult to determine the mass of the proton (and hence the value of Avogadro’s Constant), but it’s easy to determine that two moles of hydrogen reacted with one mole of oxygen yields two moles of water, or that a mole of any gas takes up 22.4 liters at standard temperature and pressure. ---
**Author:** ![dtilque](https://avatars.discourse-cdn.com/v4/letter/d/d6d6ee/32.png) [@dtilque](https://boards.straightdope.com/u/dtilque)\ **Post date:** [August 26, 2025, 5:32am UTC](https://boards.straightdope.com/t/xkcd-thread/854574/4912 "2025-08-26T05:32:49Z")
> **[Dual Roomba](https://xkcd.com/3133/)** [![](https://imgs.xkcd.com/comics/dual_roomba.png) ](https://imgs.xkcd.com/comics/dual_roomba.png) “I tried uploading it to a household appliance porn site I found, but apparently their content is limited to only fans.” Groooan! ---
**Author:** ![Alessan](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/alessan/32/465_2.png) [@Alessan](https://boards.straightdope.com/u/Alessan)\ **Post date:** [August 26, 2025, 5:39am UTC](https://boards.straightdope.com/t/xkcd-thread/854574/4913 "2025-08-26T05:39:38Z")
I think that was one of those strips where he worked backwards from the text. ---
**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:** [August 26, 2025, 11:11am UTC](https://boards.straightdope.com/t/xkcd-thread/854574/4914 "2025-08-26T11:11:51Z")
I halfway expected the hover-over text to be something like “And now I’ve got 20 mini Roombas running around out of control!” It would be neat though to have a Roomba that could empty its own sweepings reservoir. Into some sort of trashcan that could empty itself. ---
**Author:** ![Q.Q.Switcheroo](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/q.q.switcheroo/32/5713_2.png) [@Q.Q.Switcheroo](https://boards.straightdope.com/u/Q.Q.Switcheroo)\ **Post date:** [August 26, 2025, 3:01pm UTC](https://boards.straightdope.com/t/xkcd-thread/854574/4915 "2025-08-26T15:01:09Z")
Panel 2 feels like a riff on “When car chasers dream.” [https://screenrant.com/gary-larson-far-side-misunderstood-dog-comic-controversy/](https://screenrant.com/gary-larson-far-side-misunderstood-dog-comic-controversy/) ---
**Author:** ![markn\_1](https://avatars.discourse-cdn.com/v4/letter/m/f9ae1b/32.png) [@markn\_1](https://boards.straightdope.com/u/markn_1)\ **Post date:** [August 26, 2025, 4:37pm UTC](https://boards.straightdope.com/t/xkcd-thread/854574/4916 "2025-08-26T16:37:45Z")
> [@LSLGuy](#): > > It would be neat though to have a Roomba that could empty its own sweepings reservoir. > **[Robot Vacuums Self Emptying Worth Buying in 2025 — Our Top Picks |...](https://www.techgearinsider.com/robot-vacuums-self-emptying)** > > TechGearInsider.com evaluates top electronics products using in-depth analysis and verified user feedback. Discover recommended options you'll value this year. ---
**Author:** ![Kron](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/kron/32/12444_2.png) [@Kron](https://boards.straightdope.com/u/Kron)\ **Post date:** [August 26, 2025, 5:20pm UTC](https://boards.straightdope.com/t/xkcd-thread/854574/4917 "2025-08-26T17:20:18Z")
Yeah, I have a self-emptying Roomba (life-changing), but the can it empties into has to be manually cleared… ---
**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:** [August 26, 2025, 6:23pm UTC](https://boards.straightdope.com/t/xkcd-thread/854574/4918 "2025-08-26T18:23:30Z")
Truly we live in miraculous times. ---
**Author:** ![markn\_1](https://avatars.discourse-cdn.com/v4/letter/m/f9ae1b/32.png) [@markn\_1](https://boards.straightdope.com/u/markn_1)\ **Post date:** [August 26, 2025, 6:51pm UTC](https://boards.straightdope.com/t/xkcd-thread/854574/4919 "2025-08-26T18:51:21Z")
They should make one where the can empties itself too. Into, uh, a bin. And then the bin, hmm, … never mind. ---
**Author:** ![74westy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/74westy/32/3950_2.png) [@74westy](https://boards.straightdope.com/u/74westy)\ **Post date:** [August 26, 2025, 8:42pm UTC](https://boards.straightdope.com/t/xkcd-thread/854574/4920 "2025-08-26T20:42:09Z")
I really hate to say it but it’s bins all the way down. ---
**Author:** ![dtilque](https://avatars.discourse-cdn.com/v4/letter/d/d6d6ee/32.png) [@dtilque](https://boards.straightdope.com/u/dtilque)\ **Post date:** [August 28, 2025, 7:13am UTC](https://boards.straightdope.com/t/xkcd-thread/854574/4921 "2025-08-28T07:13:00Z")
> **[Wavefunction Collapse](https://xkcd.com/3134/)** [![](https://imgs.xkcd.com/comics/wavefunction_collapse.png) ](https://imgs.xkcd.com/comics/wavefunction_collapse.png) “Wavefunction collapse is only one interpretation. Under some interpretations, graduate students also have souls.” ---
**Author:** ![dtilque](https://avatars.discourse-cdn.com/v4/letter/d/d6d6ee/32.png) [@dtilque](https://boards.straightdope.com/u/dtilque)\ **Post date:** [August 30, 2025, 6:31am UTC](https://boards.straightdope.com/t/xkcd-thread/854574/4922 "2025-08-30T06:31:45Z")
> **[Sea Level](https://xkcd.com/3135/)** [![](https://imgs.xkcd.com/comics/sea_level.png) ](https://imgs.xkcd.com/comics/sea_level.png) “They’re up there with coral islands, lightning, and caterpillars turning into butterflies.” [Previous page](https://boards.straightdope.com/t/xkcd-thread/854574.md?page=245) [Next page](https://boards.straightdope.com/t/xkcd-thread/854574.md?page=247)