# ­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:** 199
**Author:** ![gnoitall](https://avatars.discourse-cdn.com/v4/letter/g/bb73d2/32.png) [@gnoitall](https://boards.straightdope.com/u/gnoitall)\ **Post date:** [February 5, 2025, 6:38pm UTC](https://boards.straightdope.com/t/xkcd-thread/854574/3963 "2025-02-05T18:38:29Z")
Maybe he just wants his 78 RPMs to play for a tiny bit longer. ---
**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:** [February 5, 2025, 11:29pm UTC](https://boards.straightdope.com/t/xkcd-thread/854574/3964 "2025-02-05T23:29:43Z")
Is a “precession adaptor” really a thing? (Search results swamped by “precision adaptor”) ---
**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:** [February 5, 2025, 11:47pm UTC](https://boards.straightdope.com/t/xkcd-thread/854574/3965 "2025-02-05T23:47:11Z")
No, it’s just a funny idea for a telescope mount. The Earth precesses every 26,000 years; way too little to ever be relevant for a telescope. A normal telescope mount only has to compensate for the 1/day revolution of the Earth. Any extra compensation would be totally swamped by other factors. ---
**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:** [February 5, 2025, 11:52pm UTC](https://boards.straightdope.com/t/xkcd-thread/854574/3966 "2025-02-05T23:52:11Z")
I can imagine that for telescopes doing very high precision observations such as parallax measurements some adjustment might be needed on a timescale of decades. ---
**Author:** ![dtilque](https://avatars.discourse-cdn.com/v4/letter/d/d6d6ee/32.png) [@dtilque](https://boards.straightdope.com/u/dtilque)\ **Post date:** [February 6, 2025, 12:20am UTC](https://boards.straightdope.com/t/xkcd-thread/854574/3967 "2025-02-06T00:20:57Z")
Not for the traditional way parallax is measured. They don’t use the direction the telescope is pointing, but rather measure the offset of the target star from much more remote stars or quasars or whatever. So they have to make sure they get several (at least three) more distant objects in all the images. ---
**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:** [February 6, 2025, 12:31am UTC](https://boards.straightdope.com/t/xkcd-thread/854574/3968 "2025-02-06T00:31:42Z")
Well… That depends on being able to resolve all the objects involved very precisely. And if you’re working on a long exposure, that in turn would depend on your telescope tracking the sky accurately. And that, in turn, would depend on your telescope mount being accurately aligned to true north. Though I suppose that wouldn’t actually vary with precession (though it might depend on things like the Chandler wobble). ---
**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:** [February 6, 2025, 1:34am UTC](https://boards.straightdope.com/t/xkcd-thread/854574/3969 "2025-02-06T01:34:38Z")
There’s quite a list of perturbations between 1x/day rotation and the ~1x/26K year cycle of axial precession. ---
**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:** [February 6, 2025, 1:35am UTC](https://boards.straightdope.com/t/xkcd-thread/854574/3970 "2025-02-06T01:35:43Z")
Even plate tectonics going to slide your telescope around faster than precession! ---
**Author:** ![Pleonast](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/pleonast/32/1183_2.png) [@Pleonast](https://boards.straightdope.com/u/Pleonast)\ **Post date:** [February 6, 2025, 1:47am UTC](https://boards.straightdope.com/t/xkcd-thread/854574/3971 "2025-02-06T01:47:52Z")
This device has rotational control over 15 orders of magnitude. Go buy some lesser brand if you only need 8. ---
**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:** [February 6, 2025, 12:12pm UTC](https://boards.straightdope.com/t/xkcd-thread/854574/3972 "2025-02-06T12:12:32Z")
I’ve never had a Dremel and I was unaware that they spin so much faster than a cordless drill. ---
**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:** [February 6, 2025, 1:40pm UTC](https://boards.straightdope.com/t/xkcd-thread/854574/3973 "2025-02-06T13:40:26Z")
Some of us learned about the surprisingly high RPM of dental drills from Don Martin: > **[Don Martin and the Essence of Cartooning.last dentist scene](http://johnkstuff.blogspot.com/2008/08/don-martin-and-essence-of.html?m=1)** > > All fields of art branch out and take in influences and skills from other fields - sometimes eventually to the point where it rejects its ow... ---
**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:** [February 6, 2025, 2:02pm UTC](https://boards.straightdope.com/t/xkcd-thread/854574/3974 "2025-02-06T14:02:46Z")
If you’d ever held one or seen a vid, the sound of the thing is scary out of all proportion to its small size. I’ve only borrowed them or used them in school shop, but to me they’re sorta like shrews: fierce for their size. I always felt like if I dropped the thing while it was running, it’d happily amputate my leg on its way down to the floor. Reality is rather more mundane, but the feeling is real to me at least. Since it’s more intended for grinding or cutting than as a tool for drilling, some of the very high RPM is about getting the linear speed of the perimeter of the tiny discs or saws up to a value not so different from an ordinary drill motor spinning a 4" diameter disc. Another aspect is that for fine work you want itty-bitty teeth or not-so-aggressive abrasive so the completed cut or surface is smooth and needs little touchup. To get a decent material removal rate under those circumstances, linear speed in the form of RPM is the only remaining variable to crank up. ---
**Author:** ![dtilque](https://avatars.discourse-cdn.com/v4/letter/d/d6d6ee/32.png) [@dtilque](https://boards.straightdope.com/u/dtilque)\ **Post date:** [February 7, 2025, 10:19pm UTC](https://boards.straightdope.com/t/xkcd-thread/854574/3975 "2025-02-07T22:19:55Z")
> **[Suspension Bridge](https://xkcd.com/3048/)** [![](https://imgs.xkcd.com/comics/suspension_bridge.png) ](https://imgs.xkcd.com/comics/suspension_bridge.png) “As a first step, they can put in a secondary deck, to help drivers try it out and find out how fun the jumps are. After a while no one will use the old flat deck and they can remove it.” ---
**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:** [February 7, 2025, 10:31pm UTC](https://boards.straightdope.com/t/xkcd-thread/854574/3976 "2025-02-07T22:31:10Z")
Incidentally, it seems like most new suspension bridges use support cables all suspended directly from the towers rather than a primary cable. Why is that? ---
**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:** [February 7, 2025, 11:11pm UTC](https://boards.straightdope.com/t/xkcd-thread/854574/3977 "2025-02-07T23:11:50Z")
The thing you’re describing is not properly a “suspension bridge”. It’s a > **[Cable-stayed bridge](https://en.wikipedia.org/wiki/Cable-stayed_bridge)** > > A cable-stayed bridge has one or more towers (or pylons), from which cables support the bridge deck. A distinctive feature are the cables or stays, which run directly from the tower to the deck, normally forming a fan-like pattern or a series of parallel lines. This is in contrast to the modern suspension bridge, where the cables supporting the deck are suspended vertically from the main cable, anchored at both ends of the bridge and running between the towers. The cable-stayed bridge is optima... The big difference is the maximum possible span between towers of a cable-stayed is significantly less than the maximum span of a suspension. So for short runs which in prior eras may have been built suspension style, a cable stay is a more economical substitute. For truly long spans between towers, traditional suspension is still the only way to go. ---
**Author:** ![Zyada](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/zyada/32/3028_2.png) [@Zyada](https://boards.straightdope.com/u/Zyada)\ **Post date:** [February 8, 2025, 6:11am UTC](https://boards.straightdope.com/t/xkcd-thread/854574/3978 "2025-02-08T06:11:40Z")
> [@Lumpy](#): > > Incidentally, it seems like most new suspension bridges use support cables all suspended directly from the towers rather than a primary cable. Why is that? (After reading LSL\_Guy’s link) Because they look hella cool! ---
**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:** [February 8, 2025, 1:33pm UTC](https://boards.straightdope.com/t/xkcd-thread/854574/3979 "2025-02-08T13:33:17Z")
They certainly do. _Tres moderne_. Here’s a very interesting hybrid sort of arch suspension bridge. Not practical to scale up, but ultra cool structurally. > **[Gateshead Millennium Bridge](https://en.wikipedia.org/wiki/Gateshead_Millennium_Bridge)** > > The Gateshead Millennium Bridge is a pedestrian and cyclist tilt bridge spanning the River Tyne between Gateshead arts quarter on the south bank and Newcastle upon Tyne's Quayside area on the north bank. It was the first tilting bridge ever to be constructed. Opened for public use in 2001, the award-winning structure was conceived and designed by architectural practice WilkinsonEyre and structural engineering firm Gifford. The bridge is sometimes called the 'Blinking Eye Bridge' or th Gateshe... ---
**Author:** ![dtilque](https://avatars.discourse-cdn.com/v4/letter/d/d6d6ee/32.png) [@dtilque](https://boards.straightdope.com/u/dtilque)\ **Post date:** [February 10, 2025, 10:58pm UTC](https://boards.straightdope.com/t/xkcd-thread/854574/3980 "2025-02-10T22:58:15Z")
> **[Incoming Asteroid](https://xkcd.com/3049/)** [![](https://imgs.xkcd.com/comics/incoming_asteroid.png) ](https://imgs.xkcd.com/comics/incoming_asteroid.png) “The bottom ones are also potentially bad news for any other planets in our solar system that have been counting on Earth having a stable orbit.” For the 10 cm - 1 m size, there’s also the possibility of finding the meteorite(s). ---
**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:** [February 10, 2025, 11:09pm UTC](https://boards.straightdope.com/t/xkcd-thread/854574/3981 "2025-02-10T23:09:48Z")
Paging @Darren_Garrison … Meteorite cleanup on aisle 3978. 😉 ---
**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:** [February 10, 2025, 11:29pm UTC](https://boards.straightdope.com/t/xkcd-thread/854574/3982 "2025-02-10T23:29:24Z")
Probably apocryphal, but supposedly in one of the few instances where a meteorite hit a house, an insurance claim was filed with the cause of damage as “falling rock”. [Previous page](https://boards.straightdope.com/t/xkcd-thread/854574.md?page=198) [Next page](https://boards.straightdope.com/t/xkcd-thread/854574.md?page=200)