explain xkcd - User contributions [en]

Talk:1366: Train

2014-05-11T22:19:26Z

Gleyshon: Physics objection, absolute rotation!

I just did an explanation from scratch for the first time, please could you tell me how I could improve it? Thanks :) [[User:Cheeselord99|Cheeselord99]] ([[User talk:Cheeselord99|talk]]) 07:02, 9 May 2014 (UTC)

Am I the only one who gets [[Inflation]] when going to xkcd.com (without the www)? This comic shows at www.xkcd.com and m.xkcd.com however. [[Special:Contributions/108.162.221.5|108.162.221.5]] 07:11, 9 May 2014 (UTC)

:I created an account. The 108.162.221.5 ip address today is me, along with 108.162.221.53 today. [[User:Mikemk|Mikemk]] ([[User talk:Mikemk|talk]]) 07:16, 9 May 2014 (UTC)
:I thought today's comic was late. http://www.xkcd.com/1366/ kept on displaying "Web-page not available" (browser thing, not server-thing), then I checked here. So. Oh, http://www.xkcd.com/ also... Hmmm... That's not right. Oh, "Ping request could not find host www.xkcd.com. Please check the name and try again." DNS errors? Only those trying via cached details get anything? Things are not working for xkcd.com or m.xkcd.com either. So, DNS poisoning or human error of some kind? Not the place to discuss this, I know, sorry... [[Special:Contributions/141.101.89.211|141.101.89.211]] 10:05, 9 May 2014 (UTC)

:Explanation is good, but there are certainly related comics or maybe what-if ... I've found [http://what-if.xkcd.com/58/ Orbital Speed], but I think there were something mentioning how fast sun goes relatively to galaxy ... -- [[User:Hkmaly|Hkmaly]] ([[User talk:Hkmaly|talk]]) 10:14, 9 May 2014 (UTC)
::Found two related comics - any other? [[User:Condor70|Condor70]] ([[User talk:Condor70|talk]]) 11:33, 9 May 2014 (UTC)

It sounds like the dark matter engine in Futurama:http://futurama.wikia.com/wiki/Dark_matter_engine {{unsigned ip|108.162.215.77}}

I think the last paragraph, considering the situation from the point of view of multiple trains, is not relevant. The whole concept of what makes this idea funny and interesting is that you MUST view the situation from the point of view of a single train (or elevator). --[[User:RenniePet|RenniePet]] ([[User talk:RenniePet|talk]]) 13:24, 9 May 2014 (UTC)
: Second-last paragraph - my comment was written at the same time as another paragraph was added. --[[User:RenniePet|RenniePet]] ([[User talk:RenniePet|talk]]) 13:26, 9 May 2014 (UTC)

I do not understand what the last paragraph is suggesting as it seems to violate the 3rd Newtonian law of motion.

The last paragraph is not correct, the Earth would also experience an acceleration (albeit a small one).--[[User:Sturmonium|Sturmonium]] ([[User talk:Sturmonium|talk]]) 13:54, 9 May 2014 (UTC)

This line:
"The logic of the comic also fails when taking acceleration into account. Whether the train or earth is moving can be determined by which one experiences a force due to acceleration or deacceleration when the train starts."
is incorrect, according to the principle of General Relativity. You cannot experimentally distinguish between your own acceleration against a fixed universe, and your position remaining fixed against an accelerating universe. This applies for rotation as well; if you fix the reference frame of the train rider, the acceleration of the universe creates gravity waves that cause any rider on the train to experience what feels like an acceleration. Therefore, the logic of the comic is indeed correct, even for accelerating trains. I will correct this edit.--[[User:JB Gnome|JB Gnome]] ([[User talk:JB Gnome|talk]]) 14:12, 9 May 2014 (UTC)
: But the comic doesn't say that the train accelerates the universe: rather, it just accelerates the Earth. Does that make a difference? [[Special:Contributions/141.101.89.225|141.101.89.225]] 14:34, 9 May 2014 (UTC)

Does anyone have an idea where "train guy" is heading? He's saying "almost", like he's almost there but wasn't sure if there was something more. Maybe he's timing when he needs to jump off the train? [[Special:Contributions/173.245.55.62|173.245.55.62]] 14:58, 9 May 2014 (UTC)Pat

I see this comic as a nice ab absurdo for the many people who think the sun rotates around us, and further to those who claim the earth has 6 thousand years etc... [[Special:Contributions/108.162.242.117|108.162.242.117]] 18:12, 9 May 2014 (UTC)

I don't have a citation, but some traditional Polynesian navigation works using this view. Their "maps" are made of a grid of bush materials where intersections are stars or islands (possibly with a pebble tied on to represent the island). They consider the map and the earth to be connected, and you don't move along the map - the map moves. So you don't go to another island, you bring it to you. At night you move the stars to the right place, and during the day you paddle the sea and land so they are in the right place and direction.--[[User:DivePeak|DivePeak]] ([[User talk:DivePeak|talk]]) 21:15, 9 May 2014 (UTC)

A train rotating the Earth is NOT physically equivalent to a train traversing the Earth. It would be true for a flat Earth, but rotation is absolute, see Newton's bucket argument. [http://en.wikipedia.org/wiki/Bucket_argument] --[[User:Gleyshon|Gleyshon]]

Talk:118: 50 Ways

2012-12-08T01:04:16Z

Gleyshon: Created page with "Might there also be a cultural reference to the Hitchhiker's Guide to the Galaxy? In the books, characters can learn to hover or fly by perfecting the art of managing to miss ..."

Might there also be a cultural reference to the Hitchhiker's Guide to the Galaxy? In the books, characters can learn to hover or fly by perfecting the art of managing to miss the ground when falling.
[[User:Gleyshon|Gleyshon]] ([[User talk:Gleyshon|talk]]) 01:04, 8 December 2012 (UTC)

User:Gleyshon

2012-12-06T01:18:52Z

Gleyshon: created article!

You only need to know three things:
1, I am a Roman Catholic Priest.
2, I have a PhD in astrophysics.
3, Yes, I am the same Gleyshon who also edits wikipedia.
[[User:Gleyshon|Gleyshon]] ([[User talk:Gleyshon|talk]]) 01:18, 6 December 2012 (UTC)

459: Holy Ghost

2012-12-06T01:17:43Z

Gleyshon: created article!

{{comic
| number = 459
| date =
| title = Holy Ghost
| image = holy_ghost.png
| titletext = Okay, everyone, cross yourselves, then cross the streams.
}}

==Explanation==
Mainstream Christian denomination hold the belief that God exists, and exists as a threefold presence within which there are three distinct 'persons' who interact with one another and the world, yet sharing one common nature. (If this sounds counter-intuitive or downright weird, please ask a quantum physicist to explain how three quarks can be bound together in such a way that they have distinct 'colour' identities yet cannot be separated from one another.) The three 'persons' sharing the property of being God are conventionally called the Father, the Son, and the Holy Spirit - but in more archaic English usage, the third person was referred to as the Holy Ghost.

The 1984 movie 'Ghostbusters' was based on the premise that ghosts (non-corporeal creatures) exist and that four unemployed men had access to technology that could trap such ghosts. These men formed a business as 'Ghostbusters' and an important tool in their arsenal was a so-called 'proton beam' powered by a wearable backpack. These beams would prod or stun ghosts, allowing them to be manouevered into traps. Throughout the movie the Ghostbusters reminded each other 'not to cross the beams' as this was supposed to cause a disasterous reaction, until the climax of the movie where crossing the beams was required to subdue the main antagonist.

The premise of xkcd cartoon 459 is that the Ghostbusters have just encountered and eliminated the divine entity of Christian theology sometimes called the Holy Ghost, and are being taken to task by a Christian bishop. The bishop points out that Christian theology requires a Trinity and is unwilling to accept the Gostbusters' apology; their identity becomes clear in the final panel where we see a group of four persons wearing backpacks identified as proton packs.

The tooltip text is a play on the fact that Christians may make the sign of the cross (by touching the forehead, chest and shoulders), colloquially called 'crossing oneself', and on the Ghostbusters concept of (not) 'crossing the beams'.

==Transcript==


{{comic discussion}}

643: Ohm

2012-12-06T00:48:25Z

Gleyshon: created article!

{{comic
| number = 643
| date =
| title = Ohm
| image = ohm.png
| titletext = More generally, with great power comes great dEnergy/dt
}}

==Explanation==
This cartoon is a play on the concepts of power as the human capacity to take action, and power as a strictly defined physical quantity, namely the amount of energy which flows from one locus to another in a unit of time. In calculus, this is expressed as dE/dt, hence the tooltip declaration that with great power comes great dEnergy/dt - though strictly speaking, great power EQUALS (is identical with) great dEnergy/dt.

The saying references the comic-book superhero Spiderman. In various versions of Spiderman's origin story, teenager Peter Parker is being brought up by his Aunt May and Uncle Ben. Uncle Ben cautions Peter that "with great power comes great responsibility". Through an incident involving a spider and some cutting-edge technology, Peter Parker acquires spider-like powers - great strength and the ability to adhere to walls and ceilings. Parker fails to use his new powers to stop a mugging; it turns out that the victim is none other than Uncle Ben, who dies from injuries sustained. This failure to save his uncle haunts Parker and drives him to use his new powers for heroic purposes. Visually, the xkcd cartoon 643 recalls the dying Uncle Ben counselling his nephew to use his power responsibly.

Physical energy can exist in many different forms. In electrical physics, current flowing through a resistor generates heat. The basic units are defined such that the power (in Watts) converted into heat is given by the square of the electrical current flowing (in Amperes) multiplied by the reistance of the component (in Ohms). The unit, Ohm, is named for physicist Georg Ohm who determined experimentally that a given resistor would pass double the current when the electrical pressure (voltage) was also doubled.

The main cartoon text is therefore simply a statement that in electrical physics, when current flows through a resistor, the power dissipated is equal to the current squared, multiplied by the resistance.

==Transcript==


{{comic discussion}}