explain xkcd - User contributions [en]

1318: Actually

2014-01-17T07:00:14Z

DrJoel:

{{comic
| number = 1318
| date = January 17, 2014
| title = Actually
| image = actually.png
| titletext = Protip: You can win every exchange just by being one level more precise than whoever talked last. Eventually, you'll defeat all conversational opponents and stand alone.
}}

==Explanation==
{{Incomplete|More detail and formatting should be added.}}

* The picture is designed to have us thinking about a planet (presumably Earth), such that when we read the first speaker's comment, we interpret it as "The Earth is flat", which was the earliest view of the planet. (The speaker does not explicitly state their subject, however, which leads to the comic's punchline.)
* The second speaker explains that the Earth is actually a sphere, tracking the progression of knowledge of the Earth's shape.
* The third speaker provides further detail on the shape, that rather than being spherical, the Earth is actually an [http://en.wikipedia.org/wiki/Oblate_spheroid oblate spheroid]. On Earth, this occurs because a rotating body tends to bulge at the equator (where the matter experiences greater centripetal forces - analogous to experiencing more force at the outside of a round-a-bout rather than the centre), and is known as the [http://en.wikipedia.org/wiki/Equatorial_bulge equatorial bulge].
* A more accurate description is the [http://en.wikipedia.org/wiki/EGM96 Earth Gravitational Model 1996] which provided a detailed map of Earth's gravitational field. This therefore refines the oblate spheroid model even further.
* The next speaker notes that this is still a very high level model of the planet (necessary because of the sizes involved) and that the true shape of the planet is given by the actual local topography (i.e., mountains, hills, valleys, etc.) which can be thought as overlaid on the planet wide models.
* Changing tack, the remaining speaker notes that our planet sits in a [http://en.wikipedia.org/wiki/General_relativity curved space-time], where our planet's gravity, as well as all other objects, bend the space and time around them. On the largest scale, this has the potential to lead to a [http://en.wikipedia.org/wiki/Shape_of_the_universe curvature] of the four dimensional space-time of the universe, hence "universe that is curved". Such a universe can either be "open" or "closed", depending on how much mass and energy there is. In an "closed" universe, if you drew a large enough triangle in space, you would find that the angles did not add up to to 180 degrees (just like if it was drawn on the surface of a balloon - in this case, the angles would add up to less than 180 degrees because the points would be shrunk). In an "open" universe, the angles would be more than 180 degrees.
* Finally, the first speaker comments again, and we now interpret this as referring not to the planet but to the universe itself - current observations suggest that the balance of matter and energy in the universe is such that the universe is, in fact, [http://en.wikipedia.org/wiki/Shape_of_the_universe#Flat_universe flat] on the largest scales. (Whether this is coincidence or reflective of underlying laws is currently unknown.)
* The arguments could continue around the circle, now referring to the universe, but aren't generally applicable.

==Transcript==
{{incomplete transcript}}
{{incomplete transcript}}
:[Six people are standing upon a white circle as if it were a miniature planet. Each person says something and the text is displayed over their heads in a closed circle that encloses the whole picture.]

:''From topmost, going clockwise...''
:Cueball: '''Actually,''' measurements suggest it's flat.
:Ponytail: '''Actually,''' it's a sphere.
:White Hat: '''Actually,''' it's an oblate spheroid.
:Megan: '''Actually,''' it's a sphere defined by the EGM96 coefficients.
:(Name unknown): '''Actually,''' it's that plus local topography.
:Hairy: '''Actually,''' it's embedded in a universe that's curved.

{{comic discussion}}
[[Category:Comics featuring Cueball]]
[[Category:Comics featuring Megan]]
[[Category:Comics featuring Ponytail]]
[[Category:Comics featuring White Hat]]
[[Category:Comics featuring Hairy]]

1318: Actually

2014-01-17T06:59:45Z

DrJoel: /* Explanation */ Incomplete tag.

{{comic
| number = 1318
| date = January 17, 2014
| title = Actually
| image = actually.png
| titletext = Protip: You can win every exchange just by being one level more precise than whoever talked last. Eventually, you'll defeat all conversational opponents and stand alone.
}}

{{Incomplete|More detail and formatting should be added.}}

==Explanation==

* The picture is designed to have us thinking about a planet (presumably Earth), such that when we read the first speaker's comment, we interpret it as "The Earth is flat", which was the earliest view of the planet. (The speaker does not explicitly state their subject, however, which leads to the comic's punchline.)
* The second speaker explains that the Earth is actually a sphere, tracking the progression of knowledge of the Earth's shape.
* The third speaker provides further detail on the shape, that rather than being spherical, the Earth is actually an [http://en.wikipedia.org/wiki/Oblate_spheroid oblate spheroid]. On Earth, this occurs because a rotating body tends to bulge at the equator (where the matter experiences greater centripetal forces - analogous to experiencing more force at the outside of a round-a-bout rather than the centre), and is known as the [http://en.wikipedia.org/wiki/Equatorial_bulge equatorial bulge].
* A more accurate description is the [http://en.wikipedia.org/wiki/EGM96 Earth Gravitational Model 1996] which provided a detailed map of Earth's gravitational field. This therefore refines the oblate spheroid model even further.
* The next speaker notes that this is still a very high level model of the planet (necessary because of the sizes involved) and that the true shape of the planet is given by the actual local topography (i.e., mountains, hills, valleys, etc.) which can be thought as overlaid on the planet wide models.
* Changing tack, the remaining speaker notes that our planet sits in a [http://en.wikipedia.org/wiki/General_relativity curved space-time], where our planet's gravity, as well as all other objects, bend the space and time around them. On the largest scale, this has the potential to lead to a [http://en.wikipedia.org/wiki/Shape_of_the_universe curvature] of the four dimensional space-time of the universe, hence "universe that is curved". Such a universe can either be "open" or "closed", depending on how much mass and energy there is. In an "closed" universe, if you drew a large enough triangle in space, you would find that the angles did not add up to to 180 degrees (just like if it was drawn on the surface of a balloon - in this case, the angles would add up to less than 180 degrees because the points would be shrunk). In an "open" universe, the angles would be more than 180 degrees.
* Finally, the first speaker comments again, and we now interpret this as referring not to the planet but to the universe itself - current observations suggest that the balance of matter and energy in the universe is such that the universe is, in fact, [http://en.wikipedia.org/wiki/Shape_of_the_universe#Flat_universe flat] on the largest scales. (Whether this is coincidence or reflective of underlying laws is currently unknown.)
* The arguments could continue around the circle, now referring to the universe, but aren't generally applicable.

==Transcript==
{{incomplete transcript}}
{{incomplete transcript}}
:[Six people are standing upon a white circle as if it were a miniature planet. Each person says something and the text is displayed over their heads in a closed circle that encloses the whole picture.]

:''From topmost, going clockwise...''
:Cueball: '''Actually,''' measurements suggest it's flat.
:Ponytail: '''Actually,''' it's a sphere.
:White Hat: '''Actually,''' it's an oblate spheroid.
:Megan: '''Actually,''' it's a sphere defined by the EGM96 coefficients.
:(Name unknown): '''Actually,''' it's that plus local topography.
:Hairy: '''Actually,''' it's embedded in a universe that's curved.

{{comic discussion}}
[[Category:Comics featuring Cueball]]
[[Category:Comics featuring Megan]]
[[Category:Comics featuring Ponytail]]
[[Category:Comics featuring White Hat]]
[[Category:Comics featuring Hairy]]

1318: Actually

2014-01-17T06:33:28Z

DrJoel: /* Explanation */ Removed Bot comment

{{comic
| number = 1318
| date = January 17, 2014
| title = Actually
| image = actually.png
| titletext = Protip: You can win every exchange just by being one level more precise than whoever talked last. Eventually, you'll defeat all conversational opponents and stand alone.
}}

==Explanation==

* The picture is designed to have us thinking about a planet (presumably Earth), such that when we read the first speaker's comment, we interpret it as "The Earth is flat", which was the earliest view of the planet. (The speaker does not explicitly state their subject, however, which leads to the comic's punchline.)
* The second speaker explains that the Earth is actually a sphere, tracking the progression of knowledge of the Earth's shape.
* The third speaker provides further detail on the shape, that rather than being spherical, the Earth is actually an [http://en.wikipedia.org/wiki/Oblate_spheroid oblate spheroid]. On Earth, this occurs because a rotating body tends to bulge at the equator (where the matter experiences greater centripetal forces - analogous to experiencing more force at the outside of a round-a-bout rather than the centre), and is known as the [http://en.wikipedia.org/wiki/Equatorial_bulge equatorial bulge].
* A more accurate description is the [http://en.wikipedia.org/wiki/EGM96 Earth Gravitational Model 1996] which provided a detailed map of Earth's gravitational field. This therefore refines the oblate spheroid model even further.
* The next speaker notes that this is still a very high level model of the planet (necessary because of the sizes involved) and that the true shape of the planet is given by the actual local topography (i.e., mountains, hills, valleys, etc.) which can be thought as overlaid on the planet wide models.
* Changing tack, the remaining speaker notes that our planet sits in a [http://en.wikipedia.org/wiki/General_relativity curved space-time], where our planet's gravity, as well as all other objects, bend the space and time around them. On the largest scale, this has the potential to lead to a [http://en.wikipedia.org/wiki/Shape_of_the_universe curvature] of the four dimensional space-time of the universe, hence "universe that is curved". Such a universe can either be "open" or "closed", depending on how much mass and energy there is. In an "closed" universe, if you drew a large enough triangle in space, you would find that the angles did not add up to to 180 degrees (just like if it was drawn on the surface of a balloon - in this case, the angles would add up to less than 180 degrees because the points would be shrunk). In an "open" universe, the angles would be more than 180 degrees.
* Finally, the first speaker comments again, and we now interpret this as referring not to the planet but to the universe itself - current observations suggest that the balance of matter and energy in the universe is such that the universe is, in fact, [http://en.wikipedia.org/wiki/Shape_of_the_universe#Flat_universe flat] on the largest scales. (Whether this is coincidence or reflective of underlying laws is currently unknown.)
* The arguments could continue around the circle, now referring to the universe, but aren't generally applicable.

==Transcript==
{{incomplete transcript}}
{{incomplete transcript}}
:[Six people are standing upon a white circle as if it were a miniature planet. Each person says something and the text is displayed over their heads in a closed circle that encloses the whole picture.]

:''From topmost, going clockwise...''
:Cueball: '''Actually,''' measurements suggest it's flat.
:Ponytail: '''Actually,''' it's a sphere.
:White Hat: '''Actually,''' it's an oblate spheroid.
:Megan: '''Actually,''' it's a sphere defined by the EGM96 coefficients.
:(Name unknown): '''Actually,''' it's that plus local topography.
:Hairy: '''Actually,''' it's embedded in a universe that's curved.

{{comic discussion}}
[[Category:Comics featuring Cueball]]
[[Category:Comics featuring Megan]]
[[Category:Comics featuring Ponytail]]
[[Category:Comics featuring White Hat]]
[[Category:Comics featuring Hairy]]

1318: Actually

2014-01-17T06:32:42Z

DrJoel: /* Explanation */ Full draft explanation.

{{comic
| number = 1318
| date = January 17, 2014
| title = Actually
| image = actually.png
| titletext = Protip: You can win every exchange just by being one level more precise than whoever talked last. Eventually, you'll defeat all conversational opponents and stand alone.
}}

==Explanation==
{{incomplete|Created by a BOT - Please change this comment when editing this page.}}

* The picture is designed to have us thinking about a planet (presumably Earth), such that when we read the first speaker's comment, we interpret it as "The Earth is flat", which was the earliest view of the planet. (The speaker does not explicitly state their subject, however, which leads to the comic's punchline.)
* The second speaker explains that the Earth is actually a sphere, tracking the progression of knowledge of the Earth's shape.
* The third speaker provides further detail on the shape, that rather than being spherical, the Earth is actually an [http://en.wikipedia.org/wiki/Oblate_spheroid oblate spheroid]. On Earth, this occurs because a rotating body tends to bulge at the equator (where the matter experiences greater centripetal forces - analogous to experiencing more force at the outside of a round-a-bout rather than the centre), and is known as the [http://en.wikipedia.org/wiki/Equatorial_bulge equatorial bulge].
* A more accurate description is the [http://en.wikipedia.org/wiki/EGM96 Earth Gravitational Model 1996] which provided a detailed map of Earth's gravitational field. This therefore refines the oblate spheroid model even further.
* The next speaker notes that this is still a very high level model of the planet (necessary because of the sizes involved) and that the true shape of the planet is given by the actual local topography (i.e., mountains, hills, valleys, etc.) which can be thought as overlaid on the planet wide models.
* Changing tack, the remaining speaker notes that our planet sits in a [http://en.wikipedia.org/wiki/General_relativity curved space-time], where our planet's gravity, as well as all other objects, bend the space and time around them. On the largest scale, this has the potential to lead to a [http://en.wikipedia.org/wiki/Shape_of_the_universe curvature] of the four dimensional space-time of the universe, hence "universe that is curved". Such a universe can either be "open" or "closed", depending on how much mass and energy there is. In an "closed" universe, if you drew a large enough triangle in space, you would find that the angles did not add up to to 180 degrees (just like if it was drawn on the surface of a balloon - in this case, the angles would add up to less than 180 degrees because the points would be shrunk). In an "open" universe, the angles would be more than 180 degrees.
* Finally, the first speaker comments again, and we now interpret this as referring not to the planet but to the universe itself - current observations suggest that the balance of matter and energy in the universe is such that the universe is, in fact, [http://en.wikipedia.org/wiki/Shape_of_the_universe#Flat_universe flat] on the largest scales. (Whether this is coincidence or reflective of underlying laws is currently unknown.)
* The arguments could continue around the circle, now referring to the universe, but aren't generally applicable.

==Transcript==
{{incomplete transcript}}
{{incomplete transcript}}
:[Six people are standing upon a white circle as if it were a miniature planet. Each person says something and the text is displayed over their heads in a closed circle that encloses the whole picture.]

:''From topmost, going clockwise...''
:Cueball: '''Actually,''' measurements suggest it's flat.
:Ponytail: '''Actually,''' it's a sphere.
:White Hat: '''Actually,''' it's an oblate spheroid.
:Megan: '''Actually,''' it's a sphere defined by the EGM96 coefficients.
:(Name unknown): '''Actually,''' it's that plus local topography.
:Hairy: '''Actually,''' it's embedded in a universe that's curved.

{{comic discussion}}
[[Category:Comics featuring Cueball]]
[[Category:Comics featuring Megan]]
[[Category:Comics featuring Ponytail]]
[[Category:Comics featuring White Hat]]
[[Category:Comics featuring Hairy]]

1318: Actually

2014-01-17T06:20:56Z

DrJoel: /* Explanation */ Next two explanations

1318: Actually

2014-01-17T06:14:33Z

DrJoel: /* Explanation */ First two points explained (draft)