Editing 1276: Angular Size
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==Explanation== | ==Explanation== | ||
+ | {{incomplete}} | ||
This comic is a comparison of the {{w|angular diameter|angular diameters}} (or apparent diameter) of various celestial objects at the surface of the earth relative to a vertex at the center of the Earth as diagrammed in the opening panel. The objects' scales are compared to actual objects on earth. Each size given is for the object at its closest approach to earth. | This comic is a comparison of the {{w|angular diameter|angular diameters}} (or apparent diameter) of various celestial objects at the surface of the earth relative to a vertex at the center of the Earth as diagrammed in the opening panel. The objects' scales are compared to actual objects on earth. Each size given is for the object at its closest approach to earth. | ||
− | London's {{w|M25 motorway}} is around 60 | + | London's {{w|M25 motorway}} is around 60 km (35 miles) across, a {{w|soccer field}} is about 100 meters long, a {{w|Table tennis table|ping pong table}} is 274 centimeters long, a {{w|laptop}} is about 35 centimeters across, the {{w|tilde}} symbol on a keyboard is about 5 millimeters long, and a cell of ''{{w|Escherichia coli|E. coli}}'' is about 2 microns long. |
− | A simple {{w|Intercept theorem|formula}} can be used to find the size on earth of a celestial object when the size of | + | A simple {{w|Intercept theorem|formula}} can be used to find the size on earth of a celestial object when the size of and distance to the object is known. This is done by taking the radius of the earth, multiplying by the diameter of the object, and dividing by the distance to the object from the center of the earth. |
The space objects referenced in the panels are: | The space objects referenced in the panels are: | ||
− | *The {{w|Sun}} and the {{w|Moon}}, and also the open cluster {{w|Messier 25}}, have approximately the same size (around 0.5 | + | * The {{w|Sun}} and the {{w|Moon}}, and also the open cluster {{w|Messier 25}}, have approximately the same size (around 0.5 degrees of arc) when seen from the Earth. |
− | *{{w|Mercury (planet)|Mercury}}, {{w|Venus}}, {{w|Mars}}, {{w|Jupiter}}, {{w|Saturn}}, {{w|Uranus}}, and {{w|Neptune}} are the other planets of the {{w|Solar System}}. | + | * {{w|Mercury (planet)|Mercury}}, {{w|Venus}}, {{w|Mars}}, {{w|Jupiter}}, {{w|Saturn}}, {{w|Uranus}}, and {{w|Neptune}} are the other planets of the {{w|Solar System}}. |
− | *{{w|Io (moon)|Io}}, {{w|Europa (moon)|Europa}}, {{w|Ganymede (moon)|Ganymede}}, and {{w|Callisto (moon)|Callisto}} are the main moons of Jupiter; {{w|Titan (moon)|Titan}} is the largest moon of Saturn; and {{w|Triton (moon)|Triton}} is the largest moon of Neptune. {{w|Ceres (dwarf planet)|Ceres}} and {{w|Pluto}} are {{w|dwarf planet}}s. | + | * {{w|Io (moon)|Io}}, {{w|Europa (moon)|Europa}}, {{w|Ganymede (moon)|Ganymede}}, and {{w|Callisto (moon)|Callisto}} are the main moons of Jupiter; {{w|Titan (moon)|Titan}} is the largest moon of Saturn; and {{w|Triton (moon)|Triton}} is the largest moon of Neptune. {{w|Ceres (dwarf planet)|Ceres}} and {{w|Pluto}} are {{w|dwarf planet}}s. |
− | *{{w|Phobos (moon)|Phobos}} and {{w|Deimos (moon)|Deimos}} are the moons of Mars. {{w|Eris (dwarf planet)|Eris}} is another dwarf planet. {{w|R Doradus}} and {{w|Betelgeuse}} are giant stars, respectively around 180 and 640 | + | * {{w|Phobos (moon)|Phobos}} and {{w|Deimos (moon)|Deimos}} are the moons of Mars. {{w|Eris (dwarf planet)|Eris}} is another dwarf planet. {{w|R Doradus}} and {{w|Betelgeuse}} are giant stars, respectively around 180 and 640 light-years away. R Doradus is the star with the largest apparent diameter (other than the sun, of course). |
− | *{{w|4942 Munroe}} is an asteroid [http://blog.xkcd.com/2013/09/30/asteroid-4942-munroe/ named] after xkcd author [[Randall]] Munroe. {{w|Proxima Centauri}}, {{W|Alpha Centauri|Alpha Centauri AB}}, {{w|Barnard's star}} and {{w|Sirius}} are nearby stars (all within 10 | + | * {{w|4942 Munroe}} is an asteroid [http://blog.xkcd.com/2013/09/30/asteroid-4942-munroe/ named] after xkcd author [[Randall]] Munroe. {{w|Proxima Centauri}}, {{W|Alpha Centauri|Alpha Centauri AB}}, {{w|Barnard's star}} and {{w|Sirius}} are nearby stars (all within 10 light-years from the Sun). |
− | *{{w|HD 189733 b}}, {{w|Gliese 581 | + | * {{w|HD 189733 b}}, {{w|Gliese 581 b}}, {{w|Gliese 667 Cc}}, {{w|82 G. Eridani#Planetary_system|HD 20794 c}}, {{w|Tau Ceti#Planets|Tau Ceti c}}, and {{w|KOI-1686.01}} are {{w|extrasolar planet}}s; the parenthetical names are references to the comic [[1253: Exoplanet Names]]. However, some of the planets' parenthetical names do not match the table in the previous comic. For example, HD 20794 c is called "Legoland" rather than "Moonchild" in [[1253: Exoplanet Names]]. The {{w|black hole}} at the center of our Galaxy is {{w|Sagittarius A*}}, a massive object containing a mass more than 4 million times of our Sun. |
− | *{{w|Voyager 1}} and {{w|Voyager 2|2}} are space probes launched in 1977, and currently around 125 and 100 | + | * {{w|Voyager 1}} and {{w|Voyager 2|2}} are space probes launched in 1977, and currently around 125 and 100 {{w|astronomical unit}}s away, respectively. |
− | The title text | + | The title text is about astronomy would be much easier if the celestial sphere were mapped to the earth, should come as no surprise; essentially, it's equivalent to asking "what if the earth were a giant telescope." That is, although there's no actual optical setup which would enable such a mapping, an earth so mapped would be functioning as a giant telescope. |
− | Approximate values for the mappings to the Earth sphere (based on mean Earth radius at 6,371.0 | + | Approximate values for the mappings to the Earth sphere (based on mean Earth radius at 6,371.0 km): |
{| class="wikitable sortable" | {| class="wikitable sortable" | ||
|- | |- | ||
Line 42: | Line 43: | ||
|- | |- | ||
| rowspan="4"| Panel 1 | | rowspan="4"| Panel 1 | ||
− | | | + | || Sun |
− | || 149,600,000 | + | || 149,600,000 km |
− | || 1,392,684 | + | || 1,392,684 km |
− | || 59.3 | + | || 59.3 km |
|- | |- | ||
− | | | + | || Moon <small>Semi-major axis</small> |
− | || 384,399 | + | || 384,399 km |
− | || 3,476.28 | + | || 3,476.28 km |
− | || 57.6 | + | || 57.6 km |
|- | |- | ||
|| Moon <small>Perigee</small> | || Moon <small>Perigee</small> | ||
− | || 363,295 | + | || 363,295 km |
− | || 3,476.28 | + | || 3,476.28 km |
− | || 60.9 | + | || 60.9 km |
|- | |- | ||
− | | | + | || Messier 25 |
− | || 2,100 light-years <br/> 19.867 × 10 | + | || 2,100 light-years <br/> 19.867 × 10^15 km |
− | || 19 light-years <br/> 179.753 × 10 | + | || 19 light-years <br/> 179.753 × 10^12 km |
− | || 57.6 | + | || 57.6 km |
|- | |- | ||
| rowspan="7"| Panel 2 | | rowspan="7"| Panel 2 | ||
− | | | + | || Mercury <small>closest approach</small> |
− | || 92 million km | + | || 92 million km |
− | || 4,879.4 | + | || 4,879.4 km |
− | || 0.34 | + | || 0.34 km |
|- | |- | ||
− | | | + | || Venus <small>closest approach</small> |
− | || 41 million km | + | || 41 million km |
− | || 12 | + | || 12.103.6 km |
− | || 1.9 | + | || 1.9 km |
|- | |- | ||
− | | | + | || Mars <small>closest approach</small> |
− | || 56 million km | + | || 56 million km |
− | || 6,792.4 | + | || 6,792.4 km |
− | || 0.77 | + | || 0.77 km |
|- | |- | ||
− | | | + | || Jupiter |
− | || 778,547,200 | + | || 778,547,200 km |
− | || 139,822 | + | || 139,822 km |
− | || 1.14 | + | || 1.14 km |
|- | |- | ||
− | | | + | || Saturn |
− | || 1,433,449,370 | + | || 1,433,449,370 km |
− | || 120,536 | + | || 120,536 km |
− | || 0.54 | + | || 0.54 km |
|- | |- | ||
− | | | + | || Uranus |
− | || 2,876,679,082 | + | || 2,876,679,082 km |
− | || 51,118 | + | || 51,118 km |
− | || 0.11 | + | || 0.11 km |
|- | |- | ||
− | | | + | || Neptune |
− | || 4,503,443,661 | + | || 4,503,443,661 km |
− | || 49,528 | + | || 49,528 km |
− | || 0.07 | + | || 0.07 km |
|- | |- | ||
| rowspan="8"| Panel 3 | | rowspan="8"| Panel 3 | ||
− | | | + | || Io |
− | || 778,547,200 | + | || 778,547,200 km |
− | || 3,643 | + | || 3,643 km |
− | || 29.8 | + | || 29.8 m |
|- | |- | ||
− | | | + | || Europa |
− | || 778,547,200 | + | || 778,547,200 km |
− | || 3,122 | + | || 3,122 km |
− | || 25.5 | + | || 25.5 m |
|- | |- | ||
− | | | + | || Ganymede |
− | || 778,547,200 | + | || 778,547,200 km |
− | || 5,262 | + | || 5,262 km |
− | || 43.1 | + | || 43.1 m |
|- | |- | ||
− | | | + | || Callisto |
− | || 778,547,200 | + | || 778,547,200 km |
− | || 4,821 | + | || 4,821 km |
− | || 39.5 | + | || 39.5 m |
|- | |- | ||
− | | | + | || Titan |
− | || 1,433,449,370 | + | || 1,433,449,370 km |
− | || 5,150 | + | || 5,150 km |
− | || 22.9 | + | || 22.9 |
|- | |- | ||
− | | | + | || Triton |
− | || 4,503,443,661 | + | || 4,503,443,661 km |
− | || 2,705.2 | + | || 2,705.2 km |
− | || 3.8 | + | || 3.8 m |
|- | |- | ||
− | | | + | || Ceres <small>Perihelion</small> |
− | || 380,995,855 | + | || 380,995,855 km |
− | || 974.6 | + | || 974.6 km |
− | || 16.3 | + | || 16.3 m |
|- | |- | ||
− | | | + | || Pluto <small>Perihelion</small> |
− | || 4,437,000,000 | + | || 4,437,000,000 km |
− | || 2,306 | + | || 2,306 km |
− | || 3.3 | + | || 3.3 m |
|- | |- | ||
| rowspan="6"| Panel 4 | | rowspan="6"| Panel 4 | ||
− | | | + | || Phobos |
− | || 56 million km | + | || 56 million km |
− | || 26.8 × 22.4 × 18.4 | + | || 26.8 × 22.4 × 18.4 km |
− | || 3.05 | + | || 3.05 m |
|- | |- | ||
− | | | + | || Deimos |
− | || 56 million km | + | || 56 million km |
− | || 15 × 12.2 × 10.4 | + | || 15 × 12.2 × 10.4 km |
− | || 1.71 m | + | || 1.71 m |
|- | |- | ||
− | | | + | || Eris <small>Perihelion</small> |
− | || 5.723 × 10 | + | || 5.723 × 10^9 km |
− | || | + | || 2326 km |
− | || 2.59 m | + | || 2.59 m |
|- | |- | ||
− | || Eris | + | || Eris <small>Aphelion</small> |
− | || 14.602 × 10 | + | || 14.602 × 10^9 km |
− | || | + | || 2326 km |
− | || 1.01 m | + | || 1.01 m |
|- | |- | ||
− | || | + | || Betelguse |
− | || 643 ± 146 light-years <br/>max. 7.464 × 10 | + | || 643 ± 146 light-years <br/>max. 7.464 × 10^15 km |
− | || 950–1,200 solar radii <br/>max. 1.671 × 10 | + | || 950–1,200 solar radii <br/>max. 1.671 × 10^9 km |
− | || 1.43 m | + | || 1.43 m |
|- | |- | ||
− | | | + | || R Doradus |
− | || 178 ± 10 light-years <br/>max. 1.778 × 10 | + | || 178 ± 10 light-years <br/>max. 1.778 × 10^15 km |
− | || 370 ± 50 solar radii <br/>max. 0.515 × 10 | + | || 370 ± 50 solar radii <br/>max. 0.515 × 10^9 km |
− | || 1.85 m | + | || 1.85 m |
|- | |- | ||
| rowspan="6"| Panel 5 | | rowspan="6"| Panel 5 | ||
− | | | + | || 4942 Munroe |
− | || 2.2 AU (1.2 AU closest to earth, 179.4 × 10 | + | || 2.2 AU (1.2 AU closest to earth, 179.4 × 10^6 km) |
− | || | + | || 9-10 km |
− | || 35.5 | + | || 35.5 cm |
|- | |- | ||
− | | | + | || Proxima Centauri |
− | || 4.243 light-years <br/> 40.142 × 10 | + | || 4.243 light-years <br/> 40.142 × 10^12 km |
− | || 0.141 solar radii <br/> 0.196 × 10 | + | || 0.141 solar radii <br/> 0.196 × 10^6 km |
− | || 3.11 | + | || 3.11 cm |
|- | |- | ||
− | | | + | || Barnard's Star |
− | || 5.980 light-years <br/> 56.574 × 10 | + | || 5.980 light-years <br/> 56.574 × 10^12 km |
− | || 0.196 solar radii <br/> 0.272 × 10 | + | || 0.196 solar radii <br/> 0.272 × 10^6 km |
− | || 3.06 | + | || 3.06 cm |
|- | |- | ||
− | | | + | || Alpha Centauri B |
− | || 4.366 light-years <br/> 41.305 × 10 | + | || 4.366 light-years <br/> 41.305 × 10^12 km |
− | || 0.865 solar radii <br/> 1.204 × 10 | + | || 0.865 solar radii <br/> 1.204 × 10^6 km |
− | || 18.6 | + | || 18.6 cm |
|- | |- | ||
− | | | + | || Sirius |
− | || 8.6 light-years <br/> 81.362 × 10 | + | || 8.6 light-years <br/> 81.362 × 10^12 km |
− | || 1.711 solar radii <br/> 2.382 × 10 | + | || 1.711 solar radii <br/> 2.382 × 10^6 km |
− | || 18.7 | + | || 18.7 cm |
|- | |- | ||
− | | | + | || Alpha Centauri A |
− | || 4.366 light-years <br/> 41.305 × 10 | + | || 4.366 light-years <br/> 41.305 × 10^12 km |
− | || 1.227 solar radii <br/> 1.708 × 10 | + | || 1.227 solar radii <br/> 1.708 × 10^6 km |
− | || 26.3 | + | || 26.3 cm |
|- | |- | ||
| rowspan="9"| Panel 6 | | rowspan="9"| Panel 6 | ||
− | | | + | || HD 189733 b |
− | || 63 light-years <br/> 596.024 × 10 | + | || 63 light-years <br/> 596.024 × 10^12 km |
− | || 1.138 Jupiter radii <br/> 159,117 | + | || 1.138 Jupiter radii <br/> 159,117 km |
− | || 1.7 | + | || 1.7 mm |
|- | |- | ||
|| Gliese 581 g | || Gliese 581 g | ||
− | || 20.3 light-years <br/> 192.052 × 10 | + | || 20.3 light-years <br/> 192.052 × 10^12 km |
− | || 1.3 to 2.0 Earth radii <br/> max. 25 | + | || 1.3 to 2.0 Earth radii <br/> max. 25.484 km |
− | || 0.85 | + | || 0.85 µm |
|- | |- | ||
− | | | + | || Gliese 581 (Parent star) |
− | || 20.3 light-years <br/> 192.052 × 10 | + | || 20.3 light-years <br/> 192.052 × 10^12 km |
− | || 0.29 solar radii <br/> | + | || 0.29 solar radii <br/> 403,878 km |
− | || 1.34 | + | || 1.34 cm |
|- | |- | ||
− | | | + | || Black Hole at the center of our Galaxy |
− | || 25,900 light-years <br/> 245.032 × 10 | + | || 25,900 light-years <br/> 245.032 × 10^15 km |
− | || Mass 4.31 × 10 | + | || Mass 4.31 × 10^6:<br/>12.684 × 10^6 km |
− | || 0.33 | + | || 0.33 mm |
|- | |- | ||
− | | | + | || Gliese 667 Cc |
− | || 22.7 light-years <br/> 214.757 × 10 | + | || 22.7 light-years <br/> 214.757 × 10^12 km |
− | || 2.0 Earth radii <br/> 25 | + | || 2.0 Earth radii <br/> 25.484 km |
− | || 0.76 | + | || 0.76 µm |
|- | |- | ||
|| Gliese 667 (Parent star) | || Gliese 667 (Parent star) | ||
− | || 22.7 light-years <br/> 214.757 × 10 | + | || 22.7 light-years <br/> 214.757 × 10^12 km |
− | || 0.42 solar radii <br/> 584,927 | + | || 0.42 solar radii <br/> 584,927 km |
− | || 1.74 | + | || 1.74 cm |
|- | |- | ||
− | | | + | || HD 20794 c (Parent star) |
− | || 20 light-years <br/> 189.214 × 10 | + | || 20 light-years <br/> 189.214 × 10^12 km |
− | || 0.92 solar radii <br/> 1,281,269 | + | || 0.92 solar radii <br/> 1,281,269 km |
− | || 4.31 | + | || 4.31 cm |
|- | |- | ||
− | | | + | || Tau Ceti C (Parent star) |
− | || 11.905 light-years <br/> 112.629 × 10 | + | || 11.905 light-years <br/> 112.629 × 10^12 km |
− | || 0.793 solar radii <br/> 1,104,398 | + | || 0.793 solar radii <br/> 1,104,398 km |
− | || 6.25 | + | || 6.25 cm |
|- | |- | ||
− | | | + | || Koi-1686.01 (Parent star) |
− | || 1033.8 light-years <br/> 9.780 × 10 | + | || 1033.8 light-years <br/> 9.780 × 10^15 km |
− | || 0.52 solar radii <br/> 724,195 | + | || 0.52 solar radii <br/> 724,195 km |
− | || 0.47 | + | || 0.47 mm |
|- | |- | ||
| Panel 7 | | Panel 7 | ||
|| Voyager probes | || Voyager probes | ||
− | || ( | + | || (Voyager 1 at 126.10 AU) 1.886×10^10 km |
− | || 20 meters | + | || 20 meters (with antennas) |
− | || 6.76 | + | || 6.76 µm |
|} | |} | ||
==Transcript== | ==Transcript== | ||
− | + | {{incomplete transcript}} | |
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{{comic discussion}} | {{comic discussion}} | ||
[[Category:Math]] | [[Category:Math]] | ||
[[Category:Astronomy]] | [[Category:Astronomy]] | ||
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