2906: Earth - Revision history

42.book.addict: added Category:Rockets using HotCat

2024-11-01T17:37:38Z

added Category:Rockets using HotCat

162.158.186.34: /* The scale of the error */ We don’t know whether they decelerated until moving backwards or they accelerated.

2024-03-24T13:05:31Z

‎The scale of the error: We don’t know whether they decelerated until moving backwards or they accelerated.

Take The A Train To Watertown: Orbital speeds

2024-03-20T00:42:28Z

Orbital speeds

B for brain: /* Explanation */

2024-03-19T20:21:35Z

‎Explanation

BunsenH: Undo revision 337546 by B for brain (talk) page is less than a week old, and still being edited

2024-03-19T04:44:10Z

Undo revision 337546 by B for brain (talk) page is less than a week old, and still being edited

172.69.194.217: /* The "pale blue" dot */ Looks like parenthesis confusion happened.

2024-03-19T04:35:46Z

‎The "pale blue" dot: Looks like parenthesis confusion happened.

Rps: /* The scale of the error */ typo: h -> s

2024-03-18T18:50:43Z

‎The scale of the error: typo: h -> s

Rps: /* The scale of the error */ burn error

2024-03-18T18:49:12Z

‎The scale of the error: burn error

172.70.85.127: /* The "pale blue" dot */ Tyop (nobody read that far, before? ;)

2024-03-16T16:53:08Z

‎The "pale blue" dot: Tyop (nobody read that far, before? ;)

B for brain: /* Explanation */

2024-03-16T11:20:44Z

‎Explanation

← Older revision		Revision as of 17:37, 1 November 2024
Line 51:		Line 51:
	[[Category:Comics featuring real people]]		[[Category:Comics featuring real people]]
	[[Category:Space]]		[[Category:Space]]
		+	[[Category:Rockets]]

@@ Line 28: / Line 28: @@
 The general lack of other visible stars, etc, would be explained by the exposure being tuned to not wash out the illuminated internal view, and not being set up for useful astronomical shots, though may then set another range of useful limits on what magnitude of reflected sunlight must still arrive from Earth in order to remain visible.<!-- Additional bonus note: This would depend upon the effective Earth-phase, Earth-albedo (e.g. ocean/land/ice-cap as prime reflector), the actual levels of the running lights by the 'cupola' viewing window and possible lower-dynamic-range capabilities/adjustments to the resulting image by the hypothetical 'comic camera', perhaps other details. On top of it being more governed by Rule Of Funny than *strict* reality, I suggest that making the actual calculation would be more troublesome than it's worth. Right? -->
-The orbital speed in low-earth orbit is ~8 km/s. A typical de-orbiting maneuver requires slowing down by about 100 m/s (which according to the ''[[What_If%3F_(book)|What If]]'' chapter "Orbital Submarine" could be accomplished with the 24 Trident missiles carried aboard an Ohio-class submarine.) However, escape speed is ~11 km/s, meaning the vessel must go faster by ~3 km/s. So Carl has indeed made quite an error if he fired the boosters thirtyfold too much and in the opposite direction.
+The orbital speed in low-earth orbit is ~8 km/s. A typical de-orbiting maneuver requires slowing down by about 100 m/s (which according to the ''[[What_If%3F_(book)|What If]]'' chapter "Orbital Submarine" could be accomplished with the 24 Trident missiles carried aboard an Ohio-class submarine.) However, escape speed is ~11 km/s, meaning the vessel must go faster by ~3 km/s. So Carl has indeed made quite an error if he fired the boosters thirtyfold too much and in the opposite direction (or 190fold in the correct direction, resulting in the spacecraft traveling in the opposite direction of previously).
 === The "pale blue" dot ===

@@ Line 26: / Line 26: @@
 The ''absence'' of a clearly visible Moon, which would have a near-identical phase to the illuminated Earth and could easily be the second brightest object in the scene, is therefore best explained by it being no more than a sub-pixel object, indistinguishable from the surrounding darkness of space, somewhere within thirty Earth diameters (and thus [[2205: Types of Approximation|approximately]], in this image, pixels) of the visible Earth. This could include being sufficiently in conjunction/opposition to Earth to blend in, or be obscured by it.<!-- Note just for those who pass by this source: This excludes the 'out there' humorous possibility that the badly-done manouver did not effect the spacecraft, so much as it somehow sent the *Earth* out of its position, leaving the ship (and the Moon, and more than half of all other satellites?) still technically continuing more or less their prior Earth-orbits - which are now technically various solar ones... (BunsenH:)This could be a remake of {{w|Space: 1999}}. (OP:)Indeed, but actually turned up several notches! -->
-The general lack of other visible stars, etc, would be explained by the exposure being tuned to not wash out the illuminated internal view, and not being set up for useful astronomical shots, though may then set another range of useful limits on what magnitude of reflected sunlight must still arrive from Earth in order to remain visible.<!-- Additional bonus note: This would depend upon the effective Earth-phase, Earth-albedo (e.g. ocean/land/ice-cap as prime reflector), the actual levels of the running lights by the 'cupula' viewing window and possible lower-dynamic-range capabilities/adjustments to the resulting image by the hypothetical 'comic camera', perhaps other details. On top of it being more governed by Rule Of Funny than *strict* reality, I suggest that making the actual calculation would be more troublesome than it's worth. Right? -->
+The general lack of other visible stars, etc, would be explained by the exposure being tuned to not wash out the illuminated internal view, and not being set up for useful astronomical shots, though may then set another range of useful limits on what magnitude of reflected sunlight must still arrive from Earth in order to remain visible.<!-- Additional bonus note: This would depend upon the effective Earth-phase, Earth-albedo (e.g. ocean/land/ice-cap as prime reflector), the actual levels of the running lights by the 'cupola' viewing window and possible lower-dynamic-range capabilities/adjustments to the resulting image by the hypothetical 'comic camera', perhaps other details. On top of it being more governed by Rule Of Funny than *strict* reality, I suggest that making the actual calculation would be more troublesome than it's worth. Right? -->
-The orbital speed in low-earth orbit is ~8km/s. Escape speed is ~11km/s. So to reentry the spacecraft must do a retrograde burn of some hundreds m/s, while to escape it must do a prograde burn of ~3km/s. So it must have been quite an error (~10 times bigger and in the opposite direction).
+The orbital speed in low-earth orbit is ~8 km/s. A typical de-orbiting maneuver requires slowing down by about 100 m/s (which according to the ''[[What_If%3F_(book)|What If]]'' chapter "Orbital Submarine" could be accomplished with the 24 Trident missiles carried aboard an Ohio-class submarine.) However, escape speed is ~11 km/s, meaning the vessel must go faster by ~3 km/s. So Carl has indeed made quite an error if he fired the boosters thirtyfold too much and in the opposite direction.
 === The "pale blue" dot ===

@@ Line 10: / Line 10: @@
 ==Explanation==
 [[File:Pale Blue Dot.png|200px|right|thumb|The ''Pale Blue Dot'' image from Voyager 1. Earth is the "pale blue dot" halfway up the rightmost color band.]]
 At first sight, this appears to be the famous {{w|Carl Sagan}} commentary, upon the ''{{w|Pale Blue Dot}}'' image of Earth, a picture taken by the {{w|Voyager 1 probe}} in 1990 (at that time 6 billion kilometers away) but having been transmitted back to Earth to be appreciated as one of the most iconic 'photos of Earth from space', along with ''{{w|Earthrise}}'' and ''{{w|The Blue Marble}}''. Sagan's written, and later spoken, words evoke how the lives of all of us are somehow confined to barely more than a single pixel's-worth of existence upon an already zoomed-in view of space.

@@ Line 10: / Line 10: @@
 ==Explanation==
 [[File:Pale Blue Dot.png|200px|right|thumb|The ''Pale Blue Dot'' image from Voyager 1. Earth is the "pale blue dot" halfway up the rightmost color band.]]
 At first sight, this appears to be the famous {{w|Carl Sagan}} commentary, upon the ''{{w|Pale Blue Dot}}'' image of Earth, a picture taken by the {{w|Voyager 1 probe}} in 1990 (at that time 6 billion kilometers away) but having been transmitted back to Earth to be appreciated as one of the most iconic 'photos of Earth from space', along with ''{{w|Earthrise}}'' and ''{{w|The Blue Marble}}''. Sagan's written, and later spoken, words evoke how the lives of all of us are somehow confined to barely more than a single pixel's-worth of existence upon an already zoomed-in view of space.

@@ Line 33: / Line 33: @@
 Although it might initially look like a white dot, the comic truly has used a pale blue color for the dot that represents Earth, with the color used in the "2x" version of the image seeming to be 0xBDCFF4.
-This can be interpreted as predominently a very light gray, with an extra hint of green and a bigger hint of blue. Or redefined as an {{w|HSL and HSV|HSV}} triplet of of 220.4 (a greenish-blue hue), 22.5% (relatively unsaturated) and 95.7% (very bright), all consistent with how the sunlit side of an Earthlike world would look with large oceans, vast swathes of terrestrial vegetation and atmospheric clouds) if necessarily abstracted down to a very limited number of pixels.
+This can be interpreted as predominently a very light gray, with an extra hint of green and a bigger hint of blue. Or redefined as an {{w|HSL and HSV|HSV}} triplet of of 220.4 (a greenish-blue hue), 22.5% (relatively unsaturated) and 95.7% (very bright), all consistent with how the sunlit side of an Earthlike world would look with large oceans, vast swathes of terrestrial vegetation and atmospheric clouds, necessarily abstracted down to a very limited number of pixels.
 Looking at {{w|File:Pale_Blue_Dot.png|an actual example of the 'original'}}, seems to give a possible RGB of 0x95B39E (which gives: hue of 138, i.e. a 'bluish-green'; saturation level of 16.8%; brightness value of 70.2%), which is of course also consistent with the above assumptions about Earth. But all such images are of course ultimately derived as a composite of the data from [https://pds-rings.seti.org/voyager/iss/inst_cat_na1.html#filters eight separate 'filters'], which don't neatly fit into the {{w|RGB color model}}, and always subject to various kinds of post-processing and image conversion techniques.<!-- Maybe someone can find an actual 'original original' from NASA/JPL/whoever, or even the original eight 'raws'..? -->

← Older revision		Revision as of 18:49, 18 March 2024
Line 27:		Line 27:

	The general lack of other visible stars, etc, would be explained by the exposure being tuned to not wash out the illuminated internal view, and not being set up for useful astronomical shots, though may then set another range of useful limits on what magnitude of reflected sunlight must still arrive from Earth in order to remain visible.<!-- Additional bonus note: This would depend upon the effective Earth-phase, Earth-albedo (e.g. ocean/land/ice-cap as prime reflector), the actual levels of the running lights by the 'cupula' viewing window and possible lower-dynamic-range capabilities/adjustments to the resulting image by the hypothetical 'comic camera', perhaps other details. On top of it being more governed by Rule Of Funny than strict reality, I suggest that making the actual calculation would be more troublesome than it's worth. Right? -->		The general lack of other visible stars, etc, would be explained by the exposure being tuned to not wash out the illuminated internal view, and not being set up for useful astronomical shots, though may then set another range of useful limits on what magnitude of reflected sunlight must still arrive from Earth in order to remain visible.<!-- Additional bonus note: This would depend upon the effective Earth-phase, Earth-albedo (e.g. ocean/land/ice-cap as prime reflector), the actual levels of the running lights by the 'cupula' viewing window and possible lower-dynamic-range capabilities/adjustments to the resulting image by the hypothetical 'comic camera', perhaps other details. On top of it being more governed by Rule Of Funny than strict reality, I suggest that making the actual calculation would be more troublesome than it's worth. Right? -->
		+
		+	The orbital speed in low-earth orbit is ~8km/s. Escape speed is ~11km/h. So to reentry the spacecraft must do a retrograde burn of some hundreds m/s, while to escape it must do a prograde burn of ~3km/s. So it must have been quite an error (~10 times bigger and in the opposite direction).

	=== The "pale blue" dot ===		=== The "pale blue" dot ===