![Please click the figure above for a larger image with annotations.
Note 1.
A paraphrase of Carl Sagan’s famous line:
“…But from a planet orbiting a star in a distant globular cluster, a still more glorious dawn awaits, not a sun-rise, but a galaxy rise.”
Carl Sagan delivered a speech about star lifetimes and globular
clusters in episode 9 of his series,
Cosmos. A clip of the original is
available on youtube. That line has recently become the
refrain of a song generated from speeches
by physicists and scientists.
Note 2.
While the local approximation that the Author gives here is well-defined and a reasonable
metric for visualization, numerous other factors are at play that could decrease the apparent
size of the gravity wells. In particular,
“gravity assist” examples such as the
Oberth effect could allow rockets to enter and exit a gravity well more easily. Other proposed
methods exist, but are largely impractical for today’s rocket technology which has difficulty
producing powerful but tightly controlled thrusts
([1]
[2]).
Note 3.
Update: Thanks to Tumblr user Menstrom for pointing out this is a Sirens of Titan reference.
To be frank, your Curators are stumped by the Author’s intent here. Several
speculations have been offered, but nothing seems consistent. The best guess
we can offer to our Dear Readers is that this is a rowing chant. This interpretation
seems plausible, as it is notable that Titan and Earth share a unique kinship as
the only planets in the Solar system with surface-exposed oceans (albeit of radically
different chemical structure).
Addenda
It was somewhat surprising to your Curator that no mention of the re-classified
dwarf planet Pluto, given the Author’s previous
work on the subject.](http://s3.amazonaws.com/xkcdexplained/gravity_wells_explained_large.png "Please click the figure above for a larger image with annotations.
Note 1.
A paraphrase of Carl Sagan’s famous line:
“…But from a planet orbiting a star in a distant globular cluster, a still more glorious dawn awaits, not a sun-rise, but a galaxy rise.”
Carl Sagan delivered a speech about star lifetimes and globular
clusters in episode 9 of his series,
Cosmos. A clip of the original is
available on youtube. That line has recently become the
refrain of a song generated from speeches
by physicists and scientists.
Note 2.
While the local approximation that the Author gives here is well-defined and a reasonable
metric for visualization, numerous other factors are at play that could decrease the apparent
size of the gravity wells. In particular,
“gravity assist” examples such as the
Oberth effect could allow rockets to enter and exit a gravity well more easily. Other proposed
methods exist, but are largely impractical for today’s rocket technology which has difficulty
producing powerful but tightly controlled thrusts
([1]
[2]).
Note 3.
Update: Thanks to Tumblr user Menstrom for pointing out this is a Sirens of Titan reference.
To be frank, your Curators are stumped by the Author’s intent here. Several
speculations have been offered, but nothing seems consistent. The best guess
we can offer to our Dear Readers is that this is a rowing chant. This interpretation
seems plausible, as it is notable that Titan and Earth share a unique kinship as
the only planets in the Solar system with surface-exposed oceans (albeit of radically
different chemical structure).
Addenda
It was somewhat surprising to your Curator that no mention of the re-classified
dwarf planet Pluto, given the Author’s previous
work on the subject.")
Please click the figure above for a larger image with annotations.
- Note 1.
-
A paraphrase of Carl Sagan’s famous line:
“…But from a planet orbiting a star in a distant globular cluster, a still more glorious dawn awaits, not a sun-rise, but a galaxy rise.”
Carl Sagan delivered a speech about star lifetimes and globular clusters in episode 9 of his series, Cosmos. A clip of the original is available on youtube. That line has recently become the refrain of a song generated from speeches by physicists and scientists. - Note 2.
- While the local approximation that the Author gives here is well-defined and a reasonable metric for visualization, numerous other factors are at play that could decrease the apparent size of the gravity wells. In particular, “gravity assist” examples such as the Oberth effect could allow rockets to enter and exit a gravity well more easily. Other proposed methods exist, but are largely impractical for today’s rocket technology which has difficulty producing powerful but tightly controlled thrusts ([1] [2]).
- Note 3.
- Update: Thanks to Tumblr user Menstrom for pointing out this is a Sirens of Titan reference. To be frank, your Curators are stumped by the Author’s intent here. Several speculations have been offered, but nothing seems consistent. The best guess we can offer to our Dear Readers is that this is a rowing chant. This interpretation seems plausible, as it is notable that Titan and Earth share a unique kinship as the only planets in the Solar system with surface-exposed oceans (albeit of radically different chemical structure).
- Addenda
- It was somewhat surprising to your Curator that no mention of the re-classified dwarf planet Pluto, given the Author’s previous work on the subject.
