0681: "Gravity Wells"

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Quicksilver
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0681: "Gravity Wells"

Postby Quicksilver » Mon Dec 28, 2009 6:21 am UTC

Image
alt text: "This doesn't take into account the energy imparted by orbital motion (or gravity assists or the Oberth effect), all of which can make it easier to reach outer planets."
http://xkcd.com/681_large/ credit to EcoReck20 for this.

MDark.Math
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Re: "Gravity Wells" Discussion

Postby MDark.Math » Mon Dec 28, 2009 6:25 am UTC

Wow, now he's just showing off

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jspenguin
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Re: "Gravity Wells" Discussion

Postby jspenguin » Mon Dec 28, 2009 6:26 am UTC

"A thrown baseball could escape Phobos"
"You could escape Deimos with a bike and a ramp"

And yet, in the original Doom, set on Phobos and Deimos, you couldn't jump out of a 4-foot pit. That BFG must be incredibly massive.

Code: Select all

from __future__ import skynet

Blaze Krakaros
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Re: "Gravity Wells" Discussion

Postby Blaze Krakaros » Mon Dec 28, 2009 6:27 am UTC

I don't see the burning cheese in this comic.

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Re: "Gravity Wells" Discussion

Postby EcoReck20 » Mon Dec 28, 2009 6:27 am UTC

MDark.Math wrote:Wow, now he's just showing off


You seem to have something against these large posters. :(

OneGyT
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Re: "Gravity Wells" Discussion

Postby OneGyT » Mon Dec 28, 2009 6:28 am UTC

Wait, I'm confused. In uber-simple terms, is this basically displaying the amount of gravity necessary to escape orbit, adjusted for our smallminded earth-centric thinking?

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Re: "Gravity Wells" Discussion

Postby IronyandParadox » Mon Dec 28, 2009 6:30 am UTC

There's...there's no Pluto. =(

Now, I know Pluto doesn't meet all the criteria for being a planet (clearing the neighborhood of its orbit? Ehhh...) and I know that classifying it as a dwarf planet makes things much neater and it satisfies my secret OCD side, but something about seeing this comic without it made a little part of me die inside.

On another note, I would *love* to have this as a poster.
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EcoReck20
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Re: "Gravity Wells" Discussion

Postby EcoReck20 » Mon Dec 28, 2009 6:31 am UTC

Why are the moons in the chart, but not Pluto? It seems pretty much everyone forgot about it and now its crying in loneliness. SHAME ON ALL OF YOU.

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Quicksilver
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Re: "Gravity Wells" Discussion

Postby Quicksilver » Mon Dec 28, 2009 6:32 am UTC

Also, Randall, get out of my head! I was just looking for your mom in past comics, and all of a sudden, there's a new "your mom" joke!

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Josephine
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Re: "Gravity Wells" Discussion

Postby Josephine » Mon Dec 28, 2009 6:33 am UTC

Randall seems to have seen the Sagan remix videos.(look at neptune guy)
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Re: "Gravity Wells" Discussion

Postby Pit » Mon Dec 28, 2009 6:35 am UTC

This comic made me so glad that I took Astronomy 101. I wish he had put Ceres and Eris though... it would have been a good excuse to stick Pluto in.
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Re: "Gravity Wells" Discussion

Postby Siguy » Mon Dec 28, 2009 6:36 am UTC

I feel like it would be possible to fit more jokes into this. I mean, there could be a lot more detail like in the other big comics (electromagnetic spectrum, etc). This was kind of bland. The well diagram is pretty interesting, though.

Also, not only is Pluto left out, Callisto is as well (we have Europa, Ganymede, and Io but not Callisto?)


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Re: "Gravity Wells" Discussion

Postby TheNextCaesar » Mon Dec 28, 2009 6:39 am UTC

HonoreDB wrote:Should be "A still more glorious dawn."

Sorry, it's the OCD in me.
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wallacoloo
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Re: "Gravity Wells" Discussion

Postby wallacoloo » Mon Dec 28, 2009 6:40 am UTC

I forgot this forum supported smileys (don't worry, I edited them out!)

That was a bit of a disappointment. But Randall was probably in a hurry to not be even more late. The funniest part of this one was the your mom joke. No real punchline =(

But it's still better than I could do =D
Last edited by wallacoloo on Mon Dec 28, 2009 6:43 am UTC, edited 1 time in total.

khaighle
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Re: "Gravity Wells" Discussion

Postby khaighle » Mon Dec 28, 2009 6:40 am UTC

Came for the "STILL more glorious dawn."

Left without being disappointed.

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Re: "Gravity Wells" Discussion

Postby Pit » Mon Dec 28, 2009 6:42 am UTC

Siguy wrote:I feel like it would be possible to fit more jokes into this. I mean, there could be a lot more detail like in the other big comics (electromagnetic spectrum, etc). This was kind of bland. The well diagram is pretty interesting, though.


@.@ I would have liked to have seen a nuclear fusion joke.
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Omegaton
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Re: "Gravity Wells" Discussion

Postby Omegaton » Mon Dec 28, 2009 6:44 am UTC

Well, looks like I'm off to Wikipedia to read about gravity wells!

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Re: "Gravity Wells" Discussion

Postby ananab » Mon Dec 28, 2009 6:45 am UTC

Pluto? Where are you? :'(

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Re: "Gravity Wells" Discussion

Postby Actaeus » Mon Dec 28, 2009 6:46 am UTC

I'm confused -- if the height difference between Earth and the plateau next to it represents energy needed to escape its gravity well, what does the steep slope just past the Moon mean? Each planet has its own local dimple, but there are also differences in height between the crests between planets.

Once you've escaped Earth's gravity, aren't you as 'free' as if you escaped Jupiter's? Is it because of distance from the Sun?


EDIT: Wait, I understand! It's because of the Sun; the jump between the Moon and Mars represents the potential energy difference because of the farther distance from the Sun. In effect, the whole thing is part of the Sun's own gravity well, just as Jupiter's satellites are partway down its well.

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Re: "Gravity Wells" Discussion

Postby morticae » Mon Dec 28, 2009 6:46 am UTC

At first I thought he missed a golden opportunity for a Pluto joke... then I realized that's the joke. We all know it. He knows we all know it. And he knows how craaaaaazy it makes us!

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Re: "Gravity Wells" Discussion

Postby firestar27 » Mon Dec 28, 2009 6:47 am UTC

Very interesting, but not very funny, and it was the just the idea of the drawing that was interesting, even though a lot more interesting ideas could have been put in. In summary: great idea, but not so great an execution. I hope he expands on this later. (Even editing this quietly later would be appreciated.)
And I miss Pluto. If you can have various moons, then you can have Pluto!

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Re: "Gravity Wells" Discussion

Postby eMan2718281828 » Mon Dec 28, 2009 6:48 am UTC

I feel like there was some writer's block going on and someone just decided to make a very elaborate "your mom" joke...

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Re: "Gravity Wells" Discussion

Postby sje46 » Mon Dec 28, 2009 6:52 am UTC

The things making noise on Titan...is that a Vonnegut reference?
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Re: "Gravity Wells" Discussion

Postby arcticfox.sq » Mon Dec 28, 2009 6:53 am UTC

I don't know, I kind of liked this, because it wasn't really funny, not despite of it.
Image

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Actaeus
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Re: "Gravity Wells" Discussion

Postby Actaeus » Mon Dec 28, 2009 6:56 am UTC

I love this type of comic -- very Tuftesque, as he mentioned with the LotR character map.

But I feel he could really have included more jokes or factoids. This is neat, but it doesn't live up to Height or Depth or (best of all) the Online Communities map.

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Re: "Gravity Wells" Discussion

Postby bakert » Mon Dec 28, 2009 7:03 am UTC

I much preferred the comic to this thread.

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psychosomaticism
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Re: "Gravity Wells" Discussion

Postby psychosomaticism » Mon Dec 28, 2009 7:03 am UTC

The autotuned Sagan music video reference was much appreciated.

Also, to some of the previous posters: why does it have to be funny. It's interesting and has a few silly things thrown in for good measure.

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Re: "Gravity Wells" Discussion

Postby CorruptUser » Mon Dec 28, 2009 7:08 am UTC

So... how much force do I need to escape your mom?

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Re: "Gravity Wells" Discussion

Postby Arancaytar » Mon Dec 28, 2009 7:12 am UTC

"Hey, you there on Neptune. Is... is that you Carl?"

Also, this shows what a bitch it would be to try to land on Mercury without landing on the sun instead. Decelerate just a tiny bit too slowly, or miss Mercury in its orbit by a hair, and it's over.
Last edited by Arancaytar on Mon Dec 28, 2009 7:20 am UTC, edited 2 times in total.
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SolkaTruesilver
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Re: "Gravity Wells" Discussion

Postby SolkaTruesilver » Mon Dec 28, 2009 7:15 am UTC

CorruptUser wrote:So... how much force do I need to escape your mom?


The jokeyard called.

They want their joke back.

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Re: "Gravity Wells" Discussion

Postby freespace » Mon Dec 28, 2009 7:19 am UTC

Earth's gravity well depth has 3 different figures: 5478, 6000, 6379km. The last one should be the correct one.

(Incidentally it is equal to the radius of the Earth used in the calculation).

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Re: "Gravity Wells" Discussion

Postby phillipsjk » Mon Dec 28, 2009 7:20 am UTC

jspenguin wrote:"A thrown baseball could escape Phobos"
"You could escape Deimos with a bike and a ramp"

And yet, in the original Doom, set on Phobos and Deimos, you couldn't jump out of a 4-foot pit. That BFG must be incredibly massive.


Well, the DOOM (and later Quake) guy also carries heavy armor, 100 shotgun shell, 200 bullets/nails, 200 cells, and 99 Rockets, Brass knuckles/axe, Single-barreled shotgun, Double-barreled shothgun, pistol/nailgun, chaingun/supernailgun, rocket launcher, lightning gun/BFG. If you assume each gun weighs 5kg, that adds up to 35kg. The ammo probably doubles that to 70kg. Since you don't want to carry more than about 30% of your weight on your back, DOOM/Quake guy must have a mass of about 233kg, or a(n earth) weight of over 500 pounds (mainly muscle)


I mainly wanted to point out that Earth's planetary status was revoked the same time Pluto's was by the IAU. Since the IAU is only concerned with "Celestial bodies," the planetary definition begins "A Celestial body that: . . ."

That said, Earth is not out of place in the chart because several moons are represented as well as a couple planetoids.
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Vagrant
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Re: "Gravity Wells" Discussion

Postby Vagrant » Mon Dec 28, 2009 7:22 am UTC

In the comic, Carl is saying "an even more glorious dawn awaits."

The actual quote is "a still more glorious dawn awaits."

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Re: "Gravity Wells" Discussion

Postby Ferahgo » Mon Dec 28, 2009 7:23 am UTC

sje46 wrote:The things making noise on Titan...is that a Vonnegut reference?


That was my thought also. If it is, then well done, as that's one of my favorite books ever.

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KTC
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Re: "Gravity Wells" Discussion

Postby KTC » Mon Dec 28, 2009 7:25 am UTC

I want Pluto!! :cry:

Nereid
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Re: "Gravity Wells" Discussion

Postby Nereid » Mon Dec 28, 2009 7:28 am UTC

phillipsjk wrote:I mainly wanted to point out that Earth's planetary status was revoked the same time Pluto's was by the IAU. Since the IAU is only concerned with "Celestial bodies," the planetary definition begins "A Celestial body that: . . ."

That said, Earth is not out of place in the chart because several moons are represented as well as a couple planetoids.


Earth is a celestial body, but not an astronomical body. http://en.wikipedia.org/wiki/Astronomical_object

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Re: "Gravity Wells" Discussion

Postby skeptical scientist » Mon Dec 28, 2009 7:30 am UTC

For those who were disappointed, like me, that the Jupiter/Sun numbers were not listed, and all those complaining about Pluto:
  1. Jupiter: 181,000 kilometers
  2. Sun: 19,500,000 kilometers
  3. Pluto: 75 kilometers
Pluto is about one quarter as deep as the moon, or too shallow for its depth to really be visible without its own cutout.

Google makes calculating these things extremely easy.
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Re: "Gravity Wells" Discussion

Postby chocolate.razorblades » Mon Dec 28, 2009 7:30 am UTC

I would love to have Randall as a physics teacher.

Arvedui
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Re: "Gravity Wells" Discussion

Postby Arvedui » Mon Dec 28, 2009 7:34 am UTC

Wonderful, but more would have been nice. Too quick of a comic. But wonderfully interesting nonetheless!


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