## What-If 0136: "Spiders vs. the Sun"

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Envelope Generator
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### What-If 0136: "Spiders vs. the Sun"

http://what-if.xkcd.com/136/
Which has a greater gravitational pull on me: the Sun, or spiders?

Why did Firefox ditch the "automatically load images" option? I don't mind surfing on spider-related topics as long as I can turn images off.
I'm going to step off the LEM now... here we are, Pismo Beach and all the clams we can eat

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rpgamer
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### Re: What-If 0136: "Spiders vs. the Sun"

Oh good, I didn't have to go through the trouble of making it.

I recently did a similar calculation (well, let Wolfra-Alpha do the calculation) when that old "Planetary alignment means gravity will be weak and you can jump in the air for several seconds" hoax was going around. The one spewing it seemed ready to believe it, so I set up the numbers to prove yo mamma so fat, she has a greater gravitational pull on you than Pluto.

My old physics professor was proud.
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sevenperforce
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### Re: What-If 0136: "Spiders vs. the Sun"

rpgamer wrote:Oh good, I didn't have to go through the trouble of making it.

I recently did a similar calculation (well, let Wolfra-Alpha do the calculation) when that old "Planetary alignment means gravity will be weak and you can jump in the air for several seconds" hoax was going around. The one spewing it seemed ready to believe it, so I set up the numbers to prove yo mamma so fat, she has a greater gravitational pull on you than Pluto.

My old physics professor was proud.

Are there any planets which have a greater gravitational pull on you than yo momma? Presuming a yo-momma of roughly 200 kg within a radius of 10 km?

I wonder how much you would have to expand Earth's biosphere (from all spiders, to all arachnids, to all invertebrates, to all animal life, to all life, etc.) before its combined gravitational pull would outweigh (yes, this is the right term) the sun's.

ConMan
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### Re: What-If 0136: "Spiders vs. the Sun"

rpgamer wrote:Oh good, I didn't have to go through the trouble of making it.

I recently did a similar calculation (well, let Wolfra-Alpha do the calculation) when that old "Planetary alignment means gravity will be weak and you can jump in the air for several seconds" hoax was going around. The one spewing it seemed ready to believe it, so I set up the numbers to prove yo mamma so fat, she has a greater gravitational pull on you than Pluto.

My old physics professor was proud.

Ah yes, that's always a good one. In fact, the gravitational effect of a perfect planetary alignment (and when you hear reports of "planetary alignment" it's usually more like "four or five planets are in the same 90° arc of the sky while the rest are wherever") is about the same as that of a full jumbo jet flying overhead.

As for the spiders, I am a little confused that the pull of a single Goliath spider is the same as that of all of the spiders in the treatment plant - I assume that it's because you can get closer to the centre of mass of the single spider as compared to the treatment plant ones? It still seems weird that they'd end up at the same order of magnitude.

On the other hand, it does raise the question - is there something on Earth whose average gravitational effect is on the same order of magnitude as the sun? We can work with the What-if calculation that there's a difference of 13 orders of magnitude between the Sun's gravity and all spiders', and try to find something that covers the Earth and weighs about as much as 10^13 spiders. According to Wikipedia, the total global live biomass of plants and animals on Earth consists of about 560 billion tonnes of carbon, which equates to about 2.8 million times the mass of all spiders, or about 6.5 orders of magnitude, so we need something that is 10 million times that. The same article says that the total biomass of bacteria is believed to be slightly larger than that of plants and animals, so that gives us another 0.3 orders of magnitude.

How about the oceans? Again, looking at Wikipedia, the total mass of the hydrosphere is about 1.4×10^21 kg, which looks to be about what we're looking for unless I've made an error (which is entirely possible).
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### Re: What-If 0136: "Spiders vs. the Sun"

I think this is one of the most amazing pictures Randall did. Lovecraft would be proud.

Neil_Boekend
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### Re: What-If 0136: "Spiders vs. the Sun"

I like spiders. They eat bugs and bugs bug me. Spiders leave me alone. I had a 5 or 6 cm (incuding legs) Tegenaria domestica living on the walls of my previous house. It was fun to see it skitter really fast across the wall. Fascinating how they walk with all those legs.

Note: there are no dangerous native spiders in my country, although sometimes an accidentally imported black widow survives until the first decent winter. For the native spiders something akin to a wasp's sting is the worst you'll get.
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### Re: What-If 0136: "Spiders vs. the Sun"

No mention of red spiders? Was the counter-red-spider offensive a success then?
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### Re: What-If 0136: "Spiders vs. the Sun"

Envelope Generator wrote:http://what-if.xkcd.com/136/
Why did Firefox ditch the "automatically load images" option? I don't mind surfing on spider-related topics as long as I can turn images off.

They seem to have moved it into a per-site option which is rather odd and annoying. Right-click menu->View page info->Permissions, scroll down to Images and turn off.
"Your mother ate my dog!"
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### Re: What-If 0136: "Spiders vs. the Sun"

rpgamer wrote:My old physics professor was proud.

Personally, I would use this in my sig (if it applied to me)
"Your mother ate my dog!"
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### Re: What-If 0136: "Spiders vs. the Sun"

sevenperforce wrote:Presuming a yo-momma of roughly 200 kg within a radius of 10 km?

That's ridiculous. It's less dense than air. Yo mamma is far more dense than that!
Mikeski wrote:A "What If" update is never late. Nor is it early. It is posted precisely when it should be.

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flicky1991 wrote:I'm being quoted too much!

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Flumble
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### Re: What-If 0136: "Spiders vs. the Sun"

Neil_Boekend wrote:
sevenperforce wrote:Presuming a yo-momma of roughly 200 kg within a radius of 10 km?

That's ridiculous. It's less dense than air. Yo mamma is far more dense than that!

Yo mamma so dense she wouldn't understand the joke!

Whizbang
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### Re: What-If 0136: "Spiders vs. the Sun"

Yo momma's so vain she probably thinks this joke is about her.

sevenperforce
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### Re: What-If 0136: "Spiders vs. the Sun"

Answering my own question...

A yo-momma of 200 kg at a distance of 2 m produces an acceleration of 3.335e-9 m/s2. At its closest approach, Mars produces an acceleration of 1.436e-9 m/s2, at its farthest, it produces an acceleration of 2.662e-10 m/s2.

Of course, the moon produces a constant acceleration that's a good 4-5 orders of magnitude greater. All the time.

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### Re: What-If 0136: "Spiders vs. the Sun"

[11] happens after [12].

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### Re: What-If 0136: "Spiders vs. the Sun"

Whizbang wrote:Yo momma's so vain she probably thinks this joke is about her.

I bet you wouldn't say that to Ben Taylor. (He knows kung fu!)
I hear velociraptor tastes like chicken.

BrianTung1967
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### Re: What-If 0136: "Spiders vs. the Sun"

I'm a little surprised that Randall didn't explore this:

We don't generally feel the force of a gravitational field from a body (celestial or arachnid) unless there's an electromagnetic force resisting our response to that field. That's weight. That's why we feel weightless in free fall: It's not that we're not subject to the force of gravity; we're merely "free" to respond to it (by falling). To first order, our entire body is subject to the force and we don't feel it. Under normal circumstances, the electromagnetic forces between the ground and our feet resist our fall, and give rise to the sensation of weight.

To second order, of course, we do feel tidal forces, which are the differentials in the force of gravitational pull and vary as the inverse cube of the distance. So although that doesn't make the spherical shell of spiders on the Earth's surface exert a greater tidal impact than the Sun (the Sun being "only" about 24,000 Earth radii away), it does seem it would flip things around in the case of the Back (not Black) River Wastewater Treatment Plant. The plant proper looks to be about 100 m across, a distance ratio of about 1.5 billion. Even if we include the entire complex, that's maybe 2 km across, a distance ratio of about 75 million.

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### Re: What-If 0136: "Spiders vs. the Sun"

BrianTung1967 wrote:celestial or arachnid

Okay, forget all I've said before. THAT is the name of my new band.
I'm going to step off the LEM now... here we are, Pismo Beach and all the clams we can eat

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### Re: What-If 0136: "Spiders vs. the Sun"

I'm curious why Randall didn't also run the math on produced spidersilk. Spiders are one of the interesting species that kind of externalize a significant portion of their body plan.
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### Re: What-If 0136: "Spiders vs. the Sun"

You know, if the Earth is carried through space by a giant turtle and four elephants, then what is carrying the Sun? What's to say it's not a giant spider?

BrianTung1967 wrote:the Back (not Black) River Wastewater Treatment Plant.

Oh. But "Black River" seemed like such a fitting name for a plant that processes large amounts of blackwater.

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### Re: What-If 0136: "Spiders vs. the Sun"

All it takes is one bad day to reduce the sanest man alive to lunacy. That's how far the world is from where I am. Just one bad day.

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### Re: What-If 0136: "Spiders vs. the Sun"

sevenperforce wrote:Answering my own question...

A yo-momma of 200 kg at a distance of 2 m produces an acceleration of 3.335e-9 m/s2. At its closest approach, Mars produces an acceleration of 1.436e-9 m/s2, at its farthest, it produces an acceleration of 2.662e-10 m/s2.

Of course, the moon produces a constant acceleration that's a good 4-5 orders of magnitude greater. All the time.

I think you'll find Jupiter can out-gravity Mars at Earth's surface, as well. (Mars 6.4e23 kg @ 5.46e7 km, Jupiter 1.9e27 kg @ 6.29e8 km, Jupiter has 22x the pull if they're both as close to Earth as possible.)

So "yo momma so light, Jupiter has more gravitational pull on you than she does". At two meters, anyway. Not if you're hugging yo momma.

Hug yo momma.

CharonPDX
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### Re: What-If 0136: "Spiders vs. the Sun"

Well, this was a What-if that there was *ZERO* chance of me following any of the links on...

NOPE NOPE NOPE

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### Re: What-If 0136: "Spiders vs. the Sun"

I still think the article missed a few corners - see, the trouble with spiders (and I'm talking in an academic sense - I'm very much an arachnophobe myself so any other way I'd be talking terrified-to-death nonsense right now) is that even the biggest one isn't big enough to scare you proper (even if you're terrified of a mouse-sized thing you don't really expect it to do serious damage to you after all once poison is out of the question). However, if one's willing to loosen the definition of "spider" to include things that merely LOOK like a spider (ie. huge long-articulated-legs-to-body size ratio) which I think is the actual thing that we find terrifying, then one finds properly scary stuff like the Japanese spider crab, which gets several METERS big. Don't come to me if you fail to un-see it after you look though...

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### Re: What-If 0136: "Spiders vs. the Sun"

Wooloomooloo wrote:Japanese spider crab

That creature looks awesome! Wonder if it could walk above water though. It seems too fragile.
It look more like a CGI creature than something real. Especially the image with the perfect black background. That just looks too much like a game monster.
The wikipedia page does note that it has a gentle disposition though.
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### Re: What-If 0136: "Spiders vs. the Sun"

What if you're in some sort of Fear Factor scenario where you are actually touching many spiders? (Let's say the guys on Fear Factor have covered you in tarantulas. Boy that was a bad show)

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### Re: What-If 0136: "Spiders vs. the Sun"

I'm disappointed he didn't go into the gravitational pull of all the world's spiders gathered together in a ball (loosely, densely, and compressed into neutronium) right next to you, which would increase their gravitational pull due to proximity.

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### Re: What-If 0136: "Spiders vs. the Sun"

The sun is just asserting it's dominance here. A few what-ifs ago it got offended when we left it's domain of heat. The 50 million times stronger gravitational pull more than makes up for this. Also if anyone was paying attention to the giant solar flare that recently occured there is proof that the sunw as offended and tried to kill us.

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### Re: What-If 0136: "Spiders vs. the Sun"

ConMan wrote:As for the spiders, I am a little confused that the pull of a single Goliath spider is the same as that of all of the spiders in the treatment plant - I assume that it's because you can get closer to the centre of mass of the single spider as compared to the treatment plant ones? It still seems weird that they'd end up at the same order of magnitude.
First we need their mass; according to a paper titled Sexual Cannibalism in Orb-Weaving Spiders: An Economic Model, it's about 20 grams for males and several times that for females.
This off by a factor of 1000, and should be milligrams. Thus the orb-weaver total mass was about 80k times the Goliath birdeater, and if we assume the sphere of orb-weavers is centered about 30m away instead of 10cm away, that works out to the same gravitational pull.
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### Re: What-If 0136: "Spiders vs. the Sun"

Neil_Boekend wrote:
Wooloomooloo wrote:Japanese spider crab

That creature looks awesome! Wonder if it could walk above water though. It seems too fragile.
It look more like a CGI creature than something real. Especially the image with the perfect black background. That just looks too much like a game monster.
The wikipedia page does note that it has a gentle disposition though.

Well, now I'm definitely not clicking that link... Here I was thinking "oh, it's a crab, it'll be fine..." and then you say it looks like a game monster spider...

NOPE NOPE NOPE

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### Re: What-If 0136: "Spiders vs. the Sun"

PhilHibbs wrote:I'm disappointed he didn't go into the gravitational pull of all the world's spiders gathered together in a ball (loosely, densely, and compressed into neutronium) right next to you, which would increase their gravitational pull due to proximity.
I was expecting the same. Fine, we can calculate it. Assuming the 200 million kilogram of spiders form a ball* with a density close to the density of water, the radius is 36m and its gravitational attraction is 0.37 mm/s^2**. This is still an order of magnitude below the gravitational pull from sun at 5.9 mm/s^2. You would have to reduce the ball radius by a factor of 4 which makes the spider ball more dense than every known material on earth by a factor of 3. Alternatively, keep the density but increase the amount of spiders by a factor ~60.

*A ball is not the right shape for maximal gravitational attraction, but the difference to the optimal shape is in the order of a few percent.

**Note: such a ball of spiders would induce large non-gravitational accelerations in most humans.

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### Re: What-If 0136: "Spiders vs. the Sun"

BrianTung1967 wrote:That's why we feel weightless in free fall: It's not that we're not subject to the force of gravity; we're merely "free" to respond to it (by falling). To first order, our entire body is subject to the force and we don't feel it.

I think it's a bit more profound than that, I think we're in an inertial frame where the gravity field from the sun is almost flat. So really the question should boil down to the difference between the sun's pull on our head and feet, and the total pull of all spiders. My hunch would be the spiders have it.

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### Re: What-If 0136: "Spiders vs. the Sun"

CharonPDX wrote:
Neil_Boekend wrote:
Wooloomooloo wrote:Japanese spider crab

That creature looks awesome! Wonder if it could walk above water though. It seems too fragile.
It look more like a CGI creature than something real. Especially the image with the perfect black background. That just looks too much like a game monster.
The wikipedia page does note that it has a gentle disposition though.

Well, now I'm definitely not clicking that link... Here I was thinking "oh, it's a crab, it'll be fine..." and then you say it looks like a game monster spider...

Then again it's a cute white-and-orange spotted gentle crab with a funny mouth-thing. Completely unlike a hairy black monster spider with a thousand eyes.
The scariest thing about the crab-and-black image is the implied perspective due to its overly long arms. (Seriously, what's the benefit of boney arms that are almost twice as long as your legs?) But you can just scroll down to the image of a smaller variant of the crab in a humble pose.

Let this artist's depiction of a giant spider crab reassure you:

click for more pixels

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### Re: What-If 0136: "Spiders vs. the Sun"

Wooloomooloo wrote:Japanese spider crab

Looking at the last picture in that article, I did not need to know that facehuggers that fit on whale faces exist in real life.

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### Re: What-If 0136: "Spiders vs. the Sun"

CharonPDX wrote:Well, this was a What-if that there was *ZERO* chance of me following any of the links on...

NOPE NOPE NOPE

Yeah, this was how I felt for the whole thing. Deeply uncomfortable. The art did not help, even though it was not especially realistic. Many of the other more...cataclysmic what-ifs seem quite reasonable and comforting by comparison.

Not clicking ANYTHING to do with this one.

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### Re: What-If 0136: "Spiders vs. the Sun"

MarvinM wrote:
BrianTung1967 wrote:That's why we feel weightless in free fall: It's not that we're not subject to the force of gravity; we're merely "free" to respond to it (by falling). To first order, our entire body is subject to the force and we don't feel it.

I think it's a bit more profound than that, I think we're in an inertial frame where the gravity field from the sun is almost flat. So really the question should boil down to the difference between the sun's pull on our head and feet, and the total pull of all spiders. My hunch would be the spiders have it.

The Sun's tidal effect is about half of the Moon's - which is why spring tides and neap tides occur. My money would still be on the Sun (and on fire...)

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### Re: What-If 0136: "Spiders vs. the Sun"

Yeah, we're about 23,500 times closer to the center of mass of the spiders as we are to the Sun, but the sun is 10^22 times more massive, so the Sun's tidal force is still about 770 million times greater than the tidal force from the spiders, and across 2m of distance still accounts for a difference of a few hundred times the total gravitational force from all those spiders.
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### Re: What-If 0136: "Spiders vs. the Sun"

What if we use more spiders?

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### Re: What-If 0136: "Spiders vs. the Sun"

Whizbang wrote:What if we use more spiders?

Sweet Cthulhu, save us from this horror!

Flumble
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### Re: What-If 0136: "Spiders vs. the Sun"

Whizbang wrote:What if we use more spiders?

You mean something like a mole of spiders?
If you manage to fit that amount of spiders in the treatment plant, the gravitational pull would be 23-8-7=8 orders (fine, 6.22ᴇ23/80ᴇ6/50ᴇ6 times as large) of magnitude larger than the Sun's.

 continuing gmalivuk's worldwide spider tidal force calculation
And, IIDTMC, the tidal force would be about 15 orders of magnitude larger.
Last edited by Flumble on Fri Apr 17, 2015 12:12 pm UTC, edited 1 time in total.