xkcd: What If?

[neufer]

Blood Alcohol

Squirrels. Why’d it have to be squirrels? I hate squirrels!

[Beyond]

Blood Alcohol

Squirrels. Why’d it have to be squirrels? I hate squirrels!

Because, IF you are what you eat, then squirrels is nuts, which fits right in with some of the nutty questions asked and answered(?) in xkcd.

[Chris Peterson]

Squirrels. Why’d it have to be squirrels? I hate squirrels!

[bystander]

Starlings

• I was watching this video and was wondering: How many birds there would need to be for
  gravity to take over and force them into a gargantuan ball of birds? — Justin Basinger

[Ann]

Starlings

• I was watching this video and was wondering: How many birds there would need to be for
  gravity to take over and force them into a gargantuan ball of birds? — Justin Basinger

I found the starlings-collapsing-into-a-star example interesting.

I note, however, that all stars that we know of, except some burnt-out specimens like white dwarfs and neutron stars, are made up predominantly of hydrogen and helium. A star made of starlings would be very deficient in hydrogen, and it would contain practically no helium whatsoever.

Would there be enough hydrogen in a "starling star" for core hydrogen fusion to get going? If not, would there be some other kind of fusion (which would require a lot of mass, though) or would the starling star simply shine by the light and warmth of its own gravitational contraction? Would it therefore be a "failed star", somewhat like a brown dwarf, except that it would fail as a star due to its lack of normal stellar "fuel"?

Ann

[Beyond]

How about methane? Or, would the methane just build up and be set off by something, and cause there to be feathers, feathers, everywhere??

[neufer]

How about methane?

See: A Mighty Wind.

[Beyond]

Yeah, I saw that. But they neglect to say what the mighty wind is. After all, a mighty wind like a hurricane or even a solar storm, is just a big blow hard, when ya gits right down to it.

[bystander]

WWII Films

• Did WWII last longer than the total length of movies about WWII? For that
  matter, which war has the highest movie time:war time ratio? — Becky

[bystander]

Plastic Dinosaurs

• As plastic is made from oil and oil is made from dead dinosaurs,
  how much actual real dinosaur is there in a plastic dinosaur? — Steve Lydford

[neufer]

[b][color=#0000FF]Sinclair Dinoland plastic brontosaurus, 1964[/color][/b]

---

<<At the Chicago World's Fair of 1933-1934, Sinclair Oil Corporation sponsored a dinosaur exhibit meant to point out the putative correlation between the formation of petroleum deposits and the time of dinosaurs, now a largely discredited misconception. The exhibit included a two-ton animated model of a brontosaurus. The exhibit proved so popular it inspired a promotional line of rubber brontosaurs at Sinclair stations, complete with wiggling heads and tails, and the eventual inclusion of the brontosaur logo. Later, inflatable dinosaurs were given as promotional items, and an anthropomorphic version appeared as a service-station attendant in advertisements. Some locations have a life-size model of the mascot straddling the building's entrance.

At the New York World's Fair of 1964–1965, Sinclair again sponsored a dinosaur exhibit, "Dinoland", featuring life-size replicas of nine different dinosaurs, including their signature brontosaurus. Souvenirs from the exhibit included a brochure ("Sinclair and the Exciting World of Dinosaurs") and molded plastic figurines of the dinosaurs featured. After the Fair closed, Dinoland spent a period of time as a traveling exhibit. Two of the replicas are still on display at Dinosaur Valley State Park near Glen Rose, Texas. Another, a model of a Trachodon, has been displayed at Brookfield Zoo outside Chicago, Illinois.>>

[bystander]

Keyboard Power

• As a writer, I'm wondering what would be the cumulative energy of
  the hundreds of thousands of keystrokes required to write a novel. — Nicolas Dickner

[bystander]

Vanishing Water

• What would happen if all the bodies of water on Earth magically disappeared? — Joanna Xu

[neufer]

Click to play embedded YouTube video.

Vanishing Water

• What would happen if all the bodies of water on Earth magically disappeared? — Joanna Xu

[bystander]

Global Snow

• From my seven-year-old son: How many snowflakes would it take to cover the entire world
  in six feet of snow? (I don't know why six feet...but that's what he asked.) — Jed Scott

[bystander]

Cannibalism

• How long could the human race survive on only cannibalism? — Quinn Shaffer

[neufer]

Cannibalism

• How long could the human race survive on only cannibalism? — Quinn Shaffer

http://en.wikipedia.org/wiki/A_Modest_Proposal
http://en.wikipedia.org/wiki/Soylent_Green
http://en.wikipedia.org/wiki/Eloi

[geckzilla]

Hah, it took me a few moments to understand that this picture was supposed to be the tournament bracket and not two sideways hills with snow on top.

[Beyond]

With two slightly leaning poles sticking up.

[neufer]

Hah, it took me a few moments to understand that this picture was supposed to be the tournament bracket and not two sideways hills with snow on top.

[b][color=#0000FF][size=150]Bifurcation diagram for the logistic map[/size][/color][/b]

---

<<The logistic map is a polynomial mapping (equivalently, recurrence relation) of degree 2, often cited as an archetypal example of how complex, chaotic behaviour can arise from very simple non-linear dynamical equations. The map was popularized in a seminal 1976 paper by the biologist Robert May, in part as a discrete-time demographic model analogous to the logistic equation first created by Pierre François Verhulst. Mathematically, the logistic map is written

• 

where:

• x_n is a number between zero and one which represents the ratio of existing population to the maximum possible population at year n, and hence x₀ represents the initial ratio of population to max. population (at year 0)
  
  r is a positive number, and represents a combined rate for reproduction and starvation.

This nonlinear difference equation is intended to capture two effects.

• reproduction where the population will increase at a rate proportional to the current population when the population size is small.
  
  starvation (density-dependent mortality) where the growth rate will decrease at a rate proportional to the value obtained by taking the theoretical "carrying capacity" of the environment less the current population.>>

[b][color=#0000FF]Pierre François Verhulst's logistic equation[/color][/b]

---

A logistic function or logistic curve is a common special case of the more general sigmoid function, with equation:

• 

It was named in 1844-1845 by Pierre François Verhulst, who studied it in relation to population growth. The initial stage of growth is approximately exponential; then, as saturation begins, the growth slows, and at maturity, growth stops.

A typical application of the logistic equation is a common model of population growth, originally due to Pierre-François Verhulst in 1838, where the rate of reproduction is proportional to both the existing population and the amount of available resources, all else being equal. The Verhulst equation was published after Verhulst had read Thomas Malthus' An Essay on the Principle of Population. Verhulst derived his logistic equation to describe the self-limiting growth of a biological population.

Letting P represent population size and t represent time, this model is formalized by the differential equation:

• 

where the constant r defines the growth rate and K is the carrying capacity.

In the equation, the early, unimpeded growth rate is modeled by the first term +rP. The value of the rate r represents the proportional increase of the population P in one unit of time. Later, as the population grows, the second term, which multiplied out is −rP²/K, becomes larger than the first as some members of the population P interfere with each other by competing for some critical resource, such as food or living space. This antagonistic effect is called the bottleneck, and is modeled by the value of the parameter K. The competition diminishes the combined growth rate, until the value of P ceases to grow (this is called maturity of the population).

Dividing both sides of the equation by K gives

• 

Now setting x=P/K gives the differential equation

• 

For r = 1 we have the particular case with which we started.>>

[bystander]

Ink Molecules

• Suppose you were to print, in 12 point text, the numeral 1 using a common cheap ink-jet printer. How many molecules of the ink would be used? At what numerical value would the number printed approximately equal the number of ink molecules used? — David Pelkey

[bystander]

Letter to Mom

• What’s the fastest way to get a hand-written letter from my place in Chicago to my mother in New Jersey? — Tim

[bystander]

Expensive Shoebox

• What would be the most expensive way to fill a size 11 shoebox
  (e.g. with 64 GB MicroSD cards all full of legally purchased music)? — Rick Lewis

[Ann]

Expensive Shoebox

• What would be the most expensive way to fill a size 11 shoebox
  (e.g. with 64 GB MicroSD cards all full of legally purchased music)? — Rick Lewis

That was a fun and thought-provoking read, as always when it comes to xkcd.

Nevertheless, it made me ponder what we actually mean when we say that something is valuable. Still more interesting is why things are valuable.

All right. I guess I can see, although I've certainly not tried it myself, why LSD would be extremely valuable to those who are, so to speak, so inclined. But gold? Why is it so valuable? Is it just because it is pretty and because it won't "rust"? If so, then I think that my own obsession with blue things is hardly more curious than people's willingness to pay through their noses to deck themselves out with gold.

Anyway, suppose you were out in the desert nearly dying of thirst. What would you rather have in that situation, a shoebox full of gold, platinum, plutonium, LSD, MicroSD cards or water? We will assume that the shoebox is watertight and doesn't leak. Seems like a pretty obvious choice.

Suppose you are an astronaut on a one-way trip to Mars. What would you rather bring along in your shoebox? Gold and platinum don't seem like the best choices. Plutonium? I think I read somewhere that some people would like to terraform Mars, and they would start by nuking it. But bringing along plutonium might make your rocket explode even before you reach your destination. LSD? Are we asking for a Major Tom situation? Maybe a shoebox of MicroSD cards full of music might be the best choice after all. There would very likely be some LSD-inspired songs among them, if you get a sudden craving. Assuming you can play the songs in space, or on Mars.

But some extra water might still be a pretty good idea.

Ann

[geckzilla]

Gold is great to bling oneself because it doesn't turn into a pile of rust or even change color over the years. It just doesn't want to react with anything and yet it's malleable. Anyway, humans value pretty things. Otherwise APOD wouldn't be so popular.