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### What-if 0077: "Growth Rate"

Posted: Tue Dec 31, 2013 4:17 pm UTC
Growth Rate
What height would humans reach if we kept growing through our whole development period (i.e. till late teens/early twenties) at the same pace as we do during our first month?

Maria

I find your lack of citations disturbing (3 only).

Happy new year from GMT+8

Posted: Tue Dec 31, 2013 4:22 pm UTC
Well, if he grew at the same rate as a proportion, he would almost reach the Moon by 20.

### Re: What-if 0077: "Growth Rate"

Posted: Tue Dec 31, 2013 4:40 pm UTC
Here's a way around the 'bones collapse' and "can't hardly even breath" problems of a human > 3 meters or so tall.

Let's have this fellow grow by budding, and thus build up a huge centipedish/replicant creature out of a few hundred (or million) merged budded sortahumanclonethingies.

Still couldn't get any taller, but could get bigger.
And would probably have a molpy for a pet.

### Re: What-if 0077: "Growth Rate"

Posted: Tue Dec 31, 2013 5:46 pm UTC
This is what always sobered me as a kid whenever I dreamed of being a T. Rex: reminding myself I wouldn't be able to ride roller coasters. Silly dinosaur.

### Re: What-if 0077: "Growth Rate"

Posted: Tue Dec 31, 2013 5:52 pm UTC
My son was born when WorldCom was still around and growing exponentially. My son was a few weeks early and had to spend some time in the special care nursery. Thus there was a chart showing his mass each day in kilograms. In the WorldCom style, I cherry picked a couple dates. Using the masses recorded on those two dates, I extrapolated what my son would weigh on his first birthday in metric tonnes. To further mimic the WorldCom math, I did the calculation to 6 significant figures.

This extrapolation stuff is not perfect. Instead of weighing in excess of 2 tonnes on his first birthday, my son actually grew to a normal weight. Likewise, in that same year, instead of continuing to report continued exponential growth, WorldCom failed in a series of spectacular accounting scandals.

### Re: What-if 0077: "Growth Rate"

Posted: Tue Dec 31, 2013 5:56 pm UTC
Oh man, the NBA video linked through the last footnote was the best part. Awesome stuff.

### Re: What-if 0077: "Growth Rate"

Posted: Tue Dec 31, 2013 6:32 pm UTC
It would be interesting to do the same extrapolations with respect to constant growth in girth or volume instead of length

### Re: What-if 0077: "Growth Rate"

Posted: Tue Dec 31, 2013 7:06 pm UTC
The reference to the square-cube law is probably not apropos for a supertall but "healthy" human being. The reference to Robert Wadlow points to an unfortunate gentleman who looks rather skinny, weighed 399 pounds, and was 8 feet 11.1 inches tall. His body mass index (BMI) was 27, making that skinny-looking person actually overweight. A "healthy" weight for Wadlow might be 330 pounds, for a BMI of 20. In mks units, his height of 2.72 meters and a weight of 148 kg. He would appear to be even skinnier.

And the mkS gives us a clue for survival - if our giant's metabolism is reduced, he can breath and pump blood at normal velocities. He would appear to move much slower - even Ray Harryhausen's movie giants got that part right.

Yes, bone strength would be a problem - our giant might not be able to stand up, certainly not jump. Blood pressure could be another problem; healthy diastolic blood pressure (the lower number) is 60 psi (400kPa) while the gravity gradient for water is 23 feet per 10 psi ( 1 meter per 10 kPa ), so a 12 meter (39 foot) giant would have 17 psi difference between head and feet. Still, people manage to survive with diastolic blood pressures of 80 or worse. Again, our giant will do better sitting down.

With a BMI of 20, a 12 meter giant will weigh 2880 kg. If their brain size is the same proportion of body mass as us midgets, it might weigh 10 to 20 times as much as our midget brains. Again, their metabolism will be lower, but imagine how many synaptic connections that brain could make! We may be talking hypergenius here!

So, by the time the giant reaches 20 years old, they will have invented antigravity and moved into space, where their weight and bones are no longer a problem. They can continue to grow larger and larger and smarter and smarter, outwitting the rest of us in the competition for food and resources, eventually consuming all the carbon in the solar system, until their antigravity system fails and they collapse into a mole planet. A disaster unanticipated by any B grade horror movie, AFAIK.

### Re: What-if 0077: "Growth Rate"

Posted: Tue Dec 31, 2013 7:36 pm UTC
keithl wrote:So, by the time the giant reaches 20 years old, they will have invented antigravity and moved into space, where their weight and bones are no longer a problem. They can continue to grow larger and larger and smarter and smarter, outwitting the rest of us in the competition for food and resources, eventually consuming all the carbon in the solar system, until their antigravity system fails and they collapse into a mole planet. A disaster unanticipated by any B grade horror movie, AFAIK.

so.... they'll turn into Galactus, then?

### Re: What-if 0077: "Growth Rate"

Posted: Tue Dec 31, 2013 10:11 pm UTC
When I saw this What-If, I thought "hey... I'm pretty sure I've read about it already".
Then I remembered: it is almost exactly the same as the plot of a certain sci-fi novel (from 1904, apparently, which is a little later than I thought it was from).
The novel even has the same eventual height for the grown-up humans (~12m/40ft), though whatever passed for the square-cube law was entirely ignored (no idea why - I'd expect that particular author, at least, to be aware of it).

### Re: What-if 0077: "Growth Rate"

Posted: Tue Dec 31, 2013 10:44 pm UTC
Randall wrote:During their first month, infants grow about 4.4 centimeters

I thought "growth rate" for most things was measured as a percentage, not a linear dimension, over time. So if you're 50 cm and you grow 4.4 cm, I'd call that a growth rate of 8.8% per month, or 175% per year. By age 20, when your growth comes to a screeching halt, you'd be some 300 million meters tall. Basically, light in a vacuum would take about 1 second to travel from head to toe.

Going by mass rather than linear dimension ... I was going to say infants typically don't gain much weight right away, but the WHO charts give the impression that, if anything, mass goes up a little faster than the expected cube of length. I read it as 3.4 kg to 4.5 kg for the same 50th-percentile boys who grow from 50 to 54.4 cm. If that trend holds, you end up at 1.64×1029 kg, about 85 times as massive as Jupiter. Your BMI would be 1.7×1012, which I believe is classified as "obese".

I was going to say something about tidal forces from the earth's gravity between your toes and your head, but I suppose the gravitational force you exert on the rest of the earth is going to be kind of a bigger deal. And yes, you're really a mole planetary body, or mole-py, by then.

Edited: A factor of 2.75 is a growth rate of 175%, not 275%.

### Re: What-if 0077: "Growth Rate"

Posted: Wed Jan 01, 2014 12:45 am UTC
ps.02 wrote:
Randall wrote:During their first month, infants grow about 4.4 centimeters

I thought "growth rate" for most things was measured as a percentage, not a linear dimension, over time. So if you're 50 cm and you grow 4.4 cm, I'd call that a growth rate of 8.8% per month, or 175% per year. By age 20, when your growth comes to a screeching halt, you'd be some 300 million meters tall. Basically, light in a vacuum would take about 1 second to travel from head to toe.

Going by mass rather than linear dimension ... I was going to say infants typically don't gain much weight right away, but the WHO charts give the impression that, if anything, mass goes up a little faster than the expected cube of length. I read it as 3.4 kg to 4.5 kg for the same 50th-percentile boys who grow from 50 to 54.4 cm. If that trend holds, you end up at 1.64×1029 kg, about 85 times as massive as Jupiter. Your BMI would be 1.7×1012, which I believe is classified as "obese".

I was going to say something about tidal forces from the earth's gravity between your toes and your head, but I suppose the gravitational force you exert on the rest of the earth is going to be kind of a bigger deal. And yes, you're really a mole planetary body, or mole-py, by then.

Edited: A factor of 2.75 is a growth rate of 175%, not 275%.

Um, the BMI is, for some confusing reason, based on the square of the height/length, rather than the cube as it really should be (assuming identical proportions anyway - I've seen calculations claiming that, to properly correspond with the square-cube law, it should really be fourth power).
If I know my scientific astronomy anywhere near properly, 1.64×1029 kg is about 8% of the mass of Sol, while 300 million meters is about 20% of its diameter. You'd basically get almost reasonable (within half an order of magnitude - even closer if you consider that a human body normally isn't a sphere) figures for a small star (a low-end red dwarf).

(Oh, and I loved your pun in the third paragraph )

### Re: What-if 0077: "Growth Rate"

Posted: Wed Jan 01, 2014 1:31 am UTC
"What do you mean 'against the rules'? Your team has a freakin' golden retriever!

Is Randall referring to Air Bud?

### Re: What-if 0077: "Growth Rate"

Posted: Thu Jan 02, 2014 12:50 am UTC
keithl wrote:The reference to the square-cube law is probably not apropos for a supertall but "healthy" human being. The reference to Robert Wadlow points to an unfortunate gentleman who looks rather skinny, weighed 399 pounds, and was 8 feet 11.1 inches tall. His body mass index (BMI) was 27, making that skinny-looking person actually overweight. A "healthy" weight for Wadlow might be 330 pounds, for a BMI of 20. In mks units, his height of 2.72 meters and a weight of 148 kg. He would appear to be even skinnier.

BMI is just a reasonably best fit curve for healthy human weights over a typical height range; it isn't a definition of healthy. In fact people at the exceptionally fit end of the bell curve will often have an overweight/obese BMI simply because it doesn't distinguish between fat mass and muscle mass.

### Re: What-if 0077: "Growth Rate"

Posted: Thu Jan 02, 2014 2:58 am UTC
Ehsanit wrote:
keithl wrote:The reference to the square-cube law is probably not apropos for a supertall but "healthy" human being. The reference to Robert Wadlow points to an unfortunate gentleman who looks rather skinny, weighed 399 pounds, and was 8 feet 11.1 inches tall. His body mass index (BMI) was 27, making that skinny-looking person actually overweight. A "healthy" weight for Wadlow might be 330 pounds, for a BMI of 20. In mks units, his height of 2.72 meters and a weight of 148 kg. He would appear to be even skinnier.

BMI is just a reasonably best fit curve for healthy human weights over a typical height range; it isn't a definition of healthy. In fact people at the exceptionally fit end of the bell curve will often have an overweight/obese BMI simply because it doesn't distinguish between fat mass and muscle mass.

Yeah, BMI is one of those things that's almost pulled out of thin air - on an individual level, it's inaccurate enough to be almost useless - you can have two individuals with the same BMI, but different heights, frames and levels of fitness, and one would be underweight and the other obese by more accurate measures.

It has some validity as a statistical measure - it's easy to measure and calculate, and over statistically significant sample sizes, correlates "well enough" that significant correlations with BMI are probably significant correlations with actual measures of body fat.

***

The idea of a child continuing to grow indefinitely is one of the central points of the Shadow series by Orson Scott Card - in which Bean, a supporting character from Ender's Game, has his story told - it turns out that he's the product of genetic manipulation, and, while he grows more slowly as an infant, both his body and his mind continue to grow throughout his life - the consequences of which are a big part of the latest volume - Shadows in Flight. The mutations also, for reasons that are never explained, left him more intelligent and aware than a typical infant even at an age where he appeared underdeveloped, but that's not relevant to the What If...

### Re: What-if 0077: "Growth Rate"

Posted: Thu Jan 02, 2014 5:12 am UTC
&amp;deg; is not an entity.

### Re: What-if 0077: "Growth Rate"

Posted: Thu Jan 02, 2014 8:42 am UTC
Turns out there is another issue with large human size, related to "Peto's Paradox". Superficially, the chance of an exponentially growing fatal cancer getting started would seem to be proportional to the number of cells times the metabolic rate; a similarly proportioned mammal with twice the mass should have twice the chance of getting cancer in a lifetime. Since blue whales weigh 1000 times as much as a human, and mice weigh about 0.001 times as much as a human, we would expect almost no mice to get cancer, and all whales to get cancer. In fact, all mammalian species get cancer in about the same proportions, per average lifetime (short for a mouse, long for a whale, given relative metabolic rates).

In this blog post, Carl Zimmer notes that humans have one copy of the TP53 cancer suppressor gene, and elephants have a dozen copies. Assuming other genes are similarly multiplied, an elephant has more genetic protection against cancer (and maybe someday, gene-mod humans will, too).

But unless our giant has a really slow metabolism, there will be a whole lot of cancer-prone flesh there, with only a normal human's genetic protection per kilogram. A 40x (12 meter BMI scaled) or 200x (square-cube scaled) mass human will have 40x to 200x times the cancer risk. Fatal cancer rates follow a Gompertz curve. For normal-sized people, the rates are about 0.8% by age 50, so they will be 28%/40x and 80%/200x . As the size or the age grows larger, the cancer rate approaches unity,

So before our hypergenius giant grows to planetary size, she/he must first find cures for all cancer. It is comforting to know that normal-sized humans may have a few cancer-free centuries before they get eaten with all the rest of the carbon.

### Re: What-if 0077: "Growth Rate"

Posted: Thu Jan 02, 2014 6:09 pm UTC
ysth wrote:&amp;deg; is not an entity.

ditto for "\&amp;deg;" (alt-text of the next to last picture).
Something is rotten in the state of html editors...

### Re: What-if 0077: "Growth Rate"

Posted: Fri Jan 03, 2014 7:11 pm UTC
ps.02 wrote:
Randall wrote:During their first month, infants grow about 4.4 centimeters

I thought "growth rate" for most things was measured as a percentage, not a linear dimension, over time. So if you're 50 cm and you grow 4.4 cm, I'd call that a growth rate of 8.8% per month, or 175% per year. By age 20, when your growth comes to a screeching halt, you'd be some 300 million meters tall. Basically, light in a vacuum would take about 1 second to travel from head to toe.[/i]

We're around 93 million miles from the Sun and it takes light just over 8 minutes to get from there to here. It'd take a shade under 27 minutes to travel 3 x 108 miles.

### Re: What-if 0077: "Growth Rate"

Posted: Fri Jan 03, 2014 7:43 pm UTC
Jackpot777 wrote:
ps.02 wrote:
Randall wrote:During their first month, infants grow about 4.4 centimeters

I thought "growth rate" for most things was measured as a percentage, not a linear dimension, over time. So if you're 50 cm and you grow 4.4 cm, I'd call that a growth rate of 8.8% per month, or 175% per year. By age 20, when your growth comes to a screeching halt, you'd be some 300 million meters tall. Basically, light in a vacuum would take about 1 second to travel from head to toe.[/i]

We're around 93 million miles from the Sun and it takes light just over 8 minutes to get from there to here. It'd take a shade under 27 minutes to travel 3 x 108 miles.

And how is that in any way relevant to the discussion at hand?

### Re: What-if 0077: "Growth Rate"

Posted: Sun Jan 05, 2014 8:30 am UTC
Jackpot777 wrote:
ps.02 wrote:By age 20, when your growth comes to a screeching halt, you'd be some 300 million meters tall. Basically, light in a vacuum would take about 1 second to travel from head to toe.

It'd take a shade under 27 minutes to travel 3 x 108 miles.

Which is just another way of saying 27×60 is about how many meters there are in a mile. Yes.

### Re: What-if 0077: "Growth Rate"

Posted: Fri Jan 10, 2014 3:44 am UTC
I find it really surprising that no one has mentioned Ender's Shadow yet.

### Re: What-if 0077: "Growth Rate"

Posted: Fri Jan 10, 2014 6:27 am UTC
rmsgrey wrote:The idea of a child continuing to grow indefinitely is one of the central points of the Shadow series by Orson Scott Card - in which Bean, a supporting character from Ender's Game, has his story told - it turns out that he's the product of genetic manipulation, and, while he grows more slowly as an infant, both his body and his mind continue to grow throughout his life - the consequences of which are a big part of the latest volume - Shadows in Flight. The mutations also, for reasons that are never explained, left him more intelligent and aware than a typical infant even at an age where he appeared underdeveloped, but that's not relevant to the What If...

### Re: What-if 0077: "Growth Rate"

Posted: Sat Jan 11, 2014 7:21 pm UTC
Pfhorrest wrote:
rmsgrey wrote:The idea of a child continuing to grow indefinitely is one of the central points of the Shadow series by Orson Scott Card - in which Bean, a supporting character from Ender's Game, has his story told - it turns out that he's the product of genetic manipulation, and, while he grows more slowly as an infant, both his body and his mind continue to grow throughout his life - the consequences of which are a big part of the latest volume - Shadows in Flight. The mutations also, for reasons that are never explained, left him more intelligent and aware than a typical infant even at an age where he appeared underdeveloped, but that's not relevant to the What If...

Hahaha...I saw that line of asterisks and immediately interpreted that as an irrelevant sig, without even reading it. I feel stupid now.

As far as why he's let more intelligent, it's because he never stops growing brain cells at the same rate an infant would, meaning he never hits that learning slump that comes with maturity.

### Re: What-if 0077: "Growth Rate"

Posted: Mon Jan 13, 2014 12:24 am UTC
KrytenKoro wrote:
Pfhorrest wrote:
rmsgrey wrote:The idea of a child continuing to grow indefinitely is one of the central points of the Shadow series by Orson Scott Card - in which Bean, a supporting character from Ender's Game, has his story told - it turns out that he's the product of genetic manipulation, and, while he grows more slowly as an infant, both his body and his mind continue to grow throughout his life - the consequences of which are a big part of the latest volume - Shadows in Flight. The mutations also, for reasons that are never explained, left him more intelligent and aware than a typical infant even at an age where he appeared underdeveloped, but that's not relevant to the What If...

Hahaha...I saw that line of asterisks and immediately interpreted that as an irrelevant sig, without even reading it. I feel stupid now.

As far as why he's let more intelligent, it's because he never stops growing brain cells at the same rate an infant would, meaning he never hits that learning slump that comes with maturity.

The asterisks were for a significant change in thought. The thing with the intelligence is not that he kept getting smarter as he grew (though that has its own problems - human intelligence appears to rely on a large-scale die-back of unwanted neurons to leave a network that actually works rather than just being a mass of cells) but that he was smarter than "normal" infants almost from birth, despite supposedly having a "slow-and-steady" pattern of growth...

### Re: What-if 0077: "Growth Rate"

Posted: Mon Jan 13, 2014 3:23 pm UTC
rmsgrey wrote:
KrytenKoro wrote:
Pfhorrest wrote:
rmsgrey wrote:The idea of a child continuing to grow indefinitely is one of the central points of the Shadow series by Orson Scott Card - in which Bean, a supporting character from Ender's Game, has his story told - it turns out that he's the product of genetic manipulation, and, while he grows more slowly as an infant, both his body and his mind continue to grow throughout his life - the consequences of which are a big part of the latest volume - Shadows in Flight. The mutations also, for reasons that are never explained, left him more intelligent and aware than a typical infant even at an age where he appeared underdeveloped, but that's not relevant to the What If...

Hahaha...I saw that line of asterisks and immediately interpreted that as an irrelevant sig, without even reading it. I feel stupid now.

As far as why he's let more intelligent, it's because he never stops growing brain cells at the same rate an infant would, meaning he never hits that learning slump that comes with maturity.

The asterisks were for a significant change in thought. The thing with the intelligence is not that he kept getting smarter as he grew (though that has its own problems - human intelligence appears to rely on a large-scale die-back of unwanted neurons to leave a network that actually works rather than just being a mass of cells) but that he was smarter than "normal" infants almost from birth, despite supposedly having a "slow-and-steady" pattern of growth...

Yeah, it's not realistic, but I think that was the only explanation they ever gave.

### Re: What-if 0077: "Growth Rate"

Posted: Wed Jan 29, 2014 1:31 am UTC
But... newborns initially LOSE weight, as their bodies convert from extracting nutrition from umbilical support to the digestive system.

If you sampled from this period, your projections would be for adults to approach 0 mass. (or 21 grams, if metaphysical)