…and, by natural extension, what’s the largest body of water you could fill with it?
I have two major problems with figuring this one out: 1) determining the amount of banked blood (for transfusion or simple research) in the world, and 2) trying to factor in the world’s children—toddlers are going to contain less blood than a full-grown man, for example.
So…can anyone help?
A few figures from the World Health Organization:
Wiki claims that the average blood donation is 450 mL (about a pint). Whole blood can be stored for up to a week, but most of the time it’s separated into components. Red blood cells, for example, can be stored for over a month, and plasma can be stored for a year. Apparently it’s the platelet fraction that goes bad quickly.
So, if you just want whole blood, the average supply at any given moment will be about 85 million pints/52 weeks =~ 2 million pints.
If, for the purposes of making this lake of “blood”, you’re willing to use reconstituted blood just containing red blood cells and plasma (ignoring the platelets), you’d get 85 million pints/12 months = ~7 million pints.
To figure out the amount of blood in children, you might want to come up with a somewhat arbitrary “average” amount of blood per child.
Doing a bit of auditing Dracula? The average adult has about 5 litres of blood.
I think this can be safely ignored, it’s not going to change the final answer by a significant amount.
Bit tricky. A ballpark figure would be that 25% of the world population are under 15. For simplicity, I’ll assume on average a child contains half as much blood as an adult.
4.5 billion people x 5 litres = 22.5 billion litres +
1.5 billion people x 2.5 litres = 3.75 billion litres =
26.25 billion litres of blood.
You’d have enough to fill Lake Zug 3 times, and still have enough left over for a pool-party.
You’d be many thousands of times short of what would be required to fill one of the great lakes (if my maths is accurate).
Enough to completely flood Megiddo?
Banked blood should be negligible. Consider: Only a small proportion of the population donates blood at all. Of that small proportion, they can donate only a small portion of the blood they have in each donation. They can donate at most once every eight weeks, and most blood donors are significantly less often than that. And the blood can be stored for a period shorter than eight weeks.
For the children, it’s simple enough to get a back-of-the-envelope estimate. There are about 6.8 billion people in the world. Assume that a quarter of the Earth’s population is children, and that children on average have about half the blood of an adult. Then that gives us about 6 billion adult-equivalents worth of blood. And each adult-equivalent human contains about 5 liters of blood, for a total of 30 billion liters.
A cube 10 cm on a side is a liter, so this could, for instance, be a lake 25 meters deep, 600 meters wide, and 2000 meters long.
When I was a teenager I calculated how much human semen is ejaculated each day. I took the number of births per day, multiplied that by four since I’d read somewhere that on average it’s four acts of unprotected sex per conception, and then by four again as a WAG that only a quarter of couples are even trying to make a baby, then that by 2ml. It came to about 10,000 liters, or a pool some 112 meters in diameter by one meter deep. I was impressed.
You failed to take masturbation into account. I say quadruple your total. 
I have one child. I’ve ejaculated WAAAAYY more than 16 times. I think your assumptions using birth statistics are really inaccurate.
Even though it would be a total guess, you’d probably be much closer if you just made up a reasonable number and say the average male between the ages of 15 and 60 (or whatever age range you pick) ejaculates “x” times per week.
I’d guess “x” would be somewhere between 1 and 14, probably in the 2-5 range (again, we’re talking average…I’m sure there are plenty of outliers on both ends)
(continued)
for very rough, back of the envelope calculations, I’ll assume there are 3 billion males on Earth. Let’s say 2 billion of them are in that age range, and assume 3x per week.
2,000,000,000 * (.429 times / day) * (.005 L) = 4,290,000 L per day, or about 50 L per second
So I’d say your estimate is underestimating by a factor of 100 or more!
All of it.
Does this strike anyone else as the kind of question Spike and Angelus would sit around discussing after getting high?
Yet who would have thought the old planet to have had so much blood in it?
Per day? Astounding!
old joke, but ‘need answer fast’ would be perfect for this thread.
3.0E+10 liters is about 24,000 acre-feet to convert to a unit often used for the amount of water in lakes and reservoirs. For anybody around the San Jose area, a bit more than the Lexington Reservoir, which holds about 19,000 acre-feet.
How much human blood exists on Earth?
Enough for Lance Armstrong to pedal around the globe 2,478 times.
Hmmm. You’re right: that would get a closer estimate, but I was recalling what I’d done some mumble mumble decades ago and the 10,000 liters was what I’d come (heh) up with then. And as AClockworkMelon points out, you have to take masturbators into account.
Plus – I dunno, 20% – to make it 60. The mind boggles. Multiplying your 4,290,000 liters by that same 20% is 5,148,000 which would be a pool 1,810 meters in diameter by 2 meters deep. To get it more in track with what the blood folks came up with, that’s more than 4 acre-feet.
Assuming that blood is related to volume, volume is related to height, and using the following data:
World population pyramid - http://www.iiasa.ac.at/Research/POP/images/image24.gif
Male growth chart - Account Suspended
Female growth chart - Account Suspended
Blood in an adult - 5.00L (male), 3.99L (female)
Age/Sex Pop Height Volume Blood
0-4 M 320m 34" 11.96% 0.60L
0-4 F 310m 34" 14.99% 0.60L
5-9 M 310m 48" 33.66% 1.68L
5-9 F 300m 48" 42.19% 1.68L
10-14 M 280m 59" 62.52% 3.13L
10-14 F 270m 59" 78.35% 3.13L
15-19 M 260m 69" 100% 5.00L
15-19 F 250m 64" 100% 3.99L
20-24 M 260m 69" 100% 5.00L
20-24 F 250m 64" 100% 3.99L
25-29 M 240m 69" 100% 5.00L
25-29 F 230m 64" 100% 3.99L
30-34 M 220m 69" 100% 5.00L
30-34 F 210m 64" 100% 3.99L
35-39 M 190m 69" 100% 5.00L
35-39 F 180m 64" 100% 3.99L
40-44 M 160m 69" 100% 5.00L
40-44 F 160m 64" 100% 3.99L
45-49 M 140m 69" 100% 5.00L
45-49 F 140m 64" 100% 3.99L
50-54 M 110m 69" 100% 5.00L
50-54 F 110m 64" 100% 3.99L
55-59 M 100m 69" 100% 5.00L
55-59 F 100m 64" 100% 3.99L
60-64 M 80m 69" 100% 5.00L
60-64 F 90m 64" 100% 3.99L
65-69 M 70m 69" 100% 5.00L
65-69 F 80m 64" 100% 3.99L
70-74 M 40m 69" 100% 5.00L
70-74 F 60m 64" 100% 3.99L
75-79 M 20m 69" 100% 5.00L
75-79 F 40m 64" 100% 3.99L
80-84 M 20m 69" 100% 5.00L
80-84 F 40m 64" 100% 3.99L
Which comes out as:
(320 * 1000000 * 0.6)
+ (310 * 1000000 * 0.6)
+ (310 * 1000000 * 1.68)
+ (300 * 1000000 * 1.68)
+ (280 * 1000000 * 3.13)
+ (270 * 1000000 * 3.13)
+ (260 * 1000000 * 5.0)
+ (250 * 1000000 * 3.99)
+ (260 * 1000000 * 5.0)
+ (250 * 1000000 * 3.99)
+ (240 * 1000000 * 5.0)
+ (230 * 1000000 * 3.99)
+ (220 * 1000000 * 5.0)
+ (210 * 1000000 * 3.99)
+ (190 * 1000000 * 5.0)
+ (180 * 1000000 * 3.99)
+ (160 * 1000000 * 5.0)
+ (160 * 1000000 * 3.99)
+ (140 * 1000000 * 5.0)
+ (140 * 1000000 * 3.99)
+ (110 * 1000000 * 5.0)
+ (110 * 1000000 * 3.99)
+ (100 * 1000000 * 5.0)
+ (100 * 1000000 * 3.99)
+ (80 * 1000000 * 5.0)
+ (90 * 1000000 * 3.99)
+ (70 * 1000000 * 5.0)
+ (80 * 1000000 * 3.99)
+ (40 * 1000000 * 5.0)
+ (60 * 1000000 * 3.99)
+ (20 * 1000000 * 5.0)
+ (40 * 1000000 * 3.99)
+ (20 * 1000000 * 5.0)
+ (40 * 1000000 * 3.99)
= 20,414,900,000 Liters
No. You forget that there is a small amount currently in orbit aboard the International Space Station in the bodies of the people there and perhaps in storage for medical emergencies.