I believe the correct answer is in the upper end of the range Amanda cited, and here’s why.

According to various sources, the following is more or less true:

Adult people (for our present purposes) weigh between 60 and 90 kg. (I’m ignoring small populations here because this is mainly for American Audiences.) The amount of bone in a body … the non-cellular part … is between 14 and 20 percent. The amount of blood that is not cellular (i.e, that is water) is about 5% of the total body mass. The mass of a typical body cell is about one gram times ten to the negative nine, or one nanogram.

… do the math …

I get about 46 to 68 trillion.

Bigger people (using these weight ranges) would have a larger proportion of lean mass in bone, and if some off that extra mass in the range of human weights is increased fat percentage, then some of that mass is accounted for by either more fat cells or enlarged fat cells. For these and other reasons, as mass goes up the rate of additional cells goes down, so the higher end of that range is probably an exaggeration. There are other things in the body that need to be subtracted as well, including connective tissue that has very few cells in it, bacteria welcome and unwelcome alike, etc. etc.

Which brings us to a comfortable estimate of “about 50 trillion, give or take a few trillion.”

Is that satisfactory?

You can get most of the base numbers here, of course.

Other posts of interest:

• How to get rid of spiders in your house
• Why is your poop green?
• How many cells are there in the human body?
• Is there really a plot hole in Harry Potter Goblet of Fire?
• How long is a human generation?
• Is blog ever really blue?
• How to not get caught plagiarizing
• The origin of the domestic chicken
• What are the three necessary and sufficient conditions of Natural Selection?
• How do I get rid of foot fungus?
• Which is better, Tap Water or Bottled Water?
• Has Global Warming stopped?

Also of interest: In Search of Sungudogo: A novel of adventure and mystery, which is also an alternative history of the Skeptics Movement.

Photo Credit: jurvetson via Compfight cc

The steep walls that define the northeastern and southwestern sides of the channel extend far below the marshy surface of the river’s floodplain. When people have built large bridges across this channel, where a highway could not simply meander through it, they found that the river sediments were five to eight times deeper than the current depth of the channel. It appears that this sediment filled in the channel after the river that formed it stopped running about 10,000 years ago. Well, it didn’t stop, there’s still that little trickle you see on the map, which today we call the Minnesota River.

But thousands of years ago, it was the Warren River that ran from left to right across this picture, and it was during it’s maximum the largest river in the world, carrying more water per minute than any other river. The river was the outlet of the largest fresh water lake that ever existed as far as we know, or at least one of the largest, which we call Lake Agassiz. The lake was formed by a combination of three factors: 1) Glacial depression of the landscape: During the Ice Age, a huge glacier pushed the crust of the earth down so far that as the glacier melted away,water ran into the depression rather than out to sea. 2) Glacial “till” ruined all the natural drainage: As the glacier melted, huge quantities of dirt and rock came out of the ice and covered the land, filling in all river valleys that might have survived the glacier’s earlier expansion. It would take time for rivers to cut down through this “till” and re-discover a path to the sea. 3) Ice blockage: As the glacier melted away, large chunks of ice … mini glaciers and buried blocks of ice with a volume approaching the average lake … were left behind, many serving for decades or a century or two as dams in the outlets that streams and rivers would eventually use after complete melting.

At some point the water in Lake Agassiz found its way out from the lake somewhere around Fargo, North Dakota. The exact outlet is a movable thing: As the lake drained, the land under the lake rebounded from the weight of the disappearing glacier, and the river eroded the outlet, the size and shape of the lake changed dramatically. It may have shrunk and grew several times but on average, it got smaller. Other outlets formed as well, draining Agassiz through Lake Superior and the Saint Lawrence River. But at certain times, water from the largest lake ever flowed through a channel that is today the Red River and the Minnesota River, joining what is now the Mississippi River south of the Twin Cities, and then down to the Gulf of Mexico.

I can not verify that the following is true, but it is what I’ve heard: An archaeologist I knew told me of a whale skeleton in a museum down in the state of Mississippi that was supposedly found in the flood plain in a position and at a level that would indicate that it came down this river from Lake Agassiz. It may be that an early version of Lake Agassiz was part of a large inland sea that ran from eastern Canada and Maine across the Great Lakes and to Manitoba, caused by the depression under the glacier. Sea life would have occupied that large gulf. We know there were whales and walruses in this sea, and their remains have been found here and there to the east. Also, there’s the trout; Trout are essentially salmon, a sea-living fish, that got trapped in freshwater lakes and, separated from their original stock, evolved into new species that can no longer live in salt water. Some of these trout may have been trapped inland in places like Moosehead Lake, Maine as the great arm of the sea became separated and changed over to fresh water. A giant inland lake with fresh water whales swimming around in it seems a bit strange, but glacial times were, indeed, strange!

So, imagine being a Clovis Indian arriving at the shore of The Warren River about 10,000 years ago, and standing where the town of Redwood Minnesota is today. The river you’d see before you would be very wide, about three kilometers from side to side. That is wider than the Nile River at a comparable distance upstream. The river would be flowing very fast from left to right, and even if this was the first time you were seeing this river you would by now have heard stories of its fury during floods, and just standing there you’d be nervous. There would be a lot of crap floating by. This river is young, having just cut its path out of the great lake to the north within a few centuries past, so it is still busy finding its way and shaping its channel. Every moment you watch, somewhere upstream, a chunk of river bank covered with brush (there are few large trees in the region at the time) falls in and breaks apart. The rocks fall to the bottom and start rolling along, the dirt muddies the river, and the vegetation tumbles along at or just below the surface. The lake from which this river flows fronts an active but melting glacier, and thus, it is full of ice bergs. As these break up into smaller and smaller chunks they float toward the Warren River, and now you see their remains as a continuous stream of dirty foamy ice that is hard to separate visually from the foamy dirty water and the dirty watery foam and the watery foam and dirt and the vegetation. To us, if we went back in time it would not look like a normal river. To the Clovis Indians of the time, it might have looked like a place you would not want to put your boat.

And then, as you’re watching, this whale goes by. Alive and struggling in the current? Long dead, bloated, and lolling in a morbid circle battered every moment by the flotsam of which it is just one large component? Alive but no longer struggling, and looking back at you, thinking “What in tarnation is that thing, I’ve not seen one of those before!”?

OK, now look back at the map. Just south of Bridge Street, on the edge of town, is where the children of Redwood Falls, who have grown up on the shores of the most amazing river that ever existed on the planet Earth, go to the Reede Gray Elementary School. The school is named after an educator who got his graduate degree in 1925 at a small but highly regarded college down river from here. You can imagine that the children have a lot of opportunities, weather permitting, to enjoy field trips to the several parks and wildlife management areas a short drive, or even a brisk walk, from school. Many live on farms, so they have a sense of the landscape because there are places you can farm and places you can’t and that is determined mainly by the Warren River’s legacy. And in the spring, the kids that come from the other side of the river probably miss some school because the bridges get closed during floods or even washed out now and then. They fish in the meandering channel or one of the small ponds left behind, or a tributary. These kids are growing up with stories and experiences played out in a context created by an ancient geological event.

And now, an opportunity. Wouldn’t it be nice to inject a little extra science into their lives, in a positive and helpful way? So that everything they see around them they will see through that powerful lens that as a science blog reader you take for granted? Wouldn’t it be great to go to that elementary school and give a talk, or send a DVD or some books appropriate for Elementary School science learning, or something? Among these kids from Redwood Falls there is potential and talent and among these kids a few are surely interested in one area of science or another, and just need encouragement, resources, sciencey stuff, handy and available for them to get their hands on and get into it and be inspired. Too bad there’s nothing you can really do from the comfort of your own home, sitting there browsing on the Internet, reading blogs and stuff.

But wait, don’t despair! There is somethings you can do! You can help Ms. Osborne, one of the teachers at the Reede Gray Elementary School! Ms. Osborne is trying to buy a human skeleton for her kids to learn anatomy! And some other body parts and stuff. (These would be plastic models designed for use in the classroom, of course, not the real thing, just in case you were thinking that.) And that’s a really great idea. I’ve taught anatomy at various levels and I can tell you that you should not actually even bother to go into this subject unless you’ve got the body parts available and a pile of good anatomy books. Ms. Osborne wants to get a skeleton, a lung, an eye, and a brain. The whole thing is going to cost about 300 bucks and she’s about half way there in raising the money.

What you can do is to CLICK HERE and make a small donation to help. Check the amount “to go” (right now it’s about $150). If it’s down to zero by the time you get there, you might want to donate to one of the other projects I’ve carefully selected for you to consider.

Your donation will be very much appreciated, and it will have a very long lasting effect. In addition to this, for all of the projects I’m asking you to help, I’ll throw in a bonus. The details will vary. I’ve got some extra anatomy books I could send to Ms. Osborne. They may or may not be useful in an elementary classroom, but teachers need books too, to stay ahead of the students! In other cases I’m offering a talk or presentation in class. I’ll let you know what I end up doing. But that’s only going to happen if people step up and help fulfill the needed funding level. Sort of a matching grant: I can’t put in money but I can put in some time and talent.

Thank you in advance for your kind donation.

Stolen from Deep Sea News