Fun Science Factoid Of The Day

[Bravus]

At our honourable host D. Allan's suggestion, I'm going to kick in a little science each day (though readers of my blog will know I don't make it every single day). I've called it 'factoids' - which are basically facts separated from all their context - but in fact I'll try to give them enough context to make them meaningful and interesting. Others are very welcome to comment, or to contribute interesting factoids of their own... but I will be fact checking!

[Gail]

This should be fun!

[Bravus]

We are outnumbered 10-fold in our own bodies by microorganisms. We have about 10^13 cells in our bodies, and about 10^14 bacteria, viruses and other microorganisms in and on us.

(Can't post a link or reference for this one because I heard it from a biologist at my university in conversation)

[D. Allan]

My oh my! Each one of us is a walking bio-environment! How does our personal populations compare with the population of our planet? Can you help this math-dunce? <

[Bravus]

The (human) population of the planet is on the order of 10^10, so our personal bugatariums are 10,000 times more populous.

[Gail]

I think I have 10^5 bacteria congregating in my ears right now, making them hurt!

[Bravus]

Ack, not good

/me sends Gail 10^6 virtual hugs

[Gail]

:)

[Bravus]

Staying on the buggy tip for a while:

Scientists have only identified about 4,000 of the estimated 400,000 species of viruses in the world.

http://www.all-species.org/wsj_012202.html (from that well known scientific journal... the one from Wall Street)

(for those moments when we think most of the science is already done)

[D. Allan]

Insects rule : 950,000 identified out of 8 million estimated species. (same source)

I wonder how they compare in their populations: more viruses or more insects?

[Bravus]

Hmm, yeah, not sure... but if say 1/10 of them there bugs on our bodies are viruses, then that's 10^13 per person, times 10^10 persons for 10^23 viruses, just in people, not in soil, water, animals and plants.

My guess is there are more virii, 'cos they're much tinier, and I couldn't find anything definitive on their relative populations.

[D. Allan]

That seems reasonable. They are our most formidable competitors, outside of our fellow humanoids!

[Bravus]

Fleas can jump 130 times higher than their own height. In human terms this is equal to a 6ft. person jumping 780 ft. into the air.

Not a direct link to this factoid (which is disputed - some say 80 times their height, which would still translate to a pretty darn impressive 480 ft), but fun anyway: http://www.ftexploring.com/lifetech/flsbws1.html

It has a lot to do with the 'square-cube law'. Strength goes up as the square of size but mass goes up (and down) as the cube. I think I may have talked about this before with the ant, mouse, cat, person, horse and elephant falling down a mineshaft...

[David Koot]

It has a lot to do with the 'square-cube law'. Strength goes up as the square of size but mass goes up (and down) as the cube.

Interesting. For any type of object or matter?

[bevin]

Basically, yes, if you simply magnify/shrink a shape, keeping its proportions, and keeping well away from the atomic scale or continental scale sizes...

It is a bit trickier than that for biological material because muscle because there are limits to how large or small cells can be - so a mouse has similar size cells to a person.

Muscle strength is basically proportional to the cross-sectional area of the muscle. Making the muscle longer does not make it any stronger - it just increases the distance over which it can exert the same strength.

In fact individual muscle cells can't vary the strength of their pull - they are either pulling or they are not. We control how hard we pull by using more or less cells, not by having each cell pull less.

Weight is proportional to volume.

This is why you can't just scale an animal up and down. A 7ft+ human has problems caused by their cross-section not being adequate for the amount of material above that point.

/Bevin

[David Koot]

Absolutely fascinating! I did wonder about some of the issues Bevin raised, in terms of mass/volume ratios for living organisms, depending on the type of body tissue involved. I did not know that muscle exertion is a function of the number of cells! Great info! Thanks, Bevin.

[Bravus]

Not a factoid today but a link... One of my friends and former colleagues in Canada, Frank Jenkins, set me this (note that there's a link to a podcast online, so you don't have to live in Canada (or listen on Sabbath) to listen):

This week on Quirks & Quarks: (CBC Radio 740 at 12:05 PM)

http://www.cbc.ca/quirks/podcast.html

It's the Great Aussie/Canuck Science Adventure.

The moose goes walkabout with the wombat, and the beaver goes camping with the kangaroo, as Bob McDonald goes Down Under for the Great Aussie/Canuck Science Adventure.

Quirks & Quarks, Canada's national science program, and The Science Show, Australia's equivalent program on ABC Radio National, are joining forces for a unique exploration of

science, north and south. And here's the kicker: both programs first went on the air at virtually the same time in 1975.

And both are now broadcast on Saturdays at noon.

In the first program, the host of The Science Show, Robyn Williams, introduces Bob to leading Australian researchers. And in the second program, Bob introduces Robyn to Canadian scientists. And both programs get to hear both of the hosts doing the interviews.

April 21: Bob interviews the Australians:

Bob learns about farming and eating kangaroos; saving the Tasmanian Devil from extinction; discovering the fossils of marsupial lions; and avoiding the deadly sting of the Irukandji jellyfish.

All this and more on Quirks & Quarks, with host Bob McDonald, Saturday right after the noon news on Radio One, or anytime on our web page at cbc.ca/quirks.

[Bravus]

Fun science fact(oid)s tend to be from biology most often... but chemistry and physics are my beloved fields of science, so I wanted to try to include some from those fields too.

Here's a fairly simple one:

A pendulum one metre long has a 'period' for its swing (the time it takes to swing out to the other end and back to where it started) of 2.0050 seconds.

Many people thought the metre should have been defined as the length of pendulum that produces a period of exactly 2.0000 seconds, because that would have made it simple to measure one metre anywhere in the world if you had a watch and a piece of string.

But as it is, if you have a ruler, a piece of string and a weight, you can make a pretty accurate 'counting clock'.

(A metre is pretty close to 39 inches)

[Bravus]

The chemical element Gallium has a melting point of just under 30 C (86 F), which means that it melts in your hand (unlike M & Ms - and don't put it in your mouth!)

Gallium is a semiconductor material, used to make some computer parts.

Bentor, Yinon. Chemical Element.com - Gallium. Apr. 23, 2007 <http://www.chemicalelements.com/elements/ga.html>

[David Koot]

Okay, then HOW can it be used in a computer, in which the internal temperature will easily go above 100 degrees F, particularly laptops with the tiny fans?

Dave

[Bravus]

Great question (someone's thinking!) The form used in semiconductors is actually a compound of gallium, gallium arsenide, so gallium combined with arsenic. This compound has a melting point of 1238 C, so it's completely safe even in hot computers.

http://en.wikipedia.org/wiki/Gallium_arsenide

[bevin]

Unfortunately the period of a pendulum's swing depends on

(a) air density

( distance from the center of the earth

( is measurable - because the earth has a bulge at the equator, so pendulums swing measurably slower there...

Then, of course, there is the problem of getting a reliable clock that does not use a pendulum - easy today, but not 200 years ago...

/Bevin

[Bravus]

I suspect that both (a) and ( would have effects smaller than the .005 in the 2.005, so yeah, you wouldn't use a pendulum clock to time the 100 m race at the Olympics, but for timing an egg or taking a pulse it'd work fine. Incidentally, you've probably noticed that clock pendulums tend to be very thin in the plane in which they swing, presumably as a means of reducing the influence of (a).

[bevin]

Actually I realized there is an age-old reliable-enough clock - the rotation of the earth! So you would adjust the length of the pendulum until it did 24*60*(60/2) swings per day, where day is measured by a star crossing a hair in a telescope....

Of course that means having someone count about 50,000 swings... unless you also invented a counting device...

/Bevin

[bevin]

Quote:

The diameter from the North Pole to the South Pole (the shortest diameter) is approximately 12,714 km. The equatorial diameter (the longest diameter) is approximately 12,756 km.

so it is about 50/12756 = 1/240 difference in radius

so g at one place is (240/240)**2 and the other ((240-1)/240)**2 so the difference is about (2*1*240/240)**2 or (1/120)**2 or about 0.0001 << 0.005

There is another effect also - centrifugal forces - but I suspect without calculation this is even more irrelevant...

A less irrelevant topic may be the shape and density of the pendulum - you would have to agree on that also...