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916902.  Thu Jun 14, 2012 9:40 pm Reply with quote

My 1st factoid
Of Adolf Hitler

While he was imprisoned he was bothering a gang of card players.
He was a lousy cardplayer himself and naturally they wouldn't wanna let him join in.

At last someone said to him; this in early stages of his imprisonement

" Go write a book
or something.... "

916937.  Fri Jun 15, 2012 3:37 am Reply with quote

tetsabb wrote:
Should I stop asking rhetorical questions?

Why would you want to?

Thinking up science fiction life forms is a fascinating challenge, and Cele has hit on some QI aspects of it.
Perhaps one could think in terms of the heartbeat issue; allegedly, a mouse and an elephant, even though they live very different lengths of life, actually get through the same number of heartbeats. Or do I hear the sound of approaching klaxons?

A claim is often made that all animals have a lifespan of 1 billion heartbeats. The first objection to this is that a simple calculation will tell you that a human who lives 70 years will have over 2 billion heartbeats (assuming an average of 60bpm, which is rather conservative). We are told that this is due to advances in medical care and we're only "supposed" to have 1 billion, which would mean a life expectancy of about 30 years.

But that aside, there is some correlation, at least with mammals.

From this abstract:

Plots of the calculated number of heart beats/lifetime among mammals against life expectancy and body weight (allometric scale of 0.5 x 10(6)) are, within an order of magnitude, remarkably constant and average 7.3 +/- 5.6 x 10(8) heart beats/lifetime.

916942.  Fri Jun 15, 2012 4:09 am Reply with quote

Saturn has 62 moons with confirmed orbits only thirteen of which have diameters larger than 50 kilometres. Titan, The largest, is bigger than Mercury in volume (though not mass) and has a Nitrogen-rich (98.4%) atmosphere that extends a long way into space because of Titan's low gravity. Atmospheric pressure at the surface is 1.45 times that of Earth and is radiation-opaque at many wavelengths, including the visible, so sunlight does not reach the planet's surface. Not that the surface is all that relevant as human-sized creatures could easily fly in the high density, low g atmosphere (if we had wings of some sort).

Titan is the only known natural satellite (moon) in the Solar System that is known to have a fully developed atmosphere that consists of more than trace gases. Titan's atmosphere is thick, chemically active, and is known to be rich in organic compounds; this has led to speculation about whether chemical precursors of life may have been generated there. The atmosphere also contains hydrogen gas, which is cycling through the atmosphere and the surface environment, and which living things comparable to Earth methanogens could combine with some of the organic compounds (such as acetylene) to obtain energy. Apparent lack of liquid water on Titan has been cited by NASA astrobiologist Andrew Pohorille as an argument against life there. Pohorille considers that water is important not only as the solvent used by "the only life we know" but also because its chemical properties are "uniquely suited to promote self-organization of organic matter". He has questioned whether prospects for finding life on Titan's surface are sufficient to justify the expense of a mission which would look for it.

[s] Quoted largely verbatim and cobbled together from various Wiki pages on Titan, its atmosphere and the chances of life being present

The page linked below is really interesting if you're interested at the chemical level - also it displays an understanding of the vital part water plays in enzyme mechanisms so it's quite likely to be accurate on other matters too. I'll not quote any of it but it's worth a read if you like that sort of thing.

People who like this sort of thing will find this the sort of thing they like.
Abraham Lincoln

All in all the much warmer and wetter Europa (a moon of Jupiter) is a better bet for life in the solar system. Perhaps another time...

916944.  Fri Jun 15, 2012 4:27 am Reply with quote

Titan, The largest, is bigger than Mercury in volume (though not mass)

Cel, could you explain to the dickheads amongst us (and me in particular) how that knowledge was established? Comparing size a vue is one thing, but mass?

916945.  Fri Jun 15, 2012 4:41 am Reply with quote

Gravitational attraction (and therefore mass) vs orbit round Saturn at a guess.

For a stable orbit F will also be equal to, erm, whatever force it is that would tend to make Titan whizz off into space (I'm gonna go with angular momentum but it's not really my thing).

I'm a bit hazy on it - you'd have to work out the mass of Saturn by its orbit round the Sun* and then go from there but NASA've flown various probes past Saturn and Titan with some success so they can't be too far out.

* making it a three component system at least if considered as a whole but perhaps Titan (and other effects from eg Jupiter) is small enough to not matter much in calculating the mass of Saturn.

Last edited by Celebaelin on Fri Jun 15, 2012 4:48 am; edited 1 time in total

916946.  Fri Jun 15, 2012 4:46 am Reply with quote

I am chuffed! I think I understood that :-)

916947.  Fri Jun 15, 2012 4:49 am Reply with quote

Bit of an edit above to cover myself for any unchecked and unverified idiocy I may have perpetrated.

916949.  Fri Jun 15, 2012 4:50 am Reply with quote

You? Never ;p

916951.  Fri Jun 15, 2012 4:57 am Reply with quote

In theory you can easily calculate the mass of Titan if you have the mass of Saturn, and the radius and period of Titan's orbit around Saturn. The trouble is you'd have to have these really accurately because the difference between the mass of Saturn and the mass of Titan is so great.

916952.  Fri Jun 15, 2012 4:57 am Reply with quote

As things work out I was not entirely wrong.

By astronomically determining the distance to the sun, we can calculate the earth's speed around the sun and hence the sun's mass.

Once we have the sun's mass, we can similarly determine the mass of any planet by astronomically determining the planet's orbital radius and period, calculating the required centripetal force and equating this force to the force predicted by the law of universal gravitation using the sun's mass.

How do scientists measure or calculate the weight of a planet?

Not actually correct either though...

The centripetal force is F = ma = rmω 2 = r−1mv 2.
The momentum of the body is p = mv = rmω.

But what's an ω between friends?

916955.  Fri Jun 15, 2012 5:11 am Reply with quote

Looks like a bum to me...

(tongue in cheek)

916956.  Fri Jun 15, 2012 5:20 am Reply with quote

'yorz wrote:
Looks like a bum to me...

(tongue in cheek)

Oh dear!

917214.  Fri Jun 15, 2012 8:30 pm Reply with quote


917222.  Fri Jun 15, 2012 10:13 pm Reply with quote

'yorz, don't be an arse!

917225.  Fri Jun 15, 2012 10:30 pm Reply with quote

Up 'yorz :)


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