dsummerstay@[EMAIL PROTECTED]
skreiv:
> How is it possible for DNA to reproduce at the speeds it does? DNA
> bases find their place at a rate of up to 1000 base pairs per second
> at a replication site.
Frequencies are size-dependant.
In general the relation****p between many forces is counterinituitive
when the size changes by many magnitudes.
In the range of sizes we're used to dealing with, say 10g to 100kg our
intuition is usually pretty close on. People used to dealing with the
much larger or much smaller develop intuition for these things too.
At -HUGE- sizes gravity is cru****ng and dominates movement of objects,
planets, suns and galaxies move primarily dominated by the gravity
between them. Inertia is very high.
At 1000s of tons, inertia is still a *****. A supertanker responds very
slowly to actions of the propeller and rudder, it needs -minutes- to
stop or accelerate. Gravity is strong enough that only sea-going
vehicles are able to be mobile at all at this size.
At 1 ton or similar we're talking a car or elephant. It still has
inertia, but a car driving at supertanker speed can stop in a second in
a few short meters. Gravity is a problem. Animals this size have
problems getting of the ground at all, I don't think a elephant is
capable of jumping. It needs a second or thereabouts to take a single
step.
At a few kgs you're talking a cat, gravity is less of a *****: despite
having a -much- lower percentage of its body-weight spent for skeleton a
cat can jump or fall many times its body-height without suffering injury
(try dropping a elephant from 5-times-body-height) Frequencies are much
higher, a cat can take 10 steps or so in the time where an elephant
manages one step. A elephant built like a cat would not be able to stand
up.
At a g or so you're talking a insect. Beating your wings 100 times in a
second is fine at this size. Try imagining an eagle beating wings 100
times in a second, an utterly ridicolous idea.
So short answer: 1000 times a second IS very slow when you're talking
something on the scale of a single molecule.
Behind it all is the square-cube law: If you double the size of
something in all dimensions, then the cross-section of bones and muscles
go up by a factor of 4 (2*2) but the *mass* (and thus inertia and
gravity) go up by a factor of 8 (2*2*2)
Eivind Kjørstad
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