

The math of faster-than-sound freefall - peterbush
http://blog.wolfram.com/2012/10/24/falling-faster-than-the-speed-of-sound/

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opminion
Question for US writers:

 _At 39 kilometers, the horizon is roughly 439 miles away_

For someone who was taught only the metric system, and told that it is good
practice to avoid mixing units (centimetres with metres, milligrams with
grams, etc), reading science written in the US using miles and Farenheit
degrees is a bit unpleasant. Fair enough, they are called imperial for a
reason :-)

But sometimes US writers mix imperial and metric units, such as in the
paragraph above. I remember a talk by some NASA guy doing the same. Is there a
_really_ good reason for that?

A separate question is, if you are willing to use metric, why use imperial?

Edit: wording

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arethuza
Do Americans actually use the term "imperial" - I'd assumed, as someone from
the UK, that this usage was only common in UK and what's now the Commonwealth.

NB Not being snarky - just wanted to know! :-)

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gecko
Where I grew up in the urban Midwest, they were called English units (despite
everyone knowing that England is metric). Kind of reminded me how the French
call French horns English horns.

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Patient0
Cor anglais: <http://en.m.wikipedia.org/wiki/Cor_anglais> French horn:
<http://en.m.wikipedia.org/wiki/Horn_(instrument)>

So what the French call an English horn is very different from what the
English call a French horn.

~~~
Evbn
Yeah, the Cor looks more like German Oboe.

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rnadna
I've not used mathematica in a long time, and I forgot how crazy-ugly the
graphs are. The cartoonish legend in the Out[18] graph is a case in point,
almost a lesson in what not to do, in terms of distracting from the content.

The syntax ain't pretty either, but one does get used to that, of course.

PS. opminion is right: the unit weaving is pretty strange. But the content of
the posting is interesting enough to make me think "oh well, it's just another
yank" and keep reading.

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cormullion
All Mathematica users hate PlotLegend...

[http://mathematica.stackexchange.com/questions/4444/labeling...](http://mathematica.stackexchange.com/questions/4444/labeling-
individual-curves-in-mathematica/)

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Jabbles
I don't think the references to "terminal velocity" are very helpful. They're
calculated from the estimates of drag coefficients and surface area, which
must have reduced as he became more upright. You can't† exceed your terminal
velocity without propulsion, that's why it's named as such.

†Well, I suppose if you're falling through an atmosphere that changes too
rapidly, you can temporarily exceed it as the TV decreases. Perhaps it's more
accurate to say "you can't accelerate if you're exceeding the terminal
velocity whilst freefalling"?

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madarco
I'd like to master Mathematica like that

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blago
_At 24.26 miles above the Earth, the atmosphere is very thin and cold, only
about -14 degrees Fahrenheit on average._

This is way off. -14 Fahrenheit is something we get in Minnesota. Most winters
:-) Any commercial flight displays temperatures in the -50 range.

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Retric
No, Temperature does weird things as you increase in altitude. So it's colder
at 10km than 50km, then dips at 90km before rising again before dropping off
in space.

<http://www.aerospaceweb.org/question/atmosphere/q0090.shtml>

~~~
blago
Very interesting. Thanks!

