Metric on Mars

(Gary W. Swearingen) writes:

(Markus Kuhn) writes:

I wonder how many U.S. readers really find 200 million miles
significantly easier to visualize than 300 million km.

Many. Because they learned in their youth that the sun is 93 million
miles away, so 200 million miles is a little over 2 AU. But given the
unfamiliarity of a huge metric figure, many won't bother with the
initial conversion from km to miles and will have almost no idea how
big 300 million km is.

Now, this is strange. First, I doubt that many readers would come up
with "93 million miles" if asked how far the sun is away from
earth. Those who know that should also know that a km is (very) roughly
two thirds of a mile, which is close enough to get an impression
of that distance as far as one get an impression of it at all.

Actually for media purposes the difference between miles and km becomes
nearly insignificant because for most readers 200/300 million miles/km
is just "fscking far away" and those who need to know it precisely will
be using metric units anyway.


Jochem

--
"A designer knows he has arrived at perfection not when there is no
longer anything to add, but when there is no longer anything to take
away." - Antoine de Saint-Exupery

(Gary W. Swearingen) writes:
(Markus Kuhn) writes:

I wonder how many U.S. readers really find 200 million miles
significantly easier to visualize than 300 million km.

Many. Because they learned in their youth that the sun is 93 million
miles away, so 200 million miles is a little over 2 AU. But given the
unfamiliarity of a huge metric figure, many won't bother with the
initial conversion from km to miles and will have almost no idea how
big 300 million km is.

Does that mean that all that is necessary to feel at home with
a system of units is to memorize just a hand full of reference
values for comparison in each field?

But these could be learned in a few minutes.

I guess in air and space science, these might be in SI units:

Distance pole to equator (Earth): 10 000 km = 10 Mm

Length of the Earth equator: 40 000 km = 40 Mm

Altitude of geostationary Earth orbit: 36 000 km = 36 Mm

Distance Earth-Sun: 150 Gm = 150 million km

Diameter of solar system: 12 Tm

Diameter of our galaxy: 1 Zm

Distance to most distant visible objects: 100 Ym

Speed of sound: 300 m/s

Speed of light: 300 000 km/s

Acceleration of free fall (Earth): 10 m/s²

Atmospheric pressure (Earth): 100 kPa

Density of water: 1000 kg/m³ = 1 kg/L

Cruise altitude of passenger planes: 10 000 m = 10 km

Cruise speed of passenger planes: 600-800 km/h


10 deca da | 0.1 deci d
100 hecto h | 0.01 centi c
1000 kilo k | 0.001 milli m
10^6 mega M | 10^-6 micro µ
10^9 giga G | 10^-9 nano n
10^12 tera T | 10^-12 pico p
10^15 peta P | 10^-15 femto f
10^18 exa E | 10^-18 atto a
10^21 zetta Z | 10^-21 zepto z
10^24 yotta Y | 10^-24 yocto y


[From http://www.cl.cam.ac.uk/~mgk25/metric-system-faq.txt ]

Markus

"Gary W. Swearingen" wrote:

(Markus Kuhn) writes:

I wonder how many U.S. readers really find 200 million miles
significantly easier to visualize than 300 million km.

Many. Because they learned in their youth that the sun is 93 million
miles away, so 200 million miles is a little over 2 AU. But given the
unfamiliarity of a huge metric figure, many won't bother with the
initial conversion from km to miles and will have almost no idea how
big 300 million km is.

That is the basic problem: Because there is no effort to make SI
measurements familiar (e.g., in our schools, road signs, retail
stores, weather reports), we can't adopt the SI. It is also a
fallacy. If we adopt the SI, it will become familiar.

My daughter moved to Canada seven years ago. Now, when we compare
weather, she always cites temperatures in Celsius. If she
travels, she even thinks in kilometers. She cooks using metric
measuring spoons and cups.

--

David E. Ross
http://www.rossde.com/

I use Mozilla as my Web browser because I want a browser that
complies with Web standards. See http://www.mozilla.org/.

David Ross scribbled the following
on misc.metric-system:
"Gary W. Swearingen" wrote:
(Markus Kuhn) writes:
I wonder how many U.S. readers really find 200 million miles
significantly easier to visualize than 300 million km.

Many. Because they learned in their youth that the sun is 93 million
miles away, so 200 million miles is a little over 2 AU. But given the
unfamiliarity of a huge metric figure, many won't bother with the
initial conversion from km to miles and will have almost no idea how
big 300 million km is.

That is the basic problem: Because there is no effort to make SI
measurements familiar (e.g., in our schools, road signs, retail
stores, weather reports), we can't adopt the SI. It is also a
fallacy. If we adopt the SI, it will become familiar.

I.e. you can't adopt the metric system because it's not familiar, and
it's not familiar because you haven't adopted it?

--
/-- Joona Palaste ) ------------- Finland --------\
\-- http://www.helsinki.fi/~palaste --------------------- rules! --------/
"A bee could, in effect, gather its junk. Llamas (no poor quadripeds) tune
and vow excitedly zooming."
- JIPsoft

(Stephen Graham) writes:

Nor is 93 million miles a easily comprehensible figure. For most people,
it's BigNumber. No-one really has an understanding of how large the sun
is either, so relative scale isn't going to help.

I easily comprehend 93 million miles as the radius of the Earth's
orbit in the drawings of the solar system I frequently see (regardless
of the out-of-scale sun and planet sizes).

But maybe that's not as common among science readers as I thought. I
remember it from a joke book of my youth: Optician asks old man how
far he can see and he says he can see the Sun 93 million miles away.


I hope, following this discussion, that I can remember 1 AU = 150
million kilometers, a nice roundish number which, when combined
with the approximate speed of light, gives exactly 500 light-seconds.
(500 = 150,000,000,000/300,000,000 = 93,000,000/186,000)


More units trivia: If the meter had been defined to be the distance
light goes in one second, Einstein's famous equation could be written
E = m (energy in Joules = mass in kilograms).

In article ,
Ool wrote:
One Polar Lander lost because of unit confusion and Murphy's Law is
probably enough...
Then again, that happened because NASA had already switched to metric
while the company they'd gotten their descent velocity data from
hadn't. They thought they were looking at m/s when the numbers were
ft/s. Thus the thing came in just a little bit to fast...

No, this is confused. :-) The probe that was lost was Mars Climate
Orbiter, which unintentionally entered Mars's atmosphere while trying to
do its orbit-insertion burn. The immediate cause was a small navigation
error, due to the combination of a units error (newtons vs. pounds) in
computing the effects of thruster burns, and a lot of bad luck. The
broader cause, though, was that the error wasn't *caught*, despite
persistent hints that something was not quite right with the navigation.

Mars Polar Lander was lost due to a software error which had nothing to do
with units of measure.
--
MOST launched 30 June; science observations running | Henry Spencer
since Oct; first surprises seen; papers pending. |

lid (John Savard) writes:

As to the relationship between a kilometer and a mile, however, a very
big fraction of Americans neither know nor care. Those who drive
through Canada on vacation would pay attention to that, but many
others simply would have no reason whatever to be concerned about the
units of distance used in far-away places.

Except those interested in (or working in) science, medicine, virtually
any area where you have to measure and calculate exactly. Even the inch
is *defined* as 25.4mm... This has nothing to do with "units of
distance used in far-away places". The US is metric deep within, too.


Jochem

--
"A designer knows he has arrived at perfection not when there is no
longer anything to add, but when there is no longer anything to take
away." - Antoine de Saint-Exupery

In article ,
Gary W. Swearingen wrote:
(Stephen Graham) writes:

Nor is 93 million miles a easily comprehensible figure. For most people,
it's BigNumber. No-one really has an understanding of how large the sun
is either, so relative scale isn't going to help.

I easily comprehend 93 million miles as the radius of the Earth's
orbit in the drawings of the solar system I frequently see (regardless
of the out-of-scale sun and planet sizes).

That's not really comprehending the distance. All the diagram gives
you is proportional scale.

Most of us comprehend how far 100 or 1,000 miles are. Those are distances
that we more or less routinely travel in this day and age. Beyond that,
well, it just gets arbitrary.
--

In article ,
John Savard wrote:
That the Sun is 93 million miles away is indeed very well known.

I doubt that more than 10% of the US population can cite that figure.
Have any statistics to back your claim up?
--

On Thu, 22 Jan 2004 23:14:48 GMT, (Henry Spencer)
wrote:

No, this is confused. :-) The probe that was lost was Mars Climate
Orbiter, which unintentionally entered Mars's atmosphere while trying to
do its orbit-insertion burn.

More correctly aerobreaking, which is design to dip it into the high
Martian atmosphere in order to create drag and therefore slowing of
the craft.

Saves on the fuel.

The immediate cause was a small navigation
error, due to the combination of a units error (newtons vs. pounds) in
computing the effects of thruster burns, and a lot of bad luck.

Things have to be precise to began with, when any error usually leads
to disaster.

So what happened to MCO is that it would have bounced off of the
Martian atmosphere and flung out into space. Makes you wonder where it
is now, not that it is working of course.

Mars Polar Lander was lost due to a software error which had nothing to do
with units of measure.

That is incorrect.

They simply do not know what happened to MPL, when the last they heard
from it was as it entered the atmosphere.

That is why they created the tone system this time, when now they can
get some information on the way down, which would tell them
information like "crap the parachute did not open".

So MPL counts as "unknown".

Cardman
http://www.cardman.com
http://www.cardman.co.uk