Re: Questions (Space)
- From: Tina_Hall@xxxxxxxxxxx (Tina Hall)
- Date: Sat, 15 Sep 2007 22:02:00 GMT+1
FennelGiraffe <sraarytvenssr@xxxxxxxxxxxxxxxxx> wrote:
Tina.Hall@xxxxxxxxxxxxxxxxx (Tina Hall) wrote
FennelGiraffe <sraarytvenssr@xxxxxxxxxxxxxxxxx> wrote:
(Accidentally called the other node, and got this among some other
posts. Plus some messages that the connection to Usenet is off/online -
they were several, and they usually only arrive here when the problem no
longer exists - so perhaps my reply will take a bit longer to arrive.)
I know how much 5 minutes are. I can (very badly) estimate how muchAh! I can't look at various speeds and "know how fast" they are,
100m are (I could guess anything from around 20m to 500m to be
100m, I'm just very bad at estimating that). Easier is 2m, I know
how much 2m are.
I don't know how fast 10km/h are. I just know it's slower than
11km/h. But the whole thing isn't tangible, in a 'to touch' sense.
either. I'm not talking about doing *that*. I can't look at "10km/h"
and visualize something moving exactly that speed. I don't have a
different picture for 10km/h than 50km/h -- it's all the same, just
something moving.
The 'something moving' has no image of its own, there's always the
'what' and the 'where' involved.
With other things, I look at either more time, or more distance (or more
of something else). (Or less, of course.) It's only one thing,
independent.
For the other stuff I know I've got 'solid' images. (Including the
photons and electrons earlier on in the thread.)
For things that can be measured, I've got either distances/areas (a
segment of a 24h clock for a day, or of a 60min or sec stretch, a
straight line for a century, an oval for a year, and for distances the
respective real distances of whatever is refered to) or feelings of
'more' (the tension at the + end of a line), or a bigger or smaller
amount (of electrons, for the current). And so on. I know that some of
those images might sound a bit funny, but it's how I see it in my mind
when I think about it.
I don't think the comparison of speed to longditude and lattitude is all
that off. You just decide that it's 1h every time, just as you could
decide that it's one degree. But with both time, and degrees, there is
the possibility of other 'amounts'.
That is exactly the same image (for me) no matter which units I use to
measure speed. I could be talking about km/h, mph, cm/s, or anything
else. The units are kind of off to the side (there's a separate image
for them).
What does that 'someting moving' look like to you?
If I want an actual picture of how fast 10km/h is, I have to stop and
compare it to something I know. As it happens, I watched a
cross-country race last weekend. My niece ran 5000m in about 22
minutes. That means 10km/h is noticeably slower than she was
running, so probably a slow jog or a fast walk.
I'd have to calculate that (how much 5000m in 22min is in km/h) to
agree, and I've gotten very bad at juggling numbers. (I think 10 years
ago it would have been obvious, while now I have to think about the
ratios, do some slow-motion expanding of both and then get rid of the
zeros. 15km in about an hour? That still doesn't automatically say
'15km/h' to me, though.)
I drive a car, so I can estimate speeds that are around typical
driving speeds. But that's just experience, because you have to pay
attention to speed when you drive.
Naturally. I never had a driving license, and only once drove my
stepbrother's Mini around a curve on a parking lot, as a training
session (in Great Britain). I stopped because the Mini was just several
shoe sizes too small. :)
(The sentence I heard in my one year there most often was "She's tall,
in'nt she?")
A speedometer (? is that the word?) on my bike might help. I've always
wanted one, anyway.
What I've been trying to talk about is understanding what *kind of
thing* speed is, what it means to say that one thing is faster or
slower than another. Maybe those are the visualizations I should be
asking you about. If I say John walks faster than Mary, can you
visualize two people walking down the street and one of them is
moving faster than the other one?
Sure. But that's thinking about the people and the street, not speed. I
think I'd be better off with something independent of the object.
The short answer is that the math is easier that way. If you do itWhen people are talking about planets and other bodies in a solar
system, or spacecraft traveling from one planet to another in the
same solar system, everything is usually expressed relative to the
center of the sun.
Why do they see it relative to the sun when they, for example, send
a probe to Mars? Does that (x,y,z) thing come in there?
relative to the Earth, the the formulas for describing how Mars moves
get really complex.
Makes sense.
The zero point is the point where all the coordinates are zero.[1] More properly, I should say it's the zero point, the "origin",
of the frame of reference.
Zero point sounds like a cool term for <something> in a sci-fi
story. :) (I think anything with 'zero' could sound cool.)
But that's all the term does for me.
Ok.
It's the point in a frame of reference that we measure everything else
relative to.
Ok.
For you, in everyday life, I suspect it's usually your home. When you
are at home, the distance you have travelled to get there is zero.
I'm lazy, so even walking to the bed or the bathroom is covering a
distance. :) I suspect my personal zero point is the position of the
chair I'm sitting on. (And in fact, there's only one optimal point.
Sitting wrong, or on the wrong chair, even gives me a backache.)
When you are somewhere else, you are more interested in how far away
from home you are that in how far away from some other place, like
London.
But for London I would start from Hannover, not my chair here. There's a
certain area around this home spot that gets considered depending on how
far away I am. If I'm in a neighbouring town (say, by train) I think
about train stations, by car I think about the city quarter I live in,
and so on. If I'm in a tram (here in Hannover) going through an
unfamiliar area, I tend to experience a sense of alieness, thinking
about the tram trips that I am familiar with.
Where did we lose speed here? (Afair, the tram does max 70km/h,
underground I think. It goes above and below ground here, on the same
rails, incase you wonder that I should call that Underground or
something.)
For people talking about latitude and longitude, it's the spot on the
equator that is directly south of the Royal Greenwich Observatory in
London.
I remember that some thing in London was the center, starting point.
Equator of course (for the other direction), because that's the 'middle'
of the Earth.
For satellites (artificial or natural) orbitting the Earth, it's the
center of the Earth.
Makes sense.
When you did math in school, did you do graphs with X and Y? Or in
three dimensions with X, Y, and Z?
We had the X and Y graphs in the job training (usually currents or
tension and time). I have no problem adding the Z. (I would be at a loss
to place a fourth line, though.)
Those graphs had a point where everything is zero. Can you imagine one
of those graphs overlayed onto the real world? Match the zero point of
the graph onto the real world point you want use as the point
everything is relative to.
Hey, I got your zero point right at the start of your explanation here.
:)
--
Tina
WIP: Space: 2666 words
WISuspension: Seasons & Elements trilogy | Magic Earth series
Posted to Usenet newsgroup rec.arts.sf.composition.
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