Re: Questions (Space)

Ric Locke <warlocke@xxxxxxxxxxxx> wrote:
Tina Hall wrote:
Ric Locke <warlocke@xxxxxxxxxxxx> wrote:

Light and radio are the same thing;

Hang on there; huh?

the general term is "electromagnetic radiation".

So you mean that it's in the same broad category, not that a radio
starts playing music if someone points a torch at its antenna.

(Electromagnetic radiation is something I can't picture.)

Don't feel bad. The scientists and engineers had a lot of problems
with the concept when it first came up, and the techniques for
dealing with radio and light look quite different. But a very bright
guy called James Clerk Maxwell came up with equations, and they work
the same way for radio as for light, and they always work, so the
scientists shrugged and went with the program.

The equations wouldn't bother me, (or that light and radio look and
behave the same, whatever they really look like) it's the lack of an
image for the broader term, so whenever it turns up there's just a
mental question mark in its spot.

Look at it this way: an elephant and a shrew look very different and
don't appear to have much in common, but both of them have warm blood
and bear their young alive. That is, they are /mammals/.

What I meant with 'same broad category'.

"Electromagnetic radiation" is the "mammal" in that analogy.

It's the terms themselves that I can't picture, not their existence as a
generic term for a group of things. I know what the word-type is like,
and I know 'electric' and have a vague idea of 'magnetic' and
'radiation', but don't know what this looks like.

Whether mammals or trains (models and real ones), or even broader;
things on wheels, I have something to imagine.

Radio gets here from the moon the same way light does -- in
straight lines, through spacetime.

Waves? Those things with frequency in Hertz? (I can follow that,
even that light and radio look the same, perhaps with different
frequencies, but I can't wrap my mind around the idea that what
lights stuff so I can see it is the same that is transmitted by
radio.)

Yeah, although in my opinion the whole "waves" thing tends to be a
distraction. There's one set of equations (Maxwell's) that describes
waves, and another set (from quantum physics) that describes
particles, and /both sets work/

A brilliant lecturer once explained to me where the waves in a
(electric) sine curve come from. (Brilliant, because he always found a
way to explain something to me.)

To give you a picture I understand (because equations don't tell me
anything, I forgot the four formulas for this, too, they were just naked
characters without intrinsic meaning [*], but still have the actual
image); the electrons are (simplified) like peas in a tube, one goes in
one end, another comes out the other, and it just looks as if one went
all the way. (That was what that lecturer started with.)

My image is actually a line (like those in circuits on a board, or the
cable behind the socket) where the little things wander from one space
to the next, if you push in more, more move (high point in a wave), if
you push in less, or even suck, less move or even go in the other way
(low or negative point in a wave). (The lecturer explained something
about something going in a circle, producing the sine wave form tension
that moves the electrons. Which would be the generators, not that I know
how they work, all I've got of them is more random snippets of vague
ideas.)

The line or cable is straight, but at any one point you've got more or
less electrons moving, which produces a shape when measured. I don't
know what's moving if you look at light or radio. I guess that's your
particles, whatever they are. (For me, that's enough to have both sets
of your funny equations work.)

[*] The only formula I still remember is R=I/U, and even these
characters don't have meaning themselves. It's like a different
language, some people (say German) have to translate each word if they
want to talk another (say English). You may be one who thinks in that
other language (like I think in English or German, no translation) but I
don't think in formulas and equations, the whole thing is just
characters and symbols, no image attached to it. I know what the R, I,
U, =, and / stand for. When I think of what it does there's no formula,
but an image of a current and a resistor and somewhere far away the
tension.

So, talking about formulas and equations doesn't help understand. I need
a picture, like the above peas, and the electrons in their line/cable.
(The cable is physically restricted, and still more or less move
through. I guess like a waterpipe.)

-- a scientist or an engineer just picks the set that works best (or
is easiest to calculate) given the problem at hand. Thinking about
radio as waves and light as particles is usually the best way to go
about it, but there are exceptions, and the math works either way. For
the rest of us, it's best not to try for too concrete a visualization;
just think of something, nebulously defined, that travels in straight
lines at the speed of light, and you'll have enough to start with.

With that, I have nothing to start with (and nothing to remember). See
above.

If it helps to unify the concepts, think of radio as big and cool,
while light is little and hot.

?

(From another very bright guy, called Stefan Boltzman.) Do you have an
electric stove or heater? When you turn it on it's first just warm,
then it starts to glow -- that is, at first it makes electromagnetic
radiation you feel as heat, then it gets hotter and starts to make
light you can see, too. Nothing changed but the temperature. It won't
make radio waves, but that's because you can't get it cool enough.

?

Electro (the power that has my computer run), -magnetic (a magnet,
however that actually works), radiation (no image), as _heat_? That's
just confusing. I don't even have an image for just the first three
terms together, and heat fits in nowhere in that.

The reality is much more complicated. I can try to explain if you
like, but it may be too much information.

If you can create a coherent image without complicated words. I
doubt that that's likely, though. (The path of comprehensive
explaining something to me is very narrow, the chance is much bigger
that you miss, I get a headache trying to understand, and both end
up frustrated.)

Yes, I've noticed that. From my side -- if I try to make an
explanation too simple, sometimes people get offended at my treating
them like children. So I have to balance it out a bit, and it's hard
to tell just where the break-point might be. Causes headaches :-)

The problem tends to be that on one side, too little knowledge is
assumed (I've got all those snippets of vague ideas picked up from all
over the place), and on another, understanding of those raw formulas or
formed concepts is expected (which are just alien hyroglyphs to me), and
both is wrong in my case.

The brilliant lecturer from above had the advantage of knowing me
(teaching us alltogether two years), and lots of imagination to come up
with different ways to describe what he understood. He knew what I knew
(as basis to work from) and what the actual problem is among the things
I didn't know.

If there's any angle to start with what I said above about electrons,
that's a way to go. Start with 'what are particles', simplified, and how
does radiation happen, also simplified. I just need an image for what
happens. :) (No formulas, equations.)

My main interest is a signal in space.

For the aliens I'd like one that's sort of stationary, covering a
certain (very, very large) area (a thick-shelled sphere, no signal
inside, no signal outside). (The weird theory thing that needn't be
humanly doable. Better understanding would of course be an
advantage. Not that I need to write an explanation, the characters
aren't supposed to find out the mechanics behind it anyway, it's
just some mysterious alien thing. But I'd like some kind of alien
signal type. :) )

Stationary I can't help you with. You're right about the "shell"
effect. If you had a radio transmitter out in space somewhere, turned
it on, ran it for a while, then turned it off, what you'd get is an
expanding spherical shell.

Ok, that makes sense.

The thickness of the shell would be speed of light times the time the
transmitter was on, and the radius would be the speed of light times
the time since you switched on (outside) and off (inside).

Okay. (I can guess that that makes sense without trying to calculate it.
:) )

A spaceship traveling faster than light could go somewhere inside the
thickness of the shell and receive the transmission; if it went
farther away it would get nothing because the signal hadn't reached
that point yet, and if it went closer it wouldn't hear anything
because the signal already went by.

Makes sense.

It's just that I want it stationary. :) And the crew (on their ship) to
enter the zone, and wonder what it means. I wonder whether they could
easily figure out it's a sphere.

For the stationary (it's supposed to be the equivalent of a sign put up,
saying something about the area it encloses), I guess I can have the
aliens do some trick that mutes the signal inside the sphere and
prevents it going any further than the outside. Humans needn't
understand how they do it. :)

But about the crew knowing the shape, would it even be possible to know
at point A that the same signal goes through neighbouring space (not
passing point A), if they don't travel all the way around in that shell
area? (Note that my wish is that they don't 'see' the rest of the shell.
If that's normal and expected, I'm happy. It's what I would expect, but
don't know enough.)

A bright light would do the same. The spaceship inside the thickness
of the shell would see the light; outside or inside the shell,
nothing.

In a very, very, very huge way, and across a long time, that's 'star
goes on, burns for eons, then goes out'. <g>

This 'how did they send something from the moon' is for the
spacefaring human crew. I assume that travels at the speed of light.
Not because you say it's the same (I still don't get that), but it's
one of those snippets floating around in my head.

Anyway. Thanks! :)

Hope it helps. Maybe after you've digested that a bit some of the
other concepts will be easier.

Well, it would help to know what it is that travels. :) I can imagine
that travelling in greater and smaller amount, outward in a shell rather
than squeezed into an electric line, once I know what it is. (Light and
radio are rather vague to describe its contents, more like looking at
the outcome of the effect it has than describing what it actually is.)

--
Tina
WIP: Space: 1123 words
WISuspension: Seasons & Elements trilogy | Magic Earth series
Posted to Usenet newsgroup rec.arts.sf.composition.

.

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