3t$1@xivic.prima.de
From: Wolfgang.Schelongowski@gmx.de
Adam writes:
>Jim Beard wrote:
>> On 06/23/2012 03:52 PM, Adam wrote:
>>> I checked, and infrared is
>>> in the 1-400 THz range. Visible light is ~405-790 THz. Does
>>> that mean RF transmissions in that range would be visible?
>>
>> RF transmissions in those ranges are infrared and visible light.
>> They are photons if described as corpuscular particles, waves if
>> described using Maxwell's equations.
>
>Which I suppose excludes them as RF transmission ranges, unless light is
>allowable. Would frequencies significantly higher than those be usable?
Wrong question. It implies that your prejudices are real. Mind you,
these prejudices are shared by _all_ human beings because they're
acquired before we could talk, maybe even before we were born.
A fancy name for them would be "anthropomorhisms".
We have no experience of the velocity of light which is about 1E6
times that of sound. We have no experience of elementary interaction
with _one_ "particle" of light because its energy h * nu is around
6E-34 * 0.5 E15 VAs. 3E-19 VAs[0] (or J) is way beyond the human
experience - our range is more or less 1E-3 to 1E3 J. Even 1E-9
Joule would be ten orders of magnitude to big.
That's the reason why it took physicists until 1900 / 1905 to come up
with (special) relativity and the beginnings of quantum mechanics (QM).
Especially QM took a few dozen years, and there was lots of wailing,
gnashing of teeth, and bumping of one's heads against the wall, all of
which was and is usually ignored by the laymen.
So, please remember:
Particles and waves are abstractions based on our prejudices.
Reality is that some "properties" of what physics up to 1900 called
particles and waves are what one would associate with the "opposite"
kind. There are worse abstractions being demasked in QM
(cf. Schrödinger's[1] Cat[2]) which will make the general public
cry out: "But that violates essential logic!!!111!!!".
For a correct and more detailed approach you need to study physics
at university level with presence during lectures absolutely
required for QM, because you may want to^W^Wwill ask questions.
There's no real shortcut to QM, although a competent lecturer will
separate off those parts which are mere (but tedious!) mathematics.
This is a case where learning will painful.
> I've forgotten what I learned in college "freshman physics", mainly
>because the course was horrible. It was one factor in my decision to
>leave that university, even though I wasn't a physics major.
Yes, you've told us about it a few weeks before. It must have been
sort of traumatic experience.
>I see that this thread has also gone OT, although the brief discussion
>of security seems to be over.
Is it? Oh well, I'll now illustrate the importance of adequate
paranoia. Management summary: Even if lots of other people believe
that you're paranoid you may not be paranoid enough.
Once upon a time, in a different millenium, there was a computer
scientist who was annoyed by all those exploits of the standard
Mail Transfer Agent[3] (MTA) under UNIX which had been created before
spam became a problem, supported quite a lot of protocols besides
SMTP, and therefore had too much problems like a lot of similarly
software with historically grown creeping featuritis. So he wrote
something which for reasons I won't go into was later named "the MTA
that shall not be named" (TMTSNBN).
One of his key objectives was security, therefore he split TMTSNBN
in a sensible way into several processes. The one which was handed
any incoming TCP/IP connections to accept the mail and close the
connection forwarded it to a different process of TMTSNBN. He had a
reputation of being very paranoid about it, and proud about that,
too. However, the first process never did check the validity of the
receivers or whether they're currently on vacation.
Now here comes a spammer who wants to exact some revenge against
people whom he hates. He puts the addresses of those people
in the envelope of his spams. The envelope is where any bounces
go, and can be set to anything which is a formally possible
e-mail address. Can you imagine what happens if the spammers
sends several million mails?
Well, the unlucky addresses in the envelopes will receive at least
thousands of bounces in a very short time. As these bounces are
unsolicited mails, they're spam in their own right.
Apart from those "on vacation, please rob my house during my absence"
there will be lots of bounces from those who run TMTSNBN. It's a
distributed denial of service (DDOS) by generating backscatter /
outscatter.
Result: The otherwise excellent MTSNBN must not face any part of the
Internet which is not under Anal-Retentive-Bastard-Fascist-From-Hell
control of those who set up TMTSNBN in order to face the above
mentioned part of the Internet. Why? Lack of paranoia of the author.
[0] Astronomers have observed the impact of particles with energy in
excess of 1 Joule, even one "Oh-MyGod!" particle whose energy was
that of a baseball hit by a bat. However, the area needed to
detect those was many square miles which is at least 10^(2*5) =
1E10 times larger than that of the human eye.
[1] The Austrians once had a 1000(?) Austrian Shilling banknote, with
the picture of Schrödinger and a Greek Psi on it. Obviously the
artists had never contacted any physicist because there wasn't
even _one_ cat on it.
[2] Anybody actually performing that Gedankenexperiment for real will
only prove that he hasn't understood QM and hates cats. Quoth my
QM professor: "It doesn't have to be a dead cat, any other
measuring device will do, too."
[3] One of those daemons (not: demons) which work in the background
and accept and transfer e-mail. For the complete story read
e.g. the Bat Book or RFCs 5321 and 5322. See also "Mail Server".
--
The first entry of Sin into the mind occurs when, out of cowardice or
conformity or vanity, the Real is replaced by a comforting lie.
-- Integritas, Consonantia, Claritas
--- SoupGate-Win32 v1.05
* Origin: you cannot sedate... all the things you hate (1:229/2)
|
