>> Interesting thing: According to Wikipedia [which is never wrong], a
>> nuclear explosion only generates an EMP because of the Earth's magnetic
>> field. Like, if it was in space, it wouldn't do that...
> 
> Huh? That doesn't sound right. An old strategic option the USSR apparently
> had was to detonate a -real- big (50 megaton) thermonuke over the US, but
> out in space / low orbit. The idea was to melt all radios and computers,
> the entire US telephone network, etc. As far as I know EMP damage is caused
> by the massive radio waves generated by a nuclear explosion (besides all
> the "hard" gamma radiation, and other nasty stuff besides heat and light).
> These induce current in conductors (i. e. they fry microchips).
> 
> Radio definitely travels in a vacuum where there is no magnetism - IMO,
> magnetism CAN effect radio but just to distort or interfere with it. So I'd
> think that a magnetic field will -moderate- or interfere an EMP pulse a
> bit, not be the part-cause of it?

According to Wikipedia, the nuke generates gamma rays, these shred the 
Earth's atmosphere and produce current, and the Earth's magnetic field 
directs this current towards the ground. (Depending on where in the 
world you are. Apparently the USA has a field alignment which makes it a 
particularly suitable target to hit.)

All of which makes it sound like if you did this in space, you'd just 
get gamma rays...

Post a reply to this message

Invisible wrote:

> Stefan Viljoen wrote:
> 
>> Not sure what it is in BHP (oh you continentals!)
> 
> Brake Horse-Power.

Yes, but I've long ago given up trying to convert to that from
joules-per-second, or from it!

-- 
Stefan Viljoen

Post a reply to this message

>>> Not sure what it is in BHP (oh you continentals!)
>> Brake Horse-Power.
> 
> Yes, but I've long ago given up trying to convert to that from
> joules-per-second, or from it!

Most people refer to that as Watts, not joules per second. But anyway:

http://www.wolframalpha.com/input/?i=brake+horsepower

1 BPH = roughly 0.75 kW.

Post a reply to this message

Invisible wrote:

> According to Wikipedia, the nuke generates gamma rays, these shred the
> Earth's atmosphere and produce current, and the Earth's magnetic field
> directs this current towards the ground. (Depending on where in the
> world you are. Apparently the USA has a field alignment which makes it a
> particularly suitable target to hit.)

Could be I suppose. Wouldn't that imply that if your PC is fried by a nuke
due to EMP, you wouldn't be far behind (since if gamma rays cause EMP, your
DNA'd be shredded too by them... right along with your electronics based
friend.)
 
Vs. where if it was the intense burst of -radio- waves that caused EMP, you
might have a chance to biologically survive (at least in the moment) when
your PC is fried by EMP from a nuke.

> All of which makes it sound like if you did this in space, you'd just
> get gamma rays...

Might be. Though I wonder if EMP is caused by interaction between oxygen /
nitrogen being bombarded with high-intensity gamma rays? Because that seems
to be what Wik implies here. Intense radio waves seems to me to make more
sense.
-- 
Stefan Viljoen

Post a reply to this message

>> According to Wikipedia, the nuke generates gamma rays, these shred the
>> Earth's atmosphere and produce current, and the Earth's magnetic field
>> directs this current towards the ground. (Depending on where in the
>> world you are. Apparently the USA has a field alignment which makes it a
>> particularly suitable target to hit.)
> 
> Could be I suppose. Wouldn't that imply that if your PC is fried by a nuke
> due to EMP, you wouldn't be far behind (since if gamma rays cause EMP, your
> DNA'd be shredded too by them... right along with your electronics based
> friend.)

No - because the gamma rays have all been turned into heat and 
electricity and filtered out by the Earth's atmosphere. (There's 
actually quite a lot of gamma rays out there, all the time. And cosmic 
rays, which are even higher energy. They just never reach the ground.) 
The electric current, however, is *not* stopped by the atmosphere...

Post a reply to this message

Invisible <voi### [at] devnull> wrote:
> >> According to Wikipedia, the nuke generates gamma rays, these shred the
> >> Earth's atmosphere and produce current, and the Earth's magnetic field
> >> directs this current towards the ground. (Depending on where in the
> >> world you are. Apparently the USA has a field alignment which makes it a
> >> particularly suitable target to hit.)
> >
> > Could be I suppose. Wouldn't that imply that if your PC is fried by a nuke
> > due to EMP, you wouldn't be far behind (since if gamma rays cause EMP, your
> > DNA'd be shredded too by them... right along with your electronics based
> > friend.)
>
> No - because the gamma rays have all been turned into heat and
> electricity and filtered out by the Earth's atmosphere. (There's
> actually quite a lot of gamma rays out there, all the time. And cosmic
> rays, which are even higher energy. They just never reach the ground.)
> The electric current, however, is *not* stopped by the atmosphere...

What I found most interesting in that wikipedia article (which is an uncommonly
good one) was that this widespread EMP effect is almost zero for very low
altitude airbursts or ground detonations, and is most effective at
nearly-orbital altitudes. Which means that a pivotal scene in the movie "Broken
Arrow" is particularly impossible. :)

Post a reply to this message

>>>> According to Wikipedia, the nuke generates gamma rays, these shred the
>>>> Earth's atmosphere and produce current, and the Earth's magnetic field
>>>> directs this current towards the ground. (Depending on where in the
>>>> world you are. Apparently the USA has a field alignment which makes it a
>>>> particularly suitable target to hit.)
>>> Could be I suppose. Wouldn't that imply that if your PC is fried by a nuke
>>> due to EMP, you wouldn't be far behind (since if gamma rays cause EMP, your
>>> DNA'd be shredded too by them... right along with your electronics based
>>> friend.)
>> No - because the gamma rays have all been turned into heat and
>> electricity and filtered out by the Earth's atmosphere. (There's
>> actually quite a lot of gamma rays out there, all the time. And cosmic
>> rays, which are even higher energy. They just never reach the ground.)
>> The electric current, however, is *not* stopped by the atmosphere...
> 
> What I found most interesting in that wikipedia article (which is an uncommonly
> good one) was that this widespread EMP effect is almost zero for very low
> altitude airbursts or ground detonations, and is most effective at
> nearly-orbital altitudes. Which means that a pivotal scene in the movie "Broken
> Arrow" is particularly impossible. :)

Also, as I mentioned, millions of films seem to assume that an EMP only 
affects devices which are turned on. (E.g., War of the Worlds, only one 
working car because it wasn't turned on. WTF? Then again... War of the 
Worlds. WTF?)

Post a reply to this message

Invisible wrote:

>> What I found most interesting in that wikipedia article (which is an
>> uncommonly good one) was that this widespread EMP effect is almost zero
>> for very low altitude airbursts or ground detonations, and is most
>> effective at nearly-orbital altitudes. Which means that a pivotal scene
>> in the movie "Broken Arrow" is particularly impossible. :)
> 
> Also, as I mentioned, millions of films seem to assume that an EMP only
> affects devices which are turned on. (E.g., War of the Worlds, only one
> working car because it wasn't turned on. WTF? Then again... War of the
> Worlds. WTF?)

Its movieland! Good science almost never makes for good drama.

Its like Captain Picard saying "Full stop!" on the Enterprise, and in ten
seconds they are at relative dead stop from going several hundred times
lightspeed. I wonder exactly how much energy you'd need to decelerate ten
grammes of mass, from, say, 100 * c to 0 in ten seconds - if
Einsteinian "thou shalt NOT exceed, or even closely approach, C" did not
apply. Nevermind a gigatonne starship.

I guess you'd need the full output of all a the Milky Way galaxy's stars for
a few minutes or something. Even 1701-D's anti-matter power generation
systems would be sucked dry in moments.

But it isn't good drama to have the crew become a biological soup one
molecule thick against the viewscreen each time Geordi or Wesley steps on
the footbrake, thus exposing them all to 100000000000000000000000000G of
deceleration.
-- 
Stefan Viljoen

Post a reply to this message

Stefan Viljoen wrote:

> Its movieland! Good science almost never makes for good drama.
> 
> Its like Captain Picard saying "Full stop!" on the Enterprise, and in ten
> seconds they are at relative dead stop from going several hundred times
> lightspeed.

Never mind the "minor detail" of the fact that "stationary" doesn't 
exist in outer space.

Or that you don't actually need engines in order to move, only to 
accelerate or deccelerate.

Or the fact that things don't make that "swoshing" noise in space. In 
fact, they don't make *any* noise!

Or the Weighted Companion Cube will never threaten to stab you and, in 
fact, cannot speak.

> I wonder exactly how much energy you'd need to decelerate ten
> grammes of mass, from, say, 100 * c to 0 in ten seconds - if
> Einsteinian "thou shalt NOT exceed, or even closely approach, C" did not
> apply. Nevermind a gigatonne starship.

Well, the fastest starships reputedly reach Warp 10 (i.e., 10c). Never 
mind the "minor detail" that this would cause the ship to travel 
backwards in time, and have an imaginary mass. (Irony?)

> But it isn't good drama to have the crew become a biological soup one
> molecule thick against the viewscreen each time Geordi or Wesley steps on
> the footbrake, thus exposing them all to 100000000000000000000000000G of
> deceleration.

Perhaps you're forgetting the Inertial Dampers?

Even the teleporters have Hiesenburg Compensators on them...

Post a reply to this message

Invisible wrote:

> Stefan Viljoen wrote:
> 
>> Its movieland! Good science almost never makes for good drama.
>> 
>> Its like Captain Picard saying "Full stop!" on the Enterprise, and in ten
>> seconds they are at relative dead stop from going several hundred times
>> lightspeed.
> 
> Never mind the "minor detail" of the fact that "stationary" doesn't
> exist in outer space.

Correct - "relative dead stop". Apparently according to The Bible (the
Enterprise Tech Manual I bought in '92) StarFleet uses the galactic center
as navref.
 
> Or that you don't actually need engines in order to move, only to
> accelerate or deccelerate.
> 
> Or the fact that things don't make that "swoshing" noise in space. In
> fact, they don't make *any* noise!

How boring would that be?! Its part of what I love about old TNG episodes,
the "thrummmm" sound of the Enterprise is orbits
yet-another-planet-with-human-looking-aliens-and-hot-alien-chicks-only-distinction-is-a-new-head-piece.

>> I wonder exactly how much energy you'd need to decelerate ten
>> grammes of mass, from, say, 100 * c to 0 in ten seconds - if
>> Einsteinian "thou shalt NOT exceed, or even closely approach, C" did not
>> apply. Nevermind a gigatonne starship.
 
> Well, the fastest starships reputedly reach Warp 10 (i.e., 10c). Never
> mind the "minor detail" that this would cause the ship to travel
> backwards in time, and have an imaginary mass. (Irony?)

... and need infinite energy to move an infinite mass that occupies all
points in the universe simultaneously. Sounds painful.
 
>> But it isn't good drama to have the crew become a biological soup one
>> molecule thick against the viewscreen each time Geordi or Wesley steps on
>> the footbrake, thus exposing them all to 100000000000000000000000000G of
>> deceleration.
> 
> Perhaps you're forgetting the Inertial Dampers?

No, I intentionally -ignored- them! :) 

As I ignored the SIF (structural integrity field) and the artificial gravity
generators, the navigational deflector, subspace radio, etc. etc. and all
the other fanciful things you apparently "need" for supralight space travel
and five year space missions. (And discovering hot alien chicks on remote
planets.)
 
> Even the teleporters have Hiesenburg Compensators on them...

:-) the thought of uncertainty with a matter dematerialisation and
transportation device gives me the willies! Or could it possibly make you
LOOSE your willy? Along with other bits?
-- 
Stefan Viljoen

Post a reply to this message

Invisible <voi### [at] devnull> wrote:
> Also, as I mentioned, millions of films seem to assume that an EMP only
> affects devices which are turned on. (E.g., War of the Worlds, only one
> working car because it wasn't turned on. WTF? Then again... War of the
> Worlds. WTF?)

Well, IIRC, it was never explicitly stated that an EMP was responsible for that.

I quite enjoyed that film actually. Very little attempt to explain anything,
which is the best way to do SF, and definitely the best way to do first-person
drama.

Post a reply to this message

>> Never mind the "minor detail" of the fact that "stationary" doesn't
>> exist in outer space.
> 
> Correct - "relative dead stop". Apparently according to The Bible (the
> Enterprise Tech Manual I bought in '92) StarFleet uses the galactic center
> as navref.

Right. So an imaginary point in space. That's great. Now all we need is 
an unambiguous way to orient a cartesian grid... oh, wait...

> Its part of what I love about old TNG episodes,
> the "thrummmm" sound of the Enterprise is orbits
>
yet-another-planet-with-human-looking-aliens-and-hot-alien-chicks-only-distinction-is-a-new-head-piece.

Yeah. Amazing how all sentient beings are humanoids who just happen to 
speak American English, eh?

>> Well, the fastest starships reputedly reach Warp 10 (i.e., 10c). Never
>> mind the "minor detail" that this would cause the ship to travel
>> backwards in time, and have an imaginary mass. (Irony?)
> 
> ... and need infinite energy to move an infinite mass that occupies all
> points in the universe simultaneously. Sounds painful.

No, an object at speed c has infinite mass. An object at 10c has a 
finite, but imaginary mass.

I have no idea what the hell kind of energy it possesses. Look up Tachyon.

>> Perhaps you're forgetting the Inertial Dampers?
> 
> No, I intentionally -ignored- them! :) 
> 
> As I ignored the SIF (structural integrity field) and the artificial gravity
> generators, the navigational deflector, subspace radio, etc. etc. and all
> the other fanciful things you apparently "need" for supralight space travel
> and five year space missions. (And discovering hot alien chicks on remote
> planets.)

In other words, everything required to make travelling through space 
EXACTLY LIKE sailing across an uncharted ocean. :-P

>> Even the teleporters have Hiesenburg Compensators on them...
> 
> :-) the thought of uncertainty with a matter dematerialisation and
> transportation device gives me the willies! Or could it possibly make you
> LOOSE your willy? Along with other bits?

Maybe it "gives you the willies" - as in, you end up with 12 of them, 
instead of just 1.

Post a reply to this message

>> Also, as I mentioned, millions of films seem to assume that an EMP only
>> affects devices which are turned on. (E.g., War of the Worlds, only one
>> working car because it wasn't turned on. WTF? Then again... War of the
>> Worlds. WTF?)
> 
> Well, IIRC, it was never explicitly stated that an EMP was responsible for that.

No. Just that the power went out and everybody's car except our hero 
stopped working due to an ignition fault.

> I quite enjoyed that film actually. Very little attempt to explain anything,
> which is the best way to do SF, and definitely the best way to do first-person
> drama.

Well, each to their own. All it seemed to be able is "hey, humanity 
sucks, maybe Earth would be better off without us".

Post a reply to this message

Invisible wrote:

> Right. So an imaginary point in space. That's great. Now all we need is
> an unambiguous way to orient a cartesian grid... oh, wait...

Yarg!
 
> Yeah. Amazing how all sentient beings are humanoids who just happen to
> speak American English, eh?

Well, what would be the point of some thing that lives at pressures we only
know as occurring at the bottom of the terran ocean, and can only
communicate by bioluminescent flashes? (Never mind that either you, or it,
will need a pressure suit of some kind so as not to either implode, or
explode, at each other's "skin" level environmental gas or fluid pressure,
or not to either burn or freeze to death at ambient temperature...)

Doesn't make for good drama. Kissing something like that would be
impossible. If Capt. Kirk doesn't get to kiss the hot alien chick at the
end of the ad-break, what's the point?!
 
> I have no idea what the hell kind of energy it possesses. Look up Tachyon.

Hah! Tardyons sonny, tardyons!
 
> In other words, everything required to make travelling through space
> EXACTLY LIKE sailing across an uncharted ocean. :-P

See? It's the romance and storytelling, not the science.
 
>>> Even the teleporters have Hiesenburg Compensators on them...
>> 
>> :-) the thought of uncertainty with a matter dematerialisation and
>> transportation device gives me the willies! Or could it possibly make you
>> LOOSE your willy? Along with other bits?
> 
> Maybe it "gives you the willies" - as in, you end up with 12 of them,
> instead of just 1.

:) well that should maybe match up with those extraterrestrial alien
chicks. "Them aliens got weird ways on them yonder remote planets, son..."

-- 
Stefan Viljoen

Post a reply to this message

Invisible <voi### [at] devnull> wrote:
> >> Also, as I mentioned, millions of films seem to assume that an EMP only
> >> affects devices which are turned on. (E.g., War of the Worlds, only one
> >> working car because it wasn't turned on. WTF? Then again... War of the
> >> Worlds. WTF?)
> >
> > Well, IIRC, it was never explicitly stated that an EMP was responsible for that.
>
> No. Just that the power went out and everybody's car except our hero
> stopped working due to an ignition fault.

Yes. Everything electrical that was on at the time stopped working. Nobody said
EMP though. Maybe the filmmakers were well aware of what an EMP would actually
do, and deliberately made it different, coincidentally echoing the common
hollywood mistake.... yeah I doubt it too ;-) But still, nobody said EMP.

> Well, each to their own. All it seemed to be able is "hey, humanity
> sucks, maybe Earth would be better off without us".

Hmm, I didn't get that at all.

Post a reply to this message

Invisible wrote:
> No chance of buying an adaptor?

Considering I already bought an entirely new case, and only have that 
one eSATA drive...

--
Tim Cook
http://empyrean.freesitespace.net

Post a reply to this message

Invisible wrote:
> Never mind the "minor detail" of the fact that "stationary" doesn't 
> exist in outer space.

Sure it does.  There does exist absolute motion that can be measured 
even if there's nothing else in the universe--rotation, for instance. 
And I personally suspect that there's some subtle difference between 
gravity and motion affecting something that we just haven't thought of 
yet, which will allow distinguishing between whether you're moving vs. 
just feeling the pull of something else.

> Or the fact that things don't make that "swoshing" noise in space. In 
> fact, they don't make *any* noise!

Actually they do.  It can be safely assumed the ship is constantly 
leaking some negligible amount of atmosphere, and if you get within the 
envelope of that, you can hear it swooshing as it moves past!

> Well, the fastest starships reputedly reach Warp 10 (i.e., 10c). Never 
> mind the "minor detail" that this would cause the ship to travel 
> backwards in time, and have an imaginary mass. (Irony?)

Actually, from what I remember of the Technical Manual, it's not a 1:1 
multiplicative correlation between warp speed and c, more like 
exponential.  Warp 1 *is* c, but warp 10 is 'occupies every point in 
universe simultaneously' and requires theoretically infinite 
energy...warp 9 is Really Really fast.  Because just 10x the speed of 
light still leaves months, if not *years* between most stars.

--
Tim Cook
http://empyrean.freesitespace.net

Post a reply to this message

>> Never mind the "minor detail" of the fact that "stationary" doesn't 
>> exist in outer space.
> 
> Sure it does.  There does exist absolute motion that can be measured 
> even if there's nothing else in the universe--rotation, for instance. 

Well, maybe.

> And I personally suspect

Prove it.

>> Or the fact that things don't make that "swoshing" noise in space. In 
>> fact, they don't make *any* noise!
> 
> Actually they do.  It can be safely assumed the ship is constantly 
> leaking some negligible amount of atmosphere, and if you get within the 
> envelope of that, you can hear it swooshing as it moves past!

1. Your ears would explode at such low pressure, so *you* can't hear 
anything. :-P

2. I rather suspect that rather than vibrating, such a gas cloud would 
simply expand outwards forever. It's not at anywhere near high enough 
pressure for audio-frequency vibrations to propogate.

Post a reply to this message

Tim Cook wrote:

> Actually, from what I remember of the Technical Manual, it's not a 1:1
> multiplicative correlation between warp speed and c, more like
> exponential.  Warp 1 *is* c, but warp 10 is 'occupies every point in
> universe simultaneously' and requires theoretically infinite
> energy...warp 9 is Really Really fast.  Because just 10x the speed of
> light still leaves months, if not *years* between most stars.

This is what always bursts my bubble about space travel - whenever I hear of
the incredible distances involved. 

Even IF we could attain, or come close to, lightspeed (and by all evidence
it is NOT like the soundbarrier, it is an absolute physical constraint,
unbreakable by any conceivable method or technology) it is still 4 YEARS in
space to the nearest start. To even get to more "close" stuff, 6 YEARS, 10
YEARS - or -thousands- of years (at LIGHTSPEED!) to another galaxy.

Of course, time dilation at high relativistic velocities might mean you can,
from your relative viewpoint, complete the journey within a human lifespan
of 70, or 80 years, depending on just how close you can get to the
magical "c". Nothing would be left back home though, since thousands of
years might have passed there...

It just somehow... sad.
-- 
Stefan Viljoen

Post a reply to this message

> It just somehow... sad.

Yup, need to come up with a faster way of travelling before the sun burns us 
up!

Post a reply to this message

On Tue, 10 Nov 2009 10:12:57 +0000, Invisible wrote:

>> There's
>> nothing, though, that says you can't create a mirrored set, let the
>> drives mirror, and then "break the mirror" and take one drive offline.
>> I've known people who have done that and used that for disaster
>> recovery when upgrading systems.
> 
> This is a very, very dumb way to do backup. A file-level copy will be
> drastically faster. (It doesn't involve mirroring all the useless empty
> sectors.) IME, mirroring a disk typically takes something like 10 hours,
> regardless of capacity. (Lower-capacity drives are usually
> correspondingly slower too.)
> 
> Also, if you do a file-level copy, you have options such as compressing
> the data and putting multiple backups on a single backup harddisk, doing
> differential or otherwise partial backups, and so forth.

Depends on what you're trying to accomplish.  If the purpose is fast 
recovery, mirroring is a very good way to ensure you have a workable 
system if you swap the drives out.

Doing a file-level copy might be faster, but then you get to go in and 
muck about with permissions afterwards.  Mirroring takes care of all of 
that for you.

Remember - I've got decates of working with server technology behind me 
here. ;-)

>>> An often-encountered backup strategy is to copy everything onto an
>>> external USB HD and then put that somewhere. I'm not sure that all
>>> this turning the drive on and off won't just wear it out faster.
>> 
>> See my anecdotal evidence in reply to Stefan.  Two identical units, one
>> powered on and off regularly, one that was left on 24x7.  Guess which
>> one failed?  Not the one that has been turned on and off regularly for
>> 5 years now.  The one that was plugged in and running for 3 years
>> solid.
> 
> In theory, until the disks are spinning at full speed, you don't get
> that "cushion of air" for the heads to "fly" on, which should result in
> wear. Of course, no doubt manufacturers know all about this and have
> come up with ways to at least reduce the problem...

I would expect they do.  I used to know a guy who worked for Quantum 
years ago (I wonder what he's up to these days), and he said the 
engineering was quite impressive.

Jim

Post a reply to this message

On Tue, 10 Nov 2009 10:17:16 +0000, Invisible wrote:

>>> I don't know, man... Backing up spinning disk to... spinning disk? Is
>>> that such a sensible idea?
>> 
>> Why not? It's a backup. It's not like you can read a tape without
>> spinning it. What are you going to back it up to, FLASH RAM?
> 
> Tape operates at much lower speeds. And since the only people who use
> tape are people who want seriously reliable backup storage, it tends to
> be very well engineered. (And stupidly expensive...)

Never used DAT drives for backup, have you? ;-)  Horrible quality of 
storage media, and terrible shelf life IME.

Jim

Post a reply to this message

On Tue, 10 Nov 2009 07:38:30 +0000, Orchid XP v8 wrote:

> Wanna take a guess what the customary place to install programs is?
> Yeah, it's C:\Program Files.

Then there's also the button that lets you choose a different location to 
install to - part of pretty much every modern installation program on 
Windows.

Jim

Post a reply to this message

On Tue, 10 Nov 2009 10:21:30 +0000, Invisible wrote:

>>> ...yeah, shopping online tends to be cheaper. Quality is another
>>> matter, of course.
>> 
>> Buy from reputable dealers, and quality isn't an issue.
> 
> I don't mean to imply that quality is *necessarily* an issue, just that
> it *can* be more of an issue. As you say, it depends who you buy from.

Exactly.  I started using newegg because system builders I know who build 
for small businesses used them.  I rarely go to a place I've never heard 
of and bought something.  Oddly, the svideo cable I mentioned before I 
did go to a relatively unknown company - but I didn't drop more than 
about 10 bucks on the cable, either, and when I do something like this, I 
usually start with something cheap.  I did this with a place that sold 
through Amazon - bought a $3 iPod battery replacement kit - that worked, 
so ordered a laptop battery from them for my stepson's laptop.  Both have 
worked well. :-)

> I often buy from Maplin because 1) I don't have to wait for it to be
> delivered, 2) their staff actually have a frickin clue, and 3) they
> don't argue about returns.

Sometimes expediency is worth the extra cost - as is the ability to get 
something replaced without a hassle.

Jim

Post a reply to this message

> In theory, until the disks are spinning at full speed, you don't get that 
> "cushion of air" for the heads to "fly" on, which should result in wear. 
> Of course, no doubt manufacturers know all about this and have come up 
> with ways to at least reduce the problem...

There's probably just a reserved portion of the platter that is used for 
spin-up/down operations.  The only tricky bit is to get the head over to 
that portion when the power is suddenly cut.

Post a reply to this message

>> Tape operates at much lower speeds. And since the only people who use
>> tape are people who want seriously reliable backup storage, it tends to
>> be very well engineered. (And stupidly expensive...)
> 
> Never used DAT drives for backup, have you? ;-)

No, only for the last 6 years.

> Horrible quality of storage media, and terrible shelf life IME.

Really?

Post a reply to this message

>> I often buy from Maplin because 1) I don't have to wait for it to be
>> delivered, 2) their staff actually have a frickin clue, and 3) they
>> don't argue about returns.
> 
> Sometimes expediency is worth the extra cost - as is the ability to get 
> something replaced without a hassle.

Maplin are pretty much the best electronics shop around.

I mean, apart from being the *only* place in all of Christendom which 
can sell you (say) a 50kohm resistor, their staff have a clue about what 
they're supposed to be selling, and if you take something back they will 
exchange it or give you your money back (provided it isn't obviously 
busted).

Their website utterly sucks, by the way...

Post a reply to this message

>> In theory, until the disks are spinning at full speed, you don't get 
>> that "cushion of air" for the heads to "fly" on, which should result 
>> in wear. Of course, no doubt manufacturers know all about this and 
>> have come up with ways to at least reduce the problem...
> 
> There's probably just a reserved portion of the platter that is used for 
> spin-up/down operations.

I'm 98% certain this is the case. However, that still means that this 
part of the disk wears down, and also that the heads themselves wear down.

> The only tricky bit is to get the head over to that portion when the
> power is suddenly cut.

This is probably fairly trivial. In the old days you used to have to run 
the "park" command. But today... well, have you ever noticed that 
"click" noise when you unplug the power? I imagine that's the magnet in 
the voice coils parking the heads. ;-)

In fact, I've disassembled a HD and observed that the arm strongly 
resists any attempt to remove it from the home position. It keeps 
wanting to click back into place, with the heads on the outer edge of 
the platters.

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>> Wanna take a guess what the customary place to install programs is?
>> Yeah, it's C:\Program Files.
> 
> Then there's also the button that lets you choose a different location to 
> install to - part of pretty much every modern installation program on 
> Windows.

There is *usually* such a button, yes. Not always though.

And it's not unheard-of for a program to malfunction if you change this 
setting during installation. (You'd think if they offered you the 
option, they'd implement it so it works. But not always...)

Post a reply to this message

"scott" <sco### [at] scottcom> wrote:
> > In theory, until the disks are spinning at full speed, you don't get that
> > "cushion of air" for the heads to "fly" on, which should result in wear.
> > Of course, no doubt manufacturers know all about this and have come up
> > with ways to at least reduce the problem...
>
> There's probably just a reserved portion of the platter that is used for
> spin-up/down operations.  The only tricky bit is to get the head over to
> that portion when the power is suddenly cut.

I think they don't park the heads on the platter any more, they're moved out of
the platter radius before spindown.
Moving the head out of the way in case of power failure is not so problematic
I'd think. The positioning coils of the heads are constantly under current and
cutting this current will create a force. You "just" have to make it so that a
power failure exerts a force in the head mechanism that whips the head into
park. ;o)

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Jim Henderson <nos### [at] nospamcom> wrote:
> On Mon, 09 Nov 2009 16:53:14 +0100, clipka wrote:
> > I wouldn't be too much surprised if HDD manufacturers would know ways
> > how to optimize drives for one usage pattern or the other, so that maybe
> > indeed powering up and down might kill a server HDD quickly, while 24x7
> > usage might shorten the life of an office computer / consumer HDD.
>
> That seems to be reaching to me.
>
> Jim

Not that reaching. WD sells HDs which are specifically for 24/7 usage.
I think the difference is the lifetime of the bearings which is dependent not so
much on actual age but on revolutions and temperature.

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Stefan Viljoen wrote:

> This is what always bursts my bubble about space travel - whenever I hear of
> the incredible distances involved. 

The distances are *astronomical*!

Literally. As in, that's where the term comes from. ;-)

> it is still 4 YEARS in space to the nearest start.

I'm glad it's not just me who constantly mis-spells "star". :-D

> To even get to more "close" stuff, 6 YEARS, 10
> YEARS - or -thousands- of years (at LIGHTSPEED!) to another galaxy.

Indeed. Without warp drive and the ability to vastly exceed the speed of 
light, it will just take such an absurdly long time to go anywhere that 
it doesn't bare thinking about. Think about it: how long ago did we land 
on the moon? And how long after that did we land on Mars? Oh, wait...

In fact, half the stars in the night sky probably DON'T EVEN EXIST ANY 
MORE. It's just that it's taken that long for the light to reach us.

> Of course, time dilation at high relativistic velocities might mean you can,
> from your relative viewpoint, complete the journey within a human lifespan
> of 70, or 80 years, depending on just how close you can get to the
> magical "c". Nothing would be left back home though, since thousands of
> years might have passed there...
> 
> It just somehow... sad.

Yeah.

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Invisible <voi### [at] devnull> wrote:
> In fact, half the stars in the night sky probably DON'T EVEN EXIST ANY
> MORE. It's just that it's taken that long for the light to reach us.

Not for naked-eye stars. There's only a couple of thousand of those, and they're
almost all within a few thousand lightyears. The galaxy is only 10-15 thousand
lightyears across, so most stars are probably still as they appear to be
(barring recent novae, etc).

It's the other galaxies which are significantly back in time.

> > It just somehow... sad.
>
> Yeah.

Optimism, people! It was only a few hundred years ago people thought you'd fall
apart if you went faster than a galloping horse... :)

Post a reply to this message

Orchid XP v8 schrieb:

> I've seen quite a few programs (mostly stuff ported from Unix, oddly 
> enough) which don't like spaces in pathnames.
> 
> Wanna take a guess what the customary place to install programs is? 
> Yeah, it's C:\Program Files.

Which is why native Windows programs have long since become a lot more 
sane in this respect.

On unix, where even now it is still quite common to do stuff in some 
command line shell, it is pretty uncommon to put blanks in filenames, 
because it would be a hassle to even "cd" there.

Post a reply to this message

Stefan Viljoen wrote:
> Darren New wrote:
> 
>> Stefan Viljoen wrote:
>>> *brrr* - I shiver at the thought of a mobile HDD as a backup device...
>> Why? If you have two copies, then crashing one doesn't affect the other.
> 
> If you use a single one? Then again, single IS NOT a backup...!

It's still a backup. You're 99% less likely to lose both than to lose one. 
Yes, you might drop the external drive on a concrete floor the same day your 
main disk quits, but how likely is that compared to either one dying alone?

And yes, even if you have six backups, they could all go bad at once. (See, 
for example, the 2012 movie. ;-)

> incident I'm thinking about I referred to in my other post, a simple fumble
> and the portable drive lands on a concrete floor...

And then you go buy another and make a new backup. It was just bad luck that 
the primary died before you made another backup.

You think dropping a tape and having the case crack and spill tape all over 
doesn't happen, or chipping or cracking a DVD? :-)

-- 
   Darren New, San Diego CA, USA (PST)
   I ordered stamps from Zazzle that read "Place Stamp Here".

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Invisible wrote:
> For the average home user, if your house burns down, you're not going to 
> give a **** about the holiday photos and the copy of Nero you just lost 
> - YOU HAVE NOWHERE TO LIVE!! 

Not true. Well, Nero, maybe, but holiday photos and pictures of people who 
are now dead and such are irreplacable. You can always get somewhere new to 
live, or fix the house.

> This is a very, very dumb way to do backup. A file-level copy will be 
> drastically faster. (It doesn't involve mirroring all the useless empty 
> sectors.) 

Depends how your RAID works. Windows doesn't mirror empty sectors because 
the RAID understands the file system. Linux and hardware mirrors empty 
sectors because you can put any file system on top of the RAID.

> Also, if you do a file-level copy, you have options such as compressing 
> the data and putting multiple backups on a single backup harddisk, doing 
> differential or otherwise partial backups, and so forth.

But it's no longer an identical copy. If you use a RAID backup, then if your 
primary fails, you can restore the backup in minutes.  Plus, there's 
(theoretically) no downtime during the backup process.

> In theory, until the disks are spinning at full speed, you don't get 
> that "cushion of air" for the heads to "fly" on, which should result in 
> wear. Of course, no doubt manufacturers know all about this and have 
> come up with ways to at least reduce the problem...

Yes, there's a finger that lifts the heads until the disk is up to speed.

-- 
   Darren New, San Diego CA, USA (PST)
   I ordered stamps from Zazzle that read "Place Stamp Here".

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On Tue, 10 Nov 2009 10:10:10 -0500, Jim Henderson wrote:

> decates

Though occasionally not that much experience in spelling words like 
"decades". ;-)

Jim

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scott schrieb:

> I wonder how long the "pulse" of radar would need to be - the engine 
> could charge up a big capacitor to discharge in a roof mounted dish - 
> hmm maybe not that sounds a bit too much James Bond :-)

That would be an EMP device then I guess.

Much more reliable than a radar when it comes to frying electronics 
(much broader spectrum, so it couples in via virtually everything), and 
allegedly pretty easy to build. Strange enough, no terrorist has yet set 
off one in NY or LA.

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On Tue, 10 Nov 2009 10:32:04 -0500, Aydan wrote:

> Jim Henderson <nos### [at] nospamcom> wrote:
>> On Mon, 09 Nov 2009 16:53:14 +0100, clipka wrote:
>> > I wouldn't be too much surprised if HDD manufacturers would know ways
>> > how to optimize drives for one usage pattern or the other, so that
>> > maybe indeed powering up and down might kill a server HDD quickly,
>> > while 24x7 usage might shorten the life of an office computer /
>> > consumer HDD.
>>
>> That seems to be reaching to me.
>>
>> Jim
> 
> Not that reaching. WD sells HDs which are specifically for 24/7 usage. I
> think the difference is the lifetime of the bearings which is dependent
> not so much on actual age but on revolutions and temperature.

Could be, or it could just be a marketing ploy by WD.....

Jim

Post a reply to this message

On Tue, 10 Nov 2009 15:33:50 +0000, Invisible wrote:

>>> Wanna take a guess what the customary place to install programs is?
>>> Yeah, it's C:\Program Files.
>> 
>> Then there's also the button that lets you choose a different location
>> to install to - part of pretty much every modern installation program
>> on Windows.
> 
> There is *usually* such a button, yes. Not always though.
> 
> And it's not unheard-of for a program to malfunction if you change this
> setting during installation. (You'd think if they offered you the
> option, they'd implement it so it works. But not always...)

That comes down to QA on the program and installer, sure.

Jim

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Orchid XP v8 wrote:
> Does that include Team Fortress 2, HalfLife 2, Counter-Strike: Source, 
> Portal, Crysis, Crysis: Warhead, and Mass Effect?

I have Thief3 installed. The Windows dir is like 4x the size of the program 
files dirs.

> Each individual game typically eats about 4GB or so...

Steam needs to give you that option, yah. Did you ask them? :-) I don't 
remember if Steam asks where to install Steam when you install it. I don't 
see any obvious way to change it after the fact.

-- 
   Darren New, San Diego CA, USA (PST)
   I ordered stamps from Zazzle that read "Place Stamp Here".

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Stefan Viljoen wrote:
> Maybe not, that's sounds like a good idea! If you can aim and modulate it
> right a one-second high intensity burst might do the job on a computerised
> injection and ignition system...

And your brain. You realize it's basically microwaves, right? Like from your 
oven?

-- 
   Darren New, San Diego CA, USA (PST)
   I ordered stamps from Zazzle that read "Place Stamp Here".

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Orchid XP v8 schrieb:

> Interesting thing: According to Wikipedia [which is never wrong], a 
> nuclear explosion only generates an EMP because of the Earth's magnetic 
> field. Like, if it was in space, it wouldn't do that...

I think I heard it was the atmosphere, not the magnetic field...

Post a reply to this message

On Tue, 10 Nov 2009 15:25:18 +0000, Invisible wrote:

>>> Tape operates at much lower speeds. And since the only people who use
>>> tape are people who want seriously reliable backup storage, it tends
>>> to be very well engineered. (And stupidly expensive...)
>> 
>> Never used DAT drives for backup, have you? ;-)
> 
> No, only for the last 6 years.

I feel for you.  I had tapes that actually verified nightly that were 
completely useless to restore from.  This is back in the DDS-1/DDS-2 
days, so maybe it's improved - but here's the thing:  DAT stands for 
"Digital Audio Tape". 

Q.  What's one difference between audio and data?  

A.  You can lose some audio data and not notice it.  You can't lose data 
and not notice it.

Using "audio tape" for backup (digital or no) is generally not a good 
idea.  It was designed for audio, not data.

>> Horrible quality of storage media, and terrible shelf life IME.
> 
> Really?

Yes, really.  With the DDS-2 tapes I was using at the time, the 
manufacturer recommended no more than something like 10 or 20 uses.

The tape also creates friction against the recording head, which rotates 
in a direction that's counter to the tape direction, so the tape drives 
burn out fairly easily.  I used to have a Compaq 4/16 DAT autochanger for 
my home server, along with a couple of standalone DAT drives, and I 
burned the heads out on *all* of them while doing alpha and beta testing 
of backup software.

I'm glad I didn't pay for the drives - otherwise I'd have been more upset 
that they burned out so quickly (about a year, IIRC - but I was running 
backups on a more or less continuous basis as part of my testing).

I had much better luck with DLT drives.

Jim

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On Tue, 10 Nov 2009 15:27:57 +0000, Invisible wrote:

>>> I often buy from Maplin because 1) I don't have to wait for it to be
>>> delivered, 2) their staff actually have a frickin clue, and 3) they
>>> don't argue about returns.
>> 
>> Sometimes expediency is worth the extra cost - as is the ability to get
>> something replaced without a hassle.
> 
> Maplin are pretty much the best electronics shop around.
> 
> I mean, apart from being the *only* place in all of Christendom which
> can sell you (say) a 50kohm resistor, their staff have a clue about what
> they're supposed to be selling, and if you take something back they will
> exchange it or give you your money back (provided it isn't obviously
> busted).
> 
> Their website utterly sucks, by the way...

Everyone's bad at something. ;-)

Jim

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Stefan Viljoen wrote:
> Its like Captain Picard saying "Full stop!" on the Enterprise, and in ten
> seconds they are at relative dead stop from going several hundred times
> lightspeed. 

Clearly they're manipulating gravity, so that's not really a problem. You 
can accelerate from 0 to 0.99c in seconds via frame dragging if you don't 
have to deal with tidal forces.

-- 
   Darren New, San Diego CA, USA (PST)
   I ordered stamps from Zazzle that read "Place Stamp Here".

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On Tue, 10 Nov 2009 11:12:57 +0100, Invisible <voi### [at] devnull> wrote:
>
> In theory, until the disks are spinning at full speed, you don't get  
> that "cushion of air" for the heads to "fly" on, which should result in  
> wear. Of course, no doubt manufacturers know all about this and have  
> come up with ways to at least reduce the problem...

http://www.storagereview.com/guide2000/ref/hdd/op/actParking.html

http://www.wdc.com/en/library/eide/79-880134.pdf



-- 
FE

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Invisible wrote:
> Yeah. Amazing how all sentient beings are humanoids who just happen to 
> speak American English, eh?

Except precisely when the plot requires otherwise. :-)

> I have no idea what the hell kind of energy it possesses. 

Negative energy (and negative gravity, for that matter). That's how you get 
the time-travel part from exotic matter.

-- 
   Darren New, San Diego CA, USA (PST)
   I ordered stamps from Zazzle that read "Place Stamp Here".

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Stefan Viljoen schrieb:
> Huh? That doesn't sound right. An old strategic option the USSR apparently
> had was to detonate a -real- big (50 megaton) thermonuke over the US, but
> out in space / low orbit. The idea was to melt all radios and computers,
> the entire US telephone network, etc. As far as I know EMP damage is caused
> by the massive radio waves generated by a nuclear explosion (besides all
> the "hard" gamma radiation, and other nasty stuff besides heat and light).
> These induce current in conductors (i. e. they fry microchips).

I think the story is slightly different:

- A nuclear explosion is caused by nuclear fission and/or fusion 
(actually primarily fission, even in a thermonuke aka H-bomb); the 
radiation given off by this is primarily gamma rays.

- As the gamma rays hit the atmosphere, they ionize it, turning it into 
a plasma.

- The plasma in turn "glows" in the whole EM spectrum.


> Radio definitely travels in a vacuum where there is no magnetism - IMO,
> magnetism CAN effect radio but just to distort or interfere with it. So I'd
> think that a magnetic field will -moderate- or interfere an EMP pulse a
> bit, not be the part-cause of it?

Mind that the earth's magnetic field does not stop outside the atmosphere...

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Stefan Viljoen wrote:
> It just somehow... sad.

Check out some of Greg Egan's stories about the Aloof. Luminous (short 
stories) or Incandescence for example.  Folks live a very, very long time, 
and regularly travel as data around the galaxy, but it's still light speed.

-- 
   Darren New, San Diego CA, USA (PST)
   I ordered stamps from Zazzle that read "Place Stamp Here".

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