The same tidal forces that slosh a liquid ocean inside Europa are strong enough to keep tiny Io volcanically active.
True, Io is much nearer to Jupiter (and thus subject to a more severe gravity gradient), you have to balace that out against Io's tiny size. A small planet has a much greater ratio of surface-area-to volume. Io loses heat very rapidly compared to its bigger neighbors. Even so, the tidal forces are enough to melt rock and create volcanoes.
To determine if Europa might have hot springs/ volcanoes/black smokers/etc, you'd need to figger out how much energy Europa absorbs in the form of tidal forces and balance it against how much energy it takes to keep an ocean of unkown volume liquid. It's a lot of unknowns. A probe in orbit around Europa would truly kick ass.
Yes. The concept of liquid water underneath Europan ice is not new. What's new in the article is the mention of tides. Jupiter's gravity makes the Bay of Fundy seem like small beans, tidally. Tidal forces will tend to make the oceans swell up and down underneath the ice. If the ice is thin enough it might crack and heave (as evidenced by the cracks on Europa). Laser measurement is a good way to measure the altitude of the ice very precisely, to see just how much it moves up and down.
I finished Cryptonomicon 2 weeks ago (got it based on/. discussion, actually) and was considering getting Snow Crash. Fate intervened, however, during a trip to the half price bookstore, where they had 1 brand new hardcover copy of Wallace's Infinite Jest (another book mentioned in the discussion). I'm up to page 50. It's quite enjoyable, but what the heck is up with "Year of the Tucks Medicated Pad" or "Year of Dairy Products from the American Heartland"?
I recall hearing some rumors about some technical-type folks (dwarves) in northern New Jersey who were tinkering with EMP devices.
Never did hear any details, just the usual "Dude! I heard that these guys built some cool stuff and tested it a few times, but then the FCC noticed some anomalous emmissions, so they got paranoid and now they keep everything real low-key."
If you're looking for a concrete example of dwarven handiwork, check out the magnetron (temorarily taken off line *grrr*) from Glubco. They've still got a neat section about tesla coils available.
They used to call one of the [president/ceo/grand-pooh-bahs/]s of Lucas the `Prince of Darkness'. Someone might jump in to mention that the Timex Sinclair had something to do with the UK. I can't remember what the relation was.
In the 10th grade I made a little zbasic program on for my school's IIgs's. It simulated 3 or 4 wheel enigma machines of 26 or 128 characters.
Enigma is not that difficult to decode with brute force and a computer. But in 1941 it was a whole different can of beans. Being hardware-based is a Good Thing when you've got to make 100s of enigma machines in a short time, with limited resources. The enigma codes were complex enough to stump the allies for quite awhile.
But ENIGMA sure was a fun time-waster in computer class back in the day. Taking the simplest configuration (3 wheels of 26) there's only 17576 unique starting positions. How long will that take to brute force? I'll leave it as an excercise:P
Right. Even if this guy was allowed to fly it, just the cost of fuel alone would be several thousand dollars an hour. Add to that the cost of routine maintenance: the tools and equipment, the facilities, the people, training, etc. Plus you've got to buy or lease a hangar somewhere to store the darn thing, and register it with 10e6 different agencies, file flight plans, keep meticulous maintenance reports..... the cost of *owning* a fancy airplane usually makes the cost of buying one seem like a relative bargain. And even if such a financial feat was actualy possible, the FAA forbids all civilian flights from exceeding M1.0. What fun is that?
This is an excellent time to recommend a good read: "Hot Air Rises and Heat Sinks: Everything You Know About Cooling Electronics is Wrong", by Tony Kordyban. http://www.amazon.com/exec/obidos/ASIN/079180074 1/qid%3D933180438/002-9119807-2855832
It's witten by a mechanical engineer, yet somehow it is very enjoyable and entertaining to read. The book kind of the thermal/HVAC version of a Feynman book, with lots of funny anecdotes.
I have a poll idea too: "How many fans are in your computer?"
[ ] 0 [ ] 1 - 3 [ ] 4 - 6 [ ] 7+ [ ] I can't tell, they're all covered with dust [ ] Do peltiers count?
FWIW, I've got 6: 2 inhaling, 1 exhaling, and 3 impinging on extended surfaces (heatsinks)
Although it's generally accepted that positive pressure is better, I'm afraid that people aren't really understanding why
Let's think about how dust really gets inside a computer. Consider the case as a control volume through which air and dust pass. By 'positive pressure' we mean that air enters through intake fan(s) and exits passively and/or via fans of lower flow. By 'negative pressure' the reverse is true.
Regardless of direction of flow, air passes through the case at a certain rate, carrying dust suspended in it. (secondary flow anyone? heh). Let's say that dust settles out of the air and re-enters the air at rates related to flow turbulence, velocity and the characteristics of the surface. By 'dust' i mean everything from microscopic volcanic ash particles on up to big stringy things and airborne dust bunnies.
If you don't filter the air that a fan is pushing into a positive-pressure case, the air is obviously going to be carrying dust. That dust will settle out onto any available surface at a rate approximated by my assumptions above. It's just a little bit of diffy-Q. Throw in some coefficients based on real-world experiments and you've got a decent model of how dust works.
A negative pressure case with the same volumetric flow rate as a positive case is going to be subject to the same rate of dust passing though it as a positive pressure case. I'd even hazard to guess that velocity and turbulence are about the same at most points in each case. There is no reason for a negative case to accumulate more dust *inside* itself. The large dust bunnies that get stuck on the way IN to a negative pressure case will simply get stuck on the way OUT of a positive pressure case.
The nugget of insight that i hope to convey through all this rubbish is that when people add big fans and tweak out their cases, the air inside the case becomes much more turbulent and high-speed, preventing dust from settling. Most negative pressure cases are cheapo low flow jobs; most positive pressure cases are higher-flow units that prevent dust buildup simply by being more windy inside. That's all.
The post above this provides a url to a story about putting a monster AC fan in a case. Though it's probably not a project for the novice, I tend to think that fewer big fans are better than a whole B-52's worth of small case fans. (note: the B-52 bomber was designed to have 8 smallish engines in stead of fewer big ones because at the time, there weren't any suitable large engines.)
Anyhow, while we're on the subject of monster fans... I've always wondered if it's really better to keep positive pressure inside a computer case. If you're not filtering the air, the direction of flow shouldn't make any difference, as dust will build up on everything regardless of flow direction. Yet, many people (myself included) will tell you that positive presure is good. Sure, it's *great* if you bother to filter the air; but if you don't, what difference does it make? Anyone care to shed light on this one?
Intellivision was great! I recall as a kid growing up in the 80's whenever a group of kids would play frisbee the game would eventually devolve into a violent form of tag (called TRON) in which the sole object was to hit the other players with a thrown frisbee. Ahh, those were the days.
The battery-powered PSAs, each about the size of a tennis ball, will need only tiny fans to move around in zero gravity. Heh. I guess that mean's they won't be very useful outside. If the spaceballs' electronics can withstand the temperature and radiation outside the station, maybe we'll eventually see little jet propelled versions that use CO2.
Absolutely. I'm still in the process of looking for a new apartment or house. My company is providing a sort of relocation service, and one of the items I listed was proximity to the telco's central office.
right. but only fluids exposed to the vacuum would do that. the most noticable symptoms would be a ear popping, a great deal of farting, belching, and shortness of (like, zero) breath.
So what were they going to do if they got stranded? slowly freeze and/or suffocate while mission control simply turns off the radio?
The movie Contact gave me the impression that astronauts had a secret suicide pill just in case. Of course, you can't believe the movies. Suicide sort of goes against 'the american way' though, so I'd imagine the government would A: tell an outright lie about a glorious, quick and violent death, or B: romanticize the sacrifice while glazing over the details
And if in fact the stranded astronauts did NOT have suicide pills, what might they have done? Going for a moonwalk without a spacesuit comes to mind...
Slashdot Mirror
Can anyone confirm or deny: One time I heard that the official language of the Finnish parliament was Latin. (I haven't a clue why)
quid quid latine dictum sit, altum viditur
Here's a few more europa links, for those who need something to do until quitting time on a friday afternoon.
http://www.jpl.nasa.gov/ice_fire/europ ao.htm
http://www.jpl.nasa.gov/galileo/s tatus970718.html
http://cass.jsc.nasa.gov/researc h/outerp/euro.html
http://www.jpl.nasa.gov/galileo/
The same tidal forces that slosh a liquid ocean inside Europa are strong enough to keep tiny Io volcanically active.
True, Io is much nearer to Jupiter (and thus subject to a more severe gravity gradient), you have to balace that out against Io's tiny size. A small planet has a much greater ratio of surface-area-to volume. Io loses heat very rapidly compared to its bigger neighbors. Even so, the tidal forces are enough to melt rock and create volcanoes.
To determine if Europa might have hot springs/ volcanoes/black smokers/etc, you'd need to figger out how much energy Europa absorbs in the form of tidal forces and balance it against how much energy it takes to keep an ocean of unkown volume liquid. It's a lot of unknowns. A probe in orbit around Europa would truly kick ass.
Yes. The concept of liquid water underneath Europan ice is not new. What's new in the article is the mention of tides. Jupiter's gravity makes the Bay of Fundy seem like small beans, tidally. Tidal forces will tend to make the oceans swell up and down underneath the ice. If the ice is thin enough it might crack and heave (as evidenced by the cracks on Europa).
Laser measurement is a good way to measure the altitude of the ice very precisely, to see just how much it moves up and down.
I finished Cryptonomicon 2 weeks ago (got it based on /. discussion, actually) and was considering getting Snow Crash.
Fate intervened, however, during a trip to the half price bookstore, where they had 1 brand new hardcover copy of Wallace's Infinite Jest (another book mentioned in the discussion). I'm up to page 50. It's quite enjoyable, but what the heck is up with "Year of the Tucks Medicated Pad" or "Year of Dairy Products from the American Heartland"?
Between this, and the govt. adopting debian linux, (and my inability to speak French) all I can say is `Yay France!'
Certainly every reader would love get one of these things, but I seriously doubt it will ever catch on or become affordable.
Recall those advertisements in the 80's for the Amazing Air Car (send $19.95 for plans!).
Or what about the autogyro? Short takeoff, vertical landing, cheap to operate, fits in a garage, cheap and easy to fly.... and hardly anyone has one.
NASA throws tons of money at all kinds of things that never come to pass. I sincerely hope they get it working.
Not that it really matters, but they claimed that the web was 19 clicks wide.
They might as well sue Department of Transportation for creating and maintaining the highways that criminals drive on to commit their crimes.
.... ummm, *g*
When you assist you make and ass of 'i' and 'st'
I recall hearing some rumors about some technical-type folks (dwarves) in northern New Jersey who were tinkering with EMP devices.
Never did hear any details, just the usual "Dude! I heard that these guys built some cool stuff and tested it a few times, but then the FCC noticed some anomalous emmissions, so they got paranoid and now they keep everything real low-key."
If you're looking for a concrete example of dwarven handiwork, check out the magnetron (temorarily taken off line *grrr*) from Glubco. They've still got a neat section about tesla coils available.
baruk-khazad! khazad aimenu!
They used to call one of the [president/ceo/grand-pooh-bahs/]s of Lucas the `Prince of Darkness'. Someone might jump in to mention that the Timex Sinclair had something to do with the UK. I can't remember what the relation was.
Because they couldn't figure out a way to make it leak oil.
* whitworth bolts
* side draft `carburettors'
* automotive parts made from wood, felt, whalebone, etc.
* `positive earth'
sounds like NT to me
..or at least the Germans thought so.
:P
In the 10th grade I made a little zbasic program on for my school's IIgs's. It simulated 3 or 4 wheel enigma machines of 26 or 128 characters.
Enigma is not that difficult to decode with brute force and a computer. But in 1941 it was a whole different can of beans. Being hardware-based is a Good Thing when you've got to make 100s of enigma machines in a short time, with limited resources. The enigma codes were complex enough to stump the allies for quite awhile.
But ENIGMA sure was a fun time-waster in computer class back in the day. Taking the simplest configuration (3 wheels of 26) there's only 17576 unique starting positions. How long will that take to brute force? I'll leave it as an excercise
Right. Even if this guy was allowed to fly it, just the cost of fuel alone would be several thousand dollars an hour. Add to that the cost of routine maintenance: the tools and equipment, the facilities, the people, training, etc. Plus you've got to buy or lease a hangar somewhere to store the darn thing, and register it with 10e6 different agencies, file flight plans, keep meticulous maintenance reports..... the cost of *owning* a fancy airplane usually makes the cost of buying one seem like a relative bargain. And even if such a financial feat was actualy possible, the FAA forbids all civilian flights from exceeding M1.0. What fun is that?
This is an excellent time to recommend a good read: "Hot Air Rises and Heat Sinks: Everything You Know About Cooling Electronics is Wrong", by Tony Kordyban.4 1/qid%3D933180438/002-9119807-2855832
http://www.amazon.com/exec/obidos/ASIN/07918007
It's witten by a mechanical engineer, yet somehow it is very enjoyable and entertaining to read. The book kind of the thermal/HVAC version of a Feynman book, with lots of funny anecdotes.
I have a poll idea too:
"How many fans are in your computer?"
[ ] 0
[ ] 1 - 3
[ ] 4 - 6
[ ] 7+
[ ] I can't tell, they're all covered with dust
[ ] Do peltiers count?
FWIW, I've got 6: 2 inhaling, 1 exhaling, and 3 impinging on extended surfaces (heatsinks)
Although it's generally accepted that positive pressure is better, I'm afraid that people aren't really understanding why
Let's think about how dust really gets inside a computer. Consider the case as a control volume through which air and dust pass. By 'positive pressure' we mean that air enters through intake fan(s) and exits passively and/or via fans of lower flow. By 'negative pressure' the reverse is true.
Regardless of direction of flow, air passes through the case at a certain rate, carrying dust suspended in it. (secondary flow anyone? heh). Let's say that dust settles out of the air and re-enters the air at rates related to flow turbulence, velocity and the characteristics of the surface. By 'dust' i mean everything from microscopic volcanic ash particles on up to big stringy things and airborne dust bunnies.
If you don't filter the air that a fan is pushing into a positive-pressure case, the air is obviously going to be carrying dust. That dust will settle out onto any available surface at a rate approximated by my assumptions above. It's just a little bit of diffy-Q. Throw in some coefficients based on real-world experiments and you've got a decent model of how dust works.
A negative pressure case with the same volumetric flow rate as a positive case is going to be subject to the same rate of dust passing though it as a positive pressure case. I'd even hazard to guess that velocity and turbulence are about the same at most points in each case. There is no reason for a negative case to accumulate more dust *inside* itself. The large dust bunnies that get stuck on the way IN to a negative pressure case will simply get stuck on the way OUT of a positive pressure case.
The nugget of insight that i hope to convey through all this rubbish is that when people add big fans and tweak out their cases, the air inside the case becomes much more turbulent and high-speed, preventing dust from settling. Most negative pressure cases are cheapo low flow jobs; most positive pressure cases are higher-flow units that prevent dust buildup simply by being more windy inside. That's all.
The post above this provides a url to a story about putting a monster AC fan in a case. Though it's probably not a project for the novice, I tend to think that fewer big fans are better than a whole B-52's worth of small case fans. (note: the B-52 bomber was designed to have 8 smallish engines in stead of fewer big ones because at the time, there weren't any suitable large engines.)
Anyhow, while we're on the subject of monster fans... I've always wondered if it's really better to keep positive pressure inside a computer case. If you're not filtering the air, the direction of flow shouldn't make any difference, as dust will build up on everything regardless of flow direction. Yet, many people (myself included) will tell you that positive presure is good. Sure, it's *great* if you bother to filter the air; but if you don't, what difference does it make? Anyone care to shed light on this one?
Intellivision was great! I recall as a kid growing up in the 80's whenever a group of kids would play frisbee the game would eventually devolve into a violent form of tag (called TRON) in which the sole object was to hit the other players with a thrown frisbee. Ahh, those were the days.
The battery-powered PSAs, each about the size of a tennis ball, will need only tiny fans to move around in zero gravity.
Heh. I guess that mean's they won't be very useful outside. If the spaceballs' electronics can withstand the temperature and radiation outside the station, maybe we'll eventually see little jet propelled versions that use CO2.
Absolutely. I'm still in the process of looking for a new apartment or house. My company is providing a sort of relocation service, and one of the items I listed was proximity to the telco's central office.
I'll be moving to Houston in about a month; it seems that SWBell and GTE are the only two telcos around that will do DSL around there. (?)
GTE doesn't cover my new neighborhood so I'm thinking about going with SWBell and nol.net dsl service.
I'm just posting to say anyone's opinions on GTE vs. SWBell, adsl, nol.net, or whatever would be greatly appreciated.
right. but only fluids exposed to the vacuum would do that. the most noticable symptoms would be a ear popping, a great deal of farting, belching, and shortness of (like, zero) breath.
'the astronauts were not aware'
So what were they going to do if they got stranded? slowly freeze and/or suffocate while mission control simply turns off the radio?
The movie Contact gave me the impression that astronauts had a secret suicide pill just in case. Of course, you can't believe the movies. Suicide sort of goes against 'the american way' though, so I'd imagine the government would
A: tell an outright lie about a glorious, quick and violent death,
or B: romanticize the sacrifice while glazing over the details
And if in fact the stranded astronauts did NOT have suicide pills, what might they have done? Going for a moonwalk without a spacesuit comes to mind...
at least, that's what Be claims.