No it isn't Re:Fiber to the door is plain silly
on
Welcome to the Fiberhood
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· Score: 4, Insightful
Yeah, sure, 640K is more than enough for anyone.
Don't forget these houses could be there for the next 50 years or more. Are you saying they will not want more than 1 Gigabit per second, over the entire life of the building?
Yes, well, clearly it affected you in more than one way.
However you've missed a few points:
a) quite a lot of the fuel cells plan to use alcohol, that's about as dangerous as a bottle of whisky.
b) hydrogen is only an issue in strong concentrations below a certain concentration it doesn't combust- ventilation is important, but then it's important anyway with laptops
c) both Hindenburg and Challenger, the H2 wasn't the issue. In both cases they were already very screwed before the hydrogen even caught. Those solid rocket boosters were/are disasters waiting to happen. The SSMEs can be shut down. SSRBs cannot.
d) hydrogen isn't much more dangerous than natural gas
e) there's a difference between detonation and conflagration. The LH2/LOX mixture wasn't a detonation- it was only a conflagration.
f) there's far, far, far more energy in your car fuel tank than in a laptop... think about it.
Actually, it proves that light travels as either a wave or particle.
Nope. Common misconception. Travels as a wave, arrives as a particle.
It depends on the experiment. An experiment looking for particles will show particles, and waves, waves.
True. But some experiments look for both. For example if you put a photomultiplier after Young's slits, you can literally watch the particles arrive (this was pointed out by Feynman).
And the interesting thing is, they only arrive where the wave doesn't cancel.
Actually, I haven't checked the US regs, but in the UK, this car may not count as a Kit Car.
Basically, it becomes a kit car if you take components from multiple cars. I don't see anything to suggest that with this car, although the windshield looks a bit suspicious.
If he's just added plastic and such like, it probably counts as a 'body kit'. The rules are very different for that. The handling should be pretty much the same for example.
It's been on a road for a while, so presumably it has passed any yearly mechanical test, so there's nothing very untoward here.
You have to make sure that all things that touch are at the same potential before they touch.
This means, in practice, that there must be a conductive, resistive path between them prior to this happening.
This is easiest to achieve if you just connect everything together, the wrist straps, the conductive shoes, the whole 9 yards.
For example of what can happen. I have a component in my hand- but that's fine, I have my strap on, and the component is at the same voltage as me. I take off my strap with the component in my hand, and walk across the floor and touch someone on the shoulder with my other hand.
Zap! That component is now toast! The problem is that myself and the component built up a few thousand volts when I walked across the floor, and the person I touched instantly discharged me, and a large current came out of the component too... 90% of such components work for a while before failing.
You don't have to have all of these gadgets, but if you don't; you have to move very deliberately, and even then you can screw up sometimes.
Unfortunately, WineX will in the long term halt or slow down development of games running native in Linux. Why would a gaming company put money in porting it, Linux users _can_ play their game.
No. I disagree. One point you've missed which dominates, which Microsoft most definitely have not missed is that a lot of people get the OS that can play their games. They won't install an OS that cannot play their games.
The more Linux can play the same games that Windows can play, the more people will install it on the desktop. The more installations there are, the more incentive there is for people to write games to run under it, or solely under it.
Besides, even if every game ever only runs under Wine, you shouldn't forget we're leaving the stage where performance is the most critical part of a system. I've seen the benchmarks with 200+ frames per second under Quake III on the current top end systems, minor percentage differences in performance are going to be far less relevant from here on in. Working/not working is always relevant though.
It's not so much the wireless network per se. It's more the connectivity to the rest of the world you want to secure- and that includes the laptops and other machines that are hanging off of the wireless network.
Still, the same is true of the internet.
Connecting to internet == connecting to wireless net
"but VASIMIR is popular these days because it offers the greatest thrust of all the electric schemes"
Ahem. Actually, it gives less thrust than most ion drives per kilowatt, noteably Hall effect thrusters.
Part of the problem is energy- for a given megawatt of power, with VASIMR most of it ends up in the extremely high velocity exhaust (5400 seconds == 54000 m/s) where you don't want it, rather than the vehicle, which you do.
There's a theorem that says that if you keep your ISP constant there is an optimum exhaust velocity for minimum energy- it's about 2/3 of the mission delta-v. To get to mars you need a delta-v of about 5 km/s not 54km/s. The reason minimum energy is important is because nuclear reactors are not noted for having a light weight- there's no point saving fuel at the cost of extra overall weight.
Of course VASIMR varies its ISP, which helps, but it goes from very-high, to way-too-high;-)
I also read a crappy book that placed the elevator on the polar axis instead of on the equator. It was written by some famous British guy who had written piles of stuff for Dr. Who and Red Dwarf among others.
Who? Who? Go on tell us, so we can laugh at them;-)
Re:Why do they have to hang straight down?
on
More on Space Elevators
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· Score: 5, Informative
But, the one thing that has always bugged me has been why the cable itself has to hang straight down from orbit.
The trouble is that the combination of rotation (which pulls at 90 degrees to the axis of the earth) and the earths gravity (which pulls directly towards the earths center)- the combination ends up pulling the end weight so that it is above the earths equator. The cable below that goes from the attachment point on the earths surface up to there.
You can move the endweight only a small amount from the earth end- the radius of the earth is only 6700 km, but GEO is 38000km, so the geometry for moving the end weight around doesn't add up.
So basically, the endweight is in the plane of the equator. So the cable comes off at an angle from the earths surface- and heads off to the weight beyond GEO. At the equator the angle is 90 degrees. But as you go north or south, the angle is lower, and the angle means that the tether is longer and weighs more, as it droops under gravity (there's little rotation force at low altitude to compensate, so it does it quite a lot.)
So if you go very far north you find that the cable leaves the earths surface horizontally... there's no point in going further north than that. Exactly how far north this happens depends on how heavy the cable is, and how much tension there is in the cable at ground level. So you can increase the tension and pull it up off the ground again. But by doing so, you are losing payload by doing this- the extra tension to make this work could be used to lift payload up the tether.
It's a bit oversimplified, but that's the main idea. You can do it, but it's probably not worth doing it.
Yes, but that would only work when the sun is out. This system works even after sunset- the chimney has a decent heat capacity and continues to generate hours after sunset.
Well, since the porn web admins probably log into your porn site using public key encryption, and a quantum computer can crack private keys in fairly short order- your disgusting porn feed could be getting quite a bit cheaper;-)
The temperature is given in terms of pressure AND volume, or density and pressure. For any given temperature you can have any pressure at all by varying the volume. THERE IS NO DIRECT RELATIONSHIP BETWEEN PRESSURE AND TEMPERATURE.
You don't understand. This is really hot. Hotter than a Beowolf cluster of 2.2 Ghz Athlons overclocked to 4.4 Ghz running Apache with the latest Red Hat distro on it, when it's being Slashdotted.
The big problem is that the whole aircraft tends to melt. At anything above about Mach 6 cooling becomes really, really tricky. Above about Mach 10 cooling is getting to be nearly impossible. Orbit is mach 25.
Rockets work around this, by avoiding staying in the atmosphere at high speeds for long.
Scramjets can't- because they need the air to breath.
There are techniques that may help- 'skip trajectories', using the fuel to cool the skin of the aircraft, and burning off the skin of the aircraft (ablative). But ultimately they're all a bit awkward.
All the time you are in the atmosphere you are fighting drag- and that costs fuel. Beyond a certain point, you are probably better off using a rocket. And they atleast work at Mach 0-3 and up, which scramjets don't.
Ok, Einstein, you've got the basic theory. Now explain:
a) the difference between mach 7.6 and mach 25
b) how you stop the thing melting at mach 10-20
c) why the term 'dry mass' is rather important to something that wants to achieve orbit and compare and contrast the thrust/mass ratio of a scramjet with a rocket engine
d) how you accelerate up to the minimum speed this engine needs to begin to work (hint: it's called a "rocket", or a jet engine (see point c))
e) how drag ultimately limits how long you can spend in the atmosphere (hint: drag goes as a square law with velocity, but oxidiser input from the air only goes linearly).
In a normal jet engine the flow has to be slowed to less than Mach 1 for compustion to occur. Faster, and it goes out.
Actually I thought the main problem was that the compressor blades tend to melt...
Slashdot Mirror
Don't forget these houses could be there for the next 50 years or more. Are you saying they will not want more than 1 Gigabit per second, over the entire life of the building?
-Ian
However you've missed a few points:
a) quite a lot of the fuel cells plan to use alcohol, that's about as dangerous as a bottle of whisky.
b) hydrogen is only an issue in strong concentrations below a certain concentration it doesn't combust- ventilation is important, but then it's important anyway with laptops
c) both Hindenburg and Challenger, the H2 wasn't the issue. In both cases they were already very screwed before the hydrogen even caught. Those solid rocket boosters were/are disasters waiting to happen. The SSMEs can be shut down. SSRBs cannot.
d) hydrogen isn't much more dangerous than natural gas
e) there's a difference between detonation and conflagration. The LH2/LOX mixture wasn't a detonation- it was only a conflagration.
f) there's far, far, far more energy in your car fuel tank than in a laptop... think about it.
The Space Shuttle didn't explode either, there was some mixing but no detonation.
Nope. Common misconception. Travels as a wave, arrives as a particle.
It depends on the experiment. An experiment looking for particles will show particles, and waves, waves.
True. But some experiments look for both. For example if you put a photomultiplier after Young's slits, you can literally watch the particles arrive (this was pointed out by Feynman).
And the interesting thing is, they only arrive where the wave doesn't cancel.
Basically, it becomes a kit car if you take components from multiple cars. I don't see anything to suggest that with this car, although the windshield looks a bit suspicious.
If he's just added plastic and such like, it probably counts as a 'body kit'. The rules are very different for that. The handling should be pretty much the same for example.
It's been on a road for a while, so presumably it has passed any yearly mechanical test, so there's nothing very untoward here.
This shows that matter is made up of waves too. Everyone knew that light was made up of waves...
Wanna bet? ;-)
This means, in practice, that there must be a conductive, resistive path between them prior to this happening.
This is easiest to achieve if you just connect everything together, the wrist straps, the conductive shoes, the whole 9 yards.
For example of what can happen. I have a component in my hand- but that's fine, I have my strap on, and the component is at the same voltage as me. I take off my strap with the component in my hand, and walk across the floor and touch someone on the shoulder with my other hand.
Zap! That component is now toast! The problem is that myself and the component built up a few thousand volts when I walked across the floor, and the person I touched instantly discharged me, and a large current came out of the component too... 90% of such components work for a while before failing.
You don't have to have all of these gadgets, but if you don't; you have to move very deliberately, and even then you can screw up sometimes.
No. I disagree. One point you've missed which dominates, which Microsoft most definitely have not missed is that a lot of people get the OS that can play their games. They won't install an OS that cannot play their games.
The more Linux can play the same games that Windows can play, the more people will install it on the desktop. The more installations there are, the more incentive there is for people to write games to run under it, or solely under it.
Besides, even if every game ever only runs under Wine, you shouldn't forget we're leaving the stage where performance is the most critical part of a system. I've seen the benchmarks with 200+ frames per second under Quake III on the current top end systems, minor percentage differences in performance are going to be far less relevant from here on in. Working/not working is always relevant though.
Still, the same is true of the internet.
Connecting to internet == connecting to wireless net
Ahem. Actually, it gives less thrust than most ion drives per kilowatt, noteably Hall effect thrusters.
Part of the problem is energy- for a given megawatt of power, with VASIMR most of it ends up in the extremely high velocity exhaust (5400 seconds == 54000 m/s) where you don't want it, rather than the vehicle, which you do.
There's a theorem that says that if you keep your ISP constant there is an optimum exhaust velocity for minimum energy- it's about 2/3 of the mission delta-v. To get to mars you need a delta-v of about 5 km/s not 54km/s. The reason minimum energy is important is because nuclear reactors are not noted for having a light weight- there's no point saving fuel at the cost of extra overall weight.
Of course VASIMR varies its ISP, which helps, but it goes from very-high, to way-too-high ;-)
"Your network. Our business."
My motto is:
"My network. None of your business." but I guess that is where they and I have a parting of the ways... ;-)
I don't think the UK telcos care really. The SMS messaging costs basically nothing for them too, the air time is miniscule.
So, basically, the UK public get charged for wireless SMS sending only. That's 10 pence for something that probably costs under 0.05 pence!
Who? Who? Go on tell us, so we can laugh at them ;-)
The trouble is that the combination of rotation (which pulls at 90 degrees to the axis of the earth) and the earths gravity (which pulls directly towards the earths center)- the combination ends up pulling the end weight so that it is above the earths equator. The cable below that goes from the attachment point on the earths surface up to there.
You can move the endweight only a small amount from the earth end- the radius of the earth is only 6700 km, but GEO is 38000km, so the geometry for moving the end weight around doesn't add up.
So basically, the endweight is in the plane of the equator. So the cable comes off at an angle from the earths surface- and heads off to the weight beyond GEO. At the equator the angle is 90 degrees. But as you go north or south, the angle is lower, and the angle means that the tether is longer and weighs more, as it droops under gravity (there's little rotation force at low altitude to compensate, so it does it quite a lot.)
So if you go very far north you find that the cable leaves the earths surface horizontally... there's no point in going further north than that. Exactly how far north this happens depends on how heavy the cable is, and how much tension there is in the cable at ground level. So you can increase the tension and pull it up off the ground again. But by doing so, you are losing payload by doing this- the extra tension to make this work could be used to lift payload up the tether.
It's a bit oversimplified, but that's the main idea. You can do it, but it's probably not worth doing it.
Nope. Don't forget these cables hang down from orbit.
So to make this work, you have to thicken the cable above you to take the extra weight. 38000 km of nanotubular cable is not cheap...
But they're an endangered species! You can't get any more endangered than the woolly mammoth!
Yes, but that would only work when the sun is out. This system works even after sunset- the chimney has a decent heat capacity and continues to generate hours after sunset.
Well, since the porn web admins probably log into your porn site using public key encryption, and a quantum computer can crack private keys in fairly short order- your disgusting porn feed could be getting quite a bit cheaper ;-)
The current cost to LEO is about $2600/kg. I predict it will be $1300/kg in 2006.
The temperature is given in terms of pressure AND volume, or density and pressure. For any given temperature you can have any pressure at all by varying the volume. THERE IS NO DIRECT RELATIONSHIP BETWEEN PRESSURE AND TEMPERATURE.
The volume of the atmosphere can and does vary.
You don't understand. This is really hot. Hotter than a Beowolf cluster of 2.2 Ghz Athlons overclocked to 4.4 Ghz running Apache with the latest Red Hat distro on it, when it's being Slashdotted.
It needs water cooling anyway.
Scramjets melt in a few minutes. Jets usually don't melt.
Rockets work around this, by avoiding staying in the atmosphere at high speeds for long.
Scramjets can't- because they need the air to breath.
There are techniques that may help- 'skip trajectories', using the fuel to cool the skin of the aircraft, and burning off the skin of the aircraft (ablative). But ultimately they're all a bit awkward.
All the time you are in the atmosphere you are fighting drag- and that costs fuel. Beyond a certain point, you are probably better off using a rocket. And they atleast work at Mach 0-3 and up, which scramjets don't.
a) the difference between mach 7.6 and mach 25
b) how you stop the thing melting at mach 10-20
c) why the term 'dry mass' is rather important to something that wants to achieve orbit and compare and contrast the thrust/mass ratio of a scramjet with a rocket engine
d) how you accelerate up to the minimum speed this engine needs to begin to work (hint: it's called a "rocket", or a jet engine (see point c))
e) how drag ultimately limits how long you can spend in the atmosphere (hint: drag goes as a square law with velocity, but oxidiser input from the air only goes linearly).
In a normal jet engine the flow has to be slowed to less than Mach 1 for compustion to occur. Faster, and it goes out.
Actually I thought the main problem was that the compressor blades tend to melt...