Catch up on stories from the past week (and beyond) at the Slashdot story archive

 



Forgot your password?
typodupeerror
×

Comment Re:Some nice backpedaling there, bud (Score 1) 336

The first bullet point is the required comment found in every pro-AGW story that the IPCC scientists have no clue at all what is going on with the Earth's climate, since their every prediction is wrong.

Quite to the contrary, all assessments in the IPCC report are given with an appropriate levels of "understanding", "confidence", "consensus", and so forth. Some elements have very high degrees of understanding, confidence, and consensus (for example, the direct forcing from CO2). Others do not (for example, the cloudcover feedback response).

Do realize, however, that any errors are just as likely to be *worse* as they are than better. In fact, "worse" has happened notably more often than better -- sea level rise, temperature rise, etc.

For some reason I don't understand the entire incredibly complex system is reduced to a single axis labeled "worse" on one end and "better" on the other

You're treading into a philosophical debate here, but basically, would you consider drought, flood, desertification, disease, pestilence, etc, bad things? Then that's "worse". And it's not so much that there's something inherently bad about a warmer world. To the contrary, warmer world tend to support more biomass and biodiversity. The problem is simply that it's not the world that we, our society, or the rest of the life on this planet are adapted to. Furthermore, the problem is not the change itself, but how rapid it is. We haven't seen change like this since the PETM. Was the Eocene somehow "worse" than the Paleocene? I seriously doubt you could make that claim. But from the perspective of many species alive during the Paleocene, it absolutely was worse. The oceans acidified, climate patterns changed (some irreversibly), whole ecosystems were disrupted. Life itself survived and flourished, but that'd be no comfort to you if your species went extinct.

than the most carefully unphysical computational models suggest.

What are you using "unphysical" for? They're physics sims. In fact, if you look at the code, what's most remarkable is how *few* aspects of the climate system are coded based on statistical observational models or the like. The overwhelming majority of it goes straight back to First Principles.

The third bullet point is pure speculation

The rates of deglaciation are very precisely measured. They're measured over time, so changes are measured to. And the total mass of the ice sheet is well measured. So what part are you calling "pure speculation"?

It is included purely for the scare value, as neither unphysical models nor actual data plausibly suggest that the Greenland icecap is likely to melt in the next 100 years

Totally melt in 100 years? No.
Partially melt in 100 years? Absolutely.
Totally or near-totally melt over hundreds of years? Yes. And if you don't trust models on it, just look at the effect of temperature changes from past glacials on Greenland ice extent. A 2C rise (which was the *goal* of Copenhagen, to limit it to "just" 2C) historically causes a 6-9m sea level rise equilibrium.

Anti-AGW folks are afraid of economic risks, pro-AGW folks are afraid of climate risks.

Climate risks are economic risks. How much do you think it'll cost to live or grow food in the desert southwest, for example, if the Colorado river flow volume declines even further? What do you think pine borer beetles are doing to the timber industry (drought + warmer winters = rapid expansion)? What do you think floods are if not huge economic damage?

Comment Re:More liberal propaganda (Score 2, Informative) 336

You mean like this?

Oh, and as for soot: while it may be news here, it was widely covered by the IPCC. See AR4 WG1 Ch. 2 Sec 2.5.4, "Radiative Forcing by Anthropogenic Surface Albedo Change: Black Carbon in Snow and Ice". They cite five different papers. Evidence for forcing is classified as "B" (moderate), consensus "3", (insufficient consensus), level of scientific understanding is "Low". In the next IPCC report, given the sizable number of papers that have come out since that, that'll probably be bumped up to "A", '2", "Moderate", and the net forcing contribution will probably be bumped up to about 0.5 W/m^2 (out of ~2.6 net and ~1.7 for CO2).

Comment Re:php is bad for the environment (Score 1) 752

Either way, the key is to use the tool that's best for the job. I have an app that uses html and javascript on the frontend to asynchronously call programs on the backend. For simple calls, such as database queries, I call python scripts, since they're quick and easy to write for that purpose. For more CPU-intensive backend tasks, I call C++ programs.

Language purity isn't a good thing, Everything has its strengths and weaknesses,

Comment Re:Article and grandparent are just wrong. (Score 1) 361

I'm not sure how I can explain this more simply, Air burst detonations are used because the secondary effects are greater then the primary effects, if energy is directed into the ground then fewer secondary effects will occur.

Air burst detonations are used because air bursts are more destructive than ground bursts, and given that we have an atmosphere and a surface, we must choose between one or the other. Since neither apply in space, it's a moot point.

A ship is quite a bit smaller then the earth, thus the amount of energy a ship can adorb is significantly less.

The amount of armor is irrelevant to how much energy is absorbed. How much energy is absorbed is based on yield, cross section, and net transparency (if anything, armor will increase the latter). The purpose of armor is not to absorb less energy, but to absorb it in a less destructive manner.

The largest nuclear weapon ever tested (whose physical size, mind you, wasn't absurd) had a yield of 50MT. However, this was dialed down from about 100MT because they wanted it to burn cleaner. Let's go with only 5MT -- 2e16J. That is a tremendous amount of energy, even at a distance.

To compare the difficulty of getting close, we can directly relate speeds. Let's say your average missile targeted at an aircraft will explode within three meters of the center of mass of the aircraft at a velocity 1/10th that of a missile in space. This corresponds to the missile in space exploding 30 meters from the center of mass of the spacecraft. This means that the 2e16J is spread out over 11,310m^2 at impact, or 1.77e12J/m^2. Let's say that the spacecraft's cross-section is 25 m^2 (5m x 5m). Steel has a specific heat of 0.452J/C, so that's enough to raise the temperature of 100 million kilograms of steel by 1000C. If you have the nuke go off ten times further away (300 meters), that's 1 million kilograms of steel by 1000C. Even if the bomb goes off a kilometer away, it's still enough to raise 90,000 kilograms of steel by 1000C. And this is only a 5MT bomb. And it gets worse because you'll be vaporizing large amounts of steel in an instant, leading to pressure waves within the craft (the same as happens in the atmosphere, except that the craft is a confined space and has no damping).

And then you get into the fact that the real problem is not heat, but radiation.

Thus the amount of energy that can be adsorbed by a few metres of steel

A few *meters* of steel encasing all craft? In outer freaking space? What year are you picturing that will be affordable, the year 2853? A *single* cubic meter of steel weighs 7.8 tonnes. You're talking about having all spacecraft be the weight of aircraft carriers.

Radiation can be easily negated, we already have the technology to block gamma and EMP radiation.

Absolutely not. We have the technology to *partially shield* against the effects, but absolutely not to block them. There are no simple formulae for this, as radiation shielding depends greatly on geometry and the mix of various types of radiation. The alpha radiation from a nuclear blast is trivially easy to shield. It all gets turned into heat upon contact with almost anything. Once you're far enough away to discount heating (which, as the above calculations show, is a tremendous distance), we can discount alpha. Low-energy X-rays can be shiedled against pretty effectively. High-energy X-rays can be shielded against moderately effectively. Beta radiation is problematic. You can shield it moderately well, but you get bremsstrahlung if your shielding is metallic (which you need for blocking neutrons, etc), and the bremsstrahlung can be worse than the beta itself. Gamma is impractical to shield against on the scale of spacecraft armor. Neutrons are difficult to shield against on the scale of spacecraft armor. So no, you can't shield very effectively against an atomic blast. Shielding that provides a 95% reduction in REM from a nuclear blast would be an extremely heavy miracle.

For the current state of technology, we are capable of effectively shielding against most solar radiation, albeit at considerable launch expense. This can be done with active or passive shielding. But shielding against GCR, which is more equivalent in terms of energy levels to a good chunk of the radiation from an atomic bomb, is considered an unsolved problem.

Comment Re:Nukes in Space. . . (Score 1) 361

Missiles will be hot, even after they stop burning.

Not true at all, unless you're talking about space "dogfights", which seem wildly improbable. Projectiles will travel on ballistic trajectories. And furthermore, even the fuel of the missile may well be extremely cold; LOX/LH is one of the best propellant combinations we have. So you don't even need a special coolant for the skin to chill it; your own propellant can do that.

The concept that we'll have colonies in space but not be able to cool a free-floating missile is beyond ridiculous.

It takes telescopes with meters of aperture to resolve relevant-albedo objects near Earth with diameters of hundreds of meters. The concept of a half-square-meter cross section object with a near-zero albedo being resolved with enough time to heat it sufficiently to melt it before impact at tens of thousands of meters per second is just not remotely realistic. And even if you could detect and resolve with good accuracy (from millions of miles away) the launch of a missile or its or orbital maneuvers, there's no way they could have *nearly* enough accuracy to precisely focus a kinetic or thermal kill vehicle against them. All it would give you is information on which region of space to look into most intently.

Comment Re:It's a Free Market (Score 5, Funny) 553

I can just imagine the slogan: "Escape your depressing real life into a matching world!"

Logging on...

"Our records show that you are an overweight high-school educated 36-year old mail in Akron, Ohio with below-average IQ, part-time employment at a Wal-Mart with an annual take-home of $16k who is a single Baptist Republican."

Creating avatar... done.

"Congratulations! Explore our virtual world with your new avatar -- an overweight, high-school educated 36-year old male with below-average IQ."

Your avatar will spawn in: Virtual Akron Ohio
You start with the following items: Bible, Pat Robertson DVD, "Going Rogue" by Sarah Palin
You start with: 0 gold
You earn: 7 gold per hour
For doing the following task: Checking groceries at the Virtual Akron Wal-Mart.

Comment Re:Nukes in Space. . . (Score 1) 361

A completely unprotected astronaut would have absorbed about 50 REM at 1AU from it... but over the course of several days, which greatly diminishes lethality.

The primary risk to astronauts from natural space radiation is long-term -- cancer and the like. Nuclear blasts expose you in an instant.

Of course, a big enough nuke close enough would do just that, but it sure seems easier to hit an incoming missile with a laser than to get close to a ship with a missile.

Actually, a projectile launched in space will be virtually impossible to track. They'll give it a near-zero albedo (probably ablative black paint over a chilled, mirrored surface), it'll have a tiny cross section, and be moving tens of thousands of meters per second relative to the target. How fast do you think you can detect and heat this thing to the point of failure? It's just not going to happen. There just won't be enough time between detection and countermeasure, if detection is even possible at all before detonation. And even if it was, the conventional techniques used on Earth, such as MIRV'ed warheads and decoys, would still apply.

Comment Re:Article and grandparent are just wrong. (Score 1) 361

The main reason we use air blasts rather then ground blasts is because with a ground blast much of that impressive energy is sent straight into the ground, which is a great absorber of energy.

I'm not sure what your point is. Are you saying that the ships will be a great absorber of energy? That's *not* a good thing; you want the ship absorbing as little energy as possible.

Due to the lack of a transmission medium in space nuclear weapons will be limited to use as direct attack munitions

Just the opposite; due to the lack of a medium in space, nothing apart from the increasing surface area of the blast attenuates it with distance. Do the math; a large nuke releases lethal amounts of radiation for hundreds or even thousands of miles.

Comment Re:Article and grandparent are just wrong. (Score 1) 361

-There is no network of telescopes dedicated to finding NEOs that approaches the equivalent of a warship's omnidirectional sensors.

What sort of magical warship is this? Object resolution in a telescope is *physically limited* by aperture. How many meter telescope are you putting on your warship? And how fast is this huge scope scanning the skies? And if your answer is radar, you need even bigger of a dish for space radar.

-NEOs are near the background temperature. A launched weapon will not be, for a variety of reasons.

Right. If they have it cool itself, it could be *just above absolute zero*. Ballistic trajectories require no thrust (heat).

-Earth based sensors have to detect NEOs through thousands of meters of atmosphere. A spacecraft will not have that problem

Atmospheric transparency is a very minor loss -- when clouds aren't present, about 25%. The actual limiting factor is the cross-sectional area of the object being detected and its albedo. An incoming nuclear projectile will have an albedo of essentially zero and present cross-sectional area of perhaps half a square meter. That's essentially undetectable.

-And, finally, a warship is much smaller than the Earth. The volume of space within 100 miles of a warship is microscopic in comparison to the volume within 100 miles of the Earth's surface.

That doesn't change how far away you can resolve an object.

Comment Re:Article and grandparent are just wrong. (Score 1) 361

The Tsar Bomba was actually dialed down to reduce the contamination of Soviet land. The reality is that we can make nuclear bombs of basically as much output as we need. And 1MT is pretty weak even by surface standards.

2) From digging around it seems that it takes a couple of thousand rem to straight out kill someone, less than that and they are going to survive for at least a few days.

Actually, that's some of the sort of calculations that came into play during the cold war. The calculus and gamesmanship of Mutually Assured Destruction was pretty nasty. For example, the US decided that, hey, if we created a *special class* of nuclear weapons (tactical) that we declared we would only use on advancing Soviet troops, and made explicit and obvious this fact, they wouldn't be willing to attack the US mainland and get a nuclear counter. So the Soviets began gaming the premise that while tactical troops may be effective at taking out poorly fortified and armored troops, the tank crews would survive for days after an attack -- during which time they could conquer much of western Europe. So the west countered with the neutron bomb....

Messed up stuff, that. :P

Comment Re:Why Are We Deferring to an Economic Organizatio (Score 1) 715

How many myths can you push in a single post? I especially love how you keep pushing the "data is withheld" myth, as though 99% of the CRU data isn't publicly available for download (they're not allowed to share data from some of the various national weather services, as it's proprietary, and so any FOI request that includes such data will be denied). That's beautiful how you in one stroke pretend like there's no peer-review "assumed without much challenge", and then pretend that despite the *definition* of modern science -- passing peer-review -- it's somehow not science.

Keep pushing conspiracy theories that almost every professional climatologist on the planet is really in on an evil scam.

Tell me: how many peer-reviewed climatology papers -- of the tens of thousands -- have you read?

Yeah, that's what I thought.

Slashdot Top Deals

The game of life is a game of boomerangs. Our thoughts, deeds and words return to us sooner or later with astounding accuracy.

Working...