Want to read Slashdot from your mobile device? Point it at m.slashdot.org and keep reading!


Forgot your password?
Compare cell phone plans using Wirefly's innovative plan comparison tool ×

Comment Re:Wow, and I thought the existing Sednoids were n (Score 1) 10

Looking at their graph (since I don't see the perihelion stated anywhere), it looks to be about 60 AU (about double that of Neptune). That's some tremendous temperature changes on that body! The equilibrium temperatures are:

((1368 / D^2 - 3.127e-6) / 4 / 5.670e-8 ) ^ 0.25 ... where D is the distance in AU. So at perihelion it'd be about 36K, but at aphelion only about 5K.

Now, this particular body is probably too small to retain significant hydrogen or helium, but you could imagine what it would be like for a large planetary one in such an orbit. It'd transition between being a hydrogen-ice planet with a helium mantle and water ice/rock core; and an ice giant like Uranus and Neptune. In its solid phase, its hydrogen-ice surface would be resurfaced entirely with every cycle and thus might be expected to be perfectly smooth, except because of the heat involved in the settling processes - and how low viscosity and structural integrity in general hydrogen ice has - I'd be willing to wager that you'd get helium volcanism and maybe even plate tectonics.

It gets even weirder if a planet at such distances as this one's aphelion were to have a moon that loses helium vapour to its planet (perhaps, for example, on an eccentric orbit getting it back at each perihelion as the planet inflates, to repeat the cycle at the next aphelion). After all, even below the boiling point, there's always some vapour pressure for helium. If you're taking that vapour away, then you're looking at evaporative cooling, and you really don't need to lose it that fast to cool to below the cosmic microwave background (because radiative exchange is so slow at those temperatures) and thus to helium's lambda point. Now you have a body with superfluid helium on it, and all of the crazy weirdness that superfluids do.

Back to our solar system - aka, a small body like 2014 FE72 - you're not going to have much hydrogen or helium. But even still, that crust is going to be going through some crazy thermal stresses at the very least. Also, neon - while not as common as hydrogen and helium, but should be more common in the outer reaches of our solar system than the inner - would pass through all three phases (melting point 24K, boiling point 27K at 1 bar; lower at reduced pressures). I wonder what sort of minerology neon would form? "Neonothermal" crystal veins, analogous to crystals in hydrothermal systems on Earth? :)

Comment Wow, and I thought the existing Sednoids were neat (Score 2) 10

A sednoid (2014 FE72) with an orbit out to 3000 AU (0,05 light years)? Talk about extreme, I would have been happy just for a couple more "ordinary" sednoids! But that's exactly the sort of thing you want to see if you're of the view that trying to group the universe into a neat collection of "stars" with "planets" orbiting them is oversimplistic. This lends credence to the notion that you're going to get shared debris between different stars, rogue planets that don't orbit stars, etc. Because with large bodies reaching that far out, it becomes pretty easy to perturb them to leave the solar system altogether.

I have no clue what the discovery of 2013 FT28 is going to say about the possibility of an additional large planet in our solar system, but I look forward to the papers on it! Hopefully it won't rule one out, and will instead better constrain an orbit

Comment Re:Next Phase (Score 1) 415

The speed is less important than energy delivered at site of impact. [...] Fan rotors move slower, but are more massive, and have more total energy behind them. You dont need something to be sharp or fast moving to cut you in half; it just needs to exert enough energy over a small area to cause mechanical shear of your body.

Okay, let's try to stay on topic.

Getting a loop of wire from a wench wrapped around a leg and slowly slooped up will chop it off just as surely as if the wire was moving fast but at less torque.

Unless the wire catches on a bone, and the wire is thin enough to snap there. But let's fucking stay on topic. We don't need ridiculous examples designed to distract people because they contain an injury to discuss the topic at hand, you sensationalist nutter.

In fact, there are multiple factors involved in determining how much force it's going to require to break the silly string, and in how much force is being delivered. One of the factors is the force applied, one of the factors is the time in which the force is applied and how that affects the material in question, one of the factors is the quantity of material the force is being spread out across. And in spite of being a lot smaller and less massive, the tip of a quadcopter blade is going to impart a lot more energy to a much smaller section of silly string than a metal fan blade is, because the fan blade is squared off (being stamped from a piece of metal) while the tip of a rotor is very sharp, and the rotor is moving much much faster and F=MA. There's a lot more A in the quadcopter system. But wait, there's more; you only have to consider the effect of its mass until the string breaks. If the string breaks at a level of force which can be achieved with the current acceleration at lower than the actual mass, then the additional mass of the rotor is irrelevant here.

There are lots of other factors, but these are the ones that we've been talking about in this discussion already.

To be a proper experiment, it needs to be a high speed metal bladed fan, with big heavy blades. I can probably find one if I look hard enough.

Only the speed is likely to be relevant, and it will still have a dramatically lower tip velocity than a quadcopter doing anything but hovering.

Comment Re:"topic of discussion for many across the world" (Score 1) 99

Since when is CNN left?

So you mean the external renaming to 'Clinton News Network' was only because the letters matched?

So you mean the external renaming to 'Clinton News Network' was only because the letters matched?

Clinton is not a liberal. She is a neocon. Trump is not a conservative. He is just a sleazebag.

I never said she was a liberal, historically liberals believe in personal liberty... she does not. She's very much a illiberal progressive.

What? You just contradicted yourself there completely, smart guy. Care to rephrase your sentence until it makes sense? Here, this might help. Don't go alone, take one of these. Maybe then you'll have some idea what the words you're using mean.

Comment Re:Next Phase (Score 1) 415

A thought occurs to me. Functionally, a desk fan with metal blades is an appropriate analog for a drone rotor if the housing is removed.

Aside from the speed not even being in the same ballpark, sure. If that doesn't work, then it certainly won't work on a drone. If that does work, it might work on a drone, or at least, one which is only hovering and not actually going places.

Comment Re:Drones might have weapons. (Score 1) 415

Umm... you really think shooting at a flying bomb overhead is a GOOD idea? If so, remind me to steer clear of you.

Bomb is extremely hyperbolic. "Incendiary device" is the term you're looking for there. Unless, of course, it runs on compressed hydrogen (or another flammable gas) with a fuel cell.

Comment Re:Next Phase (Score 2, Insightful) 415

Even I, a person who's never even held a gun, knows this is a fucking stupid thing to do.

Even you, a person who's never even held a gun, should shut the fuck up until he learns how firearms work. There are lots of pistols which are designed to be carried with a round in the chamber, probably most notably including 1911-pattern handguns.

People like you are the reason why people think anti-gun activists are morons.

Comment Re:FAA fines (Score 1) 415

I think there is still a bit of a grey area around model aircraft that are under 55 lbs and below 400 ft altitude. There are many FAA rules that apply for aircraft that do not apply to model aircraft.

And yet, they are still considered "aircraft", which is the only way the FAA is able to exercise any authority over them whatsoever. And they look down on people shooting down aircraft. As long as they want to continue their power grab (they're not supposed to be regulating model aircraft to begin with) they have to come on like a hard-on any time someone shoots down a drone.

Slashdot Top Deals

"Well, if you can't believe what you read in a comic book, what *can* you believe?!" -- Bullwinkle J. Moose