p1t1o

I dont think that can logically be called a "proof". And for one thing, they would also have to be otherwise undetectable. We have made some attempts to contact ETs but even if we hadnt, we'd be just as detectable. Even discounting our electromagnetic (radio, television etc.) emissions, the spectrum of light reflected from Earth shows signs of life (natural spectra distorted by the presence of free oxygen and chlorophyl pigments) which at least shows the presence of life, if not intelligence.

Anyone read Greg Bear's Forge of God/Anvil of Stars duology? They're a good read btw. In the above novels, it would be (They're not a critical spoilers, like the identity of a murderer or anything, but just in case you value mystery. Might spoil the first half of the first novel a bit, depending on the reader)

What I mean is, even 100k years is but a moment on these scales of distance+time. And we've only been technological for what? 5000years? Depending on your definition it could be as low as 2-500years. Theres no reason to assume that the natural state of a civilisation is eternal existence, we only know of one technological civ so far and we are already losing control of our environment, can we keep this up for another ten thousand years? A hundred? If a civ on one planet can die, a civ on two or more can as well, it just might take longer. The idea that humanity will last forever and conquer the universe is laughably arrogant if you ask me, but there is time enough for a lot of stuff.

You replicated almost exactly the omission made by the Castle Bravo scientists! Approx 60%(**) of Li is 7Li. On absorption of a high-energy neutron, it splits into an alpha particle, a tritium nucleus and another neutron. This led to the Castle Bravo burst yielding approx 15Mt instead of the predicted 5Mt. **edit Slight error, approx 93% of natural Li is 7Li, the 60% figure came from the 6Li-enriched lithium used for the Castle Bravo test.

It is my opinion that civilisations, technological ones at least, are like sparks on any timescale relevant to galactic distances. There might be millions of them over time, in any given region, but because they go POOF! and are gone in an instant, the liklihood of two sparks bursting to life at the exact right moment AND within reasonable comms range is negligible.

That is gold. Does anyone else now have a collection of high-res photos from this site that they are keeping to one day have printed off and framed? Cant wait to move into a house where I can choose what to nail to the walls...

This is the kicker - what we *know* about the prevalence of extraterrestrial beings can be written down on a very small piece of paper.

Are you perhaps suggesting a crossover between KSP and the Dune universe? 10/10 would download!

No reason I cant post this link, do you mean these?: http://nuclearweaponarchive.org/Library/Nukesims.html For estimating fireball size, thermal effects and shockwave strength, Nukemap is actually pretty good, it is based on the mathematics shown in the famous document "The Effects of nuclear Weapons" which I presume is one of the documents you refer to (and if it isnt, it should be). If you ask me the weakest part of it is the googlemaps API because it takes a 2D calculated estimate and plops it down in the real world, whereas the true results would be nowhere near as neat. Fact is, things like moisture content of the air (variable in 3D and over time), the direction the wind is blowing (variable in 3D and over time), temperature (varia...you see where Im going) amongst other factors, not to mention the topography of the land, can make very significant changes to the effects of a particular detonation and just try and calculate that!

No a rocket fired upside down wont produce any thrust either. Gas experiences drag just like solid objects do, high velocity exhaust is slowed very quickly in air. So lets remove the atmosphere and do it on an airless Earth. Earths escape velocity is 11.2km/s - that is the speed you need to have at the Earths surface, to escape the influence of its gravity. Average kerolox exhaust velocity is on the order of 5-6km/s, so even in vacuum, the exhaust will reach some altitude, and fall back to Earth. As difficult to accept as it seems, it is the gravity of the exhaust products acting on the Earth that negates the thrust. Exactly the same as when you jump of the ground a little. On takeoff, you actually do exert thrust on the Earth, and it moves a little (less than the width of a proton IIRC). When you fall back to the Earth, the Earth actually rises slightly to meet you, that is your gravity acting on the Earth to negate the thrust you imparted. Does it seem like the force exerted by your legs is much much greater than your gravitational influence? It is, but your gravity acts on the entire mass of the Earth, whereas your legs are only accelerating a few kg. Its weird but the maths adds up.

Net thrust in this situation is zero, everything is stopped by the atmosphere before it can escape (hypervelocity shrapnel is vaporised in lower atmosphere, moving gases are stopped even quicker). To push a planet with reaction force, your exhaust has to escape Earth's gravity altogether, if it falls back, theres no net thrust. Similarly, you cant speed up Earth's rotation with a horizontal rocket - the thrust is absorbed by the atmosphere and transferred back to the ground via drag quite efficiently. Note: on top of that, difficult to extract thrust from a shockwave as the net movement of mass is very low, its a wave, not a continuously moving block of air. When you push a wave through a "slinky", the centre of mass of the slinky stays pretty much where it is. Ummm, do people still know what a "slinky" is?

<windows noise>

Yup. No reason it cant be scaled up. But as Im sure we all know, a suppressor only reduces the sound, I'd imagine that a tank main gun will still be pretty loud, unless you used subsonic ammunition with a reduced charge, which would totally defeat the object of being a tank. Not very. The report of the gun has never been the main weakness in tank stealth. And to take full advantage of a supressor, other changes would be needed which would drop the effectiveness of the tank as a whole (as above). On top of that, an effective supressor would be large and heavy, lowering mobility and ironically, reducing stealth. This is how main battle tanks are used, in a very simple nutshell - Armoured charge/manouvre, firing on the move. Defensive line, firing from fortified positions. Neither of those things would be enhanced with a suppressed gun - bottom line? 15kg of tungsten hitting a neighbouring tank at Mach3 is a dead giveaway that there is a tank shooting at you.

Never underestimate the excess power available to an unladen cargo plane/airliner! Gotta say though, what kind of sociopath refers to this as anything other than a Hercules?

The thing is, you cannot talk about entropy without defining the system, and entropy in a closed system always increases, no exceptions (known to current science anyway.) It is possible to talk about a decrease in the entropy of a defined open system (an open system is just part of a closed system) - such as a living creature - but it is neither profound or unusual and all decreases in entropy are balanced and paid for by increases elsewhere (usually the sun or surrounding space). What can be said is that life harnesses an energy gradient, a flow of energy from A to B, hijacks it, slows and disperses it. Life actually creates MORE entropy (you are quite literally exhaling entropy right now), in the end, but in doing so changes its direction a small amount, in a small part of the system. To put it another way, it might seem like an entropy reversal, but anything that requires energy to happen, is by definition causing an increase in entropy. The profound, miraculous thing, would be if you could reverse entropy without energy input. This equates to something like putting an empty gas cylinder in a room with its valve open and waiting for all the air in the room to spontaneously rush into the bottle, leaving the room in vacuum. Does that sound like something that would ever happen in reality?

You ever read "the last question" by Asimov? http://www.multivax.com/last_question.html

When I was in the Cadets at school, we had annual 24-hour signals exercises where we used British Army-issue radio equipment to send and receive as many messages as possible during the exercise period between as many other stations (other school cadet teams) around the country as possible. It was pretty fun, we'd each get issued a 24 hour army ration pack and live on that for the duration, cooking on little gas stoves in the classrooms. FunFact: approx half the weight and volume of a British Army ration pack consists of a "brew kit" - tea, coffee and hot chocolate (and about half a pound of sugar).

That that is, is. That that is not, is not. Is that it? It is. That that is, is that that is. Not is not. Is that it? It is. That that is, is that that is not. Is not "is that" it? It is. That that is, is that that is not, "is not." Is that it? It is.

Nevermind, its my work firewall, sorry about that

Pics not working for me

Not doomsday cult, introvert nerds. Doing their own fanart, in a small group or alone, away from others, shunning the light and hidden from view? Standard nerds.

To be honest, since we can sustainably produce methane and to a degree, kerosene, (and LOx), Occams razor just says scale up standard rockets. That will work for quite some time into the future. What you send, and what you do with it in space, thats the thing. IMHO.

As far as we know, there has been one species capable of building a civilisation. Its a bit presumptuous, to think that from that sample set of 1, that we would assume that civilisation is the direction that all animals aspire to. How about non-civ tech? Precisely, what if there is intelligence but no wish? Must all intelligences universally wish for high rise buildings and wifi?

Physical force is only very rarely used as one would think. Its all well and good discussing when violence is justified, but on the ground, it rarely works out that way. You dont get time to think and you are under pressure, you dont make the decisions you think you would, or should. This usually come out in the form of hurting yourself, hurting the other guy not at all or way too much. Best policy is not to think you would ever resort to physical methods, if it ever becomes *really* necessary, it will happen automatically. And trust me, fighting someone never makes them back off. In fact it is contradictory. Someone hurts person A so person A hurts them back because hurting them is a deterrent? Didnt deter person A did it? Violence begets Violence. Its all well and good calling "self defence" (by the way, school is not a court of law, they dont have to abide by those rules) but it wont heal bruises or reattach your retina. Or his. (Hers? It happens) If you are physically attacked, make it known. If someone beats you up, its not "snitching", what loyalty do you owe them? Theres a reason why "telling" is frowned upon by a certain sort, its because thats the last thing they want. Do the last thing they want. The very highest pinnacle of martial arts is "the fight of no fight" master it and you will never come to harm. If that means being attacked and not getting physical revenge, it still means less risk of serious injury to yourself. Suprise surprise, the best/right/most honourable/most manly course of action is not always the easiest or most satisfying nor does it always make you look like a badmamma. And if you defend yourself and accidentally put his eye out YOU are liable. Of course Im not suggesting you stand there and act like a punching bag, but you've got legs and a voice and your arms are there if you really need them.

I would settle for not being able to see my own eyeballs in IVA view XD