Airbrush

A possible answer to the Fermi paradox is that shortly after a civilization achieves the ability to trasmit radio signals, they realize that they have nothing to gain by announcing their position in the galaxy to a predatory and more technologically advanced ETI. Therefore intelligent civilizations learn to mask their radio and TV broadcasts so broadcasts cannot be detected from other stars. They may even learn to mask their atmosphere so it will not give away signs of life, or even to appear like a hellish environment. We better hope that predatory-and-more-advanced ETs never finds us.

I suppose you mean the cloud tops are that temperature. The "surface" of Jupiter is a vague notion, it just gets hotter and denser the deeper you penetrate into the atmosphere. Until the gaseous atmosphere gets very hot and dense as a thick fog, then as dense as a liquid, and deeper yet it becomes metalic hydrogen. Could there be a solid core in Jupiter? Pretender, next time create a descriptive title, so people know what the discussion is about. Something like "Questions About Comets". There are SO MANY comets that even if only a tiny percentage of comets that encounter a strong gravity field, like a planet or another, larger comet or asteroid, will achieve near circular, planet-like orbits, that will result in many comets doing so. Circular orbits is the natural state of most comets. They orbit the sun in nearly circular, eliptical orbits, in the asteroid belt, the Kuiper Belt, and the Oort Cloud. Only those few comets that get nudged out by interaction with planets or other comets and asteroid, come sailing into the inner solar system on elongated eliptical orbits.

"...The term dwarf planet was adopted in 2006 as part of a three-way categorization of bodies orbiting the Sun,[1] brought about by an increase in discoveries of trans-Neptunian objects (objects that are farther away from the Sun than Neptune) that rivaled Pluto in size, and finally precipitated by the discovery of an even more massive object, Eris.[4] http://en.wikipedia.org/wiki/Dwarf_planets

This would be a good place to discuss the new "Cosmos" series which just ended on the Fox channel. I thoroughly enjoyed EVERY episode and saw most episodes twice. They are jam packed with data that is easy to forget. Anyone else see the series? What did you think? In early July the Science channel has new episodes of "How the Universe Works". Don't miss it!

That is a good point. The solution to our energy problem should be "all of the above" methods. Different regions would use different methods. You could also have two or more methods working in the same area. Coastal areas always have plenty of wind, so you could have power generated by wind, solar (photoelectric and solar-heat), wave, and tide ALL in the same coastal mega-power-plant structure, and desalinate sea water also to be piped to the deserts for irrigation. Geothermal would be used where the heat is close to the surface.

Which one of the following methods of renewable power generation is the cheapest, per total investment: wind, solar, tidal, or wave? My guess would be wind. If that is so, wind power beats those others, so build up the cheapest methods first. That sounds nice. You should see the last episode of "Cosmos" that deals with global warming. If you could irrigate deserts, by using renewable energy, that could save the planet.

How long after the big bang until neutrinos escaped? Maybe someday we will learn to detect neutrinos at will and can explore what happened when the neutrinos got away.

Does anyone know about these methods of harnessing energy? I've seen "wigglers" that generate power from surface waves. How about these 2 ideas: WAVE POWER - Standing on a pier at the beach looking down at the water, you see the waves surging towards shore and then the backwash flows back out. Suppose you built a pier-like structure parallel to the shoreline, maybe a mile or more long and about 50 feet wide. Suspend paddle turbines over the water just touching the water. As the water flows towards shore it spins the paddle turbines one way, and the water flowing out spins them the other way. TIDAL POWER - If you build a wall along the shoreline to the height of the mean of high and low tides, as the tide goes from mean to high tide, water flows over the wall towards shore, which can spin paddle turbines placed along the top of the wall. Then as the tide falls, open valves in the wall to allow the water to flow back out to sea and spin paddle turbines flowing out.

The fact is that if we don't start building defense systems, we may suffer for it IF we get unlucky during the next century. Something can be done soon to mitigate the threat of city killers. Globe killers just take longer to defend against. There is a big difference between city killers and planet killers, and a whole range of sizes in between. We can do something about events that occur once in a few hundred years, during the next few decades. Events that occur once in a few million years can be delt with later. Don't make the assumption that all that matters is defending against planet killers.

What does this have to do with the topic "Killer Asteroids"?

As big as practicable within cost constraints. First you build impactors that will be effective on smaller objects, and later you work on bigger, and thus more costly, deflectors that will be effective on larger objects. After that, you design indirect systems that will work on objects that won't hit us for decades.

Watch the new series "Cosmos, a Space/Time Odyssey". It will make anyone want a job in the field of science. Any astonomers out there need someone who can sweep up around the telescope?

I agree that a hollowed-out asteroid would be the better option. How could technology move an entire planet without causing great damage to it? However, suppose the ET is capable of what we think is impossible, their planet drifting away outside of any galaxy would be safe from all supernovae, black holes, asteroids, other stars, etc. It would be a totally isolated rogue planet with an entire planet of resources for a journey of Quadrillions of years.

A direct method of deflection is best in that is saves time. We can be blind-sided by a city-killer, or worse, at any time. Simply smacking against it with a good mass is fail safe. I would design a huge net that opens just before impact to soften the blow, spreading its' mass over a large area. This would work on asteroids of most consistencies. I don't know about the "cotton-candy" fluff balls. If it is a solid rock, launch a series of nukes rockets at it to explode just far enough away to heat up one side to out-gass. After you have such direct-method deflection methods up and running, you can work on better indirect methods, such as gravity tractors or landing rockets all around the asteroid as the op suggests, which is a very good idea, if you have the luxury of a long lead time.

If they could move massive objects, why not take the entire planet with? That would be a lot simpler and more practical. Survivors would live in central cities, scattered around the planet, each powered by one (or many) nuclear fusion reactors. For fuel all they need to do is chip off a piece of ice outside the door.

Could it be possible for an advanced ET to intentionally eject their home planet away from their star and exist as a rogue planet and use nuclear fusion for power to stay warm in interstellar space? Maybe they could leave their galaxy and drift for Trillions of years between galaxies.

That number is too small. Red dwarf stars can last for Trillions of years. Not forever, but a very long time.

For up, down, and all around I would think of helicopters.

Our solar system has most planets in nearly circular orbits. This regularity is unusual. After 4.5 Billion years our solar system seems very stable. So I think it would be unusual to find a sun-sized star with more planets within the orbit of Mars. Red Dwarf stars are the vast majority of stars, so I think finding habitable planets should focus on Red Dwarfs primarily. Even though Kepler is not working now, it has accumulated so much data that they will be reporting new planets for years from what Kepler already made available to us.

The Earth also absorbs heat radiated from the Sun which is trapped by greenhouse gases.

Yes I hate that tiny font and I bet everyone else does too. They just don't want to complain.

A good heart attack or stroke may cause death faster and easier than breathing volcanic dust and suffocating on cement in your lungs. That may be true for now, but in a few hundred years, who knows what can be done to make a super volcano harmless? Don't give up on the idea, just yet. Wait and see. We may even learn to control the weather.

It is one thing to destroy an enemy's cities, but to make the entire city (or entire country for that matter) UNINHABITABLE seems like WAY beyond the pale of acceptable human conduct. Any nation that makes another nation UNINHABITABLE for TENS OF THOUSANDS of years is a Crime Against Humanity. Such a country would probably face severe international punishment. New laws would be created and leaders of such countries would probably be tortured to death slowly in public, while a record-breaking international audience cheered it on. This is unprecedented and goes way beyond Rome sewing the soil of Carthage with salt. So it seems unlikely to me that a state would sponsor such an attach, and it would be more likely used by terrorists who believe they could maintain anonymity. In fact, terrorists may have SOME morals and would not see a need to make an area uninhabitable for tens of thousands of years. What good will it do them? Allah would probably disapprove especially if the land was in the middle east.

Anyone heard of a "dirty nuke"? If a state-sponsored attack involved placing a nuclear bomb close enough to a nuclear power plant, what would the effect be? Spent fuel is stored on site, so all of that would be vaporized, along with whatever fuel is inside the operating reactor.

Ok then, just get ready for the end of the human race within the next few thousand years. Nothing can be done.