Airbrush

Everything depends on how big it is and how far away it gets blown to pieces. For some sized objects it might be better to blow it into pieces to increase the surface area that gets burned up in the atmosphere. Or it could even cause some big pieces to miss the Earth entirely. I think (correct me if I am wrong) that small enough pieces will not explode in the atmosphere but merely burn up. If doing so should create an ozone hole, I think that would be the lesser of evils.

A few variables are if it explodes miles above ground, or if it impacts deep water, or shallow water closer to land, or on dry land. Composition of soil that gets vaporized and blasted into the atmosphere could matter, but I don't know how, I'm not an expert. If the Tunguska object impacted deep water a thousand miles from land then the tsunamis may have been unnoticeable but there would be significant water vapor blasted into the atmosphere. If it impacted shallow water, it would kick up dust and water vapor and tsunamis could be devastating locally. If it hit dry land then more atmospheric effects. It would be nice to get expert input on what these possibilities could mean. The 10km dino-killer impacted shallow water. Do most asteroids explode miles above ground? It must depend on steepness of angle of impact, and steeper, more direct, angles are less probable I suppose. A poster had proposed 3 or 4 rockets with a net stretched between them to slow or stop the asteroid. Of course we would rather deflect it, but maybe that is a way to deflect a loose aggregate without breaking it up into pieces. I guess that the more massive the object, the more solid it is. To find out how solid an object really is may require a mission to the asteroid to study it long before it crosses our path.

I always thought the Richter scale steps were 10 x each. So from magnitude 5 to 9.2 = Tunguska X 10 X 10 X 10 X 10 X 1.2 (X 10,200). It would take an impactor 10,200 times the mass of the Tunguska object which was about 30 meters across (how do you calculate the size of this hypothetical object which would create tsunamis comparable to the 2004 Indonesian earthquack tsunamis?), and the blast was equivalent to 1,000 Hiroshimas. An object moving at 5 to 10 miles per second will displace many times its own size in water, but the waves radiate out from only a point and dissipate more rapidly than wide-range earthquake-generated and focused tsunamis. What sized impactor could generate that much damage on that same area if the impact occurred at the center of the Indonesian earthquake ground movement.

Interesting info Mr. Skeptic. Is there a way to calculate approx what size impactor will generate a tsunami comparable to the 12-26-04 Indonesian earthquake tsunami? What earthquakes have over meteor impacts in an ocean is that earthquakes cause movements spread over hundreds of miles. Most meteor impacts displace far less water.

We are only worried about real big ones. For big ones it takes far less energy to deflect it, ever so slightly early on, than to try to slow it down. Probably impossible to stop it.

You hear that folks? Relax, enjoy life, buy a beach house. We have hundreds of years to prepare for the big one.

Not every few decades. It is possible there have been smaller impacts a few hundred years ago that went unnoticed. Not all explode miles high. Some reach the ground, or more likely the ocean. I'm not an expert, and I would like to get expert opinion on what kind of tsunamis would be experienced along the Southern California coast caused by a meteor 30 feet across impacting the ocean at a speed of 10 miles per second, 1,000 miles off the coast of California. Anyone want to venture a guess?

I agree with most of what you are saying and Tunguska-sized events, or larger, are very rare, maybe once in a thousand years, as you say. But Wikipedia estimates Tunguska as an air explosion 3 to 6 miles high and comparable to a very large nuclear weapon 10-15 megatons, or about 1,000 Hiroshimas, and it was only a few tens of meters across (about 100 feet in diameter). Consider an object only 10% the mass of the Tunguska object, and those impact Earth more frequently. If it is able to penetrate the atmosphere and hit ANY ocean, it WILL cause devastating tsunamis which will destroy high populations along coastlines. Such an impact happening hundreds of years ago would go unnoticed, except locally. But now with high population densities along coastlines, the results will be very noticeable, as we saw with the Dec 26, 2004, Indonesian earthquake tsunamis, results was 200,000 plus dead. But you are mostly correct, and not much will be invested in defense until one does damage. It will be in the news. Thanks for setting my mind at ease. http://en.wikipedia.org/wiki/Tunguska_event

Mr. Alien, my question about detecting tachyons was for the poster who was hypothesizing about them. Sorry for the misunderstanding. I will be carefull to not try to cut anything with neutrinos. Dark matter does whatever matter does, move or hang around. The point I was trying to make was that tachyons are not the only thing we cannot pin down as we like to.

Maybe so, and Mr. Alien pointed out they are called "tachyons", but how do you propose we can detect them? What is that kind of particle that can travel through light years of solid lead, like a hot knife thru butter? Dark matter cannot be seen, and it doesn't even move.

They should start working on something soon. I love to hear about the Kepler mission, but let's face the fact that Kepler will not save our planet from destruction, nor will it save anyone from a Tunguska-sized impact. First things first. More and better methods for detecting such objects, and a short-range, "last resort" defense system that can deflect the smaller objects. I envision something like a "rocket with weight" to simply crash into an asteroid at high speed to deflect it. Over time we can add redundant safeguards and longer range systems which will take much more time for development and deployment. The United Nations needs to start talking about a global tax to finance these defense systems. It may be that a common cause can bring the nations of the world together in peace. Some argue that WWII helped pull the US out of the great depression. Maybe the jobs created by Planetary Defense projects can help pull the world out of this global recession. And there much more to do. What about global warming and the energy crisis? Anyone looking for a job? I'd rather work on planetary defense than continue this lousy job as bookkeeper for a restaurant for the rest of my life. As Skeptic's Dad would say "You can't make a baby in less than nine months no matter how many women you assign to the task." Hahaha! But you can assign a number of women to work on different babies, and each baby can contribute to the overall mission of "saving the world". Unless you can find an "Octomom" to help out.

A group of countries is the best way. Since everyone on Earth would benefit, there should be a way to pass the costs along to every country on Earth, according to an equitable scale or responsibility. The wealthy have the most to lose, so the US would carry a heavy share of the costs. Transparancy about it all the way so no country would feel threatened by weapons in space.

The experts will say "We don't know" about Big Crunches following Big Bangs. There could be a Big Rip instead, or a Big Freeze after all the stars burn out. They will say we don't know anything about before the Big Bang. It could be that Big Bangs happen whenever they happen, even on top of a pre-existing universe. The last one happened ~13.7 Billion years ago.

Moth quote: "...the weapon potential would probably make it impossible to build something like this though." Which leaves the only option kinetic impactors. Unless we can put beam devices or nukes into orbit discreetly, our only option for short-term defense will be to hit the asteroid with a rocket-propelled calculated mass. By "calculated mass" I mean the mass of the asteroid is estimated. Then orbiting rockets that carry nothing but weight can shed excess mass, like ballast, so the impact is just massive enough to change the asteroid's tragectory. You don't want to hit that thing too hard so it breaks into pieces.

According to wikipedia.org: "The random probability of a planetary orbit being along the line-of-sight to a star is the diameter of the star divided by the diameter of the orbit. For an Earth-like planet at 1 AU transiting a solar-like star the probability is 0.465%, or about 1 in 215." That means they will need to look at 215 stars before there is a high probability that they are looking at a proper angle to see an Earth-like planet pass in front of the star, using the "transit method". That means if they find one, they might extrapolate and say "since we saw one, there must be about 215 stars with an Earth-like planet for every one we can detect", among a certain class of star or in a general area of space? Merged post follows: Consecutive posts merged If the first life on Earth were extremeophiles, then you have a good point. Those scientists believe there is a much higher probability of finding life in the habitable zone, where water is in a liquid state. There are other possible bases for life, such as based on silicon, and using other solvents than water. But they think those possibilities are not very likely. Wikipedia.org on "Alternative biochemistry" http://en.wikipedia.org/wiki/Alternate_biochemistry

How is the Kepler Mission more important that "saving the world"? I suppose that it is a low probability that Earth will get destroyed, or suffer a significant impact (comparable to Tunguska) over the next few hundred years. Although that recent object gave us a close shave by missing Earth by 45,000 miles, that is not too close for comfort among the experts. The lazer spread is an issue at long distance. I believe lazers shot at the moon spread out to miles wide, and that is only 240,000 miles away.

To answer my own questions. The region of energetic reaction is a disk shape and can be very wide or small, ranging from light hours, to light months across. They are really flattened ring shapes, but the supermassive black hole at the center is so small that it would be invisible. http://en.wikipedia.org/wiki/Quasar "Quasars are found to vary in luminosity on a variety of time scales. Some vary in brightness every few months, weeks, days, or hours. This means that quasars generate and emit their energy from a very small region, since each part of the quasar would have to be in contact with other parts on such a time scale to coordinate the luminosity variations. As such, a quasar varying on the time scale of a few weeks cannot be larger than a few light-weeks across. The emission of large amounts of power from a small region requires a power source far more efficient than the nuclear fusion which powers stars. The release of gravitational energy by matter falling towards a massive black hole is the only process known that can produce such high power continuously."

I don't know where to post this, but what is the significance of these words that appear after usernames? They must have some kind of hierarchy, from beginner to advanced? What is their order? Or numbers of posts? When do posters get to create their own?

Either they will find Earth-like planets or not. With what kind of confidence will they find out how common Earth-like planets are?

You are correct Moth. A beam weapon is a quicker responder than a rocketship. Suppose a very powerful solar-powered laser or particle beam, in a high Earth orbit, could hit the object with a series of pulses at the speed of light from millions of miles away and change the path of the asteroid. In the future we may find the money to add reduntant deflection systems, both long and short range, so if one system fails another can also try.

The deflection methods I saw on THC The Universe involve a rocket going to meet the asteroid, and then reversing direction and match the speed of the asteroid headed towards Earth. Then explode, or blast pulses of a lazer beam, or land a device, or hover as a gravity tractor, or whatever method. But as SH3RLOCK rightly pointed out that if you can reach the asteroid while it is still very far away from Earth, then nearly any kind of impact would change its' course enough to miss Earth. Someone stated this above, maybe a calculated mass based upon the estimated mass of the asteroid would hit the asteroid at a closing speed of 15 to 25 miles per second without breaking the object into pieces. Or a conventional explosion just before impact to soften the blow, spread the surface area of the impact.

Yellowstone going off would be an extinction level event. It would totally destroy North America, and send the world into a "nuclear winter". The bad new is that she is thousands of years over due. The good news is there is no current seismic activity that comes before an eruption. Merged post follows: Consecutive posts merged"Due to the vastness of space, a small push in any direction is almost certainly going to be the proper direction to avoid hitting the earth." That is a good point assuming you can push it when it is still very far away. The closer it gets to Earth, the more critical the maneuver becomes.

I like the particle beam or lazer that could alter its' path from long distance, but that technology will not be ready for a long time. Also the asteroid will probably be rotating so the beam needs to hit very precisely, over and over, which is hard to do from millions of miles away. We already have plenty of nukes. You need a lot of time to send a rocket to the object and change speed and direction to match the path of the object. It has to fly along with it and then explode at the correct distance and perfect angle to give it a little push in the proper direction. People will not take the threat seriously until we experience a minor disaster. Merged post follows: Consecutive posts merged It would be much easier to have a few stations on mountain tops around the world, IF they could be so sensitive that they can cover wider areas. It is hard to imagine just how difficult it is to detect the smaller ones.

The best place to keep radar detectors and rockets with deflection systems ready for launch would be in orbit around Earth, outside the orbit of the GPS satellites. If the deflection rockets were nukes, which I believe to be the simplest and most fool-proof deflection method, other countries would complain about USA nukes in orbit. But imagine how much political capital the US would gain by saving the planet Earth from destruction.

They already use CCD (charged-coupled device) technology on telescopes in sky survey for asteroids and comets. Is there a way to combine radar astronomy with CCD technology? Then a computer does the watching for small position changes in objects that reflect the radar waves. As Baub suggested, besides detection stations on the dark side of the moon, that would also be a good place to launch rockets with deflection systems. The low gravity and 240,000 miles head start would be a wonderful advantage. But that would work only for immediate threats coming from that general direction. We would also need other rockets in orbit around Earth ready for launch at a moment's notice in the opposite direction. We could not receive signals directly from the dark side of the moon, but there could be satellites in orbit around the moon to pick up signals from the moon station and relay them to Earth.