Airbrush

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.

That sounds great, the best so far! The moon orbits the Earth once a month, the dark side always faces away from Earth, and the moon's orbit is on the plane of the solar system which is where most NEOs travel. The monitoring station(s) on the dark side of the moon would have a great view of space surrounding Earth, and could do the motion sensor scans of broad swaths of space. Hey NASA, check this out!

I like the idea of exploding a nuke next to the object, not too close to break it into pieces, but just close enough to heat up one side. This will cause outgassing (or something like that) from the object. The reaction would nudge it a little and hopefully enough. But all those ideas are useless when you don't know it exists until less than 36 hours before impact!

The Tunguska-sized object raced by Earth at 1:44pm GMT on Monday. Even if it was discovered at 1:00am GMT on Saturday, that gave us only 36 hours notice..... at the most! Merged post follows: Consecutive posts merged Even the most massive satellites in orbit would be nothing compared to even a very modest-sized NEO, which will pass through the space debris like a hot knife thru butter!

Dr.DNA quote: "What might be more viable than lasers would be a bunch of satellites in orbit, like GPS satellites, emitting radio waves or microwaves outward." That sounds good. Something like an outer space radar network of satellites. It can start with just a few satellites and then increase in number and improved coverage as money becomes available. The motion-sensing radar could make sweeps of broad areas of space. Most NEOs travel on the plane of the solar system, so that would vastly reduce the coverage needed, as compared to the GPS system.

Then the escape hatch should be a sliding door! The story at the top of this thread said that the object was discovered only 2 days before it passed by (seen on Saturday and flew by on Monday). Can coastal areas be evacuated in less than 2 days? If I had a beach house I would be skeptical about the prospects for a safe escape to high ground. Many areas have no high ground nearby. A Tunguska-sized impact in the middle of the Pacific may cause waves that are so massive that all coastal areas would be buried so deep in debris that there would be no way to exit an underground shelter. The shelter would only ensure survival from smaller impact tsunamis, but it may be your ONLY chance. For all we know, it can happen next week!

Mr. Alien, you are correct, it could take days or hours depending on the magnitude of the event. Dr DNA, you may be right, depending on how much time you have and your escape route options. Just build the thing watertight. The hatch should open INwards in case it is blocked from the outside. You should have a saw and ax, along with an assortment of tools, to cut your way out, and there should be a portal so you can see if you are still under water. On the other hand, you might get around the traffic jams on a off-road motorcycle, like the kid in Deep Impact.

Seriously, for most coastal dwellers, there would be no time to reach high ground to escape a series of waves over 100 feet high. In a standard flood you would be better off finding high ground. Impact-induced tsunamis are a different scenario entirely. Roads would quickly become massive parking lots. Your best hope would be underground in a personal shelter. Within a few hours the waters should subside so you can exit. Your house will be gone, and the shelter hatch will be covered with debris, so it will take some digging out. The entrance to the shelter should zigzag so you exit horizontally through a vertical doorway using tools you stashed inside.

We are being hit by smaller ones every day, the question is when will one big enough (at least 10% the size of Tunguska) to cause significant damage hit us? Nobody knows but it COULD happen in our life times. Maybe not as likely as I made it sound. I don't know about "enormous resources to prevent a repeat" but public opinion would force governments to devote substantial resources to the threat. The main threat from the smaller ones would be tsunamis from an ocean impact. I propose that everyone living near the ocean should have an underground tsunamic shelter. You beachfront dwellers should start digging.

"Millions of high-powered orbital telescopes"? Certainly the reason we don't is COST and economic priorities. But when a smaller one hits us somewhere, which is likely in our lifetimes, then public opinion can change 180 degrees. Not millions of orbital telescopes, but dozens for starters, and more can come on line in the future.

Motion detection is exactly how they find those things. Doing that from a network of satelites sounds like a great idea. Why don't they do that?

Not to get off topic of universe expansion and "bounce back"! But why put lightbulbs in the atmosphere? Solar panels could collect all the energy humans could need, positioned right here on Earth, IF there were not too many people on Earth, and IF there were enough solar panels. That power source will last as long as the Sun does, Billions more years, and it is totally benign environmentally, except for the process of their manufacture? Anyhow, it is fun to wonder what the universe will do over astronomical time scales and hear educated guesses.

That story means that objects that big come that close to us before we even know they exist. Last I heard is that Tunguska-sized impacts occur about once every 500 - 1,000 years. Long before that I heard they happen once every 100 years, but that must be way off. Such impacts would have been widely recorded throughout history. Anyone heard of any different frequencies?