Airbrush

Interesting post Djrams80. Is that your picture in the top right? What I would like on the Moon is an NEO detection station on the far side of the moon. That would always face away from Earth and sweep space for moving dots. What makes helium-3 a must have? I still would rather spend most of our space exploration money on planetary defence systems. Why not have bases in Antarctica that learn to be self-sufficient? That would prepare them for the Moon. The low Moon gravity will cause serious physical problems over the long term. Unless they figure out how to have artificial gravity on the Moon.

See the story below. I heard on the radio it was moving between 50 to 100 Kilometers per second. They said crashing into gas clouds created a greater explosion than if it hit a solid surface. http://news.cnet.com/8301-19514_3-10291824-239.html

A supermassive white hole? What makes cosmologists so sure the origin of the universe started with a singularity or a tiny point? The big bang could have started expanding from a region of indeterminable size. Think of a gateway thru which the universe passed into this space-time. If you walk thru a doorway, you don't emerge as a tiny atom on the other side.

The big bang erased all trace of whatever existed before it. I doubt there was "nothing" before the big bang, but there is no way to prove it. It is hard to imagine what existed then. Something certainly existed before the big bang, the conditions that caused it.

We probably won't get hit, but it CAN happen any time. Tunguska-sized objects are not all identified and can destroy a city or worse. If they want to play around in space, then do it for something that has real tangible benefits, like survival of our species, rather than bases on the Moon or Mars. There would be more world-wide appreciation for the country(ies) that develop the means to defend ALL people, along with other species. It is the most altruistic of all space missions, better than just frolicking around on the Moon or Mars to answer science questions which robotic probes can do just as well and at far less cost. Such a noble mission of the US and others defending all people and life on earth could cut back on terrorism against the US. So that adds up to political benefits. Then other countries may help out with environmental conservation. Most people in the world don't think so much in probabilities, the way scientists do. If you are a country working on a defense system, you will be admired for that. Even if we do start missions to NEOs it will be a hundred years before viable defense systems are tested and on line, ready for action.

The answer is NEOs! Men have been to the Moon. Send robots there and to Mars. What we really need to do to win the respect of the world is develope a fool-proof defense against bolides. The other projects are very expensive, just for fun. A defense system can save the planet. Yes an extinction level event is very, very unlikely in the near future, but we don't know all the threats. Better to be safe than extinct, or living in the stone age, again.

My bet is that superclusters are gravitationally bound and ALL expansion is BETWEEN superclusters. The reason so many question expansion by saying "Hey look at Andromeda, it is not moving away from us!" is because not enough emphasis is placed on large-scale structure of the universe.

Interesting how often this question is asked. Even in this discussion, after it is explained, the same question is asked again. Here is my question. Do superclusters (which are clusters of clusters) expand at all? Or is all expansion BETWEEN superclusters?

A few years ago the Discovery Channel had a special "If We Had No Moon" or something like that. They speculated that if the massive collision that probably created the Moon had not occurred, the Earth's oceans would be much deeper and there would be little, if any, land above sea level. Had anyone heard that one? Recently I heard on Michio Kaku's radio program "Explorations" that the fact the Moon stabilizes Earth's rotational axis is not as big a factor as previously supposed. If we had no Moon, the Earth's axis would wonder, up to 90 degrees, but major movement would take tens of millions of years and would not be so disasterous to life on Earth.

The Kuiper Belt objects are so far away, they don't concern us as much as NEOs (Near Earth Objects) that cross our path. Yeah, let's get some target practice on some dastardly NEOs!

I don't believe there are any moon-sized asteroids around. So relax, all you need to worry about are Tunguska-sized asteroids and some bigger ones. No big deal.

Yeah, we need to think about "in a pinch". A quick and dirty method may be our only chance with the unannounced objects. Recently a Tunguska-sized object passed us by without us knowing it existed until a couple of days before closest approach. We can get blind-sided any day, with at best only a few days notice, if it comes "out of the Sun", the way fighter planes attack. For short-notice objects we need to take advantage of high closing speed with the object. It will be headed, more or less, directly at us at a very high speed, 10 miles/second or faster. Our only hope will be kinetic impactors or nukes speeding towards it at a comparable speed, so the closing speed will be 20 miles/second or faster. If you can slam enough mass into it, you might divert it just enough. Or nukes timed to explode at the exactly proper moment just a short distance from it so you heat up one side to vaporize and push it just enough. I don't know why we are not already practicing short-notice techniques on nearby asteroids.

Well said. Generally speaking, all the planets in the solar system follow elliptical orbits around the Sun, but NEARLY circular.

I always scan Astronomy magazine when I shop for groceries. If it has a story that keeps me reading for more than 10 minutes, I have to buy it. I don't have a college science education, I just love to watch programs about cosmology on TV.

That's a great answer to a simple but difficult question. 33%C is an incredible speed. They think the 2 outbursts are caused by the smaller one punching thru the accretion disk of the larger one, swinging around the larger one and punching back thru the accretion disk to be flung way out to far side of the ellipse. I wonder how long the interval between the 2 outbursts is? It must be a very tiny fraction of a second if it is moving at 33%C. http://www.caha.es/18-billions-of-suns-support-einstein.html

"OJ-287 over 3 Billion LY away, 18 Billion solar masses has a 100 Million solar mass SBH in a 12-year orbit around it. They estimated the outer edge of the accretion disk of the bigger one as only about 10 light weeks in diameter. "Ten light weeks is about 0.19 light years, or over 1.1 Trillion miles if my math is correct (60 x 60 x 24 x 70days x 186,000mi/sec = 1.116 Trillion miles) or 10,750 AU, or extending to about the middle of the inner oort cloud. The event horizon radius of an 18-Billion-solar black hole is about 54 Million kilometers or 33.5 Million miles, about a third the distance from the earth to the sun, inside the orbit of Mercury." ~from a few months back How fast does the smaller one whiz past the larger on closest approach?

Wikipedia on OJ287: They think the two super-supermassive black holes will merge in about 10,000 years. They think the 11 or 12-year periodic outbursts are caused by the smaller one crashing thru the larger one's accretion disk. "The maximum brightness is obtained when the minor component moves through the accretion disk of the [more] massive component at perinigricon." and the feeding frenzy begins and ends. http://en.wikipedia.org/wiki/OJ287

"...they seem to have caught a pair of black holes which are spiraling down into each other, on the way to merger, and radiating off the excess energy (which they have to do in order to spiral in closer) by having their orbit generate undulations in the geometry around them---gravity waves carrying off the excess energy." Have they calculated how long until the merger? Why do they have to radiate off excess energy as they spiral together? Will they accelerate in speed as their orbit gets closer and tighter (like the ice skater with arm out spinning faster as they bring their arms inward)? Are those 12-year periodic outbursts the result of each black hole crashing through the others' accretion disks? Imagine that, the most massive object ever detected. And as a bonus, it has a massive parter.

That's the kind of stuff I like to hear about! Thanks Martin.

Where did you read "receding at 6C"? The furthest quasars were much closer to us than 14.5 (you mean Billion) LY away when their light left them. Objects near the edge of our current visual horizon are not receding that fast. Now the furthest visible quasars and galaxies are about 30 Billion LY away, and they were between 12 and 13 Billion LY away when the light we now see started traveling towards us. The cosmic microwave background is now about 50% further, or about 45 Billion LY away. Maybe someone can resolve this better than I can.

You are right. Either the universe is infinite, or it is finite, but surrounded by infinity. Beyond the border of this bubble is the unknowable.

I like the theory the universe was created by a collision of higher dimensions. Like two bed sheets hanging parallel and very close together on clothes lines. When a wind blows the sheets will come into contact with each other (big bang) not at one point (not at a singularity), but at various regions of indefinite sizes. Our universe is the result of a collision of our local region on one bed sheet.

This is the first I heard of the "eddy effect" of a black hole. Would you care to elaborate in more detail? It seems like all black holes must spin, because motion is the norm in the universe, nothing seems static or stationary. But consider the conservation of angular momentum of a collapsed star. Like the example of a ice skater spinning with arms out, then when they bring their arms in their spin increases. What must happen with black holes? It must be far more of an effect. It seems like the spin would reach relativistic speed very easily.

Fascinating explanation of motion of the spiral arms, thanks Martin. Nice density waves Granpa. Anyone know how close we are to the nearest high-density spiral arm? When will we pass thru another arm and how close will our neighbor stars get to us when we do? I will try to look these up, unless someone knows offhand. When spiral galaxies collide does that mix them up so much that they either form irregular shapes or become ellipticals? Merged post follows: Consecutive posts merged Yes and the motion of density waves. I bet that if the SBH at the center of our galaxy is spinning that it is spinning in the same direction as the galaxy is rotating.

Take a look at wikipedia.org "black holes" which will answer most of your questions. Sure they may spin, in fact most of them must spin to conserve angular momentum of the star that collapsed. It is hard to imagine something with no volume spinning. What is spinning? The space and matter surrounding it. I recall that black holes may spin up to about 1,000 revs per second. I don't believe spin of the supermassive black holes (SBH) at the center of galaxies has anything to do with the galaxy's spiral shape. Can anyone explain why many galaxies have a spiral shape?