Airbrush

Darkness is simply the absence of light. Light moves at light speed and when it is gone darkness replaces it at light speed. Light comes and goes at light speed, and so does darkness.

One major component to rising health care costs is the fact that people are generally less responsible for healthy living habits. Junk foods should be taxed to discourage people from their junk food, overeating, nonexercising life styles. People cling to their bad habits and then go to a doctor to "fix them". Emphasis should switch to preventative practices. People need to be constantly reminded to eat right, cut out cigarettes and booze, and exercise.

Baryonic dark matter CAN be seen, but because it is difficult to see it is called dark matter. In general, I believe, dark matter is any matter that cannot currently be detected other than gravitational effects, but it is possible to detect it. The term "dark matter" generally means nonbaryonic dark matter which is far more elusive, like neutrinos. Some black holes should be detectable because of accretion disks, but probably most have not yet been detected, and therefore the ones not yet detected fall into the category of dark matter. So much for baryonic dark matter. Most dark matter is nonbaryonic. I like your explanation for why galaxies over time will take a flattened shape. Very nice.

There are 2 kinds of dark matter, baryonic and nonbaryonic. Baryonic matter is normal matter made up of protons, neutrons, and electrons, but nonbaryonic matter is not, but rather strange particles like neutrinos. Baryonic dark matter is normal matter that we cannot see which can include all kinds of small objects like dust, rocks, even black holes. Dark matter, which they say is mostly nonbaryonic, is noticed only on galactic scales. We would not notice its' effects within our solar system. It seems to cluster all around each galaxy in a spherical shape, not the flattened shape that most visible matter in galaxies seem to take. I don't think you will find much of it between galaxies. That is about all I know about dark matter. Maybe someone can help us out. Martin?

The fly will feel the car's acceleration very little compared to the wind resistance of stationary air inside the car. If you stand in a high wind, along with a fly, the wind will blow the fly away but the wind will not budge you.

Considering the unimaginably vast volume of space, even small densities of nonbaryonic matter will add up to large masses over cosmic scales. Nonbaryonic matter, such as neutrinos, may be denser far away from normal matter. Even though galaxies are flattened shaped, the dark matter exists in a spherical shape centered on the galaxy center. One example of nonbaryonic matter are neutrinos, which move close to light speed, and more than 50 trillion solar electron neutrinos pass through the human body every second. No wonder that kind of stuff is hard to detect. There is far more gas and dust in the universe than all stars, black holes, planets, asteroids, comets, etc combined. The finer the material the more there is of it. http://en.wikipedia.org/wiki/Neutrino They think dark matter is mostly nonbaryonic (not normal) matter because of this: "The total amount of baryonic dark matter can be calculated from big bang nucleosynthesis, and observations of the cosmic microwave background. Both indicate that the amount of baryonic dark matter is much smaller than the total amount of dark matter. "In the case of big bang nucleosynthesis, the problem is that large amounts of ordinary matter means a denser early universe, more efficient conversion of matter to helium-4 and less unburned deuterium that can remain. If one assumes that all of the dark matter in the universe consists of baryons, then there is far too much deuterium in the universe. This could be resolved if there were some means of generating deuterium, but large efforts in the 1970s failed to come up with plausible mechanisms for this to occur. For instance, MACHOs, which include, for example, brown dwarfs (balls of hydrogen and helium with masses ), never begin nuclear fusion of hydrogen [1] but they do burn deuterium. Other possibilities that were examined include "Jupiters", which are similar to brown dwarfs but have smaller masses and do not burn anything, and white dwarfs. Actually, objects with masses around or below the hydrogen-burning limit could be baryonic dark matter." http://en.wikipedia.org/wiki/Baryonic_dark_matter

Yes that is true, but another eruption is inevitable. Geologic records show they happen periodically, not as regular as buses, but on the average every 600,000 years. The hot spot has migrated because of the motion of the North American plate. Now it is building up steam under Yellowstone. A History Channel special about it says the ground is rising at an accelerating rate.

Yellowstone is 40,000 years overdue. It must go off again within, what?, about another few tens of thousands of years, or it can start going off next year! Is there any defense against a supervolcano? All I can think of is allowing it to release pressure so the BIG eruption won't happen. The theory is to extend the amount of time over which the inevitable eruption occurs. It could be something like a mega-gyser of magma that blasts half a mile high over a period of months, and covers the Yellowstone state park area with mega-ash, but in so doing saves humanity from near-extinction. Losing a beautiful state park is a small price to pay for the survival of humanity.

Releasing too much pressure could cause areas to collapse. So they need to regulate the pressure over many square miles to keep it optimal according to any buildup of pressure. Excess pressure gets released and used to generate electricity. Maybe there is a way to do phased caldera collapses, so the entire supervolcano does not go off, only little sections. When Yellowstone explodes it will destroy a large portion of the USA and start a nuclear winter. We want to prevent an explosion.

I think the only way to curve a bullet is if the bullet has a spherical shape. How do you put spin on the bullet as it passes down the barrel, like with a curve ball in baseball, or a soccer ball?

Yes, Metal Halides and HPS create a LOT of heat and therefore a a hazard for indoor growing. They can start a fire if you don't vent the heat properly with electric fans. Not for beginners. Flourescents remain cool to the touch even after hours of use. I purchased a 250w MH and a 250w HPS many years ago and never actually used them because I've come to prefer the simplicity of good old-fashioned sunshine in my back yard.

It sounds like somebody wants to grow something naughty indoors. Ordinary flourescents work just fine especially at early stages of growth. If you want to get fancy there are metal halides and high pressure sodium.

The word "rifle" comes from rifling which are spiral grooves in the barrel of a rifle that cause a bullet to spin, but the axis of spin is parallel to the path of the bullet. That increases accuracy by gyroscopically stabilizing the bullet, improving its aerodynamic stability. The kind of spin needed to curve the path of a bullet would be perpendicular to rifling spin. It would cause the bullet to tumble the wrong way and be totally out of control. http://en.wikipedia.org/wiki/Rifling

Maybe some of the long gamma ray bursts are from merging SBHs. Wiki says that the long GRBs (longer than a couple of seconds) are from massive stars collapsing into black holes, and the short ones come from merging neutron stars. I propose that when supermassive black holes merge they would look like binary quasars until the final moment.

Look up "El Nino" on wikipedia and it also discusses "La Nina". "La Niña is the name for the cold phase of ENSO, during which the cold pool in the eastern Pacific intensifies and the trade winds strengthen. The name La Niña originates from Spanish, meaning "the little girl", analogous to El Niño meaning "the little boy". It has also in the past been called anti-El Niño. "La Niña causes mostly the opposite effects of El Niño, for example, El Niño would cause a wet period in the Midwestern U.S., while La Niña would typically cause a dry period in this area." http://en.wikipedia.org/wiki/El_Nino#La_Ni.C3.B1a

What if there was a way to tap into the magma at Yellowstone as an unlimited source of energy for the entire North American continent? Is there a way to "disarm" Yellowstone to release the inexorable energy build-up, and use the energy at the same time? What I envision, if possible, is a way to allow Yellowstone to "let off steam" at a steady rate so it won't explode, and use the energy to generate electricity for the USA? It would require a lot of exploration and testing to find a safe way to tap into Yellowstone. A series of either small nuclear or conventional explosives could open a passageway for the magma and allow a giant magma gyser on the surface where it could be used to power steam turbines. But they better be careful or they could accidentally trigger the Big Eruption, and game over.

The merger of two SBH seems like the ultimate heavyweight fight. Some SBH have a billion solar masses or more. Consider that a quasar's tremendous energy output is probably the result of an accretion DISK. What if the two SBHs have accretion disks that are not parallel? As they approach each other each tears away the other's accretion disk resulting in matter crashing into both over much broader areas. Instead of accretion DISKS this could result in a chaotic disbursion of matter all around each in an accretion SPHERE, a shell of massive energy outbursts. This could vastly multiply the energy output of both. After each strips away the other's accretion disk then there would be little left but 2 naked black holes which would spin around each other at relativistic speed, and then merge at near light speed. Their tremendous gravity would suppress any other outburst. So I propose that the most energetic phase of the merger would be binary super-quasars leading up to the merger, as each tears appart and starts a feeding frenzy on accretion material, with huge amounts of gas and dust falling every which way into each black hole, all over the spherical event horizons, and not the moment of merger which would only end with a unpresedented spike in gravity waves.

If a quasar is a supermassive black hole (SBH) devouring matter at the rate of solar masses per month, then my guess is that when two SBH collide, after a long dance around each other, it happens very quickly and a lot of accretion disk material gets dragged around and forced fed into each as they get closer. It should look like a couple of quasars orbiting each other and in the critical moment of collision, there is a massive burst of energy greater than all the galaxies in the observable universe, but just for an instant. Then it settles down to a long meal of accretion disk material so it shines like a mega-quasar for a long time afterwards, unless the impact blasts all the accretion disk material away and out of reach. Or as Martin stated that the intense gravity would slow the energy release? I don't understand gravitational waves so maybe someone else can explain that aspect. I think the processes in quasars are more energetic than gravitational waves. The gravity waves is how we could detect these mergers. Here is an animation of 2 black holes merging and tell me what you think of the discussion that followed it. http://www.newscientist.com/blog/space/2007/05/battle-of-black-holes.html

Thanks Sisyphus, that is the kind of stuff I like to hear.

Would you care to elaborate? Does the magnetic field depend upon currents in the Earth's core? I agree that gliding thru solid rock by means of a rotating lazer cutting a pathway sounds far-fetched, but long-term human space travel to the stars seems almost as preposterous.

Sorry Mr. Alien, you are correct. On second thought, I can't imagine how heavy 13.1 grams would be for something only one cubic centimeter. What I need is a common object, one that I pick up often, and the weight of that object in units I grew up with. Sorry, but I am not a scientist. I miss a lot of good science when the standard units of measure just whizz over my head.

Did anyone see the movie "The Core"? Was it realistic? Apparently magnetic pole reversals do not cause mass extinctions. "Because the magnetic field has never been observed to reverse by humans with instrumentation, and the mechanism of field generation is not well understood, it is difficult to say what the characteristics of the magnetic field might be leading up to such a reversal. Some speculate that a greatly diminished magnetic field during a reversal period will expose the surface of the earth to a substantial and potentially damaging increase in cosmic radiation. However, Homo erectus and their ancestors certainly survived many previous reversals. There is no uncontested evidence that a magnetic field reversal has ever caused any biological extinctions. A possible explanation is that the solar wind may induce a sufficient magnetic field in the Earth's ionosphere to shield the surface from energetic particles even in the absence of the Earth's normal magnetic field. "Although the inspection of past reversals does not indicate biological extinctions, present society with its reliance on electricity and electromagnetic effects (e.g. radio, satellite communications) may be vulnerable to technological disruptions in the event of a full field reversal." http://en.wikipedia.org/wiki/Geomagnetic_reversal

Why complicate the density? It is far easier to visualize the density your link gave (for the Earth's lower core) as 13.1 gm/cm^3 than to gross it up to a cubic meter. Same goes for speeds greater than 3,600 mph, better call it one mile per second. That you can visualize. Or if your audience is not in the US, call it km/second. Scientists need to consider their audience, unless they want their only audience to be other scientists.

Another thing, missions into space are very physically demanding. Astonauts must be in tip-top physical condition, like a fighter pilot. A pregnant woman should never be subjected to such abuse as strenuous physical conditioning before launch and then withstanding several G's to fly into orbit, followed by weightlessness.

There is absolutely no reason for giving birth in zero gravity, nor for extended human space missions in zero gravity. Artificial gravity, by means of cabin rotation, is a must for long-term human space exploration. Giving birth in space is only something that would happen during long multi-generational space missions to the stars. Robotic probes are far more cost-efficent than sending people anywhere further than the Moon.