Airbrush

"Is Jupiter ALMOST a dwarf star?" Brown dwarfs have the lowest mass of dwarf stars, with masses between 13 Jupiters, at the low end, up to about 75 to 80 Jupiters at the high end. So Jupiter is not almost a dwarf star, not even almost a brown dwarf. "Brown dwarfs are sub-stellar objects with a mass below that necessary to maintain hydrogen-burning nuclear fusion reactions in their cores, as do stars on the main sequence, but which have fully convective surfaces and interiors, with no chemical differentiation by depth. Brown dwarfs occupy the mass range between that of large gas giant planets and the lowest mass stars; this upper limit is between 75 and 80 Jupiter masses (MJ). Currently there is some debate as to what criterion to use to define the separation between a brown dwarf from a giant planet at very low brown dwarf masses (~13 MJ ), and whether brown dwarfs are required to have experienced fusion at some point in their history." http://en.wikipedia.org/wiki/Brown_dwarf

If ETs decided to invade Earth, there would be no contest. If they had the technology to bring them here, they also have technology to easily exterminate selected species. The idea of thousands of spaceships crashing thru the atmosphere, enough to heat it up, sounds ludicrous. There must be many better ways to get rid of us and take over Earth. We would not stand the chance of an ice cube on the Sun.

Interesting stuff above, thanks for that. In your estimation, if you traveled in a straight line at the speed of light in one direction, how long would it take before you arrived at your starting point, IF space is slightly curved? Since the universe is expanding, it must be a lot longer than 900 Billion years, or not? If space is not curved, then you will travel towards infinity forever in one direction, right?

Nice explanation Martin. "What would happen if the universe stopped expanding?" Taking another look at the question, we would notice expansion SLOWING tens of Billions of years before it stopped expanding.

The question should be "What is the speed of gravity?" How do we know gravity moves at light speed? wiki on "speed of gravity": http://en.wikipedia.org/wiki/Speed_of_gravity "The speed of gravity, and of all disturbances, is more often called the speed of light c. Within the well accepted theory of special relativity, the parameter c is not about light, it is a unit conversion factor for changing the units of time to the units of space in a Lorentz transformation. It is then also the only speed which does not depend on the motion of the observer, and equals the speed of gravity and of light and of any other massless particle."

My problem with the "balloon analogy" is it expects you to imagine 3-D space as 2 dimensional. My mind just refuses to make that imaginative leap. Space is 3-D and the surface of a balloon is 2-D and the balloon exists within 3-D space. Raisin bread is a better analogy. I prefer the tub of soap bubbles analogy. Each bubble is a universe. Some bubbles are expanding, some are shrinking or popping.

Correction, wiki just told me Apophis is about 1,100 feet long and may come as close to us as 23,000 miles. The density is unknown, maybe iron or stoney, or something softer?

Cool illustrations! I wonder how you did that? Anyhow, since nobody sent your post to speculations, your post can't be so bad. You just need to provoke discussion somehow. I can't follow your reasoning much beyond the first illustration. Can you put your theory into a few sentences and plain English for novices such as me?

The balloon analogy just doesn't work for me. My mind refuses to imagine the universe curving like the surface of a balloon. And IF 4D space can somehow be curved like a balloon, curved within what? I much prefer to think of space as extending to infinity in every direction.

"...the Kepler mission continuously and simultaneously observes more than 150,000 stars." and it will do that for 3 years. So they must keep track of each of the individual stars in question over a period of years. Tough record keeping. "did the NASA researchers calibrate their Kepler telescope on stars known to have planets...?" No, they are observing all the stars in a dense region of the habitable zone of the Milky Way. Kepler is looking for the first signs of possible planets.

The Russian said no nukes will be used but they will send a "special purpose" spacecraft. Apophis will fly by in 2029, so we have 19 years to plan and deploy something. It will be a great chance to experiment with methods of deflection. It is 885 feet in diameter. If it did impact Earth how fast will it be moving? depends upon the angle? what kind of kinetic energy would that impact be in megatons? Will it explode in the air? Wikipedia on Apophis: "As of October 7, 2009, the impact probability for April 13, 2036, is calculated as 1 in 250,000. An additional impact date in 2037 was also identified; the impact probability for that encounter is calculated as 1 in 12.3 million. "Many scientists agree that Apophis warrants closer scrutiny. To that end, in February 2008 the Planetary Society awarded $50,000 in prize money to companies and students who submitted designs for space probes that would put a tracking device on or near the asteroid. Several other groups have studied or plan to study missions to Apophis."

I'm glad someone is thinking about getting a mission going. What if they push the asteroid the wrong way and cause an Earth impact? Why don't they trust the NASA estimate of such low probability for impact? OK, better to be safe than permanently sorry.

I don't understand this very well but does this suggest that intergallactic space is more dense than space within a galaxy? Also I recall that estimates of the density of matter in the middle of the great voids between superclusters was about one atom per cubic meter. Could it be that the average density of matter in the entire universe, including all stars, black holes, planets, etc, is approximately the same as the average density in the middle of the great voids? And the reason being is that space is so vast, that no matter how much matter there is, the average density of the entire universe is insignificantly greater than the density of empty intergallactic space?

Interesting stuff, but the math is beyond me. Anyone want to explain what he is saying in 50 words or less? It would seem like the effect of dark energy is opposite to matter, so call it "negative mass". Why not? And not to be confused with antimatter.

That's what I was thinking teranko, that dark matter occupies higher dimensions of M-Brane Theory. It is a "Ghost Gravity" that leeks thru to our 3 spatial dimensions. It can never be detected in these 3 dimensions. I don't know how dark energy can be explained this way. You want to elaborate? Dark energy is simply an underlying repulsive property of empty (or nearly empty) space. It has such a weak force that it is effective only over the vast distances between superclusters of galaxies. Mlich, the difference between dark matter and dark energy is one is about matter and the other energy that acts on matter. I don't know what the equivalence of matter and energy has to do with it. You care to elaborate?

Fascinating pictures! Thanks for sharing. What a wide range of terrain. Are those pictures enhanced or is that very much what we would see if we were there?

"...What about light at the extreme edge of this singularity, what would be holding it back ?" Because of cosmic inflation, maybe there is no extreme "edge". Or that is long gone, beyond our visual horizon. This kind of stuff is very strange and hard to imagine.

And thanks to iNow for the following cool Einstein quote about space-time needs matter as a pre-condition: "People before me believed that if all the matter in the universe were removed, only space and time would exist. My theory proves that space and time would disappear along with matter." Interesting that he called it "space and time" and not "space-time". When did he start calling it "space-time"? How about using the word "space" for the condition preceeding matter. Space-time is post-matter. So space is timeless, but space-time begins with a Big Bang.

Could dark matter be "ghost gravity" of an overlapping higher dimension? It could never be detected other than its' gravitational effects. Thanks for the cern link moth. Interesting stuff.

"My theory proves that space and time would disappear along with matter." ~Einstein So it is correct to say that space-time would not exist without matter.

How about space-time is a seething expanse of virtual particles popping in and out of existence constantly? Is it correct to say that except for the occasional hydrogen atoms in otherwise empty space, space-time is nothing?

The word "nothing" is too extreme for my comfort. He used the term rhetorically. He should have said that something can come from "zero total energy". Or at least he should have explained in advance what he meant by "nothing". Scientists are supposed to be precise. Nothing is an absolute term, and I don't believe it ever existed. I am also a novice at cosmology, but I got a lot from his talk. Maybe because he said things like "something always comes from nothing". Hehehe.

Can something come from nothing? What exactly IS "nothing"? I don't believe "nothing" is as simple as the word makes it sound.

That was a wonderful talk. Thanks for sharing. "Everything that happens has [VERY] small probablity." Yes Moth, near the end he said if a new universe began, from the outside it would appear to be as a black hole. Very interesting. Anyone care to explain? How massive a black hole? Recently I posted that "nothing" is so improbable. All we can see is something. In a flat universe, with total energy of zero, something will always come from nothing, especially if something has infinite time and space to pop out of nothing.

Anyone know when the Kepler Mission will start reporting results?