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Oh, I also found some info about random non-galaxy stars that theoretically might be "picked up" by a galaxy.

http://starchild.gsfc.nasa.gov/docs/StarChild/questions/question29.html
http://www.astronomycafe.net/qadir/q2486.html

Safe speeds for current technology would be only slightly higher than space shuttle speeds especially if interstellar space contains chunks of comet ice.

If this is true... forget your 100s years. Make it 10000s.

You mean one for electrically charged stuff, and one for electrically neutral stuff, no? Sure, yea, that ends up mostly being ionized gas vs dust, but the reason there are two is because one is affected by the solar magnetic field in the guise of the solar wind, and one isn't.

Oh, okay, I used Google. We're both wrong. There are three tails, as shown in the figure here http://www.astronomycafe.net/qadir/q2805.html --- one for ionized gas, one for neutral gas (hydrogen, apparently), and one for dust.

Pardon in advance for any meanderings. Several interruptions while composing this.

And yet the Moon might well be the cause of several other factors.

The Moon is massive enough in comparison to the Earth that it is reasonable to consider the two to be a binary planet system in many ways. While the barycenter of the binary revolves around the Sun in a highly predictable ellipse, the Earth itself does not; it meanders inside and outside that elliptical orbit due to the Moon's influence. As a consequence, the location of the Earth's perihelion can shift more than one degree from one year to the next (varies from Jan 2 to Jan 4). The barycenter of the binary system is displaced from the center of the Earth toward the Moon by 75% of the Earth's radius (quick reference here), which from the point of view of a flat Earth theorist means that the barycenter is rushing along 1,000 miles beneath our feet at about twice the speed of sound.

And of course there are the tides.

Not just the ocean tides, but also the much greater tidal bulge of the atmosphere. And a definite tendency to a tidal bulge in the liquid core. IANAGeologist so I don't have a clue how the tidal forces and the weight of the mantle would interact... but then I think that most geologists have never considered this either since they are always looking down into the Earth and the Moon is for them a whoosh in the finest Slashdot meaning.

As far as evolution of life goes wrt planet Earth, the Moon is at the very least a major, significant stirring rod. It is really hard to say how major, since we are in the position of being stirred so everything else that is also being stirred with us looks very normal. It could be that both meteorology and geology need their Copernican revolution and won't really make sense until they meet their Galileos.

Hmm. I would have thought that the ellipsoid shape of the Earth would have less influence on an equatorial orbit than the changing relationship of that orbit to the Earth - Moon barycenter.

Relative to our frame of reference on the surface of the Earth, a geosynchronous orbit would of course be stationary above someone's head, while the barycenter would be rushing around some 2,000 km below our feet at an angular speed of 15 degrees/hr, wandering more than 30 degrees north and south of the equator on a seasonal basis. Since all Earth satellites orbit around the barycenter rather than the geometric center of the Earth, you would expect the Earth's dense core to be the primary cause of orbital perturbations.

But what do I know? Any astronomers or rocket scientists want to jump in here?

As an aside, the barycenter does its dance in the bottom of the mantle, just a little bit above the liquid outer core ( here is a quick depth guide. My understanding is that to date, geologists are not trained to look at possible astronomy influences when building models of the Earth's interior, and astronomers do not consider the inside of the Earth to be in their province. So perhaps something very interesting is going on in this region that has so far been overlooked. Or perhaps the barycenter dancing on the margins of the liquid core is just one of those weird coincidences that only a whacko would consider. You know, like continental drift.

It would be really nice to hear from some persons who know a thing or two about this kind of stuff.

First, the "bottom of a well" story is false. Some discussion here: http://www.astronomycafe.net/qadir/q241.html as well as at snopes. Got a piece of pipe? Try it for yourself.

Second, light pollution of the night sky is a massive problem for astronomers. The lights of Los Angeles reduced the Griffith Observatory to a tourist attraction, and the city of San Diego spent a bucket of money on shielded lighting to mitigate what it was doing to the Palomar installation.

rj

My nit-pick was that timeOday's assertion was correct, that our exploration of other planets has so-far been carried-out 100% robotically. Sure, the moon is another planetary body with resources we could potentially harvest some day. I suppose the important part of the distinction is not that it's a moon, but that it's our own moon. The distances, and thus times involved, are thus trivial compared to the distance between the earth and any other planetary body.

Now, given that round trips to mars are gonna take about 21 months, I don't think we can really justify exploring them with humans any time soon. On top of what is needed for robots, a manned mission would also require space and facilities needed by humans (toilets, showers, etc), their food and oxygen supplies (or possibly hydroponics capable of supporting the astronauts if that'd be smaller/lighter), enough fuel to bring the humans (and, presumably, hydroponics) back home at the end of it all, and the extra fuel required to boost all of the above to mars's orbit in the first place. Note that fuel is heavy, so having more fuel means you need more fuel to carry it, not to mention larger (heavier) fuel tanks. I'm no expert, but in the weight of these extra costs I don't think Teancum's call of manned missions to the moon is realistic or deserving of being modded to +5 insightful.

Shame there's no option to mod as 'Hopeless Romanticism'.

The probability of a cosmic ray at precisely the right angle and speed to cause a single bit error and cause an app to crash is somewhere on the same order as your chances of getting hit by a car, getting struck by lightning, getting torn apart by rabid wolves, and having sex in the back of a red 1948 Buick convertible at a drive-in movie theater on Tuesday night, Feb. 29th under a blue moon... all at the same time....

Nice analogies, but there are never any blue moons in February, as the lunar month is 29.53 days and the longest February is only 29 days ...

(For somebody who doesn't know, a blue moon is when you get two full moons in one month.)

By this definition, Neptune isn't a planet, it's a dwarf planet, because it hasn't cleared Pluto out of it's neighbouring region...

And interestingly enough, it never will.

http://www.astronomycafe.net/qadir/q364.html[www.astronomycafe.net]

The daytime SURFACE temperature is about 80 F during rare summer days, to -200 F at the poles in winter. The AIR temperature, however, rarely gets much above 32 F.
The temperatures on the two Viking landers, measured at 1.5 meters above the surface, range from + 1 F, ( -17.2 C) to -178 F (-107 C). However, the temperature of the surface at the winter polar caps drop to -225 F, (-143 C) while the warmest soil occasionally reaches +81 F (27 C) as estimated from Viking Orbiter Infrared Thermal Mapper.
In 2004, the Spirit rover recorded the warmest temperature around +5 C and the coldest is -15 Celsius in the Guisev Crater."

All sorts of stuff goes badly wrong when you're looking at that kind of temperature, not least anything with a hint of moisture in it. Rubber will crack, and metals will become brittle. But yes, I guess there's a chance that they can 'park' and wait for it to thaw in the summer, gather enough juice to power it's stuff, and boot up. It's more likely though that it'll just never start up again, as a system critical component is degraded by the extreme cold to the point where it doesn't work any more.

That's before you start looking at other environmentals, such as dust - get a joint clogged due to dust, and you may find you're only burning out motors when it's thawing time.

This isn't where I originally read this, but it's all I could find online:

http://www.astronomycafe.net/qadir/q1347.html

So getting to .5 C is not a problem (except for the massive expenditures of energy). Also - based off that link, Alpha Centauri will probably never be closer than 8 years away.

Correction: There seems indeed a kind of Warp Drive as extension to the anti grav drive possible (according to the theory).

This link: http://www.uibk.ac.at/c/cb/cb26/heim/theorie_raumf ahrt/hqtforspacepropphysicsaip2005.pdf (someone else posted it already in this thread) is a modern paper about the drive (2004). Its a joint work from an austrian and a german Phd student.

The paper is 15 or some sides and quite understanable, if you don't look to close at the formulas ;D According to the paper, the magnetic fields needs to be somewhere in the range of 20 to 30 Tesla, which is quite a lot.

Just for refference: the earth has a magnetic field with the strength of ~1 Gauss.
1 Gauss is 1 * 10E-4 Tesla, so 10.000 Gauss is 1 Tesla and 20 Tesla is 200.000 times the earth magnetic field strength. See: http://en.wikipedia.org/wiki/Gauss

This page: http://www.astronomycafe.net/qadir/ask/a11654.html gives a table about natural magnetic fields and claims man made magnetic fields can get as strong as 40 Tesla.

Another site I found is this: http://www.sciencedaily.com/releases/2005/12/05121 4220120.htm the actual record for a magnetic field is claimed as 35 Tesla there.

angel'o'sphere

Unfortunately for them, the highway has only been around since 1930...

As someone else pointed out, the early sightings aren't very well documented -- the first substantiated reports of the early sightings were made years after the fact and date from well after the highway was built. Even Ellison, it turns out, never actually wrote about the event in his memoirs (1937) -- he told his family about it, and they later told the story to historian Cecilia Thompson or to her source.

The earliest report that researcher could verify was a 1957 magazine article. That doesn't mean the earlier sightings didn't happen, just that they couldn't be verified.

As I suspected, a bit more detective work reveals that early sightings were first reported well after the event and that folks digging for serious contemporary documentation can find none:

http://www.astronomycafe.net/weird/lights/marfa15. htm

Turns out that Mr. Ellison never did mention the supposed 1883 sightings in his memoirs (written in 1937 when the man was in his 70's), according to local historian Cecilia Thompson.

Don Witt, then a physics professor at Sul Ross University in Alpine, coordinated a monumental effort to locate the lights' source. Using the Sul Ross Society of Physics Students, the Big Bend Outdoor Club comprised of community members, and local pilots, short-wave radio amateurs, and a few outside professionals, Witt's group was positively unable to form any sort of solid conclusion. They did say, however, that sometimes the lights that people claimed were "Marfa Lights," were really artificial lights from area ranches or automobile headlights merely passing behind unseen obstructions along distant Highway 67, which winds through the Chinati Mountains between Marfa and Presidio.

On topic:

Fudge factor (Einstein) == fudge factor (dark energy/matter)

What exactly is surprising about this? They were/are both added to represent something unknown, a pure speculation which is likely to fall (or be changed to the extreme) by Occams razor as science and knowledge progresses.

http://www.astronomycafe.net/anthol/fudge.html

Einstein retracted his fudge while still alive and I have a suspicion those championing dark matter/energy will have to as well :)

Slightly off topic:

Hmm was this the first valid and correct reference to Occams razor on Slashdot ever? Probably the first time here it wasn't used in a faulty manner applying it with anti-religious or ideological/political arguments (one would think people would get a clue from the fact that Occams razor was created by a Franciscan friar).

religion != science
Occams razor = intended for scientific theories (given two equally predictive theories, choose the simpler)
Occams razor != rational to apply to religion

*doesn't even need a flameretardant suit*

The daytime SURFACE temperature is about 80 F during rare summer days, to -200 F at the poles in winter. The AIR temperature, however, rarely gets much above 32 F.

http://www.astronomycafe.net/qadir/q2681.html

Even if I'm off by many orders of magnitude (IANAP), the required field strength will be unattainably high.

i meant to put the link on there and noticed that i forgot to...BUT since we cant edit our posts(why not??) i was unable to..i thought i had until i read your post..here is the link.. :) enjoy!

trip to mars?

Apparently this is not a black hole, merely an object that exhibits some black-hole like properties. However, so far as I know, the formation of a black hole depends only on the volume to mass ratio being small enough. I assume that as one pushes matter together, even on the subatomic scale, there comes at point where the gravitational force will become dominant. Certainly this Black Hold FAQ answer seems to indicate that subatomic black holes are theoretically possible.

You are also correct to assume that Hawking Radiation does not happen in a true vacuum, i.e. a piece of space devoid of mass and energy. However, quantum physics suggests that there is no such thing as a true vacuum; on the subatomic scale, the fabric of space froths. Particle/anti-particle pairs are created from nothing. These virtual particles zip apart, then are pulled back together again and annihilate themselves. The total mass/energy gained through these interactions always remains at zero.

However, in my rough, layman's grasp of Hawking Radiation, this changes near the event horizon of a black hole. If one of a virtual particle pair crosses the event horizon, and the other does not, then a curious thing happens (at this point, my understanding of the process breaks down quite a bit). As far as I know, the virtual particles are created in a sort of quantum flux; because they haven't been observed, the particles have not 'decided' which of them is to be the anti-particle, and which is to be made of normal matter. The act of falling into a Black Hole makes a virtual particle into an anti-particle, and thus, the virtual particle outside the black hole becomes a piece of normal matter.

The overall effect is that a black hole gives off radiation, and shrinks due to small particles of antimatter passing through the event horizon.

Note that IANAP, and thus I am probably mostly wrong :)

I am no geologist, but I wonder too about the relationship here between Earth's magnetic field changes and the two recent high magnitude quakes. Yes I know that these quakes are linked to subduction zones of the major plates, but at the same time I am thinking about the rotation of earth's magnetic core. If there is a major flip of the field, can we assume it is purely associated with field changes, or might there be some physical turbulence at lower levels, which manifest as quakes.

How can we test this hypothesis? Simple. Do some comparitive measurements of magnetic field strength and direction at the two locations which experienced major quakes. I suspect there may be a correlation, and further predict major tremblors in the near future, linked to an acceleration of magentic field changes, especially ELF magnetic signals.

The following contains some links to mostly non-technical explanations of planetary roundness. I'd like to point out that part of this explanation, by "Derek Sears, professor of cosmochemistry at the University of Arkansas and editor of the journal Meteoritics and Planetary Science," is wrong. He says "Planets are round because their gravitational field acts as though it originates from the center of the body and pulls everything toward it." But this is a circular argument (pardon the pun). Generally a non-spherically symmetric distribution of matter doesn't have a gravitational field that acts as if it originates from the center of the body (the "center" being the center of mass). Spherically symmetric mass distributions do have this special property, so what Sears really implied is that planets that are already round will have gravitational fields that point towards the object's center of mass. This does absolutely nothing to address cases of objects that deviate from perfect roundness, i.e. all celestial bodies. This explanation by Dr. Sten Odenwald suffers from the same argument, and there's even a hint of it here. Nonetheless, these explanations are approximately true, and require bizarre shapes to break them.

For example, imagine a homogenous, perfectly shaped doughnut (a torus with a circular cross section). At the center of the doughnut hole we'd feel no gravitational field at all (a perfectly balanced tug-of-war). But deviate from the exact center just a tiny amount, and the closer side of the doughnut becomes more attractive than the other. One suddenly experiences a gravitational field that points away from the center of mass.

Did you see this when you posted?

<URL:http://example.com/> will auto-link a URL (underneath the Submit and Preview buttons)

So, with just five extra characters, http://www.astronomycafe.net/qadir/q525.html becomes http://www.astronomycafe.net/qadir/q525.html!

My point is that the one on March 31st was closer, it was pretty small, the one I remember was much much larger, and it wasn't spotted until days after it passed behind us.

1) quite possibly. Jury is still out.

2) No. Big bang is still the best bet and universe definitely appears to be finite (which doesn't mean there is a boundary or edge, just that it doesn't go on forever).

3) Yes, space curves back on itself. That is the only way to have a boundless finite universe.

References:

Physics 110 cosmology FAQ

No Edge, No Centre

Will better images ever show the edge of the universe?

How old is the universe? Finite or infinite? Have an edge?