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.
Do you have a link to a proof of this? I know that this is not the case for a point inside a hollow spherical shell. At the center there's no field at all as you describe. As you move away from the center you are closer to the side of the sphere you experience a greater attractive force to that side, BUT there is now more mass "behind" you, i.e. a greater fraction of the sphere. The two effects cancel out perfectly so that there is no gravitational field ANYWHERE inside a sphere.
Is the torus different? If so, why? Do the integrations just work out differently that way?
Not that favourable. Radiation from Jupiter's equivalent of the Van Allen belts gives a dose of about 600 Rem/day on Europa (a certain lethal dose for a human). Admittedly it's a far cry from the 45000Rem/hour a spacecraft would catch orbiting in the middle of the Jovian magnetosphere, and perhaps simple life could handle a few rays.
Heavy oils on Earth are generally created by chemical processes acting on dead microorganisms over geological time. The "oil" on Titan is hardly oil at all, it's light short-chain hydrocarbons such as methane (CH4), ethane (C2CH6) and propane (C3CH8) which would be gases on Earth. These are much easier to form "abiotically", i.e. without life. In face the gas giant outer planets Uranus and Neptune have large amounts of methane in their atmospheres.
(IANAAstronomer)
That is true, but more to the point antiprotons much much harder to store since they lack net charge and therefore you can't use electric or magnetic fields to keep them away from the walls of your vacuum chamber.
If you split the hydrogen out of water and then burn it, no, you won't get much energy.
I'm sure you already know this, but to clarify: Not only will you not get much energy, you will lose energy. The energy released in burning a molecule of H2 in O2 is the same as that used to split one molecule of water. Thermodynamics says you can't even recover all of it.
Often, geeks are they only people qualified to decise whether something should be built. Witness the recent retardedness in the UK about nanotechnology after Prince Charles said a bunch of bullshit about it.
I think your lander point is totally false -when did they examine landers that had been there for YEARS? Astronauts have never returned to any lunar landing sights so how would they know? In any event the landers were protected from the heat of take-off inside the launch vehicle and they never went through reentry.
Apollo 12 landed within walking distance of the Surveyor 3 probe, which had touched down 2.5 years earlier. this page has more details - although you are right about the bacteria not having to survive reentry.
I don't think that's necessarily true... This explanation makes sense - the water does expand at freezing point, but contracts again as it continues to get colder. Unless it's a particularly sunny part of the antarctic, I think it would be cold enough that the whole lot could freeze. I'd put my bets on geothermal.
It didn't fly -through- the rings, rather through the gaps between them (which still have some crap in, but not really a huge amount of it). Also I think that it doesn't necessarily matter too much if the dish gets a few tiny holes - it should still behave the same, electrically.
Next to an incandescent lightbulb? wow... I can see you getting something from a fluorescent bulb, but I'd be surprised at lighting a normal filament lamp.
There isn't an awful lot of RF coming out of a cellphone - 1W at the very most. That isn't enough to cause significant heating effects, and is not a health risk as numerous studies have shown.
The reason it interferes with a hearing aid is the same reason it interferes with some speakers: The amplifier in the hearing aid picks up a small amount of noise and amplifies it by 80dB or so!
Re:First things first
on
GPS on Mars?
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· Score: 1
The short horizon isn't an advantage for towers, it's a disadvantage. You'd need to build them much taller to cover the same area. Of course when gravity is barely 1/6 of Earth normal, perhaps that isn't so hard.
Slashdot Mirror
Thanks for the link. Very interesting.
Do you have a link to a proof of this? I know that this is not the case for a point inside a hollow spherical shell. At the center there's no field at all as you describe. As you move away from the center you are closer to the side of the sphere you experience a greater attractive force to that side, BUT there is now more mass "behind" you, i.e. a greater fraction of the sphere. The two effects cancel out perfectly so that there is no gravitational field ANYWHERE inside a sphere.
Is the torus different? If so, why? Do the integrations just work out differently that way?
Cheers
Henry
Question from the ignorant: what is a left handed cigarette? A cannabis joint?
15 minutes? More like 25 seconds!
Could you tell me which story that is? I'd like to read it :)
How not to test a magnetron...
Not that favourable. Radiation from Jupiter's equivalent of the Van Allen belts gives a dose of about 600 Rem/day on Europa (a certain lethal dose for a human). Admittedly it's a far cry from the 45000Rem/hour a spacecraft would catch orbiting in the middle of the Jovian magnetosphere, and perhaps simple life could handle a few rays.
Those molecular formulae should be CH4, C2H6 and C3H8 respectively. Improper backspacing, sorry.
Heavy oils on Earth are generally created by chemical processes acting on dead microorganisms over geological time. The "oil" on Titan is hardly oil at all, it's light short-chain hydrocarbons such as methane (CH4), ethane (C2CH6) and propane (C3CH8) which would be gases on Earth. These are much easier to form "abiotically", i.e. without life. In face the gas giant outer planets Uranus and Neptune have large amounts of methane in their atmospheres. (IANAAstronomer)
That is true, but more to the point antiprotons much much harder to store since they lack net charge and therefore you can't use electric or magnetic fields to keep them away from the walls of your vacuum chamber.
I'm sure you already know this, but to clarify: Not only will you not get much energy, you will lose energy. The energy released in burning a molecule of H2 in O2 is the same as that used to split one molecule of water. Thermodynamics says you can't even recover all of it.
Bullshit. Prime numbers, Fibonacci sequences - any alien capable of communicating would know and understand them. Maths is universal.
I have one and can confirm that's exactly what it is.
If they can figure out how to play their format on the iPod, I say more power to them.
Sort of - the plane has to maintain some power because of air resistance in order to keep a proper parabolic path.
:D
No. Tesla was not a magician, just a good physicist and engineer with some incorrect ideas.
Often, geeks are they only people qualified to decise whether something should be built. Witness the recent retardedness in the UK about nanotechnology after Prince Charles said a bunch of bullshit about it.
Apollo 12 landed within walking distance of the Surveyor 3 probe, which had touched down 2.5 years earlier. this page has more details - although you are right about the bacteria not having to survive reentry.
I don't think that's necessarily true... This explanation makes sense - the water does expand at freezing point, but contracts again as it continues to get colder. Unless it's a particularly sunny part of the antarctic, I think it would be cold enough that the whole lot could freeze. I'd put my bets on geothermal.
It didn't fly -through- the rings, rather through the gaps between them (which still have some crap in, but not really a huge amount of it). Also I think that it doesn't necessarily matter too much if the dish gets a few tiny holes - it should still behave the same, electrically.
Next to an incandescent lightbulb? wow... I can see you getting something from a fluorescent bulb, but I'd be surprised at lighting a normal filament lamp.
The reason it interferes with a hearing aid is the same reason it interferes with some speakers: The amplifier in the hearing aid picks up a small amount of noise and amplifies it by 80dB or so!
The short horizon isn't an advantage for towers, it's a disadvantage. You'd need to build them much taller to cover the same area. Of course when gravity is barely 1/6 of Earth normal, perhaps that isn't so hard.