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Science questions not worth a thread I: I'm a moron!

Discussion in 'Science & Technology' started by The Imp, May 4, 2010.

  1. SS-18 ICBM

    SS-18 ICBM Oscillator

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    3) Lots of material and a relatively stable environment compared to the inner solar system.

    4) Everywhere.
     
  2. peter grimes

    peter grimes ...

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    Is it possible to determine the purpose of an antenna just by the shape, or is it necessary to know the characteristics of the material and receiver as well?
     
  3. uppi

    uppi Deity

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    Material is not that important, but these days you can always compensate for bad antenna design by putting good electronics behind it. So I would guess that today the device that the antenna should fit into has greater influence on its shape than its purpose.
     
  4. Wrymouth3

    Wrymouth3 Emperor

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    In regards to the quantity of absorbed dose, what is the difference between "weighted absorbed dose" and just "absorbed dose?"
     
  5. Souron

    Souron The Dark Lord

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    Bigger antenna are needed for lower frequency, so AM radio and aerial TV needs a bigger antenna then your cellphone or FM. But a bigger antennae could also compensate for a weak signal (so putting a tv aerial on your cellphone will give you great reception ;)). What frequency is used for what kind of transmission is largely incidental and determined by the FCC and similar organizations in other countries. The allocation is largely arbitrary.

    Other than that, no. The only way to determine the purpose of an antenna is to examine the device using it. Material doesn't matter, except that it's gotta be a good conductor. Shape doesn't depend much on frequency either.
     
  6. Bluemofia

    Bluemofia F=ma

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    1) They do orbit the sun's equatorial plane. Angular momentum reasons when the nebula was collapsing into a disk makes planets form along the rotational plane of the disk, and the accretion forces the sun to rotate with the disk.

    2) Maybe not tend to, but they are much more randomly distributed, because of the comets forming in mostly random orbits which were not scattered out or deflected to moving in the same direction due to angular momentum.

    3) Ices were able to condense, allowing it to have sillicates and icy bodies to use the process of accretion, followed by acquiring large gaseous envelopes. Uranus and Neptune are more of a mystery because their locations should not be able to form such large planets, but they are believed to be planets which migrated outwards. The most probable theory actually had 5 gas giants formed in the solar system, but one of them was ejected, which caused Jupiter and Saturn to migrate inward a bit, and Uranus and Neptune to migrate outwards.

    4) Yes, everywhere. Late Heavy Bombardment was caused by Jupiter disrupting orbits in the asteroid belt (the common misconception that Jupiter absorbs the majority of asteroids is wrong, because of orbital energy arguments. The asteroids are more likely to be deflected on hyperbolic orbits, rather than captured or accreted because of the large distance away from Jupiter), causing lots and lots of Earth crossing asteroids. There is some inclination in their orbits because of interactions and deflections, so you get impacts everywhere on the Earth, poles, equator, etc.
     
  7. Berzerker

    Berzerker Deity

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    1) I was under the impression the planets are up to 7 degrees off the sun's equatorial plane

    3) and that the "freeze" line in the early solar system was the asteroid belt

    4) not where on the Earth's surface these impacts occurred, but where in the solar system - how far from the Sun. I imagine a massive collision would likely move the Earth's orbit closer to the Sun
     
  8. SouthernKing

    SouthernKing crickety cricket

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    1. It's only dwarf planets (Pluto, comets, etc,) that really do that, and that's because they formed differently from the 8 planets.

    4. It was pretty much just an inner system thing. and that's the thing; the LHB wasn't one massive impact, it was thousands of smaller ones, that impacted everywhere, so AFAIK it didn't affect earth's orbit too much.
     
  9. uppi

    uppi Deity

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    Absorbed dose is the energy absorbed per tissue mass, disregarding any differences in biological effect. Some types of radiation are more dangerous than others, so they get assigned a weight factor (e.g. beta rays have a weight of 1, alpha rays a weight of 20). The weighted absorbed dose is the supposed to tell how much biological damage has been done (on average).

    So for beta rays 1mGy (= 1 mJ/kg) absorbed dose becomes 1mSv weighted absorbed dose, which would be of no concern for a singular event, but for alpha rays the same absorbed dose would become 20mSv weighted absorbed dose, which is already maximum dosage according to some radiation safety standards.
     
  10. PlutonianEmpire

    PlutonianEmpire Socially Awkward Goofball

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    I think I recall that the nearest star with GRB (gamma ray burst) potential that could affect Earth is about 7, 8 thousand light years away, or something. Which star is that? On a related note, how wide, in degrees, is a grb in general, if looking at it while at the ill-fated star? And from the nearby star inquired about in the first sentence, would the GRB be wide enough to affect the whole solar system or any nearby stars?
     
  11. SouthernKing

    SouthernKing crickety cricket

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    You're thinking of Eta Carinae (sp?), I can't say about the rest.
     
  12. Bluemofia

    Bluemofia F=ma

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    1) That is basically in the same equatorial plane. 7 degrees is miniscule.

    3) Probably not actually. There aren't so many ice asteroids in the asteroid belt. Those are mostly rocky and stony asteroids, with a few metallic ones. The ices would have condensed a bit further out. But it's hard to say, because the primordial populations are long since destroyed.

    4) The energies invoved? Miniscule really. The only way to noticibly move the Earth closer to the sun is by throwing stuff in retrograde orbital motions to cancel out angular momentum. As stated earlier, that is not happening often because of collapsing nebula making everything orbit in generally the same direction. Adding mass to the Earth that is orbiting in the same general direction as Earth will not modify its orbit much.

    Also, LHB was everywhere in the solar system. It is Jupiter throwing all of the asteroids into the sun, or out of the solar system. So everything was hit. And everything is either interior, at, or exterior to the asteroid belt. XP
     
  13. PlutonianEmpire

    PlutonianEmpire Socially Awkward Goofball

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    Well, I know it will produce GRB's, I was under the assumption it's poles pointed elsewhere and a different, slightly nearer star might be aiming at us.

    And yes, Eta Carinae is spelled correctly, I believe. :)
     
  14. Saxony

    Saxony Chieftain

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    How do gravity assists work?
    What are Larangian points(L1, L2)
    What would happen if you are in a land vehicle moving with the same speed as the Earth's rotation around its own axis but in the opposite direction? (West to East)
     
  15. peter grimes

    peter grimes ...

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    In the yard nextdoor to my old apartment there was a very curious parabolic antenna. It was aimed, as near as I could tell, directly at the UN across the east river. There was what looked to be a coaxial cable running up to the collector / receiver. I had always wondered what it might be. Too bad I don't live there anymore, but I might try and get a better photo if I visit my old neighbor:



    EDIT: here's a google map:
    http://maps.google.com/maps/ms?ie=UTF&msa=0&msid=216018913917290721342.0004dfab2f40c41062dbc [you might need to zoom out before the location of the antenna is visible]
     
  16. SS-18 ICBM

    SS-18 ICBM Oscillator

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    Well, it's definitely not for satellite TV or anything like that. You'd have to point south towards geostationary satellites over the equator for that.
     
  17. SouthernKing

    SouthernKing crickety cricket

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    Lagrange points are where the gravitational fields of two objects cancel each other out, so that an object placed there will remain there. There's five of them, here's a diagram
     
  18. peter grimes

    peter grimes ...

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    The "dish" is some sort of metal, I'm guessing Al, and it's been spray painted - the photo is too poor to show the way the paint is wearing off. It's definitely a home-made sort of thing. The mast, if I remember correctly, looks totally jury-rigged. You can see some of the wire stays that are slack. It's a very curious arrangement.
     
  19. Cutlass

    Cutlass The Man Who Wasn't There.

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    Why hasn't artificial rubber caught up to natural rubber in chemical properties, such that it could fully take over and make rubber tree plantations obsolete?
     
  20. madviking

    madviking north american scum

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    Link to video.

    it would fall into the ocean, eventually.
     

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