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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. GoodGame

    GoodGame Red, White, & Blue, baby!

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    Pretty improbable to do more than very rough estimate.
    You'd have to mass all elements on Earth and then be able to tell the inorganic from the organic, and then you'd have to guess how much of the organic forms was actually in a species. It's easy to see how problematic it in considering organic waste molecules----are they part of biomass or are they already excreted into the environment. And then you'd need to actually measure the elemental composition, say by some spectral analysis that required minimal sample preparation.

    It'd be easier to due random samples of different biomes, figure the dominant species in each biome multiplied by the biome's prevalence and call it a day. It's easily a microbe, and probably a bacteria, that is the most prevalent in each biome.

    The top of list would probably be the most common topsoil bacteria, but then who knows about the oceans?



    Jesus, in the VelociRAPTURE!
     
  2. emzie

    emzie wicked witch of the North

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    Soil food webs are diverse, not really dominated by a single species of bacteria. While the total biomass of bacteria might be immense, a single species -- again, ignoring how hard it is to define species here -- is not going to be so.
     
  3. Veritass

    Veritass Chieftain

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    I was listening to a "Scientific American 60-second science" podcast this morning, and it talked about looking for signs of light on exoplanets by trying to find reflected light from the planet among the starlight from the associated star. They mentioned that light reflected from the planet would be polarized. They are examining the light that the Earth reflects to the moon.

    By what mechanism would light reflected from Earth be polarized? I would think that the light would be just as scattered as light emanating from the sun.

    See, for example, http://www.space.com/14645-alien-planets-atmospheres-scattered-light.html.
     
  4. uppi

    uppi Chieftain

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    I don't think that they are looking at scattered light, which should indeed have isotropic polarization. I guess they are looking at directly reflected light. That light is reflected because the atmosphere of the planet has a higher refractive index than the vacuum in space.

    If you take a look at the Fresnel formulas that are relevant in that case, you'll see that they depend on polarization if the incident light is not perpendicular to the surface. Especially interesting is the case when the light is shining on the surface at the Brewster angle: In that case the reflection of the polarization parallel to the plane of incidence drops to zero, while the polarization perpendicular to the plane of incidence is still partially reflected. So if you reflect unpolarized light at a surface with a real refractive index at the right angle, the reflected light will have perfect linear polarization.

    For the atmosphere of planets you have to generalize these formulas to deal with a gradient change in refractive index, but the principle is the same. So if you collect light that has been reflected from an atmosphere on an angle that is not perpendicular to it, the light will be polarized. If you can measure the angle where the light is maximally polarized, you could then calculate the refractive index of the atmosphere. If you then do that for different colors, you might get some information about the density and composition of the atmosphere.

    At least that is what I guess is the basic principle.
     
  5. PlutonianEmpire

    PlutonianEmpire Socially Awkward Goofball

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    I was Googling the Venus surface pics from Venera, and I noticed that you can see quite a ways away. How can that be, considering the air there is 100 times thicker than Earth's air at sea level?

    I was under the assumption it'd be like pea soup fog or something?
     
  6. emzie

    emzie wicked witch of the North

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    I think with fog, you're not seeing water in a gaseous state. Rather, you're seeing a bunch of tiny droplets of water that are diffusing the light.

    Carbon dioxide is just a bunch of molecules swimming in the air, so there's not much to absorb light, hence clearer pictures than what you might expect.
     
  7. Bluemofia

    Bluemofia F=ma

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    Also, keep in mind that CO2 doesn't really absorb or scatter much light in the visible. On Earth, the scattering of light is mostly due to the Nitrogen, and to a smaller extent, Oxygen. To get the same effect with Rayleigh scattering with CO2, you're going to need a significantly greater amount to compensate for the effective cross section of CO2 to visible light.
     
  8. Gigaz

    Gigaz civoholic

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    I have read somewhere that the cattle is the animal species with the highest total biomass and that sounds reasonable to me. But pines and spruce together cover huge parts of Canada and Russia so the species with the highest total biomass is propably one of them.
     
  9. r_rolo1

    r_rolo1 King of myself

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    Besides what contre and Bluemofia said ( none of the gases in the lower venusian atmosphere is a strong absorvent in the visible spectra ), I could point that the higher venusuian atmosphere is actually like you would expect ... but because of the sulfuric acid cloulds , that scatter light in the same way that our water clouds do ;) In fact you can see that direcly in the Venera images, that show the surface iluminated by a diffuse glow and without much of discernible shadows, the same effect you would have in a cloudy day in Earth
     
  10. PlutonianEmpire

    PlutonianEmpire Socially Awkward Goofball

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    Google has failed me. Can anyone find a complete list of EVERY celestial event that has happened in the last 30 years or so? (I mean, eclipses, transits, comet sightings, etc. No man-made stuff.)
     
  11. emzie

    emzie wicked witch of the North

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    Are we talking just Earth? Even that sounds like a tall order. I'd recommend compiling it yourself.

    Keep in mind that there's many comets visible every year, just rarely brilliantly so like Halley's or Hale-Bopp
     
  12. Bluemofia

    Bluemofia F=ma

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    "Celestial event" is kinda vague... What do you define as an event? Does an Io eruption count as an event? What about meteor impact on an object (On the Moon? Jupiter? Earth? etc.)? Does it have to have a minimum size for the meteor impact? Solar flares? CMEs? Gravitational microlensing events? Supernova events? Nova?

    Harvard's minor planet center site is actually a good starting place. They publish a lot of IAU catalogs for events and stuff.


    What about asteroid sightings/discoveries? Start searching. This will take a while. You've got comets in this list too.
    http://www.minorplanetcenter.net/ (General page)
    http://www.minorplanetcenter.net/iau/lists/CometLists.html (More specific comet list)

    If you just want bright comets:
    http://www.icq.eps.harvard.edu/brightest.html

    Transits are actually quite easy, because they only occur for Mercury and Venus:
    http://eclipse.gsfc.nasa.gov/transit/transit.html

    Eclipses there's a database for them because they're easy to predict, and spectacular enough for people to want to see/plan ahead to see (I planned to go to China in 2009 to see the eclipse in 2006; pity it rained on that day):
    http://eclipse.gsfc.nasa.gov/SEsearch/SEsearch.php

    Supernova list:
    http://www.cbat.eps.harvard.edu/lists/Supernovae.html

    Nova list:
    http://www.cbat.eps.harvard.edu/nova_list.html
     
  13. PlutonianEmpire

    PlutonianEmpire Socially Awkward Goofball

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    Actually, I was aiming for solar and lunar eclipses (the ones here on Earth, that is; cuz I know they happen elsewhere in the Solar system too :p ), major comet sightings, and objects transiting the sun (not just Venus. ;) ). :)

    Because I want to check the dates those happened and compare them with weather records so I can see for myself if my perception of "always missing out on these events as a result of clouds and other inclement weather" is accurate or not. :)
     
  14. _random_

    _random_ Jewel Runner

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    Why are objects in mirror so much closer than they appear?
     
  15. emzie

    emzie wicked witch of the North

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    As in the passenger-size mirror? I believe it's slightly concave (as opposed to the driver's side which is flat) and as such, it makes objects appear smaller. So in your driver's-side mirror an object 25 feet away looks X size, but in the passenger-side mirror, the same object at the same distance looks smaller. Your brain interprets that as further distance.
     
  16. Dreadnought

    Dreadnought Chieftain

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    For all you java programmers out there, I have a question.

    I've recently written a class involving a while(true) loop involving Thread.sleep. My emulator issued a heads-up to me, stating that I've used a Thread.sleep in a loop. Some googling has informed me that it may cause performance issues if I use a Thread.sleep during a loop. The program compiles and all; the emulator is merely introducing a tip to me that doesn't influence whether the program can run or not.

    My question is: is it truly a problem if I use a Thread.sleep in a loop? Or can I reasonably ignore this warning?
     
  17. PlutonianEmpire

    PlutonianEmpire Socially Awkward Goofball

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    I'm not sure, but I think that question might be better off put in the "Computer Questions" thread, here http://forums.civfanatics.com/showthread.php?t=337877 . :)
     
  18. Dreadnought

    Dreadnought Chieftain

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  19. PlutonianEmpire

    PlutonianEmpire Socially Awkward Goofball

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    You're welcome. :)
     
  20. PlutonianEmpire

    PlutonianEmpire Socially Awkward Goofball

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    New question:

    Let's say we have an asteroid in the main asteroid belt. It is rocky, and a diameter of 68.1162 kilometers. Now, a foreign object comes in. It is icy, and has a diameter of 46.84 kilometers. The icy object collides with the asteroid, coming in from the side, at an angle of 80 degrees. The distance between the two shrinks by 28.57 kilometers per second.

    The collision occurs 3.5893 AU from Earth. Would we be able to detect the collision?
     

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