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physics question

Discussion in 'science, nature and environment' started by DotCommunist, Dec 18, 2017.

  1. Signal 11

    Signal 11 Ich bin maroon!

    Black holes are made of actual matter (most commonly collapsed stars).

    The strength of gravity depends on how much matter there is and how close to the centre of it you are (without being inside it). A black hole is where there's a distance outside of it where the gravity is strong enough to prevent light escaping. i.e. you need enough matter squashed into a small enough space.

    To make the Sun into a black hole you'd have to squash it down to a few km diameter, but at the Earth's distance its gravity would be the same strength as it is now.
     
  2. 2hats

    2hats

    Neptune and/or Uranus but most likely (if at all) a diamond shell around the core. Quite possibly they experience a fine diamond rain (experiments suggest).
     
    kabbes likes this.
  3. NoXion

    NoXion Give me space communism or give me death

    I'm pretty sure that's not been established with any certainty. I think it would be more accurate to say that black holes form from actual matter. The mathematics we've got (GR and QM) for describing the interiors of black holes don't play nice with each other and result in infinities, which strike me as unphysical. Our models aren't complete enough to say what black holes are really made of.
     
    moon likes this.
  4. Signal 11

    Signal 11 Ich bin maroon!

  5. moon

    moon Happy Happy Jo Wonderland

    I'm calling it negative space for now...
    I have another slightly related question.
    Is there much evidence of seed germination and subsequent healthy plant growth in space? For example on a space station.
    The key thing here is healthy germination.
     
  6. NoXion

    NoXion Give me space communism or give me death

    How about this:

    Plants Grow Fine Without Gravity
     
  7. moon

    moon Happy Happy Jo Wonderland

    It only talks about roots...
    I have seen no evidence of shoots.. I even read somewhere that they have only just managed to get lamps for growing plants onto the space station, and claimed to have conducted ALL previous plant growth experiments in the dark..
     
  8. Signal 11

    Signal 11 Ich bin maroon!

  9. moon

    moon Happy Happy Jo Wonderland

    Firstly the image on the header of that webpage is CGI, also why did they use red leaved lettuce and not green?
    I still can't see any evidence of healthy germination, the guy in the video (from 'Veggie') even said that the plants were delivered to them, I am assuming pre grown.
     
  10. Signal 11

    Signal 11 Ich bin maroon!

  11. NoXion

    NoXion Give me space communism or give me death

    You can't get roots without first germinating seeds. Do you really think that NASA would not actually try germinating seeds in orbit? Seems like a massive and obvious oversight for a scientific organisation with the mission of investigating how to support human life in space.

    Is this image real enough for you?

    [​IMG]

    Why does the colour of the lettuce matter?

    As for evidence of germination, did you not see the little pads in the video? Why do you assume pre-grown? Here's another NASA video where they talk about sending seeds up to the ISS:



    "We've done it a couple of ways but the easiest way, the most effective way to do plant growth on the International Space Station is quite naturally to send seeds. Seeds are the dormant life storage form of plants" - Dr Rob Ferl, Co-Principle Investigator, Advanced Plant Experiment (APEX) - 03

    As for whether that germination is healthy, that depends on how strict your definition of healthy is. See the results plainly in the above picture and judge for yourself. Looks alright to me; I've been served worse here on Earth.
     
    Signal 11 likes this.
  12. Signal 11

    Signal 11 Ich bin maroon!

    They're probably just negative plants though.
     
    moon likes this.
  13. moon

    moon Happy Happy Jo Wonderland

    NoXion roots emerge first in germination, followed by shoots.
    I'm interested in protein assembly, folding and tertiary structures in zero gravity environments, specifically the proteins involved in photosynthesis.
     
  14. NoXion

    NoXion Give me space communism or give me death

    Still, the fact that seeds can produce roots at all, let alone produce reasonably healthy looking plants, would seem to be a good indicator of the viability of growing plants in free-fall conditions. This means that in any future long-duration mission, the vehicle's designers will likely not need to devote room on any rotating sections of it. This would mean a simpler design as the rotating section can be smaller.

    I wouldn't have thought that free-fall conditions would have much impact down to the scale of protein molecules - gravity doesn't mean much to objects so small that even water is like jelly. Nevertheless, I had a quick look and found this:

    Along with the results from studies of root structure development in free-fall previously mentioned, it seems that plants are not reliant on gravity to ensure the functional development of their microscopic structures.
     
  15. moon

    moon Happy Happy Jo Wonderland

    But I'm not talking about microscopic structures, I'm talking about the components of the photosynthetic processess by which energy is generated from light.

    It involves a protein cascade yes? Where the protein changes both chemically and structurally becoming more folded in its tertiary form and emitting energy along the cascade?
    I was wondering how or if this was affected by gravity.
     
  16. NoXion

    NoXion Give me space communism or give me death

    If microscopic structures like chloroplasts are not significantly affected by free-fall conditions, then it hardly seems likely that the proteins essential to their functions would be.
     
  17. moon

    moon Happy Happy Jo Wonderland

    Nullius in verba...

    The reason i was asking about germination in space was to be sure that no precursor or 'template' proteins involved in photosynthetic energy transfer were present in the plant prior to them being shipped to the space station.
    I queried the red lettuce used onboard the space station as the red pigments could have masked any chlorophyll deficiencies etc..
     
  18. NoXion

    NoXion Give me space communism or give me death

    Well here's a video about the first lettuce harvest:



    So if you don't want to take their word for it, you can see the lettuce leaves in more ordinary lighting, rather than that weird fuchsia lighting they've got going on when actually growing the plants.
     
    moon likes this.
  19. moon

    moon Happy Happy Jo Wonderland

    That still doesn't explain why they used red lettuce..
     
  20. Signal 11

    Signal 11 Ich bin maroon!

    They've grown red lettuce amongst other things, as you've been shown.
     
  21. squirrelp

    squirrelp Well-Known Member

    Are they? That's a bit like saying I am made of sausages.
     
  22. Signal 11

    Signal 11 Ich bin maroon!

    Yes they are. I don't know whether you're made of sausages.
     
    squirrelp likes this.
  23. DotCommunist

    DotCommunist my world is fire and blood

    you'd smell like cooking pork if you burned, so maybe in a way you are made of sausage
     
  24. squirrelp

    squirrelp Well-Known Member

    "In a meaningful sense, a black hole is its event horizon, since we can’t observe anything inside it by any method. The interior is nature’s biggest secret, enshrouded by a barrier that lets everything in but nothing out."
     
  25. Signal 11

    Signal 11 Ich bin maroon!

    Yes, that prevents us being sure what state the matter is in.
     
  26. squirrelp

    squirrelp Well-Known Member

    To put another way: if you imagine the universe had a boundary, an 'edge' which you fell off to oblivion so to speak - well that's much like a black hole. I don't really think it makes sense to say a black hole is comprised of anything. It is entirely defined by things outside it. Everything that 'matters' in the universe is outside a black hole.
     
  27. Signal 11

    Signal 11 Ich bin maroon!

    It has mass because it is comprised of matter.
     
  28. moon

    moon Happy Happy Jo Wonderland

    The thing is, you can put a plant in the dark and it will still grow, some of the 'green' plants they've shown look seriously etiolated..
    Maybe the red lettuce looks healthier because the red pigments gather energy via a different metabolic pathway to chlorophyll??

    They even used genetically engineered Arabidopsis that glows green in the dark onboard the space station.
     
  29. squirrelp

    squirrelp Well-Known Member

    I don't accept this. It has mass because it exerts a gravitational pull to the outside. I don't see that it makes any sense to say that it is comprised of anything. I don't think you could say that time or space exist on the inside. I don't know even if you could say they have an inside.
     
  30. Signal 11

    Signal 11 Ich bin maroon!

    That's another one to add to the list then.

    No, it's the other way round.
     

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