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Large amount of mercury in space

  1. Jan 7, 2016 #1
    What happens to a large amount of mercury in space (that is to say, no gravity), assume room temperature. Because the mercury is dense and agile and offers more cohesive strength, will this mercury collapse on itself?
     
  2. jcsd
  3. Jan 7, 2016 #2

    Bystander

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    What is the vapor pressure of mercury at room T?
     
  4. Jan 7, 2016 #3
    Assume 20°c, ie 1.2mmhg
    If possible, assume any other favourable condition
     
  5. Jan 7, 2016 #4

    phinds

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    So, what do YOU think will happen, and why?
     
  6. Jan 7, 2016 #5
    Since mercury has a high surface tension and cohesiveness, due to its large density will there be any force from the surface to the centre
     
  7. Jan 7, 2016 #6

    phinds

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    This question makes it sound as though you are posing a question regarding a sphere of mercury. Your original question seemed to be asking about a more random distribution of mercury. Please clarify what you are asking. Exactly what are the starting conditions that you want considered?
     
  8. Jan 7, 2016 #7
    A sphere of liquid mercury, in zero gravity. Since there will be gravity at its centre, accompanied by surface tension and cohesiveness, will it collapse
     
  9. Jan 7, 2016 #8

    ZapperZ

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    Er... hang on. This appears to be a simple problem from "Gauss's law equivalent for gravitational field" from classical physics.

    If you have a sphere with uniform density, what is the gravitational force at the very center of the sphere? The inverse square law no longer applies inside the sphere!

    Zz.
     
  10. Jan 7, 2016 #9

    phinds

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    No, a sphere of mercury would have no reason to collapse, as it is hardly compressible at all. It will simply remain a sphere. I'm not sure about surface evaporation but the cold of space will have a much more immediate effect. The ball will freeze since the temperature of space is about 3 degrees absolute.
     
  11. Jan 7, 2016 #10
    So there won't be any force on the surface from its core?
     
  12. Jan 7, 2016 #11

    ZapperZ

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    Who says that?

    I pointed out your claim ".... gravity at its centre ... " is not necessarily correct.

    The force at any point is due to the sum of ALL the forces from a unit volume of the object. After all, you are on the surface of the earth and you are not floating in space with no gravity, are you?

    Zz.
     
  13. Jan 7, 2016 #12
    So the centre will exert some force on the surface and vice versa, How much small the sphere can get?
     
  14. Jan 7, 2016 #13
    Thank you, I'm talking about zero gravity and room temperature.
     
  15. Jan 7, 2016 #14

    ZapperZ

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    This is getting to be very puzzling. Why are you ignoring the repulsive forces between the Hg atoms? Why do you think it will "collapse" in zero g, but not when it is on the earth's surface? Why would you consider that Hg liquid will collapse, while water doesn't, especially when water has an added property of having a more pronounced surface tension?

    You have provided VERY little effort in elaborating the issues here.

    Zz.
     
  16. Jan 7, 2016 #15
    I'm new here, lot less experience,still learning stuffs zz. I'm saying if the mass is large enough the surface will excerpt some force won't it?
     
  17. Jan 7, 2016 #16
    Why mercury, is because of its density and cohesive property
     
  18. Jan 7, 2016 #17

    ZapperZ

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    You have explained nothing. What "cohesive property"? Why is this cohesive property that you are using not relevant when we have Hg on the earth's surface? Why hasn't it collapsed onto itself? Why do you think it will collapse onto itself in zero g?

    Water also has a cohesive property. The hydrogen bond and the weak polar properties of water all contribute to that! Why won't it collapse in space? After all, those astronauts have to drink!

    Zz.
     
  19. Jan 7, 2016 #18
    I'm sorry if I'm wrong or disturbing with silly questions. Mercury tends to stick to each other more than water does. So I wanted to know if a large amount mercury is kept in zero gravity (room temp), will it become a sphere? If it does due to its large density, will there be a high density core? Will there be Any force from the core to the surface? And it has a very less viscosity, will this help in any way to becoming a stable sphere? If so the centre is higher density so will it create a gravity and holds the sphere intact?
     
  20. Jan 7, 2016 #19
    Surface tension will hold it in close to a spherical shape. I assume the droplet is inside a spacecraft so that its vapor can saturate the air within the craft, and then it won't evaporate.

    Chet
     
  21. Jan 7, 2016 #20
    Any kind of substantial amount of matter in empty space will gradually pull itself gravitationally into a spheroidal shape, that's how planets form out of diffuse clouds of dust and gas.
    The spheroid will eventually reach a point where it has become dense enough that it cannot collapse further, but this no different for Hg than any other kind of substance.
    If your original ball of mercury is huge, about the size of the Sun I guess it might collapse further into a neutron star, but then so would a sphere of any stuff if it was massive enough.
     
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