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Pressure scales depending on size and super dense materials

  1. Nov 4, 2011 #1
    I could not decide where to post this, it concerns astronomy to a degree but my question mostly involves pressure which I assumed was a physics question mostly so I put it here.

    My question is that, if were actualy interested in designing a space suit that could survive crushing pressures, like at the core of the planet, or even worse, the core of a star like our sun (lets assume for arguments sake we already knew how to mitigate the heat and other things that would kill humans in this environment).

    Do we need a suit that is far more durable than planets themselves, at least in the suns example, wouldnt putting the Earth under the pressures at the suns core crush it? I am a little green on the subject but would a human beings size in the sun be under less or more pressure than something as large as the earth?

    I guess my real question really is not could a man survive in the sun depending on what protection he wore but does the objects size reduce or increase pressure it may feel at the suns core, would a smaller, more durable piece of metal or non yet discovered super dense material have more chance of surviving the pressures at the core of a planet or the sun than an actual planet would?

    Also, I will just clarfiy this is just a pressure question, I know theres more than just pressure at the core of said celestial bodies.

    Thank you for your time.
  2. jcsd
  3. Nov 4, 2011 #2


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    A balloon full of a gas would change a lot in volume when under pressure. A ball of the same size, made of a solid, would change a lot lot less. The amount that it would compress is determined by the 'modulus' of the material. The modulus is determined more by the molecular structure than just the density but the modulus changes as the pressure changes. There are a number of places on the web which you could browse on those topics.

    As for your 'thought experiment'. I think you would find it more useful to consider what happens at more modest high pressures - when materials still behave a bit like you might have expected to. (Even high stress in engineering design) Inside a Star is a real enough situation but not really somewhere where you could just consider pressure. A bit like love and marriage, extreme pressure and extreme temperature tend to go together in nature.
  4. Nov 4, 2011 #3
    I see, I read a bit about it and apprently iron is solid in the earths core ,despite the temperature that should make it more fluid thanks to pressure.

    My question is only relevent to these things because I am interested in knowing would it be harder assuming we had the materials to make things as pressure resistant to survive in such areas to make the Earth protected against the pressure in the core of a star or a human. Would it be easier or require less protection to protect the Earth or would the Earth be under more pressure than a human sized entity in a suit.

    Also, if we could make an object, or if for arguments sake if humans could survive under such pressure, would they also survive the heat? purely because the pressure itself would stop them from going to mush kind of like iron does not in the earths core?

    This is probably complicated, more so than I realise but I appreciate any input on these subjects. most of my interest comes from thought no matter how illogical on fictional characters who can survive the pressure of such but I wonder what else they would need other than just pressure resistance to survive in such climes. If a super human could survive the pressures in the sun, does that make it more durable under pressure than something as large or as dense as a planet like Earth, considering Earth would probably get crunched down.
  5. Nov 4, 2011 #4


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    Sounds like you're getting into the realms of SiFi here.
  6. Nov 4, 2011 #5
    Not really, its a theoretical question on whether or not pressures on a human being in the sun would be the same as those on a planet. Its probably got a pretty basic answer of "yes" or "no" because of reason X or Y.

    The example of suits and super men was a way of trying to get past the fact that its practically impossible for more ways than one. I am trying to understand how pressure may work specifcally on these two bodies.
  7. Nov 4, 2011 #6


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    The pressure on anything is the same at a given depth inside the Sun or under the ground here. Pressure is measured in Pa, which is Newtons per metre squared. Just by changing size, you can't affect the pressure; that's imposed by the medium you're immersed in. It's what we call an Intrinsic Quantity - it's independent of size.

    The problem with what you are wanting is that substances behave so differently when they are in those extreme conditions that they cease to be the substances we would recognise. For a start, Chemistry stops working. The electric forces that keep molecules together are too weak to support the structures.

    Even the strongest substances you can think of can be torn apart (in tension) with relatively modest forces. That's when the electric forces have been overcome. The sort of pressures you are talking about would have the same effect (in compression) but more so.

    Bottom line: is this a question about the basics of mechanics and materials and you are using the Sun scenario to help you understand or is it really about diving into the Sun?
    If it's a matter of basics then what I wrote above about pressure may be what you need.
  8. Nov 4, 2011 #7
    I see, yes this helps a lot. So the pressure is the same, regardless of size? so in theory, anything regardless of what it is, the planet earth, a human being, a piece of metal would be, the heat at the core of the sun or the planet earth aside be torn apart because its electric chemistry is overcome? Nothing in the universe should be able to actually survive the pressure in the sun then?

    So it has nothing to do with size of the object in these cirumstances? You see, I was under the impression that because its per meter squared, the force or pressure would be either more or less on less suface area such as a human body as opposed to a planet kinda like how if you push a drawring pin into a wall, its small point creates more press due to less surface area.

    I am using the sun because its core is the most extreme pressure I can actually think of that you can place the Earth in, and I need the Earth in my example because I want to compare differences of pressure from a planet to a human being but if I am right in the understanding of what you have said, the size is irrelevent here because the pressure breaks apart the electrons or something? its just not possible for the matter to remain solid?
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