Could Giants Be Real?

Discussion in 'Science and Nature' started by Oni~, Aug 24, 2015.

  1. If humans developed on a planet the size and gravity of Earth, and we attain the size we have, then is it not possible that a species developing on a far larger planet, with much higher gravity, would be gigantic in proportion to us, or even our largest dinosaurs? I am not saying because a planet is significantly larger, then ALL species on it must be accordingly larger. I am raising the possibility of a far larger planet producing far larger creatures in general.

    While Jupiter is ill suited for developing life as we know it, I am using it just for size comparison. Even as a mostly gaseous planet, its gravity is still around 2.4 times that of Earth. As such, would beings that are indigenous to such a world not have to be structurally far sturdier than us, or would a stronger gravitational pull suggest just the opposite, evolutionarily more favoring beings that weigh less? Consider that a planet that size that is not mostly gaseous like Jupiter, would have a far stronger gravity.

    If we consider the sheer size difference, and we already know there are far larger objects in just the known universe, then does it not seem plausible that lifeforms could be orders of magnitude larger than us?

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  2. I've always been one to think that in an infinite universe.. there very well could be an organism somewhere in the cosmos whose eye is the size of our moon. So there could very well be life out there that would be giants to us.. no doubt. Personally, I think the gravity of a planet is more dictated by not just its mass, but its speed of rotation. If there was a planet the size of Earth and spun faster, there would be a stronger gravity.. spun slower, a weaker gravity. So there could be a planet 100 times the mass of Earth, but spun 100,000 times slower and have a weaker gravity. With that, gravity might not even be the main factor in the general size of life on the planet. To me, I'd think life would be smaller on a planet with a stronger gravity.. more of a compression going on to where it would be easier for life to live small. With less gravity, bigger life in general. That is assuming the main factor in size is gravity. Something we can only speculate until we find different planets with different gravities with life on them.
     
  3. #4 Deleted member 839659, Aug 25, 2015
    Last edited: Aug 25, 2015
    gigantopithecus blacki


    sort of irrelevant but interesting nonetheless


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    edit:read OP and ^ is completely fucken irrelevant. my bad

     
  4. #5 Smoka-Cola, Aug 26, 2015
    Last edited by a moderator: Aug 26, 2015
    I just so happened to come across this same question on quora the other day! This person gives a great answer, I'll quote it here for you:


    Jay Wacker, Evolutionary Biology:
    Jay has 20+ answers in Planetary Science.

    There is a direct scaling with the largest possible animal and the strength of gravity. This has to do with the fact that the animal shouldn't break its own bones (or whatever structure they use to support themselves. [1]



    The relevant equation comes from realizing that when a force is applied to rigid body, it bends. In this case, the force is gravity and setting that equal to the restoring force of a rigid body gives

    mg=EAδL/L

    where E is Young's modulus, A is the cross sectional area, L is the length of the object and δL is the deflection of the material. Now the key thing is that the mass is proportional to volume since the densities of objects are not arbitrary

    m∝ρAL

    This means that the cross sectional area of the body cancels out. The body becomes stronger by being thicker, but it becomes more massive at the same rate. So we're left with

    ρgL∼EδL/L

    Young's modulus only vary over a relatively small range.



    Now we could try to construct what we think the best living form is, but let's just imagine that evolution has done a pretty good job of exploring the benefits of being large and small. So we can take the largest dinosaurs as being close to the upper end of what is possible on our planet [2].



    The Universe is a big and diverse place and we can't imagine the range of planets or forms of life that exist on them. However, that is the wonderful thing about physics -- it's the same everywhere regardless of the life or planet. The key thing is that most rigid body materials have relatively similar Young's moduli [3]. Young's moduli is being dictated by atomic physics, so you shouldn't expect it to vary hugely regardless of how weird the composition of extraterrestrial life is [4].



    Alternatively, you could imagine taking life on one planet and transplanting it to another, terraforming the new planet along the way, and the waiting a billion years and looking to see at the the range of sizes of living beings.



    All this discussion is just allowing us to see what effect the size of the planet and gravity has on the size of life, rather than focusing on other differences.



    The way we can address this is by taking the ratio of two similarly composed beings at the upper end of the size range for life on their respective planets and take them to have the same densities and Young's moduli. Almost everything drops out except for the sizes and gravity:

    g1L1g2L2=δL1/L1δL2/L2

    Now the amount of deflection for the two objects is going to be fixed before the objects breaks (before the material is no longer elastic). So the right hand side is 1 and we find

    g1L1=g2L2 .



    Assuming that dinosaurs were near the upper limit, we'd guess that if you went to a planet that had 10 times the gravity, the largest species would be 1/10th the size. Since dinosaurs were around 100m, on this new planet, the largest animals would be around 10m. Similarly, on a planet that was 1/10th the surface gravity, it would have life that could be 10 times larger with 1000m sized mobile, living beings.



    The gravity of a planet is given by

    g=GMR=4π3GρR2

    Most small planets have the same density, but once planets start to become the size of Earth, they start to become denser because the rocks at the center start to compress. Ignoring this change in densities

    R21L1=R22L2

    so that doubling the radius of the planet will lead to the maximal size of life being one quarter as big. Really, due to the density increase, the maximal size of life will shrink even more.



    Footnotes:

    [1] One possibility that this analysis does not take into account would be flat puddles on the ground. They'd be essentially 2 dimensional beings, unable to explore up. I think it's safe to say that we won't be having contact with beings of this form (their complexity would be greatly limited).



    [2] One piece of evidence for this is that dinosaurs had a to of bone breaks, and apparently had an amazing ability to heal themselves. As animals approach the upper end of the physical limits to size, their bones will break due to small additional forces, for instance, falling and at the extreme limit of size, big accelerations caused by motions like running will cause bone breakages.



    [3] This statement may seem strange to non-physicists because most fields are defined by understanding the difference between the subjects of study rather than the commonalities. So for instance, Young's modulus is always proportional to

    E∝Ry/r3B≃α5m4e(ℏc)3

    where Ry is the Rydberg constant and r_B is the Bohr radius and alpha is the fine structure constant, m_e is the electron mass and hbar and c are Planck's constant the speed of light. All the variation between different materials is in the pre-factor which is a basically geometry and is typically a factors a few and a factor of a 100 at most. That may be a lot to an engineer, but when considering all the varieties that can occur in the Universe, that's not a lot. This scaling tells us that 100 Giga-Pascals is the right scale for Young's modulus you will never find something 10000 GPa.



    Similarly for densities

    ρ≃α3mpm3eℏ3c

    where m_p is the proton mass. This is true regardless of the composition of the solid material. You can verify that water has a density of 1.0 g/cm^3 and iron has a density of 7.8 g/cm^3 -- only a factor of 8 going from a liquid made out of hydrogen and oxygen to a solid metal -- even lead is only 11.3 g/cm^3. There are a few heavy metals that get to 19 g/cm^3 and even 22 g/cm^3, but that's it. This scaling tells us that grams per cubic centimeter is the right scale for densities and you will never find something 100 g/cm^3.



    Since Young's modulus and the density are related to the speed of sound in a material, you find

    cs=Eρ−−√≃αmemp−−−√c

    for all solid materials. This tells us that 10 km/s is the right range for speeds of sound in materials -- you aren't going to find something that is 10,000 km/s.



    It's these types of universalities that lets us understand that, while the Universe is vast and complicated, there is a finite range of possibilities being dictated by the basic laws of physics.



    [4] As an example, human bones have a Young's modulus of 80GPa. Carbon nanotubes, one of the strongest materials known has a Young's modulus in the range 200-1000GPa -- only a factor of 3 to 10 larger -- in other words evolution has found pretty good material to build life out of. You might think that carbon nanotubes might have dramatically different densities than bon, but it has a density of 1.6g/cm^3 versus bone which is 1.8 g/cm^3. So you might get a factor of 3 to 10 variation in size due to compositional differences, but most likely you'll get closer to a factor of 2 differences."



    http://www.quora.com/Does-a-bigger-planet-command-bigger-sized-life-forms-Or-smaller-ones'>http://www.quora.com/Does-a-bigger-planet-command-bigger-sized-life-forms-Or-smaller-ones'>http://www.quora.com/Does-a-bigger-planet-command-bigger-sized-life-forms-Or-smaller-ones</a></a>
     
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  5. This is not the case. Gravitational force (at a given distance) is proportional to mass of the planet in question. That is all.
     
  6. It is, in my opinion quite likely that life forms on planets with different proportions to earth would have different scales. There is however a limit on this imposed by chemistry and physics.
     
  7. And mass increases with speed.. so mass and speed are proportional themselves, which means that the rate of travel of matter through spacetime affects it's mass which affects it's gravity.
     
  8. I don't think that's quite right

    But I'm no physicist

    -Yuri
     
  9. When you speed an object up, you are putting energy into it. That energy increases it's relativistic mass.. not it's rest mass. Thing is, energy itself creates gravity.. but being that mass is basically a ton of compressed energy, gravity created by energy often goes overlooked for gravity created by mass. The gravity increase might be next to unnoticeable.. but being that energy itself creates gravity, the gravity of an object will increase when you add energy to it.. and when you speed an object up you are adding energy to it.


    Now for a planet, when we look at it's mass.. the energy (that isn't part of it's mass) from it's movement through space is already factored in. It might be a minute fraction in comparison to it's gravity created by mass.. but it is there, already factored in. Now if we were able to find a planet where EVERYTHING was exactly the same as Earth.. like an alternate reality Earth, where it moved a lil faster through spacetime.. there would be a lil increase in the overall energy of alternate Earth and therefore have a lil increase of gravity. If you could travel there, you'd weigh a lil bit more.

     
  10. According to Einstein


    The mass m of a body is not constant.
    It varies with the body's velocity, according to the equation:
    m=m01−v2c2−−−−−−√where:
    v is the magnitude of the velocity of the bodyc is the speed of lightm0 is the rest mass of the body.
    The value m is known as the relativistic mass of the body.
    The factor 11−v2c2−−−−−−√ is known as the Lorentz Factor.
     
  11. I'm no expert.. in anything, so formulas aren't really my forte.. but think I have a gist of the concepts. Thing about relativistic and rest mass.. rest mass itself is relative. Like if you had an object sitting on a table.. you would say it is at rest, but in reality.. it isn't in terms of the cosmos. As it is sitting on the surface of Earth.. Earth is spinning at about 1,000 mph.. while traveling around the sun at 60,000 mph.. while the sun is moving around the center of the galaxy at about 500,000 mph. All that is technically already being factored in while the object is at rest on Earth.. same with a planet. When a planet is spinning and orbiting a star that is orbiting the galaxy.. all that movement is part of it's rest mass. It is a small percentage in comparison to the mass from the matter itself.. but it is part of it. If our solar system wasn't orbiting the center of the galaxy at 500,000 mph.. that would cut back the total velocity of Earth relative to the universe, which would decrease it's rest mass ever so slightly.. which would mean a slight decrease in our gravity.

    Anyway.. back on topic. I was thinking the other day about DNA and such. If life on another planet is say 3 times as big, I wonder what it's DNA would look like. I doubt the molecules themselves would be a different size.. but feel like something would be different. Then again.. the way DNA formed for us might be nothing like how it forms for other life.
     
  12. I have found zero concrete evidence to suggest they actually have found giant bones. There are many pictures, however a picture is not worth a thousand words on the internet.
     
  13. I think gravity plays a smaller role in size. Remember, giants once roamed earth in the form of dinosaurs and mammals.
    It's about available oxygen co2 etc and food.


    maybe all life supporting planets, when first colonized, go through stages. Micro to plant size, then to animals then massive animals. Then slowly everything shrinks.


    Just a guess.


    maybe in the future brains will learn to work with less and get smaller and smaller, which would be efficient.


    Imagine a 1 foot tall human looking up at a 6 foot tall cannabis plant.
     
  14. gravity certainly plays a role on our biological structure.

    for instance, if we were from a planet with much less of a gravitational pull than earth, we would be thinner, lighter, and possibly taller.

    gravity be trippin'

    🐜
     
  15. Ever hear of Bruce Depalma's spinning ball experiment? He did find slight gravitational anomolies between spinning and non-spinning ball bearings.
     
  16. I haven't, but I could see it. People like to talk about resting mass, but in reality.. nothing is at rest. You might have a ball bearing that isn't in movement to you, but in reality it is sitting on a planet that is spinning.. while circling the sun.. in a solar system that is moving around the center of the galaxy.. while that galaxy is cruising through space. Add a lil spin to it and you have it moving through spacetime a hair faster.. which will add energy to it, which will add mass, which will increase its gravity. Unless.. maybe the spinning action actually cancels out some of the movement that is already there? It's all crazy to think about.
     
  17. Yea it is odd, apparently in his experiment (fairly rudimentary) the spinning ball went higher, but also hit the ground sooner it was 18,000rpm btw.
     
  18. It would be interesting if he tried multiple angles or rotation to see if that had any effect.
     
  19. I'll have to check it out then.. the way I was imagining it, they would have one ball bearing at "rest" and then spin the other one on a solid surface. If they're throwing them both up in the air, I could see flaws in the experiment.
     

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