That makes practical sense, although approximations can sometimes result in
models that deviate significantly from reality. Remember when I used a
simplified mathematical model of a pendulum to design a perpetual motion
machine?
Harry
On Sat, Dec 3, 2016 at 6:28 PM, Stephen A. Lawrence wrote:
> Re: Lighter materials migrating to where the gravity is lower: It doesn't
> work that way. A pingpong ball on the surface has no way of knowing that
> 1000 miles down it would be lighter.
>
> What migrates up, and what migrates down, depends only on the local
> gravitational field, and the relative densities of the items in question.
> Locally, over the regions where convection is actually sorting things out,
> the strength of gravity can be considered to be constant.
>
> Convection, just like the buoyancy force, is due to differential pressure
> on the bottom and top of an object. When we're dealing with tiny objects,
> the differential pressure is due essentially entirely to the density of
> other "stuff" around the object, which results in increasing pressure with
> depth. Again, on the scales which are relevant to sorting molecules, fine
> particles, tiny bubbles, etc, gravity can be treated as constant.
>
>
> On 12/03/2016 11:21 AM, H LV wrote:
>
>
> Q: why don't lighter elements find there way to the centre of the Earth if
> gravity is lowest at the centre?
>
> Harry
>
>
> New study indicates Earth's inner core was formed 1 - 1.5 billion years ago
> October 7, 2015
> http://phys.org/news/2015-10-earth-core-billion-years.html
>
> On Sat, Dec 3, 2016 at 10:47 AM, H LV wrote:
>
>> Possible generation of heat from nuclear fusion in Earth’s inner core
>>
>> http://www.nature.com/articles/srep37740
>>
>> <> not yet been determined. Some research groups have proposed that the heat
>> is supplied by radioactive decay or by a nuclear georeactor. Here we
>> postulate that the generation of heat is the result of three-body nuclear
>> fusion of deuterons confined in hexagonal FeDx core-centre crystals>>
>>
>> Harry
>>
>
>
>