Friday, March 16, 2007

Gravity of the situation hypothetically speaking

Last night I wondered as I always do about what earth would be like if the earth's core cools down? How would the cooling of magma affect life on earth? Would several if not all the species on earth get wiped out? Is it another doomsday scenario? If it is a doomsday scenario where is the movie on it? Turns out there is some movie called 'The Core' which is based on reversal of earth’s magnetic poles. Reversal? They can reverse?!? So I dug up an article on geomagnetic reversal which said that every 200,000 years or so the earth’s magnetic poles switch (Me: WTF?) although the last time it flipped was some 780,000 years ago. So it’s due in a “not in our lifetime” sort of near-distant future (nobody knows when exactly). But the scientists assure us that it’s not a big deal since humanity has survived the last reversal (as Borat would put it, that’s a relief…not!). Every time I discover a novel concept, writer, musician or artist and I get excited to share it with my friends I am greeted with, “yeah I already knew that”. Well why didn’t you ever mention it before then smartass? Party poopers!

But anyway, I will focus on the question I started with or it will turn into a 100 different tangents far from where we began like my thesis project. Since my knowledge of physics and geology is rudimentary at best, I asked a couple of enlightened souls to speculate. The speculation began with both my sources agreeing on one of the consequences being that the magnetic poles would cease to exist. In other words there would be no North Pole or South Pole magnetically speaking. So I began to wonder how that would impact life on earth. Being a biologist, the first thing that popped into my head was that the migratory birds would get screwed. Sinister possibilities like earth radiated and fried by cosmic rays did not pass my mind. I was busy thinking about life without working compasses and GPS based navigation system. I was still deducing the perils of living in a magnet-less society while my non-biologist sources had moved onto questions like would earth’s gravity be the same?

So no poles, what about gravity? What would be the impact of magma cooling on earth’s gravity? For occurrence of change in earth’s gravity, there has to be a change in mass because mass and gravity are somehow related (don’t ask me how but if you know how do tell).

When the magma cools there may be changes in its density. Which means that when the magma was in its hot liquid form, the molecules had more space to be in but as it cools and solidifies there are more molecules in lesser space (or less molecules in more space like ice?) hence the change in density (no. of molecules in a defined space). Phew!

So an important factor determining the density of the magma would be volume and there would be two scenarios available for the magma:
(1) Solid crust scenario: the earth’s crust is rigid enough to keep the volume available for magma expansion/condensation a constant.
(2) Elastic crust scenario: the magma will not be restricted by earth’s crust during the cooling process which means volume is not a constant.

We were not completely sure about which of these two scenarios are more likely to occur so we explored both.

The debate in the solid crust scenario was whether there would be a change in a mass (and therefore gravity) of the earth when the volume is a constant.
Caution: Equation ahead.
To address the possibility of a change in mass of the magma, the following equation comes in handy,
Density =Mass/Volume
Wow! I didn’t think I would ever need to refer to that equation after I graduated but here we are.
So, if the volume remains constant due to the earth’s restrictive crust and the density of the magma changes due to the cooling process, would the mass have to change to satisfy the equation? Would that change gravity? Does that equation even apply here? Even though the equation suggests there will be a change in mass, where is this change in mass of the earth coming from. In other words, we had ‘X’ amount of magma and ‘Y’ amount of crust, mantle and other stuff the earth is made of. After cooling we still have the same amount of mass. Unless now I will be directed to some complicated thermodynamics equation where the energy transfer needs to be factored in or some such jazz I will continue assuming thermodynamics will not be crashing this party.

Okay. So to continue on the “mass should not change” line of thought, one of the sources proposed a thought experiment. Imagine there is a closed glass container which is half filled with liquid. The glass does not expand/contract by the temperature of the liquid and it is suspended in nothingness like earth. While this analogy of a glass that does not expand or contract was being constructed to better understand the impact of magma cooling on earth’s mass, I went back to a memory of a physics class in school. The biggest turn off for me in physics was that the lessons started with some arbitrary assumptions for no apparent reason. It would begin with sentences like, ‘imagine a weightless, frictionless piston’. I would never get past this ‘imagine weightless frictionless piston’ line. First of all there is no such thing and secondly why are we imagining this imaginary piston? But before I could get past that thought the teacher would have moved on to some complex sleep inducing equation derivation which would comatose my interest completely. But here I was imagining imaginary glasses that don’t expand or contract according to the liquid in them. Anyhow, getting back to the magma story, the glass container would restrict the volume and the liquid would change density as it cools but the mass would remain the same (the closed container avoids loss of liquid by evaporation and there is no condensation on the exterior of the glass container as it is suspended in vacuum). But what about the air in the empty part of the glass or is that irrelevant? Sources had to get back to work so will ponder on this with me tomorrow.

Moving on to elastic crust scenario, the crust accommodates for the changes in volume as magma condenses. So the earth will end up shrinking (or expanding?) and this would result in a change in volume but not in mass. But there would be a change in the center of gravity perhaps? At this point one source wandered out trying to figure out how gravity is calculated. The remaining source concluded that we would no longer be walking perpendicular to the surface but rather at an angle…matrix style. Back problems anyone? Needless to say Kamasutra will be updated. The discussions about the disappearance of earth’s electromagnetic shield resulting in increased cosmic radiation, ozone depletion and such were left for another day as I wandered off imagining the various amusing sexual positions possible.

On a side note: I hope that this biologist’s venture into a physicist’s domain will be a frictionless ordeal.

6 comments:

Nobody said...

"To say Kamasutra will be updated."
Thats a good one !!!
May i guess who'll update the Kamasutra ??

Ambuj Saxena said...

Nice try. BTW, if are interested in more "End of the world" scenarios, you would find yourself addicted to Exit Mundi. You will get a lot to think about from that site.

Cruel Intentions said...

Would "V" and "G" Stil be around?

Crystal blur said...

Nobody,
I am not starting anymore series thats for sure :)

Hey Ambuj,
Thanks for the link. Will definitely rummage through.

Cruel,
Haha...lets leave that to our imagination ;)

cheti said...

well .. nice ramble and all ! Too many profound questions!

saw the movie core recently too ... the Solar Power generator that is created by soldering a bunch of torn out wires to something : BRILLIANT ;) !

another brick in the wall said...

wish i was a science student :(.. cud only understnd ths in parts :(