A Weighty Topic

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The other night I initiated a short debate with my niece by asking a simple question.  I’d like to pose this question for debate here on Writerbeat and then see how this might lead to a much weightier discussion.  The simple question was this:  How much do you think you would weigh at the center of the earth?

 

After agreeing to ignore such problems as how one might get there and avoid being incinerated by molten iron she decided that your weight would be so great that you would be crushed.  I acknowledged that her answer seemed obvious but that I thought you would actually be weightless.

 

My explanation was that weight is simply the attraction that mass has upon another object. At the center of the earth, all of the earth’s mass would be equidistant from you and any directional attraction would be cancelled out by an equivalent attraction from the exactly opposite direction.  All of this is predicated, for argument’s sake, that the earth is uniform in composition throughout.

 

The idea of being weightless at the center of the earth is hard to conceptualize, I believe, because we live on the surface where all of earth’s mass is either directly or radially below us.  All of our experiences and frames of reference are surface oriented.  If I tried to model this, for example, and created a 100 foot sphere of iron on earth’s surface I would be crushed at the center.

 

Now I will admit that I have no formal training in physics but my musings lead to a question that perhaps one of you on Writerbeat may be able to answer. Physicists know that the majority of a star’s fusion occurs at the core where the greatest pressures exist.  The pressures, apparently, are not caused by the cumulative weight of the outer parts of the star but by the incredible density of the core itself.  But what gives?  Wouldn’t the core itself experience equidistant opposing gravity?  If so then could this imply that the great pressures of continual nuclear fusion are held from normal rate expansion by the core’s tremendous density leading to further fusion in a feedback loop until all of the hydrogen is consumed?

 

This all hurts my brain but trying to understand what’s going on inside the beltway is worse.  Maybe I should try Keeping Up with the Kardashians.

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