Re: How do we know that the inner core of the Earth is hot?

We suspect that the core of the Earth is hot based on indirect evidence.  
This is so because no one has ever been deep into the earth.   Even deep 
drilling has only gone down a number of miles (probably less than 10).  I 
personally found out one form of evidence when I went into a deep mine in 
Montana....    down to the 5,000 foot level where the wall rock in the mine 
was 150 degrees hot!   Deep drilling and deep mines tell us that the earth 
gets hotter, the deeper you go.   There are other types of indirect 
information that tell us about the interior of the Earth.   Some of them 
are:

   - Measurement of seismic waves from earthquakes and how the shock waves 
     travel through the Earth.  These mearsurements suggest that the Earth 
     has a liquid core of very dense materials.   It is believed that below 
     very hot rocks, the core of the earth is made up of liquid iron and 
     other liquid metals.

   - Studies by astronomers of the way that the Earth travels in its orbit 
     around the Sun and how it rotates on its axis.  These studies show    
     that the Earth is very dense.

For more interesting information on this subject, try the following web 
site:


Earth's Formation