>Hi Hilmar,
>
>Do we yet know where the earth is going, or from where it came. I suppose we know
>at what speed it is traveling. I can't think of any reference point we can look to
>for judging these thing. Everything seem to be moving, and the most we can tell is
>that the defined universe seem to be expanding.
>
>Light only has one speed, which is very fast, approxiamtely 186000 miles per second
>This could be used to determine at what speed earth is moving through space. How do
>we judge the distance of star far away from earth. Since straight lines and circles
>may not be exact and a star 300 millian light year away from earth would make
>trianglation unusable, since we could not form a base of a triangle with enough
>distrance between two point to provide the angles needed.
>
>Is earth moving in a straight line as it travel through space. Earth revolves 360
>degrees on its axis once each day. Earth also revolves once around the sun
>approximately once every 365.25 days. Our solar system may be revolving around
>some other object. The entire galacy may also be revolving around yet something else.
>Earth may well be moving in a circle within another circle.
>
>It make me feel a little powerless to consider that we are moving through space
>at some high rate of speed, not sure of either our point of origin or our point
>of destination, yet if someone asked if I had moved within the last fifteen minute,
>I would answer no.

Leland;

My background is electronics engineering, history and political science. Since I was ten I have enjoyed reading everything I could on astronomy and related subjects. I also took everything I could in college related to this topic. For fifteen years I was an engineer and worked as a Metrologist. Metrology is the “Science of Measurement”. We worked with any physical object and measured such things as transition time of an electron from one orbit to another, and time to 2 parts in 10 to the minus 12th.

The speed of light is different and dependent upon the medium. To give you an idea of what this means here are some values.

speed of light in a vacuum 	        299 792 458 m/s 
speed of light in air    	        299 702 547 m/s 
speed of light in ice 	                228 849 204 m/s 
speed of light in water 	        225 407 863 m/s 

As was noted by someone I believe it was Hilmar, the earth is slowing down. However to compensate for this we agree internationally to redefine the definition of the second. This sometimes occurs each year and sometimes there is no change. Our instrumentation and ability to measure constantly improves. Mathematically, someday the earth will stop rotating and then…

By the way the Mayan Civilization had a more accurate definition of the length of a solar year that Europe did at the same time. The Mayan also used base20.

The Mayan solar year is equal to 365.242036 days, which is slightly more accurate than the 365.2425 days of the Gregorian calendar.


Tom