Just an observation that may open some discussion on just how fragile the earths condition is. When we look at the changes in seasons from winter to summer we know that this is caused by the angle of axis of the planet as it orbits the sun ( am I correct in say ing this). So in summer for the northen hemisphere the northern hemisphere is closer to the sun by let us say approximately half the earths radius in distance ( closer to the sun than in winter). When considering the distances to the sun in total this amount of change is so insignificant to the distance overall to the sun. So Earth radius = 6356ks Distance to sun equals 149,500,000ks Radius as a percentage of distance to sun = 0.0004251505% IF one assumes hypothetically the planets obit reduces, say, by the radius again. radius as a percentage of the distance to the sun would =0.0004251685% so to move the planet 6356 ks closer to the sun as happens with our seasons would see an overall change of 0.00000018% difference in the relationship with the overall distance. The observation is this. For a change of distance to the sun of less than .00000018% we see an increase in temperature of a hypothetical 25 degrees celsius .00000018% change in radial orbit = 25 degrees C. Assuming we move the planet only the radius distance again, only 6356ks closser to the sun. we would see a > 50 degree change in the average global temperature. I am sure someone out there can do the maths so much better I am absolutely hopeless at it is shown above. But the object of this post is that the gain in temperature by such a small amount of orbital change shows just how fradgile our existence on earth is. If the orbit where to change Just 0.00000018% either increase or decrease in distance (R) life would more or less cease to exist on this planet. Hypothetically. what do you think? Might be a good maths excersise to do it properly. I am assuming here for instance 1. that seasonal change requires a 6356 k difference. ( I know this figure is excessive) 2. That the heat from the sun can be linea in nature as one gets closer to the sun ( it may be more exponential)( this to is probably wrong) 3. That i am assuming stuff I have no idea about. I don't for a moment consider this observation to be new I am sure it has all been observed before.