Suppose the orbit of the earth were 5% Smaller (a = 0.95) than it is today (a = 1.0). What would be different?

We'd be closer to the sun so warmer temperatures is my best guess.

We wouldn't have a 3rd ice age. Darn, I really wanted one of thoughs. LOL

Kriscool

Yep that's about it, warmer temperature and shorter years. More UV radiation would make sunbathing more dangerous :)

It sounds like a alien plot to wipe out all life on earth by changing its orbit.

But most likely the heat and radiatin would make life not possible, also since all the other planets are also in relationship to each other it is possible that the entire solar system would be effected.

It would probably make us more susceptible to a runaway greenhouse effect like that on Venus. But I doubt it would affect the other planets that much; the Sun is far and away the dominant player in our Solar System's planetary orbits.

We would all have dark skin and wear sunglasses.
If we were closer, we would probably be moving faster, and length of day would probably
Be shorter. Probably loose some days in our calender.
We would get older, faster. Relativey speaking.

I disagree with the length of day, I think that would be longer.

Moving the earth 5% closer to the sun would reduce the length of time in a year by about 8.4% (Kepler's law says that the square of the period of revolution is inversely proportional to the cube of the radius of the orbit). So that would mean that we'd have birthdays more often, and so we'd be 8.4% older in terms of years than we are now.:rolleyes: