Funny you say this..
From a BBC Article in 2005
Why the Sun seems to be ‘dimming’
We are all seeing rather less of the Sun, according to scientists who have been looking at five decades of sunlight measurements.
They have reached the disturbing conclusion that the amount of solar energy reaching the Earth’s surface has been gradually falling.
Paradoxically, the decline in sunlight may mean that global warming is a far greater threat to society than previously thought.
The effect was first spotted by Gerry Stanhill, an English scientist working in Israel.
Cloud changes
Comparing Israeli sunlight records from the 1950s with current ones, Dr Stanhill was astonished to find a large fall in solar radiation.
“There was a staggering 22% drop in the sunlight, and that really amazed me.” Intrigued, he searched records from all around the world, and found the same story almost everywhere he looked.
Sunlight was falling by 10% over the USA, nearly 30% in parts of the former Soviet Union, and even by 16% in parts of the British Isles.
http://news.bbc.co.uk/2/hi/science/nature/4171591.stm
The total amount of sunlight reaching our planet must be diminishing slightly every day, because ... “A trillion comets orbit the sun. The gravel that surrounds them appears, should it hit our atmosphere, as a shower of meteors. The Earth gains a ton in weight every hour from their dust.”
My thought is that the added mass continuously increases the Earth’s relative distance from the sun.
Quote is from page 218 of “Darwin’s Ghost” by Steve Jones.
Then too, the sun’s mass must be continually decreasing because the sun is releasing energy and ... E = MC^2
And that decrease in Sun’s mass would also result in an increasing distance between sun and Earth.
Another factor about light and distance is that the intensity of light from a stable source varies inversely with the distance between the emitting and receiving objects.
In other words, if another planet like Earth orbibted the Sun at twice the distance between Sun and Earth, that planet would receive sunlight at 25% — one fourth — the intensity received by Earth.