Samuel Chiltern answered
The distance between the Earth and the Sun is not a constant - in the course of a full rotation around the Sun, the distance varies by about 3 million miles.
So, in short, if the Earth were to move just one mile closer to the Sun, the difference would be negligible. However, your question raises some interesting points which I'll discuss in the rest of my answer.
The Earth, and the Goldilocks Zone
When scientists began searching for life in the rest of the solar system, they started by looking at the other terrestrial planets.
All they could see were worlds that were either too hot (Mercury, Venus), or too cold (Mars). Earth was in the middle, and as luck would have it, it was just right to support life as we know it. This is where the term Goldilocks zone came from, (referring to the children's story of the same name).
This early research suggested that the Goldilocks zone was remarkably small, and that not even the whole of the Earth fell within it - as, high up, the atmosphere became too thin to support life, and species could only survive a short distance underground, too.
However, recent discoveries have uncovered new species that are capable of surviving in far more extreme environments that had previously been thought possible. For example, we now know that microbes can survive in acids, boiling water and even nuclear reactors.
Given what we now understand, scientists are approaching the search for extra-terrestrial life in a new light, since it now seems much more likely that primitive life could survive elsewhere in the universe too.
Furthermore, it seems likely that some forms of life would survive, even if the Earth were to move substantially closer to the Sun - although sadly, in this event, we ourselves would probably perish.
So, in short, if the Earth were to move just one mile closer to the Sun, the difference would be negligible. However, your question raises some interesting points which I'll discuss in the rest of my answer.
The Earth, and the Goldilocks Zone
When scientists began searching for life in the rest of the solar system, they started by looking at the other terrestrial planets.
All they could see were worlds that were either too hot (Mercury, Venus), or too cold (Mars). Earth was in the middle, and as luck would have it, it was just right to support life as we know it. This is where the term Goldilocks zone came from, (referring to the children's story of the same name).
This early research suggested that the Goldilocks zone was remarkably small, and that not even the whole of the Earth fell within it - as, high up, the atmosphere became too thin to support life, and species could only survive a short distance underground, too.
However, recent discoveries have uncovered new species that are capable of surviving in far more extreme environments that had previously been thought possible. For example, we now know that microbes can survive in acids, boiling water and even nuclear reactors.
Given what we now understand, scientists are approaching the search for extra-terrestrial life in a new light, since it now seems much more likely that primitive life could survive elsewhere in the universe too.
Furthermore, it seems likely that some forms of life would survive, even if the Earth were to move substantially closer to the Sun - although sadly, in this event, we ourselves would probably perish.
