The Earth is a tiny and fragile world. It needs to be cherished.
1. More precisely, an impact crater 10 kilometers in diameter is produced on the Earth about once every 500,000 years; it would survive erosion for about 300 million years in areas that are geologically stable, such as Europe and North America. Smaller craters are produced more frequently and destroyed more rapidly, especially in geologically active regions.
2. The albedo is the fraction of the sunlight striking a planet that is reflected back to space. The albedo of the Earth is some 30 to 35 percent. The rest of the sunlight is absorbed by the ground and is responsible for the average surface temperature.