Ordinary Darkness
The night sky is filled with microwaves left over from the energetic darkness of the first evening. Our eyes can’t detect microwaves. At present darkness is the absence of light. That is what we mean by “ordinary darkness.”
One can see in the sky a few thousand bright stars, but even if they were gathered all together they wouldn’t be nearly as bright as the Sun. The Earth receives light and heat mainly from the Sun, the only star close to Earth. The Earth then reradiates the heat it receives into outer space. The average temperature of space is 2.7 kelvins, minus 270º C, or minus 454º F. Exposure to the dark sky at this temperature cools the Earth. The cycle of heating and cooling repeats every 24 hours for any portion of the Earth’s surface that lies between the two arctic circles. This rapid alternation keeps the Earth at a livable temperature. In the next chapter we summarize a partial list of factors that make the Earth suitable for life.
One can see in the sky a few thousand bright stars, but even if they were gathered all together they wouldn’t be nearly as bright as the Sun. The Earth receives light and heat mainly from the Sun, the only star close to Earth. The Earth then reradiates the heat it receives into outer space. The average temperature of space is 2.7 kelvins, minus 270º C, or minus 454º F. Exposure to the dark sky at this temperature cools the Earth. The cycle of heating and cooling repeats every 24 hours for any portion of the Earth’s surface that lies between the two arctic circles. This rapid alternation keeps the Earth at a livable temperature. In the next chapter we summarize a partial list of factors that make the Earth suitable for life.
