Answer to Question 1
When the Sun first formed 4.6 billion years ago, it is believed to have been about 30 less luminous than it is today. The Sun's luminosity increased slowly at first and then more rapidly as the buildup of helium in its core continued. At present, the Sun is thought to be brightening by about 1 every hundred million years.
Answer to Question 2
Stratosphere ozone is important to living organisms because it absorbs many of the Sun's harmful ultraviolet rays. Ultraviolet radiation causes skin cancer and other health problems in humans.
Photoaging solar elastosis; senile keratosis
What Happens to Incoming Solar Radiation?
Solar energy heats the atmosphere, creates seasons, and causes air to circulate
Approximately 40 percent of farmers in the United States are 55 years old or older
Average Distribution of Incoming Solar Radiation
Trends in employed mothers with a child/children younger than 3 years of age