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.
Solar Airplane
During drought years on the Galapagos, small, easily eaten seeds become rare, le
Earth’s history spans 4.5 billion years. Geologists and paleontologists have pieced together the his
How Axis Tilt Affects the Intensity of Solar Radiation
The Last 10,000 Years of Greenhouse Gas Concentrations
Average Global Temperature Rise over the Past Century