Fusion reactions power the sun. By fusing hydrogen to helium, the sun releases vast amounts of energy towards Earth.
The early stage was fast and catastrophic with tons of impacts and tremendous heating. Next, Earth had a period of cooling down starting in the Archean Eon.
How do fusion reactions heat the Earth?
As described in the core accretion model, the sun is so massive that it gathered up 99.9% of gas and dust in the solar system. Solar wind swept in hydrogen and helium closer to the sun because these particles were smaller in size.
But the sun left just enough behind for gravity to build up other things. For example, heavier elements like iron and zinc coalesced to the core of Earth and terrestrial planets.
According to Einstein, you can’t lose mass. But you can convert mass to energy. Stars are a thermonuclear reaction where four hydrogen atoms are combined together into helium through heat.
So, all stars do during their lifecycle is just burn hydrogen into helium and releases energy. Typically, main sequence stars like our sun go through this process for about 95% of its life.
How much solar radiation reaches Earth?
It takes light 1 astronomical unit to reach us. It’s because of this solar energy that Earth is the only planet known to harbor life. Planets that are in this “just right” distance are in the Goldilocks zone.
By providing a healthy portion of UV rays, plants use it for photosynthesis. Without sunlight, you cut plants off from the energy needed for photosynthesis.
The balance of Earth’s temperature relies on how much energy enters and leaves the planet’s system. When incoming energy from the sun is absorbed by the Earth system, Earth warms.
When the sun’s energy is reflected back into space, Earth avoids warming. So, when absorbed energy is released back into space, Earth cools.
Will the sun ever burn out?
Just like any fire, eventually it burns out. Similarly, stars all have life times. Heavyweight stars have the most fuel. But burns it at the fastest rate.
The smallest stars live the longest at a minimum of 50 billion years. If you compare this to the universe, it’s only 13 billion years old. That means that the lifespan of a star is longer than the creation of our universe up to this point.
Our sun is 1 solar mass (SM) and is classified as a lightweight. In the lightweight category, this means that it has a life expectancy of about 10 billion years.
Currently, we’re into 5 billion years for our sun. It’s at the middle age of its life and has about 4 billion more years. Unlike red supergiants, our sun won’t become a supernova and will collapse into a white dwarf.