Red Giant Phase:
* Expansion: The Sun would swell dramatically, engulfing Mercury, Venus, and likely Earth. Even if Earth somehow survived the engulfment, the intense heat from the red giant Sun would vaporize all water and life on the surface.
* Increased Radiation: The Sun's output of energy would increase significantly, baking the Earth and making it uninhabitable long before engulfment.
White Dwarf Phase:
* Cooling and Dimming: After shedding its outer layers, the Sun would become a white dwarf – a dense, hot remnant. While it would still emit some light, it wouldn't be enough to support life on Earth.
* Planetary Nebula: The outer layers shed by the Sun would form a beautiful but deadly planetary nebula. This nebula would be a vast cloud of gas and dust, but it wouldn't be hospitable to life.
The Bottom Line:
The Sun's transformation into a red giant and then a white dwarf is a natural part of its lifecycle. While it will take billions of years for this to happen, the process will ultimately render Earth uninhabitable and spell the end of life as we know it.
However, it's important to note:
* This process won't happen for billions of years. Our sun is currently in its stable main sequence phase, and we have plenty of time to find solutions or even relocate humanity to another planet.
* The exact fate of Earth during the red giant phase is complex and debated. It's possible Earth could be ejected from the solar system, or it might survive for a while before eventually being destroyed.
