The Earth has approximately four billion years of lifespan remaining.
"like we have four billion years left in the Earth, right?" (said at 0:54:13)
The statement requires clarification regarding whether it refers to the physical existence of the planet or its habitability. The Sun is estimated to remain on the main sequence for approximately another 5 billion years, after which it will expand into a red giant. Stellar evolution models indicate the Earth will physically survive until it is engulfed by the expanding red giant Sun approximately 7.59 billion years from now. However, Earth's habitable lifespan is much shorter: increasing solar luminosity will trigger a moist or runaway greenhouse effect and ocean evaporation, ending complex and microbial life within roughly 1 to 2 billion years.
- context: Distant future of the Sun and Earth revisited (Sussex Research Online (University of Sussex) 2008)
"Using the new and well-calibrated mass-loss formula of Schroder & Cuntz (2005, 2007), we find that the mass lost by the Sun as an RGB giant (0.332 M_Sun, 7.59 Gy from now) potentially gives planet Earth a significant orbital expansion, inversely proportional to the remaining solar mass... We find that planet Earth will not be able to escape engulfment, despite the positive effect of solar mass-loss." (abstract, results, passage verified)
openalexfull study (doi)