Transcript: The existence of life in the universe is also very sensitive to the electromagnetic force and its absolute strength. If the electromagnetic force were slightly stronger than it is now, stellar luminosities would be sharply lower then they are in the present day universe. Stars would be too cold to have any kind of extensive habitable zones, and no elements beyond iron would have been created in the history of the universe. If the electromagnetic force were much weaker than it is now, all stars would be very hot and have very short lives. With stellar lifetimes typically a million years or less for stars of any mass, as compared to billions of years or more for current day stars of low mass, there wouldn’t have been long enough for complex biological life to have developed even if there had been habitable planets. Thus, the existence of life on Earth and life elsewhere in the universe is fairly finely tuned to one of the strengths of a fundamental force of nature.