List of Unsolved Problems in Physics - Problems Solved in Recent Decades

Problems Solved in Recent Decades

Pioneer anomaly (2012)

There was a deviation in the predicted accelerations of the Pioneer spacecraft as they left the Solar System. It is believed that this is a result of previously unaccounted-for thermal recoil force.

Long-duration gamma ray bursts (2003)

Long-duration bursts are associated with the deaths of massive stars in a specific kind of supernova-like event commonly referred to as a collapsar. However, there are also long-duration GRBs that show evidence against an associated supernova, such as the Swift event GRB 060614.

Solar neutrino problem (2002)

Solved by a new understanding of neutrino physics, requiring a modification of the Standard Model of particle physics—specifically, neutrino oscillation.

Age Crisis (1990s)

The estimated age of the universe was around 3 to 8 billion years younger than estimates of the ages of the oldest stars in our galaxy. Better estimates for the distances to the stars, and the recognition of the accelerating expansion of the universe, reconciled the age estimates.

Quasars (1980s)

The nature of quasars was not understood for decades. They are now accepted as a type of active galaxy where the enormous energy output results from matter falling into a massive black hole in the center of the galaxy.