Current scientific discourse if full of mysterious and obscure concepts such as: dark energy, dark matter and inflaton fields. To be sure each term was invented for a good reason such as explaining galactic acceleration, the galaxy rotation curve or the homogeneity of the cosmic microwave background. Dark energy is the most accepted hypothesis to explain the observations indicating that the universe is expanding at an accelerating rate. The accelerated expansion was discovered in 1998, by two independent projects, the Supernova Cosmology Project and the High-Z Supernova Search Team, which both used distant type Ia supernovae as standard candles to measure the acceleration. The discovery was unexpected, cosmologists at the time expecting that the expansion would be decelerating due to the gravitational attraction of the matter in the universe. Three members of these two groups have subsequently been awarded Nobel Prizes for their discovery. Confirmatory evidence has been found in baryon acoustic oscillations and in analyses of the clustering of galaxies. Assuming that the standard model of cosmology is correct, the best current measurements indicate that the conjectured dark energy contributes 68.3% of the total energy in the present-day observable universe.