Friday marks the 55th anniversary of the United States dropping the first airborne hydrogen bomb on the Bikini atoll in the Pacific Ocean. The test was a success and symbolized a huge leap in the nuclear arms race.
According to the History Channel, people who witnessed the test remarked the resulting fireball "measured at least four miles in diameter and was brighter than the light from 500 suns."
In honor of the anniversary, LIFE.com has published a series of bomb-test photos that are both frightening and beautiful (see the full LIFE.com collection on the website). You can check out the images below, and see not just the fireballs and explosions, but also the bomb's impact on "test houses" and mannequins that researchers used to measure the bomb's terrifying power.