What Is A Gamma Ray Burst? Gamma Ray Bursts are the result of an Exploding Star and are the most powerful explosions in the Universe. Most of the energy released from an Exploding Star is released as Gamma Rays in very short bursts lasting from micro-seconds to as much as 100 seconds, hence the name Gamma Ray Burst. The Gamma Ray Burst is released in a focused "beam" much like the light from a laser and is sometimes referred to as a "Death Ray."
Since the Gamma Ray Bursts that have been observed happened millions of years ago, to stars millions of light years away, and since the chances of a focused Gamma Ray Burst from one of those explosions hitting the Earth is almost non-existent, there is little to be concerned about.
If a star within our own Milky Way Galaxy were to explode, and it was close enough...within about 6,000 light years,...and the focused beam of Gamma Rays were to hit the Earth, it COULD trigger a mass extinction.
The absorption of the radiation from the Gamma Rays in the upper atmosphere would cause the nitrogen to generate nitric oxide that would act as a catalyst to destroy the ozone layer. With even one half of the ozone layer destroyed, the direct UV irradiation from the Gamma Ray Burst combined with additional solar UV radiation passing through the diminished ozone layer, would have significant impact on the food chain thereby triggering mass extinction. IE: STARVATION!
NASA scientists are positive this type of mass extinction occurred on Earth hundreds of millions of years ago. Their models show that a Gamma Ray Burst originating within approximately 6,000 light years, and lasting for just 10 seconds can cause years of devastating ozone damage.
The most extreme "theory" is that a HUGE Gamma Ray Burst from within our own Galaxy would INSTANTLY kill everything on Earth, but that we wouldn't know anything about it since it would be over before we knew it began.
What are the chances of a Gamma Ray Burst hitting the Earth in our life-time? ... What are the chances of winning the lottery? ... Getting hit by lightning? ... the Cubs winning the World Series? ... It COULD happen. It IS POSSIBLE. But is it probable? No one knows!
Could anyone survive a Gamma Ray Burst? Yes they could. But as is the case in any of the "extreme natural disaster events," it would require a lot of luck, being in the proper location and having the necessary supplies to be able to survive until "things" returned to normal. In addition it would probably be necessary to reside underground during that time period. For the average person ... the probability of surviving a massive Gamma Ray Burst is pretty much zero.