Fast answer for period-30 searches
The Gosper glider gun has period 30. After 30 generations, the core returns to the same phase while one glider has escaped, so the pattern can keep producing moving signals instead of settling.
The standard starting pattern has 36 live cells in a 36 x 9 bounding box. Those numbers are useful when you are checking whether a simulator loaded the right gun, not just something that happens to emit gliders.
Observation path
What to watch in the simulator
Generation 0
Start with the gun body
Check the two stable blocks and the central reaction area before pressing play.
Around generation 15
The reaction opens
The middle of the gun expands while the stable side objects keep the reaction bounded.
Generation 30
The core returns
The gun body is back in phase. That repeat is the period-30 fact users usually need.
After the cycle
A glider has escaped
The same core plus an escaping glider is the proof of repeated output from a finite seed.
A gun is a repeating factory
A glider gun is a periodic pattern that fires gliders. The Gosper glider gun is the famous first example: 36 live cells in a 36 x 9 bounding box, period 30, discovered by Bill Gosper in 1970.
Every 30 generations the core reaction returns while a new glider escapes. The gun does not stabilize into ash. It keeps increasing the total live-cell history by exporting motion.
Why this mattered
Before a gun, a finite Life seed could plausibly be expected to settle into still lifes, oscillators, and escaping leftovers. The Gosper gun gave a concrete counterexample: a finite starting pattern with unbounded growth.
That changed the emotional center of Life. The game was no longer only about watching what a seed becomes. It was about building mechanisms that keep producing signals.
Why the gun keeps emitting gliders
The gun is easier to understand if you ignore the full board at first. Watch the two stable blocks, then the central collision, then the departing glider stream.
After one full period, the core should look like it did at the start, apart from the glider that has moved away. That is the signature of a working gun.
Working takeaway
Load the gun, run to generation 30, pause, and compare the core. The repeated core plus escaped glider is the whole story.
Fast answers
Common search questions
What is the period of the Gosper glider gun?
The Gosper glider gun has period 30. Every 30 generations, the core repeats and a new glider has moved away from the gun.
Why is the Gosper glider gun important?
It was the first known finite Life pattern with unbounded growth. A finite starting object can keep emitting gliders forever under the standard B3/S23 rule.
How is Gosper different from the Simkin glider gun?
Gosper is the historical period-30 gun discovered in 1970. Simkin is a newer compact period-120 gun, useful as a comparison after the classic example is understood.