Two horses started running in the same direction from the same place at the same time. One horse ran 16 m/sec, and the other ran 18 m/sec. How far apart were the horses in 1 minute? 5 minutes? 8 minutes?

In 1 minute, the first horse would have traveled 16 x 60 = <<16*60=960>>960 meters.

The second horse would have traveled 18 x 60 = <<18*60=1080>>1080 meters.
Therefore, the two horses would be 1080 - 960 = <<1080-960=120>>120 meters apart.
In 5 minutes, the first horse would have traveled 16 x 300 = <<16*300=4800>>4800 meters.
The second horse would have traveled 18 x 300 = <<18*300=5400>>5400 meters.
Therefore, the two horses would be 5400 - 4800 = <<5400-4800=600>>600 meters apart.
In 8 minutes, the first horse would have traveled 16 x 480 = <<16*480=7680>>7680 meters.
The second horse would have traveled 18 x 480 = <<18*480=8640>>8640 meters.
Therefore, the two horses would be 8640 - 7680 = <<8640-7680=960>>960 meters apart. Answer: \boxed{960}.