IRST = eyes. Passive sensor. Can't tell distance. Radar = bat's echo location. Active sensor. Can.

[Yongpeng Sun-Tastaufen]

Only bats have active sensor. All other animals have passive sensor. Active sensor sends out wave, bounce back, you can use the time between wave sent out and wave returned to judge how far the object is because distance = speed * time, and speed of light = 299 792 458 m / s.

 

[war&peace]

Only bats have active sensor. All other animals have passive sensor. Active sensor sends out wave, bounce back, you can use the time between wave sent out and wave returned to judge how far the object is because distance = speed * time, and speed of light = 299 792 458 m / s.

This is the speed of light in vacuum but in other media, it is lower than this value.

 

[nahtanbob]

Only bats have active sensor. All other animals have passive sensor. Active sensor sends out wave, bounce back, you can use the time between wave sent out and wave returned to judge how far the object is because distance = speed * time, and speed of light = 299 792 458 m / s.

is that true ?