Complex sentence: To understand the physical meaning of imaginary mass for a field, there is a simple mechanical analogy that illustrates that tachyonic fields do not propagate faster than light, and why they represent instabilities.
Split into simpler sentences: To understand the physical meaning of imaginary mass for a field, a simple mechanical analogy is useful. The example illustrates that tachyonic fields do not propagate faster than light, and why they represent instabilities.