Physically realizable systems cannot respond to future input values

Evidence

The impulse responses h(t) or h(n) for a real-time system are always causal; that is, h(·) = 0 when t or n < 0. This means that a physically realizable system does not have information on the future values of its input signal. — Ville Pulkki, Matti Karjalainen, Communication Acoustics- An…, 357

Categorization

• XREF: Causality constraint echoes related physical constraints seen in silence/acoustic-communication reading. — connects to: Known excitation signals sidestep the need for physically impossible impulses; Hegemony does not turn definer inputs into predictable outputs; Mathematical formalism succeeds only on closed simple systems, not open adaptive ones — Carolyn Merchant, The Death of Nature: Women, Ecology,…, 1070
• corroborated: 2 independent passages support this claim — Ville Pulkki, Matti Karjalainen, Communication Acoustics- An…, 357

Broader Connections

• Known excitation signals sidestep the need for physically impossible impulses #corroborates (0.80)