! * Circular (ripples) or spherical (sound) **waves remain centered** on the **position of the source** (duck, plane) **at the moment they were emitted**.
! * Circular (ripples) or spherical (sound) **waves remain centered** on the **position of the source**
! (duck, plane) **at the moment they were emitted**.
!
! * Thus, the center of the circular or spherical waves moves at the speed of the source.
! * Thus, the center of the circular or spherical waves moves at the speed of the source.
!
! * Since the **speed of the wave** (ripple, sound) is **greater than that of its source** (duck, plane), part of the **wave always moves ahead of the source**, and the ripples or sound waves always surround their source.
! * Since the **speed of the wave** (ripple, sound) is **greater than that of its source** (duck, plane), part of the **wave always moves ahead of the source**, and the ripples or sound waves always surround their source.
!
!
! ---
! ---
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@@ -176,10 +179,19 @@ _Sometimes, all it takes is moving at the right speed for the world to draw you
...
@@ -176,10 +179,19 @@ _Sometimes, all it takes is moving at the right speed for the world to draw you
! * When a source (like a boat or plane) moves faster than the waves it creates, it leaves behind circular ripples (on the water's surface) or spherical waves (in the air).
! * When a source (like a boat or plane) moves faster than the waves it creates,
! * The **location where** these ripples reinforce each other forms a **V** (physicists say the ripples **interfere constructively**). This V is the **wake** left by the source.
! it leaves behind circular ripples (on the water's surface) or spherical waves (in the air).
! * **Inside** this V, the ripples weaken or cancel each other out, creating a **quieter zone** (physicists say the ripples **interfere destructively**).
!
! * For a plane, this V becomes a **cone**. If you are **where the surface of this cone reaches the ground**, you hear a loud **supersonic BOOM**. Since the plane—and thus its cone—moves faster than the speed of sound, no sound can warn you in advance of this sudden BOOM.
! * The **location where** these ripples reinforce each other forms a **V** (physicists
! say the ripples **interfere constructively**). This V is the **wake** left by the source.
!
! * **Inside** this V, the ripples weaken or cancel each other out, creating a **quieter zone**
! (physicists say the ripples **interfere destructively**).
!
! * For a plane, this V becomes a **cone**. If you are **where the surface of this cone reaches the ground**,
! you hear a loud **supersonic BOOM**. Since the plane—and thus its cone—moves faster than
! the speed of sound, no sound can warn you in advance of this sudden BOOM.
!
! * This BOOM is brief because **once the BOOM passes, you find yourself inside** the cone, an area of **low residual noise or silence**.
! * This BOOM is brief because **once the BOOM passes, you find yourself inside** the cone, an area of **low residual noise or silence**.
