This is a fantastic question that delves into the fascinating implications of changing one fundamental rule of physics. Here is a breakdown of what the crew of the nearby spaceship would experience, and the physics behind it.

### The Experience in the Cockpit

The experience would be deeply unsettling and completely counter-intuitive to everything we know. The crew would hear the explosion before they see it.

**Phase 1: The Sound (Instantaneous)**

The very instant the enemy ship explodes, the cockpit of the nearby ship is filled with an invasive, terrifying sound. There is no warning. The view outside the main screen is still of a stable, intact enemy vessel.

*   **What they hear:** The sound wouldn't be the muffled *'whoosh-boom'* we often hear in movies, which is the sound of an explosion moving through air. Instead, it would be the raw, unfiltered sonic signature of the event itself.
    *   It would start with an impossibly sharp, high-frequency **CRACK** — the sound of the warhead detonating or the reactor containment failing.
    *   This would be immediately followed by a brutal, grinding **SHriek** of metal under unimaginable stress, as the ship's superstructure is torn apart from the inside out.
    *   Underpinning all of this would be a deep, gut-wrenching **BOOM** that feels less like a sound and more like a physical pressure wave hitting the ship. The entire hull of their own ship would resonate, vibrating in sympathy with the transmitted shockwave. The crew would feel this vibration in their teeth and bones. The control panels might rattle, and unsecured items might jump.

The key here is that the sound arrives *from everywhere at once*. It doesn't seem to come from the direction of the enemy ship, but rather, it simply *erupts* into existence within their own vessel, transmitted perfectly from the aether-sonis to the ship's hull, and then to the air inside the cockpit.

**Phase 2: The Light (Delayed)**

A fraction of a second *after* this auditory and sensory assault begins, the visual spectacle happens.

*   **What they see:** A silent, blindingly brilliant flash of light erupts from the enemy ship. For a moment, the cockpit is washed in white, overwhelming all the sensors and forcing the crew to shield their eyes. As their vision recovers, they see a rapidly expanding fireball of superheated gas and plasma where the ship used to be. This fireball doesn't create a mushroom cloud (there's no atmosphere or gravity to shape it); it's a perfect, growing sphere that cools and dissipates quickly, leaving behind a new, expanding field of glowing-hot debris and twisted metal.

### Would they be simultaneous? No.

The sound would arrive **before** the light. This creates a terrifying chronological reversal of what we experience on Earth with lightning and thunder.

### The Physics Explained

The reason for this bizarre sequence lies in the stated properties of 'aether-sonis' and the fundamental speeds of light and sound.

1.  **The Speed of Light:** Light (and all electromagnetic radiation) travels through a vacuum at the speed of light, denoted as **_c_**. This is the universe's ultimate speed limit, approximately 299,792,458 meters per second. No matter what, the visual information of the explosion cannot reach the observing ship any faster than this.

2.  **The Speed of Sound in Aether-Sonis:** The speed of a mechanical wave (like sound) is determined by two properties of the medium it's traveling through: its **elasticity** (how well it returns to its original shape) and its **inertia** (how much it resists being accelerated, related to its mass/density). The general formula is:

    *   *Velocity = √(Elasticity / Inertia)*

    The prompt gives us two critical, and physically contradictory, properties for aether-sonis:
    *   It **"perfectly transmits vibrations,"** implying it has a perfect, or perhaps near-infinite, elasticity.
    *   It is **"massless,"** meaning its inertia (or density) is zero.

    When we plug this into our equation, we are dividing by zero. In physics, this leads to a result of **infinity**. Therefore, the speed of sound through the massless aether-sonis would be **instantaneous**.

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### **Conclusion: The Chronological Timeline**

Let's assume the ships are 30,000 km apart (a very close engagement in space terms).

*   **Time T = 0:** The enemy ship's reactor breaches. A massive wave of vibrations instantly expands through the aether-sonis.
*   **Time T = 0 (Still):** That vibration wave reaches the nearby ship. The aether-sonis vibrates the ship's hull, which in turn vibrates the air inside the cockpit, creating sound. The crew hears the violent, metallic death of the other ship.
*   **Time T = 0.1 seconds (approx.):** The light from the explosion, which left at the same time as the vibration, has now traveled the 30,000 km at the speed of light and finally reaches the cockpit. The crew is blinded by the flash, *after* already hearing the event that caused it.

This experience would be profoundly disturbing. It breaks a fundamental cause-and-effect relationship that we take for granted: you see the lightning, then you a long time later hear the thunder. In this universe, the thunder is instantaneous, a harbinger of the light that is still racing to catch up.