In this hypothetical scenario where 'aether-sonis' exists, a massless, invisible, and pervasive medium that perfectly transmits vibrations throughout the vacuum of space, the experience for the crew in the nearby spaceship during an explosion would be quite different from what we typically envision.

### **What They Would See:**
- **Visuals of the Explosion:** The crew would still see the explosion as they normally would in the vacuum of space. The sudden release of energy from the exploding ship would cause a bright flash of light, likely accompanied by a burst of radiation (X-rays, gamma rays, etc.), and a visible shockwave expanding outward. The debris from the ship would also be visible as it flies off in various directions.
  
- **Afterglow and Glow of Debris:** Depending on the nature of the explosion, there might be a lingering afterglow or thermal radiation from the hot debris. If the explosion was nuclear or involved antimatter, there could even be a brief moment of intense light followed by a fading glow.

### **What They Would Hear:**
- **Transmission of Vibrations via Aether-Sonis:** Since 'aether-sonis' is present everywhere and can transmit vibrations, the explosion would create pressure waves (similar to sound waves) that propagate through this medium. These vibrations would travel at the speed of sound within 'aether-sonis,' which we can assume is very fast, perhaps close to the speed of light, given its properties.
  
- **The Sound of the Explosion:** The crew would hear a sharp, loud, and possibly deep-throated "crack" or "boom" as the pressure waves reach their ship. The exact pitch and volume would depend on the intensity of the explosion and the distance between the ships. If the explosion is very close, the sound might be extremely loud and potentially damaging to their eardrums, even if the sound is transmitted through 'aether-sonis.'

### **Would They Experience Sight and Sound Simultaneously?**
- **Simultaneity Depends on Distance:** In the vacuum of space, light travels at approximately 299,792 kilometers per second, while vibrations in 'aether-sonis' could theoretically travel at a similar speed. Therefore, if 'aether-sonis' vibrations also travel at the speed of light, the crew would likely experience both the visual and auditory effects of the explosion almost simultaneously, with any delay being imperceptible to human senses.
  
- **If 'Aether-Sonis' Vibrations Travel Slower:** However, if 'aether-sonis' vibrations travel at a slower speed (even if faster than sound in air), there would be a slight delay between seeing the explosion and hearing the sound. For example, if 'aether-sonis' vibrations traveled at 10% the speed of light, there would be about a 3 millisecond delay for an explosion 300,000 kilometers away. This delay would be noticeable but brief.

### **Physics Explanation:**
- **Light vs. Vibrations:** Light travels through the vacuum of space as electromagnetic waves, which do not require a medium. The crew would see the explosion as soon as the light reaches their eyes, traveling at the speed of light.
  
- **Vibrations in Aether-Sonis:** The 'aether-sonis' medium allows for the propagation of mechanical waves, similar to how sound travels through air. These vibrations would travel at the speed determined by the properties of 'aether-sonis.' If 'aether-sonis' vibrations travel at the speed of light, the crew would hear the explosion at essentially the same time they see it. If they travel slower, there would be a perceptible delay.

### **Conclusion:**
In this universe with 'aether-sonis,' the crew of the nearby spaceship would see the explosion first as a bright flash of light, followed by the transmission of vibrations through 'aether-sonis.' Depending on the speed of these vibrations, they would either hear the explosion at the same time they see it or with a slight delay. The combination of visual and auditory cues would provide a more realistic and immersive experience of an explosion in space, blending the sensory inputs of sight and sound in a way that reflects the unique properties of this new form of matter.