Final answer:
The speeds of light and sound are vastly different, allowing us to calculate the time difference in their arrival. If the speed of light were similar to those familiar speeds, it would alter our perception of relativistic effects. Observations of galaxies demonstrate the Doppler effect with light just as it occurs with sound, giving insights into cosmic movements.
Step-by-step explanation:
The subject question revolves around the comparison of the speed of light and speed of sound, and scenarios involving electromagnetic waves and relativity. When a lightning strikes 10km away from an observer, since light travels at approximately 3 × 108 m/s, it reaches almost instantly, while sound, traveling at 340 m/s, takes some time to reach.
If the speed of light were only 3000 m/s, as in a hypothetical scenario, and a jet fighter shoots bullets with a muzzle velocity of 1000 m/s while traveling at 800 m/s towards a target, the bullets' velocity relative to the target would simply be the sum of the velocities, since relativistic effects only become significant at speeds approaching the speed of light. In real life, with the speed of light being 3 × 108 m/s, relativistic effects are not noticeable in everyday phenomena.
Moreover, if we consider a galaxy moving away from Earth at 1000 km/s emitting 656 nm light, we would observe a longer wavelength due to the Doppler effect, which is a change in frequency and wavelength due to the relative motion between the source and the observer. This kind of light is within the visible spectrum, indicating that we would still see it as visible light albeit with a shifted frequency.