Lightning appears instantly because light travels roughly a million times faster than sound.

Light travels through a vacuum at a constant speed of approximately 299,792,458 meters per second, or about 186,282 miles per second. Sound in air at 20°C travels at roughly 343 meters per second, or about 767 miles per hour. This makes light approximately 874,000 times faster than sound in our atmosphere.When lightning strikes, it superheats the surrounding air to nearly 30,000 Kelvin—five times hotter than the sun's surface. This rapid heating causes the air to expand explosively, creating a shock wave we hear as thunder. Because light reaches your eyes in microseconds while sound must travel through air molecules, a significant delay occurs over distance.The "flash-to-bang" method is a scientifically established technique for estimating storm distance based on these physical principles. Since sound travels about one mile every five seconds, or one kilometer every three seconds, observers can accurately track whether a storm is approaching or moving away. Meteorologists and outdoor enthusiasts have used this method for decades.According to the National Oceanic and Atmospheric Administration (NOAA), a delay of 30 seconds or less means the storm is within 6 miles and poses a lightning risk. Interestingly, thunder rarely carries more than 10 to 15 miles because atmospheric refraction weakens the pressure wave. This is why distant "heat lightning" is visible without sound—the thunder has dissipated before reaching you.