The "sound barrier" is a popular term, often conjuring images of supersonic jets breaking the limits of speed. But what exactly is the sound barrier, and how fast is it in feet per second? This article delves into the physics behind the sound barrier, explains its speed in various conditions, and explores its significance in aviation and beyond.
What is the Sound Barrier?
The sound barrier isn't a physical wall, but rather a dramatic effect caused when an object moves faster than the speed of sound. Sound travels as waves, and when an object approaches the speed of sound, it begins to "catch up" to the pressure waves it creates. This creates a buildup of pressure in front of the object, resulting in a sonic boom. Breaking the sound barrier involves exceeding this speed and transitioning to supersonic flight.
Speed of Sound: Feet Per Second
The speed of sound isn't constant; it varies depending on several factors, primarily temperature and altitude. At sea level and at a temperature of 68°F (20°C), the speed of sound is approximately 1,116 feet per second (fps) or 767 miles per hour (mph). This is often used as a general reference point.
Factors Affecting the Speed of Sound:
- Temperature: The higher the temperature, the faster the speed of sound. This is because warmer air molecules move faster, transmitting sound waves more efficiently.
- Altitude: The speed of sound decreases with increasing altitude in the troposphere (the lowest layer of Earth's atmosphere) due to decreasing temperature. In the stratosphere, however, the temperature profile changes, and the speed of sound can increase with altitude.
- Medium: The speed of sound also varies depending on the medium through which it travels. It travels faster in solids and liquids than in gases.
Calculating Speed of Sound:
A more precise calculation can be made using the following formula:
v = 1086.9 * √(T/273.15)
Where:
- v = speed of sound in feet per second
- T = temperature in Kelvin (K) (K = °C + 273.15)
This formula provides a more accurate calculation, taking temperature variations into account. For example, at 0°C (273.15K), the speed is approximately 1086.9 feet per second.
The Significance of Breaking the Sound Barrier
Breaking the sound barrier was a major milestone in aviation history. The challenges involved in overcoming the immense pressures and forces generated during supersonic flight required significant advancements in aircraft design, materials science, and pilot training. The first supersonic flight, achieved by Chuck Yeager in 1947, marked a pivotal moment in aerospace engineering.
Beyond the Sound Barrier
The understanding and manipulation of supersonic flight have continued to evolve. Modern supersonic aircraft, like the Concorde (now retired), were designed to efficiently manage the effects of supersonic flight, although the sonic boom remained a significant challenge. Ongoing research focuses on reducing the intensity of sonic booms and developing quieter supersonic travel for the future.
Conclusion
The speed of sound, while often approximated as 1116 feet per second, is actually variable. Understanding the factors that affect this speed is crucial for various applications, from aviation and acoustics to meteorology and other scientific fields. Breaking the sound barrier was a monumental achievement, and the ongoing pursuit of supersonic flight continues to push the boundaries of human innovation.
