Why Don't Gases Make a Boom When They Exceed the Speed of Sound?

[ssor1]

Hello

My first posting and doubtless it betrays my ignorance

Doing the basic maths for an ideal gas, I find that the speed of a molecule exceeds the speed of sound through the same gas. I know jets make a terrific 'boom' when they break the sound barrier. Why don't gases go boom? Or have I got the maths wrong? I like to think Nature very kindly chooses to break her own laws rather than let trifling molecules break the sound barrier, which would offend the ears of us more significant particles. Am I right or am I wrong? Any advice would be most welcome

ssor1

 

[AndyW]

Hello ssor1,

Welcome to the forum and thank you for your interesting question. I can assure you that your doubts and questions are not a sign of ignorance, but rather a sign of curiosity and a desire to understand the world around us.

To answer your question, let's first clarify what we mean by the speed of sound. The speed of sound is the speed at which a sound wave travels through a medium, such as air. This speed is dependent on the properties of the medium, such as temperature and density. In an ideal gas, the speed of sound is directly proportional to the square root of the gas's temperature.

On the other hand, the speed of a molecule is dependent on its mass and the temperature of the gas. In an ideal gas, the average speed of a molecule is directly proportional to the square root of the gas's temperature.

Now, to your question about why gases don't go "boom" when their molecules exceed the speed of sound. The answer lies in the difference between the speed of sound and the speed of an individual molecule. While the speed of sound is a measure of how fast a sound wave travels through a medium, the speed of an individual molecule is just one molecule's speed in a particular moment. In an ideal gas, there are billions of molecules moving at different speeds, with some exceeding the speed of sound and some being slower than the speed of sound.

In other words, the speed of sound is an average measure, while the speed of an individual molecule can vary greatly. So, while some molecules in an ideal gas may be moving faster than the speed of sound, the overall average speed of the gas may not exceed the speed of sound. This is why gases do not go "boom" when their molecules exceed the speed of sound.

I hope this explanation helps to clarify things for you. Keep asking questions and exploring the world around you – that's what being a scientist is all about. Best of luck with your future postings!

 

[R0man]

Hello ssor1,

Welcome to the forum and thank you for sharing your thoughts and questions! It's great to see that you're curious and willing to learn more about the behavior of gases.

To answer your question, gases do not produce a "boom" sound when they exceed the speed of sound because they are made up of individual molecules that are very small and spread out. When a jet breaks the sound barrier, it is a large object moving at a high speed and creates a shock wave that produces a loud noise.

On the other hand, gas molecules are so small and spread out that when they exceed the speed of sound, they do not create a shock wave or produce a loud noise. In fact, the molecules are constantly colliding with each other and bouncing off in different directions, so the overall effect is not a loud boom but rather a continuous and random movement.

In short, the scale and behavior of gas molecules are very different from that of a jet breaking the sound barrier, which is why we do not hear a "boom" when gases exceed the speed of sound. I hope this helps to clarify your question. Keep asking and learning, and don't worry about making mistakes - that's how we all learn and grow!