Does the particles in a solid object vibrate or does the solid object itself vibrate?

Question

Solid objects do not vibrate. (That we can see and/or feel and/or hear. However, molecules inside a solid vibrate. Does this mean the solid structure or object itself vibrates or just the particles that make up the solid?

Answer 1

Hi Hailey! Excellent Question. Technically, it's all possible!

1. A still object is warming up: the object is not moving nor necessarily vibrating to the naked eye, but the temperature of the object is going up.. How is this possible? Well, you can imagine four particles connected such that they form a square. Molecules can stay in basically the same spot, but to be moving back and forth within their respective spots. If you zoomed out, you would notice that since they are staying in basically the same spot, the square they form is not vibrating. It appears to be still.
2. If you imagine instead the square moving around you might assume that the particles are vibrating. But don't! Because the particles can collectively move in unison without vibrating. They can choose to move up or to the left or to the right.
3. Finally, imagine you're holding a tennis ball. You shake it side to side. Left to right. Back and forth. Can you shake the tennis ball while moving it up? You likely could! Now, imagine four tennis balls connected such that they form a square. If shake all the tennis balls in one direction (side to side or up-down) and then move all four in unison in another direction simultaneously, then the tennis balls will vibrate as the square moves too! This would be the example where an object can macroscopically vibrate while also heating up because its particles are vibrating too.

Hope this helps, Hailey!