Ziggurat
Penultimate Amazing
- Joined
- Jun 19, 2003
- Messages
- 61,746
Tiny. 500 microns.
Exactly. That makes them much smaller than the optical depth most of the time.
The bubbles demonstrate the principle of pressure broadening in the lab.
And pressure broadening is the same thing as decreasing optical depth. If you don't know why, you don't understand optical depth.
And you can track the spectrum with changes in pressure that are not normally available in the lab. It was this that gave me the first clue that lead to an examination of blackbodies.
Keep examining them, because you haven't figured them out yet.
And they give you some number as to what to expect in the way of pressure vs continuum. 9000 atmospheres just to get a continuum, not even a blackbody..
In a 500 micron bubble. Because that's what it takes to make the optical depth that short. But we don't need to go to 9000 atmospheres if we just make the object thick enough. Either way, the critical parameter is the ratio of optical depth to physical thickness. If your object is thinner than the optical depth, you won't get blackbody radiation. If it's thicker than the optical depth, you will. Quite simple, really.
The "bottom"(IR opacity 1) of the photosphere is nowhere near that pressure.
And it's nowhere near 500 microns thin, either. Optical depth, brantc. You still haven't figured it out.