I have found my phals which have many roots compacted in the pot do like to put out roots out of the pot. These do look very similiar to the normal roots, but of course do shivel and dry up.
The photo i will post may (or may not
) help to clarify what an aerial root looks like. This is from my biggest phal, which now has lovely thick roots, a cm or more in diameter.
But the root i want to show is the thick grey/silver one. From what i have read, the silver colour means it is an aerial root, and has its own chlorophyll for photosynethesis. The roots are grey when dry, but when are wet will turn green. This is because the roots have taken in moisture, so the plant "thinks" that it is humid enough for it to photosynethise from the roots. (this involves opening stomata to let CO2 in and O2 out, which will invariably cause water loss. This is most obvious in vanda's which have many aerial roots, and the change from silver to green is apparent.
As a side note, some plants put out aerial roots when their soil becomes too saturated and stagnent, though i think this is more to do with swamp plants.
*The biological explaination there has been done with school biology learning and abit of thinking, do not take it word for word
*
heres the picture of what i think is an aerial root