RINGS

what are the concentric ring s visible on the wood of a cut tree trunk?

Concentric rings visible on the wood of a cut tree trunk or other woody stem are the annual rings . Each ring represents a period of growth when new xylem is laid down to replace tissue being converted into wood . The wood formed from xylem produced in the spring and early summer has larger and more numerous vessels than the wood formed from xylem produced in autumn when growth is slowing down. The result is a clear boundary between the pale spring wood and the denser, darker autumn wood. Annual rings may be used to estimate the age of the plant, although occasionally more than one growth ring is produced in a given year.we can also estimate the amount of rainfall with the help of gap between the rings.



Why do some planets have rings around them and the rest do not?

If an orbiting object approaches a planet then it may be torn apart by the
tidal force of the planet. The exact distance at which this happens depends
on the composition of the orbiting object. This object could be a moon or a
passing comet or asteroid. A ring is formed by the debris of such objects.
So the planet has to be lucky enough to get an object within the correct
range and at not too oblique an incidence.