This could be a dust particle, or even a random fluctuation in the density of the water itself.
The interesting issue with random fluctuations is the variance.
These small disturbances occur due random fluctuations in loads and generation levels.
They were produced entirely by the action of gravity on random fluctuations in the early universe.
Do the 50 delta-distances exhibit random fluctuations about the level indicated by the single larger window?
There is a 1% chance that the Atlas result could be due to a random fluctuation in the data.
At five-sigma there is only one chance in nearly two million that a random fluctuation would yield the result.
So if you see something interesting, you need to make sure it's not just a random fluctuation.
This is in contrast to the random fluctuations about this average value.
Now, in all populations, there are always random fluctuations of gene frequencies.