why in a soda drink, bubbles come up from a few certain points and how come without a source?

Soda, like other carbonated beverages, contains dissolved carbon-dioxide gas. The way to get gas to dissolve in liquid is to pressurize the mixture, meaning that the pressure inside a soda can is greater than the pressure outside the can. When you open a soda can, breaking the seal depressurizes the mixture, causing the gas to come out of solution, starting with the gas closest to the top (that's where the pressure decrease starts).This is why you see little bubbles spray out.

Small bubbles caused by shaking help to hasten the escape of the soda's carbon dioxide. If the can is shaken, or if the liquid is poured quickly into a glass, then the bubbles formed by turbulence provide an easier way for the dissolved gas to escape.

It's difficult for the gas to escape from an undisturbed liquid because of the liquid's surface tension, which is the energy required to separate the liquid molecules from one another as a bubble forms. For a tiny bubble just getting started, the amount of energy required per molecule of gas in the bubble is relatively large. So getting started is the difficult stage. Once it is formed, however, a smaller amount of energy (again on a per molecule basis) is needed for additional liquid molecules to vaporize and expand the bubble. The basic reason for this dependence on bubble size is that whereas the volume of the bubble is proportional to the number of molecules inside (at constant pressure), the surface area of the bubble is proportional to the number of molecules to the 2/3 power.

Because shaking the can introduces lots of small bubbles into the liquid, the dissolved gas can more easily vaporize by joining existing bubbles rather than forming new ones. By avoiding the difficult step of bubble formation, the gas can escape more quickly from shaken soda, thus resulting in more fizz.

Bubbles in soda come from carbon dioxide expanding out of solution. Bumps or dust or any difference in the liquid can help provide a point to focus the gas coming out. The gas will tend to keep coming out from the same place until it has to come from far enough away in the liquid that another point will take over.

well, i will tell the actual reason behined it. Soda drinks are nothing but "aerated" drinks i.e they contain a gas called carbon dioxide suspended in water. hence we see the formation of gas bubbles. so the source is pressurized carbon dioxide.

It's a good question. There must be some sort of magnetic bubble field there. Or else I'm completely wrong.

I often ponder that myself. They just keep coming from that same spot.

the bubles come from dust in the glass