Shaken vs stirred, is there a difference? I was looking up tequila Drink recipes for the up coming holiday, and I kept seeing ones calling to be shook and other to be stirred. So I wondered: is there really a difference? does stirring provide a less substantial form of mixing? 
I mean, the Drink alcohol content wont change. I get that some things have different densities, and will sink etc, as in the case of a tequila sunrise, but that particular drink isn't mixed (shaken or stirred).
Can someone explain the difference between shaken vs stirred, and how it affects the quality, or consistency of a mixed drink? Lets use the martini for an example. Will the world really if its stirred not shaken?
 A: The purpose of shaking or stirring a drink is to cool it and to distribute the ingredients.  Stirring is a much less violent way of achieving this, but it will take a longer time than shaking, if you want to fully distribute all the ingredients.  Shaking a drink often allows bubbles of air to enter the mixture.  This affects the way the drink tastes and looks.  By the time the bubbles disappear completely, the temperature of the drink may no longer be optimal.  Also, shaking may break up any ice in the drink, which dilutes the taste.
A study performed by biochemists at the University of Western Ontario found that shaken martinis have better anti-oxidant properties than stirred martinis.  The study found that the shaken gin martinis were able to break down hydrogen peroxide which had been injected into the drink, and left only 0.072% of the peroxide behind, versus the stirred gin martini, which left 0.157% of the peroxide. Therefore, shaken may be healthier than stirred.
A: Although this question might be better addressed in a foods forum, there are some physics going on. The discipline of concocting drinks is known as mixology. The article here gives a mixologist's reason for shaking or stirring, based mainly on what the drink's constituents are and how much dilution you want to take place by the amount of ice added.
From a physics standpoint, and my own experience making drinks, shaking provides a greater rate of heat transfer in a shorter period of time (to the ice) and thus results in a colder however more diluted drink. The shaking action causes more chaotic movement of the fluids past the ice crystals and greater opportunity for that heat transfer to take place. Drinks that have heavy, sugary syrups benefit from this dilution.
In stirring you are creating a more simple movement in the glass as a vortex, and the streamlines of flow around the vortex limit the heat transfer and melting of the ice crystals.
