Do you ever wonder how the tradition of hugging to express affection got started? Are the positive feelings associated with a hug to some degree a learned, enculturated response, or are they purely natural?
As it turns out, there is some science behind this! In addition to chemical and hormonal processes, most organs of the body emanate electromagnetic (and perhaps subtle) fields that can extend beyond the organ, and sometimes beyond the physical body itself (that's how EEG and ECG monitors function). The Institute of Heartmath in Boulder Creek, California in particular has done a lot of research on heart-related physiology and its effects. They've found that the heart muscle emanates the strongest EM field of any bodily organ, being actually detectable several meters from the body.
One property of fields is that their strength varies exponentially as the distance changes geometrically. The "inverse square law" means that if you move twice as far from the source of a field, it's strength will only be one-fourth the previous value. And of course it works the other way - as you get closer, the field strength increases exponentially.
In addition to the above, the heart is also an oscillator (anything that regularly cycles between two or more states - like the pendulum on a clock). There is a phenomenon with some oscillators known as "entrainment" whereby when they are placed in close proximity, their cycles tend to synchronize.
What does all of this have to do with hugging? In the social realm, we often speak of people being in harmony, in synch, "on the same wavelength". Emotionally, we often seek "coherence", "resonance", and "coupling" with others (all wave physics terms). In view of the above, our heart fields are always intermingling with those of the people around us. If we wish to increase the chances of coming into "alignment" with another, to experience harmony and resonance with them, an effective way is to get physically close as possible. Since we sense that the heart-area is a primary locus of emotional experience, it makes sense to get two hearts as physically close as possible. Moreover, in view of the above-mentioned Inverse Square Law, the few extra millimeters of closeness provided by a hug make an exponential difference.
So, bottom line, if you want the world to be a more harmonious place, find someone you're fond of, and who's fond of you (otherwise another principle comes into play: "destructive interference" - but let's not go there). Then put sternum to sternum and squeeze. You'll brighten the world, and this is one supply of renewable energy that only increases with use!