What exactly is happiness? (IM 606)

Some researcher argue that happiness depends on one and one thing only - pleasant sensation in our body. It doesn't depend on objective condition like health, wealth or even prestige. Rather it depends on the correlation between objective condition and the subjective expectations. When things improve, expectation enhances, and even good objective conditions may leave us deserted and dissatisfied. When things go wrong, expectation shrinks and even bad objective condition may make you as happy as before. Some social scientist believe that the key to happiness are in the hand of biochemical system. They believe that lasting happiness comes only form serotonin, dopamine and Oxytocin. Aldous Huxley, in his novel Brave New World, published in 1932 during the Great Depression, states the only way to make people experience high level of happiness is to manipulate their biochemical system. Some scholars, on the other hand, believe that happiness consists in seeing one's life as entirely meaningful and worthwhile. A meaningful life can be extremely satisfying even if it's full of hardships. But from scientific point of view, human life has no goal or purpose or a meaning and if our earth were to blow up tomorrow, the whole universe will keep doing its business as usual. Thus any meaning that we ascribe to our lives is just a delusion. So, perhaps happiness is synchronizing one's personal delusions of meaning with prevailing collective delusions. Now the real question arises... If happiness is based on feeling pleasant sensations, can we be happy if we re-engineer our bio-chemical system? Why aren't we investing billions in understanding our brain chemistry and developing appropriate treatments, ignoring all the revolutions? And if happiness is based on feeling that life is meaningful, then is it true that to be more happier we need to delude ourselves more effectively? Or is there any other alternative?