I saw the news about Mars-One project a few days ago. I was immediately fascinated by its beauty. It’s certainly the kind of cause I have always believed in. However, the thought of leaving my wife for the rest of my lifetime didn’t feel right. I would only be able to see her through delayed video call with an 8 minutes telecommunication delay between Mars and Earth. (For what it means to be space-long-distance-lovers, check out Makoto Shinkai‘s Voices of a Distant Star) Some hollow, sorrow feeling starts to fill up my chest. It is, and has always been, these moments of imagining the scene of an indefinite farewell, telling me how much I love her.
People always say, you don’t know a good thing until it is gone. I think it certainly applies to love. Love might have a different meaning to different people. But for most of us, love carries our happy memory and good feeling about someone, and it drives us to make them happy, or sacrifice for them. How much you love someone or something, means how important it is to you, so how much you are willing to sacrifice for it? Because of the design of our genes and oxytocin, when others see an action as sacrifice, people in love actually feels joy.
Sixteen years ago, I first came to know the existence of my wife when her name appeared on the “Top 50 in final exam of 7th grade” of my middle school (there were about four hundred some kids in my year so she did a good job to get into top 10%). Would I sacrifice my career for her at that point? Certainly not, I even wanted to get on that blackboard without caring much whether that action meant squeezing her out. But after all these years, now my favorite Chinese old song containing a line like “sun is setting, skyline is blurring, we two are also walking into our evening, looking back to sweets and bitters, ups and downs, I never regret to share this life with you”, I hesitate on the idea of once in a lifetime chance for space travelling, for the fear of breaking that twilight imagined in my head. I never knew I would sacrifice the universe for someone.
From PPV (physics point of view), when you ask “how much”, or try to make comparison, you need a measuring method. To perform a correct measurement, you need a clear definition of the object. So, before measuring love, what is love? Wait, this is not the right question. We don’t need a theoretical definitions, which usually leads to philosophical arguments. We need an operational definition here. Let’s exam the love in operation (only the general cases, defects and doping are not the consideration of a generalized physics model): People in love, they usually feel happy (spiritual or sexual attractions). They feel happy when being together, so they usually want to stay together longer (attachment). When they decide that probably no one else can make them happier, they go get a marriage certificate. With time passing by, if the happiness sustains, nothing would happen. But if they don’t feel happy anymore, or they encounter something or someone which can grant them more happiness, they will start comparing. If they feel it isn’t worth to continue, they will choose to separate.
Wait. Stop. Right here.
So, now the question is: when they choose to separate, what happened to the love? Some of them will deny the previous love or blame on the other party. But those actions are due to outrage, it is usually amplified and misleading, not the truth. The truth is that they are not willing to sacrifice their own happiness for staying in the relationship, or say that they predict the level of joy will only go down and never bounce back. (Like you are going to sell a stock when you think it is not going to raise again. Love is an investment for future happiness.)
Thus, here comes the operational definition of love: love is a status you find joy in sacrificing for the other party’s happiness and well-being.
To measure the level of love, ask how much you are willing to pay to stay in that relationship.
A physicist's thoughts 