Best-selling author Kabir Sehgal explores the future of money during the age of space exploration. How will we pay to tour the galaxy? What form of currency will reign dominant in the year 2515? Sehgal goes on to explain why it’s better to pay attention to predictions of science-fiction than those of economists.

Sehgal is author of The New York Times Bestseller Coined: The Rich Life of Money and How Its History Has Shaped Us.

Kabir Sehgal: So what will our currency be 500 years from now? I like to think that we might be space tourists and space travel is going well. And what will we use as currency in space? Well, you know, if you we do a transaction in space, the distances are quite far. So if you're on one planet and I'm on another planet and we do a transaction, considering the theory of relativity like how do you calculate interest rates and what time is relative? Where do you put that clock to calculate interest rates? You would have to build arguably a distributed network throughout the galaxy so that when you're doing the transactions, you could basically calling on information systems throughout the different moons and different planets and it may be that we had to find a new rare metal to use as a currency. Like what do they use in Star Wars? They use something called the Intergalactic Banking Unit or The Credit and that was based on a rare metal.

So it might be that as we start to see space tourism we have to use some kind of new metal that we find in the galaxy; we might have to build a distributed network throughout the galaxy so we can verify local transactions. And even here in America, or in the world, on the Earth, we might be building systems where it's like an energy grid. We're all plugged into the same grid and we're trading vitamin B and calories and we are rebalancing our energy. Because if you look throughout the natural world, energy is the currency of the natural world; the further we get into the future maybe money will remain the same and remain as energy.

It's not so crazy to look at science fiction. In fact, the first time the credit card was ever mentioned was in a book in 1887 called Looking Backwards by a man named Edward Bellamy. It's about this guy who falls asleep, wakes up in the year 2000 and what does he see? He sees the government creating credit cards for their citizens and the government issues money on these credit cards. And so it was more of a socialist utopia, but if you look to the future, you can look at what economists say about the future, but I like to think about what are the science fiction people saying about the future? What is the idea of money in the future? And so some science-fiction writers say well maybe in the future if you can have a pacemaker embedded into your body, why not a payment device? So you just wave your hand over a payment reader. What about a reputation chip where you walk into a store and everyone knows your reputation already?

I mean that already happens. I walked into a store the other day or a restaurant the other day and I took out my cellphone because of the maître d' said, "I'm sorry I don't have your reservation." And I took out my cellphone and I was just texting my friend, "You can take your time," and the maître d' said, "Well sorry sir, like, please don't write a negative review on me on Yelp or on Google." I said, "I'm not going to do that." But to him his reputation was currency. If I put a negative review on him on Yelp or the internet, I might be intruding or I might be damaging his future business. In that case we don't need a brain chip for reputation; reputation is already a currency.