Imagine waking up tomorrow to find that aliens have wiped clean every digital financial system on the planet. Banking app? Gone. Venmo? Dust. Credit cards? Worthless plastic.

Thankfully, these aren’t your typical War of the Worlds destroyers, so to prevent the economy from collapsing these oddly considerate ET’s have also left neat little gold bags on everyone’s doorstep, carefully measured to match your previous net worth. Through some alien wizardry, they’ve even managed to keep society running smoothly—no panic or toilet paper hoarding, just a world suddenly stripped back to physical transactions.

Chipotle bowls are now worth a few sprinkles of gold dust, rent is a bag of coins, and paying tuition means lugging a suitcase of heavy bars to Wyman Park. Paying the bill at restaurants suddenly becomes a nuisance when you have to break out a scale to precisely measure 0.23 grams plus tip.

The state of affairs quickly becomes annoying for ourselves and the people we transact with the most, like our close friends. Without the convenience of Venmo requests, am I just a dick for telling Will to shave off 0.05 grams of gold for those 4 slices of pizza? Am I supposed to ship 0.02 grams through UPS for the shared Netflix account I have with that friend 500 miles away?

Being the best and brightest, we decide to take matters into our own hands: rather than “settle up” every transaction on the spot, we’ll create a shared Google Sheet where people can record things like “TJ owes Will $10 of gold on November 25th.” Once a month, we’ll sit in an intimate circle, tally up how much everyone is owed minus how much they owe others, then exchange gold chips until everyone’s satisfied.

For a while, this system is brilliant. Most of my daily expenses can now just be recorded as rows in a spreadsheet (interchangeably referred to as a ledger) and I find myself peeling back the floorboards to get into my gold stash less and less.

When I spend my last $50 on drinks at CVP, I still get to confidently tell Will I owe him $5 for a hangover smoothie the next morning because, on paper, the amount Ramy owes me for the previous night is far greater. In fact, Will doesn’t have to take my word for it—the proof is immediately available in the spreadsheet. Importantly, the system works smoothly because we all trust each other and know that at the end of each month, everyone will settle up and pay or receive their due.

People around campus start noticing our newfound freedom from hauling pounds of gold in our pockets. When asked, we explain that it’s really simple: just record debts in a shared ledger and trust everyone will settle up eventually. The idea catches on fast, because we were brilliant to recognize that good friends actually pay each other back, and soon other groups are spinning up their own spreadsheets.

Eventually, you meet someone that wants to buy your used MCAT prep books, but they’re using a different spreadsheet. Rather than break out the gold once again, we decide to do something radical—just combine our spreadsheets. Not only can you now transact with twice as many people, but so do I, and in fact everyone else in both circles.

As more groups assimilate, our monthly meetings soon become laborious town halls. We start spacing out the monthly settlements to every two months, then six, then twelve. As time goes on, it matters less that we actually settle up, and more that people hold the shared belief that settlement would eventually happen.

Fast forward a few years, and the entire Hopkins community—students, faculty, and businesses along St. Paul’s—operate on a single, massive, shared ledger that technically settles once every 1000 years. At a certain point, the spreadsheet’s credibility and reach made writing “TJ owes Chipotle $10” just as meaningful as handing the cashier literal gold. The ledger became the currency. Everyone’s gold collects dust in safes as real wealth simply exists as a running tally of debts in the spreadsheet.

We’re getting ahead of ourselves. In the process of hitting fast forward we glossed over a few crucial improvements that allowed our protocol to maintain its integrity. After all, we’ve yet to address humanity’s age-old plague—people trying to game the system. Two critical issues emerged:

1. What’s stopping me from just writing “Will owes TJ $1,000,000?”
2. Who will notice if I delete a year-old row saying “TJ owes Alek $10?”

Problem (1) was solved quickly when we realized that we needed a robust way to verify that each transaction was actually intended by the debtor. After putting our heads together, we developed a clever solution: each row of the ledger must not only record the transaction details, but also attach a selfie of the debtor holding up the transaction details and today’s newspaper (I forgot to mention the aliens also destroyed all deepfake and photoshop technology).

This new information tells everyone else with a copy of the sheet that Will must have agreed to sign off on the transaction, otherwise why would he have taken that selfie? When rows are added without a selfie or the selfie doesn’t look like the sender, they’re thrown away.

Problem (2) had an even simpler solution—we just turned off all delete permissions on the ledger. Annoyance is guaranteed but it’s a relatively small price to pay for true safety. After all, we expect people to be careful with the stakes at hand.

Having addressed these limitations, our new fangled system seems nearly perfect. The humble ledger slowly engorges Baltimore, then the entire East Coast, and eventually all of North America. Taking a step back, we realize that our humble solution to navigating the alien apocalypse somehow became a whole ass global currency.

Of course, things don’t stay rosy forever. As table stakes grow to truly global scale, we’re forced to confront some unfortunate truths.

Preventing deletions in the spreadsheet means it quickly grows large and unwieldy, especially when millions of people start trying to create rows at once. Plus, who exactly should host this new financial system? Google’s servers seer a bit precarious… hell, even AWS S3’s 99.999999999% reliability seem laughable.

There’s also the obvious political complications. What happens when China wants their citizens to use a different spreadsheet? Or when the EU demands that certain transactions be blocked? Could Google engineer’s be coerced by state actors to destroy the servers? When the inevitable crash happens, how do we agree which backup is the “true” ledger?

Come to think of it, in the aftermath of the aliens’ great reset, how had we worked our way back to the exact system they had just wiped out?