Global debt hit a milestone recently. If you add up the debt of all of the countries on Earth, you end up with a stunning $91 trillion. More than a third of that comes from one country: the United States.  

This nation’s gross cumulative debt has hit $35 trillion — a number so large, the International Monetary Fund warns that it’s putting the entire global economy at risk. 

But it’s hard to even imagine what the number 35 trillion looks like, much less 91 trillion. So, I decided to employ a time-honored journalistic device: break the number down to make it easier to visualize. 

So, say you had 35 trillion actual dollar bills, and you put them end to end, starting from Earth. How far up would they reach? Like, maybe, the moon? 

As it turns out, the moon is not even close. It only takes about 2.5 billion bills to get to the moon. It’s no wonder the IMF is worried: U.S. debt has boldly gone where no human has gone before.

“Yeah, these are big numbers,” said Peter Blair Henry, an economist at Stanford University’s Hoover Institution. To get a sense of just how big they are, Blair Henry agreed to join us as we followed our dollar bill trail out into the solar system. 

Call it “Debt Trek.” Our $35 trillion debt is so huge, our trail of dollars would breeze past Mars, which is 140 million miles away (roughly 1.5 trillion dollar bills). The next planet out: Jupiter, the giant of the solar system. But not nearly giant enough. (It takes roughly 4.5 trillion bills to reach Jupiter.) Next up: Saturn. But at a measly 9 trillion bills away, on average, even Saturn can’t put a ring on U.S. debt.

We continue to the outer planets. We pass Uranus and arrive at Neptune. Neptune is just under 30 trillion dollar bills away. We’ve reached the last official planet in our solar system, and we still have about $6 trillion in debt to go.

Keep in mind, a dollar bill is just over 6 inches long, and 35 trillion of them would almost reach Pluto. I ran the calculations over and over again because, truly, I was stunned, no phasers needed.  

“Honestly, the best way to deal with huge numbers like that is to think about ratios,” Blair Henry said. “What really matters is: How big is the debt relative to the size of the economy?”

In other words, America’s practically-Pluto debt isn’t a problem as long as America is generating practically-Pluto money. The trouble is, it’s not. The U.S. is only making Neptune money.

Our economy is producing roughly $30 trillion worth of stuff this year as measured by gross domestic product. And our debt, which has been piling up for decades, is $35 trillion. Right now, our debt-to-GDP ratio is around 120%. We owe more than we’re making — that’s what worries Blair Henry. 

“As your debt ratio rises, your finances are just getting tighter and tighter,” he said. “And the danger is, at some point, your creditors look at your debt situation and say, ‘Oh my gosh, you are not going to be able to pay me.’”

So those creditors will start demanding higher interest rates when they lend money. 

“Your borrowing costs go up dramatically, and that can lead to a financial crisis,” Blair Henry said.

In fact, that has already started to happen. For the U.S., borrowing costs were really low for a long time. The government could basically borrow money for free because people were confident the country would pay it back. The size of the debt didn’t seem to matter. 

But as that debt has ballooned, lenders have started demanding higher interest rates from the U.S. “We’ve hit a turning point,” said Harvard economist Kenneth Rogoff. “At least I believe that.” 

Rogoff was chief economist at the International Monetary Fund for years. He calls the rising interest on our debt a huge economic problem.

“This is the biggest thing that’s happened in the global economy in the last five or 10 years,” he said. That’s because the U.S. has practically-Pluto debt, so even a small jump in interest rates gets galactic real fast. 

“The interest payments that we have to make on U.S. debt have soared,” he added. “I think the interest payments alone is the equivalent of our military budget.”

This year, the interest bill is expected to approach $1 trillion. That’s $1 trillion we can’t spend, for instance, on roads, health care or growing the economy. Our debt isn’t just big, it is draining our resources.    

“People got this idea that it was just free — ‘Don’t worry about what your debt is!’” said Rogoff. “That’s the big change that’s happened in the world, is a bucket of cold water on this idea that debt doesn’t matter.”

Rogoff said if another global crisis, like COVID, hits and the U.S. needs to spend a lot of money fast, borrowing could get even more expensive. That gets risky — it could even destabilize the economy. And nobody could step up to save the day because almost every other major economy is in intragalactic debt too.

Rogoff said debt is a great tool, but it should not be a free-for-all. “You want to use debt for a rainy day, but you don’t want to just declare every day a rainy day.” 

On Neptune, it apparently rains diamonds. But until we can get our hands on those, reining in the debt isn’t that complicated, Rogoff said. It would require Congress to make some tough decisions: cut spending and raise taxes. We would need to tighten our belts as a country, and Congress would need to compromise.

Maybe it would be more realistic to look into those diamonds on Neptune. 

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