In an interconnected world, why can a local crisis (e.g., financial crisis, pandemic) rapidly spread globally?

Hello! That’s an excellent question, and it’s very relevant to our lives today. The underlying principle isn’t complicated—think of it as us all living in a vast "global village" or a massive spiderweb. This web connects each person, company, and country.

Let me use a few everyday metaphors to explain why trouble in one place makes the whole world "catch a cold."

1. Movement of People: A "Virus Highway" with No Speed Limit

Imagine a time before planes and high-speed trains, when traveling between continents took months. If someone fell ill during the journey, they might recover or sadly pass away on the ship, preventing the virus from reaching its destination.

But now?

• Ultra-convenient travel: If you feel unwell in Beijing this morning, you might not even realize it. By afternoon, you're on a plane, landing in New York or London hours later. The virus travels internationally with you. By the time you realize you’re sick, it may have already spread silently in the new city.
  This explains why pandemics like COVID-19 swept across the globe at lightning speed. Our air routes form a "global highway" laid out for viruses.

2. Flow of Capital: A Row of "Dominoes"

Money flows globally today—this is "financial globalization." Your savings might be deposited in a bank that invests abroad or buys foreign government bonds.

• One falls, all fall: Take the 2008 financial crisis. It began with the U.S. housing bubble bursting, leading to the collapse of banks like Lehman Brothers. But these banks owed money not just to Americans—they were indebted to institutions across Europe and Asia. Meanwhile, banks worldwide held massive amounts of U.S. housing-linked "financial products."
• Chain reaction: The first domino fell in America, knocking over Europe’s dominoes next, followed by Asia’s… Soon, banks globally panicked, stopped lending to each other, businesses couldn’t get loans, factories halted, and workers lost jobs. A crisis that started in the U.S. snowballed into a global recession.

3. Supply Chain Links: "Grasshoppers Tied to One String"

Look around at your phone, clothes, or car—they’re rarely made entirely in one country.

• "Intertwined existence": Your phone’s chip may be designed in the U.S., manufactured in Taiwan; its screen comes from Korea, camera from Japan, and final assembly happens in China.
• One break, total paralysis: Suppose the chip factory shuts down due to an earthquake or pandemic. Suddenly, phone makers worldwide can’t get chips, halting new production. Likewise, if an auto plant misses one small part, the entire assembly line stops.
  So when a factory halts in one place, you might face shortages or soaring prices for goods on another continent. We enjoy globalization’s affordable, high-quality goods but must also bear the risk of "shared prosperity, shared peril."

4. Information Spread: A Super "Emotion Amplifier"

In the internet and social media era, information (fact or rumor) spreads faster than viruses.

• Contagious panic: A rumor about a country’s weak economy can reach traders globally in seconds. Panic may trigger mass selling of its stocks and currency, turning the rumor into reality and sparking a market crash.
• Collapse of confidence: During the pandemic, seeing online videos of panic-buying due to shortages spread fear instantly. People elsewhere wondered, "Will we run out too?" and hoarded supplies, causing needless shortages.

Summing Up

Simply put, globalization is a double-edged sword.

• The upside: It enables the free flow of capital, goods, people, and information, boosting economies and letting us enjoy global products/services.
• The downside: Such interconnectedness means risks are "shared." Any disruption sends shockwaves through the entire network like ripples, triggering worldwide tremors.

In this linked world, no nation is truly an "isolated island." We must learn to manage these global risks together—because all our fates are already tightly woven.