Watch what happens when a fix treats the symptom that's visible, without confirming it's actually the cause — and why the price of finding out late is rarely just money.

In September 2016, Samsung recalled 2.5 million Galaxy Note 7 phones after a string of batteries began overheating and catching fire. The company moved fast: within two weeks, it had a fix — replacement units built with batteries from a different supplier.

Then the replacements started catching fire too.

The first recall had addressed the symptom that was visible — one supplier's battery — without fully confirming that was the entire cause. By October, Samsung recalled every remaining unit, including the replacements, and discontinued the Note 7 for good. The total cost ran past five billion dollars, on a phone that had been on sale for less than two months.

Prostate cancer is the second most commonly diagnosed cancer among men worldwide — more than 1.46 million new cases and 396,000 deaths in 2022 alone. The biology of the disease barely changes by country. The outcome does, enormously, and the reason is almost entirely about timing: caught while still confined to the prostate, five-year survival is close to 100 percent. Caught after it has already spread elsewhere in the body, that number falls to roughly 30 percent.

The cost tells the same story from another angle. In the United States, treating localized prostate cancer costs a median of about $31,000. Treating it after it has metastasized costs more than double that — upward of $75,000 — before counting the lost income of a man too sick to work.

That gap shows up starkly between countries, too. In wealthy nations, prostate cancer mortality has been falling for decades, driven by earlier detection. In many lower-income countries, mortality is rising — not because the disease is more aggressive there, but because it's far more often found only after it has already spread. Between 1990 and 2019, the death and disability this disease causes fell by more than a quarter in high-income countries. In the poorest countries, over those same years, for the same disease, it rose by nearly 14 percent.

The Hubble Space Telescope launched in April 1990. Two months later, NASA announced the $1.5 billion instrument was flawed — its primary mirror had been ground to the wrong shape, off by about 2.2 micrometers, roughly one-fiftieth the width of a human hair. Every image came back blurred.

The cause traced back to the device used to check the mirror while it was being polished. That testing instrument had its own undetected error — so the mirror had been polished beautifully, to match a flawed measurement. Nothing independently cross-checked the check itself.

Hubble flew nearly blind for three and a half years, until a 1993 shuttle mission installed corrective optics — built, essentially, as a pair of glasses for a telescope. An investigation into the flaw later put a number on the delay itself: catching the error before launch would have meant a $2 million fix. Catching it after Hubble was already 355 miles up meant a repair mission costing $86.3 million for the mirror problem alone. It worked. Hubble went on to become one of the most productive scientific instruments ever built — but not before paying, in full, for the years it took to notice.