What if, while making popcorn, all the cores popped at the same time? Should I be worried?
– Skye M., Portland, Maine
Don’t worry, not all of your popcorn kernels will pop at the same time.
The popcorn kernels burst because the water inside heats up and boils. When water boils, it usually expands, but the hard outer shell of the core keeps the vapor contained. For a while, the steam continues to heat, until the pressure builds enough to break the outer shell, releasing the pressure with a snap.
A typical bag of microwave popcorn can hold 300 kernels. If all 300 were to blow up at the same time, the bag might break and do some damage, but your microwave would probably be fine. According to the 3M Noise Navigator Sound Protection Database, the average popcorn produces about 80 decibels of sound power. A sound wave 300 times louder than the sound of a typical popcorn would be about as loud as a nightclub and quieter than many power tools. If your microwave can survive the vibrations of being near a nightclub speakers, I bet it could survive a mega-pop.
But what is the probability of a mega-pop?
A popcorn kernel appears when its internal temperature reaches around 180 degrees Celsius. The critical temperature is different for each core – it depends on how much moisture it contains, how hard the shell is, and how quickly your microwave heats the particular area where the core is located. Most cores will take about the same time to appear, but some will cross the line earlier or later than others by chance. If we assume that they are heated independently, there is no reason why they couldn’t reach their critical internal pressure at the same time – it’s just statistically unlikely.
To estimate how unlikely a mega-pop is, we need to know a little more about the timing of the popcorn. I don’t usually do experiments to answer questions, but I love popcorn, so I decided to personally collect data. I put a bag of popcorn in the microwave, recorded the sound with my phone, and then watched the audio in a spectral analyzer, which clearly showed each individual pop.
The tally of the results showed that most of the bursts occurred within 30 seconds of around the minute and a half.
Since an individual pop lasts about 40 milliseconds, let’s say they all have to appear within a 40 millisecond window to count as “at the same time.” Using my microwave pop distribution, any kernel would have about a 1 in 1750 chance of popping at the same time as any other. The chances that all 300 nuclei will burst at the same time are about 1 in 10⁹³⁵.
How improbable is that?
At the time of his death in 1995, popcorn mogul Orville Redenbacher had 24 living descendants – suppose he has about 50 now and they all have phones with US numbers. You now decide you want to talk to them. You pull out your phone and start dialing random numbers, and somehow you hit 50 on your first round of calling – without a single wrong number. As they drop out, you correctly guess their birthdays and the last four digits of their Social Security numbers. Once you’ve completed those calls, you take a sheet of paper and write down the winning Mega Millions jackpot numbers for the next seven lottery draws. Finally, you guess the result of 100 consecutive throws.