Who invented the automatic sliding door?
It wasn’t Edison. Nor Westinghouse. Nor any of the many engineers who reached the peak of their powers in the 20th century.
Believe it or not, the first functioning automatic door was the brainchild of a Greek inventor who lived during the time of Jesus.
Heron of Alexandria (also known as Hero) is credited with the first steam-powered engine, the first vending machine (a nifty device that dispensed water for religious ablutions with the deposit of a coin), various special effects apparatuses for use in the theater, and the world’s first machine powered entirely by wind. Whatever you choose to call him, the world’s inventors think he’s a Hero.
One of Heron’s most ingenious creations was his “automatic” door at a local temple.
Worshipers gathered outside must have felt they were witnessing a miracle when the priest stepped up to the altar, lit the fire, then turned toward the door – whereupon it would swing open all by itself. The gods must be pleased! In truth, the heat generated on the altar activated a hidden counterweight and pulley arrangement that rotated the door’s hinges.
Very clever.
The automatic doors that we have come to know arrived on the scene in 1931. A pair of engineers named Raymond and Roby installed a system at a Connecticut hotel that allowed servers to walk in and out of the kitchen toting platters of food, never needing to pause to turn door handles.
How do automatic sliding doors work?
Some have strategically placed pressure sensors. If you step on a mat, the doors slide apart. Of course, one needs to be carrying a minimal weight – which is why Buzz Lightyear and friends have to jump up and down at the same time to trigger the entrance to Al’s Toy Barn in Toy Story 2.
Most automatic doors currently utilize motion detectors or optical sensors. A microwave beam points downward and outward toward the space directly in front of the door.
Still other doors use infrared technology to detect temperature changes. As a person approaches, sensors detect his or her heat signature and respond by sliding open.
We’ve come a long way from Heron of Alexandria.
No matter how it happens, it still seems miraculous. We walk forward in faith – and seemingly without warning, a closed door opens.
When we turn to the Bible’s last book, we learn that no one opens and closes doors like Jesus.
“These are the words of him who is holy and true, who holds the key of David. What he opens no one can shut, and what he shuts no one can open. Behold, I have set before you an open door, which no one is able to shut” (Revelation 3:7-8).
Those powerful words have informed the church’s missionary efforts for generations.
One hundred years ago, the door of evangelism seemed to have closed forever in Russia. During seven decades of state-sponsored atheism, Moscow’s churches became museums. Orthodox priests were silenced – sometimes permanently. But when the Soviet house of cards collapsed in 1989, observers were stunned to discover that more than 70% of Russia’s citizens acknowledged belief in God – even though most of them had no living memory of a time when religion could be practiced openly.
At the same time, something similar was happening in China.
For more than a century, Western missionaries had invested lavish gifts of time and treasure in the hope of introducing Christ to the world’s largest nation. Progress was meager. Then things got worse. After seizing power in the late 1940s, Communist dictator Mao Zedong slammed the door on all foreign influences.
Communication went dark. Followers of Jesus went underground. After Mao’s death 30 years later, however, sociologists learned that the church had not only survived, but thrived. During the next 24 hours it’s almost certain that more people will come to faith in Christ somewhere in China than any other spot on earth.
A door was closed. Then it reopened. Why did that happen?
Only the Lord of Open Doors can say for sure.
Likewise, he alone knows why doors seem to open and close in a seemingly random fashion in our own lives.
Here’s what we can count on: Automatic doors only work when you approach them. A rocket may be equipped with a sophisticated guidance system, but that system is irrelevant as long as it’s sitting on the launching pad. Nothing changes until its engines fire and the rocket begins to rise.
So it is with our walks with God.
You may worry and pray and wonder and hope and read great books and talk to every wise person you know, yet still not be able to discern what God is about to accomplish in your life.
But there is something you can do.
Get up and walk. See what door opens.
You don’t have to be a Hero to follow Jesus. Just keep going forward.
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