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hearts of cities. Th e story eerily foreshadowed the development, 30 years later, of nuclear weapons.
    Th e box is now soaring through the air. Each time it nears the ground, it superheats the surface, and the plume of expanding air hurls it back into the sky.
    Th e outpouring of 1.875 terawatts is like a house-sized stack of TNT going off every second.
    A trail of firestorms — massive conflagrations that sustain themselves by creating their own wind systems — winds its way across the landscape.
    A new milestone: Th e hair dryer is now, impossibly, consuming more power than every other electrical device on the planet combined.
    Th e box, soaring high above the surface, is putting out energy equivalent to three Trinity tests every second.
    At this point, the pattern is obvious. Th is thing is going to skip around the atmosphere until it destroys the planet.
    Let’s try something different.
    We turn the dial to zero as the box is passing over northern Canada. Rapidly cooling, it plummets to Earth, landing in Great Bear Lake with a plume of steam.

    And then . . . 

    In this case, that’s 11 petawatts.
    A brief story:
    Th e official record for the fastest manmade object is the Helios 2 probe, which reached about 70 km/s in a close swing around the Sun. But it’s possible the actual holder of that title is a two-ton metal manhole cover.
    Th e cover sat atop a shaft at an underground nuclear test site operated by Los Alamos as part of OperationPlumbbob. When the 1-kiloton nuke went off below, the facility effectively became a nuclear potato cannon, giving the cap a gigantic kick. A high-speed camera trained on the lid caught only one frame of it moving upward before it vanished — which means it was moving at a minimum of 66 km/s. Th e cap was never found.
    Now, 66 km/s is about six times escape velocity, but contrary to common speculation,it’s unlikely the cap ever reached space. Newton’s impact depth approximation suggests that it was either destroyed completely by impact with the air or slowed and fell back to Earth.
    When we turn it back on, our reactivated hair dryer box, bobbing in lake water, undergoes a similar process. Th e heated steam below it expands outward, and as the box rises into the air, the entire surface ofthe lake turns to steam. Th e steam, heated to a plasma by the flood of radiation, accelerates the box faster and faster.

    Photo courtesy of Commander Hadfield
    Rather than slam into the atmosphere like the manhole cover, the box flies through a bubble of expanding plasma that offers little resistance. It exits the atmosphere and continues away, slowly fading from second sun to dim star. Much of the Northwest Territories is burning, but the Earth has survived.

    However, a few may wish we hadn’t.
    1 Th ough not necessarily those plugged into a second device. If a charger is connected to something, like a smartphone or laptop, power can be flowing from the wall through the charger into the device.
    2 Note: If you’re ever trapped with me in a burning building, and I suggest an idea for howwe could escape the situation, it’s probably best to ignore me.

weird (and worrying) questions from the what if? INBOX, #2

    Q. Would dumping anti-matter into the Chernobyl reactor when it was melting down stop the meltdown? —AJ

    Q. Is it possible to cry so much you dehydrate yourself? —Karl Wildermuth

Th e Last Human Light
    Q. If every human somehow simply disappeared from the face of the Earth, how long would it be before the last artificial light source would go out?
—Alan
    A. Th ere would be a lot of contenders for the “last light” title.
    Th e superb 2007 book Th e World Without Us, by Alan Weisman, explored in great detail what would happen to Earth’s houses, roads, skyscrapers,farms, and animals if humans suddenly vanished. A 2008 TV series called Life After People investigated the same premise. However, neither of them answered this particular question.
    We’ll start with the