Astrophysicist: Traffic Jams Replicate What In Black Holes

One big reason black holes are feared is that once you go in, you can't get out. That's due to the event horizon, the boundary beyond which information can never escape back into the wider universe, astrophysicist Paul M. Sutter wrote for Space.com.

Photo Insert: The physicists found the same black hole scenario plays out in their simple model of traffic.

In a new paper, two physicists have developed a mathematical model of traffic jams and found that they could use the language of relativity — and black holes — to describe what's going on. What's more, this mathematical insight could potentially give urban planners better tools to cut down on traffic problems and warn drivers before they reach vehicular "event horizons."

The setup is pretty simple, according to the paper, published online in the preprint database arXiv. Imagine a line of cars, all of which are traveling in the same direction and at the same speed down a single lane of highway with a fixed distance between them. If the car in front taps its brakes, the next car in line will see the brake signal and know that something's up. In response, that car will also begin to brake. This process continues down the line of cars

The physicists found the same black hole scenario plays out in their simple model of traffic. There simply isn't enough time for the brake signals to propagate down the line. In effect, the information gets "trapped" behind the event horizon. Cars within the horizon will learn about the brake signals in front of them, but the cars outside the horizon never will.

The end result of this process is a pileup of car crashes. This is exactly what happens to matter that falls into a black hole.

Because it can never escape, it's forced to continue toward the center of the black hole, drawn by the immense gravity there. That center is the singularity, a point of infinite density where all the matter that formed the black hole has been crushed into oblivion.

So goes for black holes, so goes for traffic: As soon as a vehicular event horizon appears, it signals that that singularity — a pileup of car crashes — is imminent, Sutter said.

And it isn't just a fun analogy; the physicists found that this situation is baked into the mathematics that describe traffic, the same way it's baked into the mathematics of black holes.

Knowing that this situation can arise can help urban planners — not to mention, autonomous-vehicle designers — prevent it.

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