An interesting aspect here is that an object can be visible only to those other objects that receive a stream of data from it.

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So far, Nord Stream engineers say the majority of objects that they have found were boulders, ship-wrecks and even a few shopping trolleys and washing machines.

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For those objects that cannot receive that stream of data it is invisible.

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The Z Backscatter Vans, or ZBVs, as the company calls them, send a narrow stream of X-rays off and through nearby objects and read which ones bounce back.

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