Pentagon has a laser that can identify people at a distance by their heartbeat

Re:Pentagon has a laser that can identify people at a distan... by ben_w on Friday June 28, 2019 @03:14AM (#20302162)

I thought the mean free path of x-rays in air would limit you to, effectively, “radiation mines”? (Or short-range death-rays, robot-mounted because the backscatter would kill a human operative)?

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Re:Pentagon has a laser that can identify people at a distan... by TeMPOraL on Friday June 28, 2019 @04:26AM (#20302452)

If I'm reading this chart correctly[0], visible light has much worse mean free path than x-rays, so wouldn't x-ray lasers work even better than visible ones?

As for backscatter, that's only an argument for a shell instead of a ground installation - you pulse the laser high up, where the backscatter is of no concern to you.

[0] - https://en.wikipedia.org/wiki/Mean_free_path#/media/File:Pho...

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Re:Pentagon has a laser that can identify people at a distan... by ben_w on Friday June 28, 2019 @08:47PM (#20310050)

I saw the same chart, but I thought it’s only showing down to 1 keV photons? Whereas blue light is about 2.6 eV?

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Re:Pentagon has a laser that can identify people at a distan... by TeMPOraL on Saturday June 29, 2019 @03:37AM (#20311313)

My mistake, I confused the scales when reading the chart. Indeed it doesn't extend below 1keV.

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