As any backyard stargazer knows, one simply has to look up at the sky on a cloudless night to see light whose origin was quite a long time ago. Here, due to the fact that the mean scattering and absorption lengths are greater in size than the observable universe, one can record light from stars whose origin occurred around the time of the big bang. Unfortunately for oceanographers, the opacity of sea water to light far exceeds these intergalactic limits, making the job of collecting optical images in the ocean a difficult task.

Jaffe, J.S., K.D. Moore, J. McLean, and M.P. Strand. 2001. Underwater optical imaging: Status and prospects. Oceanography 14(3):64–75, https://doi.org/10.5670/oceanog.2001.24.

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