human color vision different spectra same color

Different kinds of light can look exactly the same to us

Our eyes reduce the full spectrum of incoming light to signals from three kinds of cone cells. Very different mixtures of wavelengths can produce the same three signals. When that happens, physically different light looks like the same color.

A geography mistake helped convince Columbus that Asia was close

180° of Earth’s circumference

Ptolemy thought Europe and Asia stretched across 180° of Earth's circumference. This made the Atlantic seem much narrower than it really is and helped convince Christopher Columbus that he could reach Asia by sailing west.

In Sweden, a jury can protect someone even from the judge

In certain Swedish press-freedom trials, a jury of nine decides whether the defendant is guilty. At least six must vote for conviction. Even then, a judge can overturn the guilty finding. But if the jury acquits the defendant, the judge cannot reverse it—giving the jury a special power to protect freedom of expression.

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human color vision different spectra same color

Different kinds of light can look exactly the same to us

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