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Enjoy features only possible in digital – start reading right away, carry your library with you, adjust the font, create shareable notes and highlights, and more.

Discover additional details about the events, people, and places in your book, with Wikipedia integration.

Ask Alexa to read your book with Audible integration or text-to-speech.

Prime numbers are one of the most basic topics of study in the branch of mathematics called number theory.

Primes are numbers that can only be evenly divided by themselves and 1. For example, 7 is a prime number since I’m left with a remainder or a fractional component if I divide 7 by anything other than itself or 1. 6 is not a prime because I can divide 6 by 2 and get 3.

Circa 2014 o.o


On a late summer afternoon it can seem like sunlight has turned to honey, but could liquid—or even solid—light be more than a piece of poetry? Princeton University electrical engineers say not only is it possible, they’ve already made it happen.

In Physical Review X, the researchers reveal that they have locked individual photons together so that they become like a solid object.

“It’s something that we have never seen before,” says Dr. Andrew Houck, an associate professor of electrical engineering and one of the researchers. “This is a new behavior for light.”