Here is a link to this week’s instalment of the book club for From Eternity to Here by Sean Carroll:
In the blog, Sean Carroll writes black holes are important for two reasons:
… we care about the entropy of the universe and gravity plays a crucial role in how the universe evolves … when the system is a black hole; Bekenstein and Hawking gave us a formula that allows us to calculate the entropy with confidence.
… the answer that Bekenstein and Hawking derive is somewhat surprising, and ultimately game-changing. The entropy is not proportional to the volume inside the black hole (whatever that might have meant, anyway) — it’s proportional to the area of the event horizon. That’s the origin of the holographic principle …