The Ptolemaic kings of Egypt were aggressive collectors. Ships entering Alexandria's harbor were searched; any books found were confiscated, copied, and the copies returned to the owners. The originals stayed in the Library. Athens was persuaded to lend the original manuscripts of the great tragedians - supposedly for copying. Egypt paid a massive deposit, then kept the originals and forfeited the deposit.

The Library wasn't just a collection - it was a research institution. Scholars from across the Mediterranean world came to study and work. Euclid developed geometry there. Eratosthenes calculated the Earth's circumference. Archimedes studied there. The Library represented the apex of ancient intellectual achievement.

The Library's destruction is often blamed on a single event - Julius Caesar's fire of 48 BC, or the Arab conquest of 641 AD, or the Christian patriarch Theophilus in 391 AD. The truth is messier. All these events may have damaged the Library, but none definitively destroyed it.

Caesar's fire burned ships in the harbor and spread to warehouses near the docks - probably book warehouses, but perhaps not the main Library. Theophilus destroyed the Serapeum, a temple that housed part of the collection. The Arab caliph Omar allegedly ordered the books burned, saying 'If they agree with the Quran, they are unnecessary; if they disagree, they are heresy.' But this story appeared 300 years after the supposed event and may be apocryphal.

The real destruction was probably gradual. Roman conquest reduced Alexandria's importance. Civil wars disrupted scholarship. The rise of Christianity brought hostility to pagan learning. Funding dried up. Scholars left. Books deteriorated without replacement.

By the time of the Arab conquest in 641 AD, the great Library may have already been effectively dead - its collections dispersed, destroyed, or rotted. The Arabs found a diminished city with little of its former intellectual glory. The destruction of the Library of Alexandria wasn't a single tragedy but a long decline, each generation losing more of what the previous had preserved.

What was lost can only be estimated. The complete works of the three great tragedians (Aeschylus, Sophocles, Euripides) numbered perhaps 300 plays; only 33 survive. The Library's catalog, compiled by Callimachus, listed works by authors whose names we no longer know. Scientific treatises, historical accounts, poetry, philosophy - all gone.

Some works survived through copies made in Constantinople or the Arab world. Aristotle, Plato, Euclid, and others reached us through this circuitous route. But for every work that survived, dozens or hundreds were lost. We know enough to know how much we don't know - and to mourn what was erased.

The Library of Alexandria became a symbol of knowledge lost - a warning about the fragility of civilization. Every subsequent library, every archive, every digital backup exists partly in response to Alexandria's ghost. The fear that everything we know could be lost drives preservation efforts worldwide.

A new Bibliotheca Alexandrina opened in 2002, near the site of the ancient Library. It holds 8 million books - far more than the original - plus digital archives designed to survive catastrophe. It's a deliberate attempt to recreate what was lost, though what was actually in those ancient scrolls remains unknown. The Library of Alexandria is defined by its absence - a hole in human knowledge that can never be filled.