We're used to thinking of black holes as places where gravity is so strong not even light can escape—where an unnoticed crossing by a hapless astronaut over an unseen and un-felt “event horizon” nonetheless means a point of no return. “According to Einstein's general theory of relativity, no signposts would mark the spot where the chance of escape dropped to zero,” writes physicist Joseph Polchinski.

But in this issue's cover story, “Burning Rings of Fire,” Polchinski paints a new picture, courtesy of his and others' work in a discipline that Albert Einstein found vexing: quantum mechanics. Replacing the unknowable border to an eternity of darkness is a stormy “firewall” of instantly lethal high-energy particles. “If quantum mechanics is to be trusted, firewalls are the consequence,” Polchinski notes. The controversial finding arose from scientists' attempts to resolve apparent contradictions of physics that occur in extreme environments, a challenge highlighted by Stephen Hawking, among others.

Nanotechnology can be equally invisible to the eye but promises far more benign—in fact, salutary—encounters. In our special report on the “Future of Medicine,” we examine what benefits nanomedicine is bringing us already and how those will take shape in the future. We can look forward to improvements in cancer-fighting therapies, diagnostics, wound healing, delivery of drugs with nanomotors, and more.

A different class of unseen actors is at work in the worrying trend of cyberattacks. Software vulnerabilities have led to hacked networks, servers, personal computers and online accounts—with theft of information from millions. Your own PC or corporate network can become enslaved to further the ends of cybercriminals.

How to Survive Cyberwar,” by Keren Elazari, takes an unsettling look at the growing problem. Taking a military point of view, Elazari argues, will ultimately not be the most successful approach—indeed, “it might just make things worse.” Instead she suggests thinking of it as a public health issue. Government agencies are key players, “but they cannot stop the spread of [cyber]diseases on their own.” Success will mean that all of us play important roles. Read on to see how we can, as cybercitizens, do the equivalent of washing our hands and getting our vaccines.