A purely hypothetical scenario has threatened the very core of physics by pitting Albert Einstein's long-standing theory of general relativity against the principals of quantum mechanics and string theory. 

The scenario is as amusing as it is morbid: if an astronaut were to fall into a black hole what would happen?

Obviously death would occur. But how the astronaut dies has fired an intense debate in the physics community.

The old line of thinking went that the astronaut would not feel anything out of the ordinary at first, even as he passed the point of no return: the black hole's event horizon, the boundary beyond which nothing can escape. But as he falls ever downward into the back hole he would eventually be ripped apart by the effects of powerful gravitational forces.

But, as the journal Nature reports, a string theorist from the Kavli Institute for Theoretical Physics in Santa Barbara, Calif. has a different solution. Based on his calculations, Joseph Polchinski thinks that the event horizon is a seething firewall that would instantly incinerate anything that fell into it.  

According to Nature:

Such firewalls would violate a foundational tenet of physics that was first articulated almost a century ago by Albert Einstein, who used it as the basis of general relativity, his theory of gravity. Known as the equivalence principle, it states in part that an observer falling in a gravitational field - even the powerful one inside a black hole - will see exactly the same phenomena as an observer floating in empty space. Without this principle, Einstein's framework crumbles.

University of California, Berkeley string theorist Raphael Bousso said the firewall idea shakes the foundations of what most scientists believe about black holes."It essentially pits quantum mechanics against general relativity, without giving us any clues as to which direction to go next."

The rest of the story gets pretty dense, but it makes for a good read. The short of it is that the firewall principle is not a new idea, but the new calculations supporting it have proven to be indefatigable, shaking the physics community at its core.