what is the "K T" barrier?

Answer 1

this is not a question about astronomy. i have never heard of a "kt barrier".

http://en.wikipedia.org/wiki/Astronomy

the cretaceous-tertiary boundary is the boundary between two geologic periods, and was about 65 million years ago. it is marked by a world-wide layer of black clay that has a high concentration of iridium, an element rare on earth. it might also be called the cretaceous-paleogene boundary because the name tertiary is no longer used and is obsolete.

http://en.wikipedia.org/wiki/Cretaceous-Tertiary_extinction_event

the greatest mass extinction occurred between the permian-triassic periods about 251 million years ago. 96 percent of marine species and 70 percent of terrestrial vertebrate species became extinct.

http://en.wikipedia.org/wiki/Permian-Triassic_extinction_event

Answer 2

It's not the KT "barrier" but the KT boundary. No big deal : -) The KT boundary is a geological time separation where the Cretaceous period ended and the Tertiary began. The boundary is interesting for two reasons --
1. The boundary layer was laid down some 65-million years ago, just about the time when the dinosaurs went extinct;

2. All around the world, the boundary layer contains a thin layer of the element iridium in more abundance than could occur naturally. A research group headed by Dr. Alvarez showed that this high concentration of iridium is probably the debris tossed into our atmosphere by a disastrous asteroid impact. He theorized that the dinosaur extinction happened then because of the global effects from that impact.

All of the Alvarez theory was borne out when a great crater was located in the Gulf of Mexico and dated at some 65-million years.

Answer 3

THERE IS a difference between the KT Boundary and the kT barrier (namely, one has 2 capital letters, but more precisely, the word "Barrier" vs. "Boundary". The asker wanted the definition of the "barrier".

The kT barrier represents a quantity of energy computed by multiplying the temperature of the computing environment (room temperature/72 is generally used, or ~300 degrees Kelvin) by Boltzmann's constant.

The only way to penetrate this barrier is to either lower the temperature of our computers or to develop thermodynamically reversible computers which do not generate entropy and therefore do not dissipate nearly as much heat as conventional, irreversible computers.

As the densities and switching speeds of our computational devices continue to increase exponentially, the amount of energy dissipated by these devices must remain at a certain level, otherwise economically impractical cooling apparatus is required.

Conventional computers perform thermodynamically irreversible logic operations, that is, it is not possible to extrapolate prior machine states based solely upon information from future states. Information, in the form of bits, is erased. This bit erasure represents "entropy" (link below) , which is correlated to heat dissipation.

Answer 4

Dinosaurs died and new life arose rapidly at KT "boundary "

New research suggests the dinosaurs may have been annihilated in as little as 10,000 years – the merest wink of a geological eye. A study of rocks in Italy and Tunisia supports the theory that a single, giant impact of an asteroid or long-period comet led to a rapid extinction 65 million years ago. Sujoy Mukhopadhyay and colleagues report in this week's Science how they analysed the amount of helium-3 in the rocks of the K-T boundary to establish that it was deposited in about 10,000 years – too short a period to support the rival view that vulcanism caused a more gradual (100,000-year-long) extinction. The constant rate of accumulation of helium-3 also indicates that the impactor was not part of a comet shower or bombardment. More intriguing, however, than the fast demise of the dinosaurs and up to three-quarters of all the other life on Earth at this time is how rapidly new species arose to replace them. This encourages the view that impacts in general – providing they are not too frequent and catastrophic – may actually accelerate evolution rather than slow it down.