# Category Archives: Computer Science

## Q: Is it possible to write a big number using a small number? Is there a limit to how much information can be compressed?

Physicist: Although there are tricks that work in very specific circumstances, in general when you “encode” any string of digits using fewer digits, you lose some information.  That means that when you want to reverse the operation and “decode” what … Continue reading

## Q: Why are numerical methods necessary? If we can’t get exact solutions, then how do we know when our approximate solutions are any good?

Physicist: When a problem can be solved exactly and in less time than forever, then it is “analytically solvable”.  For example, “Jack has 2 apples and Jill has 3 apples, how many apples do they have together?” is analytically solvable.  … Continue reading

Posted in -- By the Physicist, Computer Science, Equations, Math | 11 Comments

## Q: How good is the Enigma code system compared to today’s publicly available cryptography systems?

Physicist: Freaking terrible. The Enigma machine used a “rolling substitution cypher” which means that it was essentially a (much more) complicated version of “A=1, B=2, C=3, …”.  The problem with substitution cyphers is that if parts of several messages are … Continue reading

## Q: How do I encrypt/hide/protect my email?

Cryptographer: Lots of people have been asking “how do I encrypt my email” or “how can I hide from NSA surveillance”. It turns out that the answer to the first question is fairly straight forward, while the second is not, … Continue reading

Posted in -- Guest Author, Computer Science, Paranoia | 4 Comments

## Q: What does it mean for light to be stopped or stored?

Physicist: We’ve gotten a handful of questions since this was published and led to articles like this, this, and, this.  In a nutshell, some dudes in Germany (Georg Heinze, Christian Hubrich, and Thomas Halfmann) have found a method to shoot … Continue reading

## Q: Since the real-world does all kinds of crazy calculations in no time, can we use physics to calculate stuff?

The original question was: I’ve heard somewhere that they’re also trying to build computers using molecules, like DNA. In general would it work to try and simulate a factoring algorithm using real world things, and then let the physics of … Continue reading