Category Archives: Computer Science

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 | 10 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

Posted in -- By the Physicist, Computer Science, Math, Number Theory, Paranoia | 12 Comments

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

Posted in -- By the Physicist, Computer Science, Entropy/Information, Experiments, Physics, Quantum Theory | 14 Comments

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

Posted in -- By the Physicist, Computer Science, Engineering, Entropy/Information, Physics | 8 Comments

Q: How do you write algorithms to enycrypt things?

Physicist: There are several algorithms, but almost all of them are all based on “trap-door encryption”.  The idea is that you find some kind of mathematical process that’s easy to run forward, but effectively impossible to run backward, unless you … Continue reading

Posted in -- By the Physicist, Computer Science, Math, Number Theory | 8 Comments