[GatoNegroPeludo (OP)]

Why do we have electronic devices and no positronic devices?

[evan_au]

The science fiction writer Isaac Asimov (of "I, Robot" fame) imagined robots with positronic brains. But in reality this was just a scientific-sounding way of saying "I have no idea how you could build a computer that is the size, flexibility and power consumption of a human brain, but it really doesn't affect the storyline".

Positrons are really hard to manipulate, because as soon as they come in contact with electrons, they annihilate each other in a blaze of gamma rays. Particle accelerators manipulate positrons with magnetic and electric fields in a high vacuum, keeping them well away from normal matter.

These days we have tiny computers made out of semiconductors like silicon, which conduct signals by a flow of electrons and "holes".

• The electron is an "extra" one made available by replacing a silicon atom by one like phosphorus, which has 5 electrons in its outer shell, compared to 4 for silicon
• The hole is the "absence" of an electron which comes from replacing a silicon atom by one like boron, which has only 3 electrons in its outer shell, instead of 4 for silicon.

The hole is unusual, because it acts mathematically like a positively-charged electron (ie a positron) flowing through the silicon, and will migrate towards the negative terminal of a battery, but without the risk of annihilation. (It is actually formed from a flow of negatively-charged electrons heading in the opposite direction.)

So in a sense, the hole acts like a positron, and we now have a form of Asimov's "positronic brain".

http://en.wikipedia.org/wiki/Doping_(semiconductor)#Group_IV_semiconductors

(To give credit to Isaac Asimov, we still can't make computers which have the flexibility, size and power consumption of the human brain - but we are a lot closer than the room-sized computers which existed when he started writing his robot stories...)

[chris]

It must be possible, because Commander Data in Star Trek has a positronic brain

[GatoNegroPeludo (OP)]

So, lets say positrons have a tendency to explode things if molested...

thank you!