Welcome! I very rashly decided to do this A-to-Z business again – but hey, it should be fun.
For A, I’ll talk about ansibles. The term was first used by Ursula K. Le Guin, and has since found its way into many works of science-fiction. Perhaps the most memorable use is in Orson Scott Card’s Ender series, where ansibles figure very heavily into the story.
An ansible is a communication device that allows for instantaneous communication over great distances. For example, if you want to call up a rover on Mars, it can take anywhere from 4 minutes to 24 minutes, depending on the positions of the two planets. With an ansible, you could call it up and get data back from it instantly.
Einstein told us that this can’t happen – information is limited by the speed of light.
Max Speed: 1,079,252,848 km/h or 670,616,629 mph
Any faster than that, and information would effectively travel backward in time (which, as far as anyone can tell, is impossible). So that’s why ansibles and other ways of FTL communication (like Star Trek’s subspace transmissions) remain in the sci-fi realm.
Now, there might be a way to pull it off with quantum entanglement. The best way to explain this is with a quote from livescience.com:
In quantum physics, entangled particles remain connected so that actions performed on one affect the other, even when separated by great distances. The phenomenon so riled Albert Einstein he called it “spooky action at a distance.”
The rules of quantum physics state that an unobserved photon exists in all possible states simultaneously but, when observed or measured, exhibits only one state.
Spin is depicted here as an axis of rotation, but actual particles do not rotate.
Entanglement occurs when a pair of particles, such as photons, interact physically. A laser beam fired through a certain type of crystal can cause individual photons to be split into pairs of entangled photons.
The photons can be separated by a large distance, hundreds of miles or even more.
When observed, Photon A takes on an up-spin state. Entangled Photon B, though now far away, takes up a state relative to that of Photon A (in this case, a down-spin state). The transfer of state between Photon A and Photon B takes place at a speed of at least 10,000 times the speed of light, possibly even instantaneously, regardless of distance.
So there might be a way to use entangled particles to transmit over distances , but it remains to be seen if usable information can actually be sent this way.
In my current fiction:
I haven’t mentioned any ansibles in Far Flung yet. But hey, the story is made up of logs that are somehow transmitted to Earth, so there must be something similar coming into the story!
More about ansibles and FTL communication possibilities: