How huge is a 1mm beam when it hits the moon (and visa-versa) ? I wonder if wolframalpha can tell me... Actually, I don't even know how to ask it the proper question. Can anyone make this formula work in wolfram? http://laserpointerforums.com/attachments/f51/17952-calculat... update: I think I figured this out as ((λ * L) / d)* 2 (((630nm in meters)*(380000km in meters)) / (1mm in meters)) * 2 Which would be a nearly…
Somewhere on a cover event when they launched LADEE, someone asked that, which they answered the receiver had to be within a spot with a (radius or diameter, I can't remember) of 3 km on earth
I'd imagine TCP, as a protocol starts to fall over with moon-to-earth latencies. Or would it? Perhaps simply increasing the retransmission timer would give us interplanetary internet. I wonder.
That's why I always found moon people to be lame at quake!
One day technology will really have to do something about lightspeed to allow interplanetary quake!
Solution for the lag will be a special category "bot play". The bot will not be programed but will behave like a black box, computer ai will record you every time you play in a local game and will slowly build the bot around. Then the bots will compete on a server, maybe separated by categories determined by previous recording time.
Why is it easier to transmit from the moon to earth? Here we have more power and larger/better/faster/more tuned lasers than the space vehicle does. Seems like getting earth's transmit rate way up would be relatively easy while getting the vehicle's transmit rate up would be really really hard.
I don't work in this field, but here's an educated guess (or two). Lasers are not perfectly coherent, parallel beams. They're close but, over the distance between the Earth and the moon, even the most powerful, carefully adjusted and perfectly focused laser will expand much like a flashlight beam. Take the laser pointer you use for presentations and shine it across the room and you'll see a substantially larger spot…
And fortunately in most use-cases, we'd prefer a spacecraft to have more upload bandwidth to Earth than download bandwidth from Earth. The largest data NASA would send to the craft would probably be software updates, megabytes or a few gigabytes at most, while the craft might want to send thousands of images and even videos, gigabytes or terabytes of data, limited only by its energy budget and length of transmission window. (Note: I don't work in this field either).
The article cites 622 Mbps down, 20 Mbps error-free up. Is the implication that the 622 Mbps down is before error correction? Either way, it's pretty incredible. Even if the 622 Mbps down isn't completely error free, but maybe 99%, you just need to use a video compression algorithm that is error tolerant.
Why is it easier to transmit from the moon to earth? Here we have more power and larger/better/faster/more tuned lasers than the space vehicle does. Seems like getting earth's transmit rate way up would be relatively easy while getting the vehicle's transmit rate up would be really really hard.
Firstly, the spacecraft is not a big data consumer so it makes sense to concentrate on downlink bandwidth. Secondly, the telescopes on Earth can be much larger and use much better equipment so it's easier to pick up weaker signals.
I think that's a debatable topic. Some say it is just a pure geometric effect of curved space (and thus instantaneous), not a force of nature that propagates.
The pure geometric effect propagates at light speed also (unless you want to discard relativity).