Just…wow.
I was just reading about this amazing fix on CNN.
And in case Voyager 1’s distance from Earth of 24 billion kilometers (16 billion miles) is not readily comprehensible, it takes a radio signal 22.5 hours to travel between it and Earth. So, about 0.27% of a light-year away now.
Good news!
Thanks for that. I had no idea that it was so far away. Jeez, 22.5 hours just to receive a message.
“Send this message to Voyager. ‘Something-something’. Wait for a response.”
“Yes, sir. But we’ll be waiting until Wednesday for a reply.”
Was there a delay due to distance in radio transmissions between the Earth and the Moon, when the astronauts visited in 1969, and subsequently?
The speed of light was not that different in 1969, nor subsequently. [Distance to Moon is, let’s say roughly speaking, about 1.3 light-seconds]
Thanks. I know that the Moon is about 238,000 miles away from Earth, so a 1.3 second delay is negligible. But 22.5 hours? Holy hannah!
Yes, well, you may think it’s a long way down the road to the chemist’s, but that’s just peanuts to space.
https://www.joshworth.com/dev/pixelspace/pixelspace_solarsystem.html
Not that negligible. At least if you’re in a conversation. Even if the other person responds immediately, there’s going to be a two and a half second delay before you hear them. If you don’t make allowances for this, it makes for a difficult conversation.
Sure, but for those of us on Earth, it was pretty negligible. The astronauts’ transmissions were clear, and we didn’t really care if there was a three-second difference between what Armstrong and Aldren said, and what Houston said.
I still remember watching the astronauts taking their first steps on the Moon. I’ll never forget that.
Shouldn’t that be 22.5 light-hours? 0.27 light-years implies that it would take a communication from Voyager 0.27 of a year to reach us.
0.27%, not 0.27 of a lightyear
Whoops.
A couple-second delay does call for a certain level of communication discipline, though. You need clear signals when one person is done talking and it’s the other person’s turn, because any sudden statement is likely to mean both sides talking over each other.
I’ve even noticed it when using cell phones. That’s the only thing I prefer about landlines. Cell phones have a tiny bit of delay that results in people talking over each other occasionally. Internet calls and videoconferencing have an even greater latency and are more likely to result in talking over each other, except that they are also less likely to be used conversationally and more likely for people to wait for the last person to stop speaking. But none of them are remotely like 1 1/2 seconds except in exceptional circumstances.
If we ever set up a tourist colony on the moon, the first call would be interesting for the novelty but it would quickly become annoying.
I remember my dad calling me from Germany to the US in the mid 70s and there was an annoyingly long delay. It took a little getting used to.
Communications between Earth and Luna are complicated by more than just the transmission delay caused by distance; the power required and the range of suitable frequencies in the UHF and SHF means that even with sophisticated multiplexing methods the bandwidth for signals as information-dense as near real-tme voice or video is going to be limited. Apollo was able to use S-band and X-band transmission for video/voice and data respectively only by using the NASA Deep Space Network but ground stations like that wouldn’t be practical for large scale communications, and an Earth-Moon communications network would almost certainly use Earth orbit satellite relays (and in Lunar orbit for backside communications) so there would be additional latencies and limitations on the quantity of calls.
Practically speaking, except for time-critical communications, it would be more reasonable to just use whatever the future equivalent is of text/voice/video messaging rather than attempting synchronous communication at the Moon and certainly farther distance. But that doesn’t make for very good drama, so movies and television ignore (or the writers don’t understand) they physics of these communications delays.
Stranger
One instance where the time lag to the Moon caused a problem during the Apollo missions is the first time they had a TV camera aimed at the lunar module during liftoff. It had to be manually controlled from Earth. By the time the signal to tilt the camera up during lift off arrived the module was already well out of frame.
For later missions they trained to start the tilt up signal a bit before the countdown hit zero.
Thank goodness - now we can send more Chuck Berry!
It makes me mad that those details don’t convince the moon hoax fools that the moon landings really did take place. Horrible people.
On a more optimistic vein:
That’s resilience! And an excellent and dedicated team on the ground. Congratulations!