My understanding is that there was supposed to be a delay between the communication from the moon to Earth. Why were the communication instantaneous?

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    $\begingroup$ The delay is about 1.25 seconds each way. What makes you think it was instantaneous? $\endgroup$ May 20, 2015 at 19:36
  • $\begingroup$ I don't suppose you're asking about a "tape" delay (as used in TV broadcasting for censorship purposes)...? Would have been a political landmine to implement such a thing. $\endgroup$
    – Anthony X
    May 21, 2015 at 0:29
  • 8
    $\begingroup$ This question shows a lack of research and is based on an incorrect premise. $\endgroup$ Jun 5, 2015 at 5:07
  • 3
    $\begingroup$ I suppose it was instantaneous because it was faked :-) $\endgroup$
    – mins
    Jun 5, 2015 at 6:27
  • $\begingroup$ They weren't @Kaomi Matos $\endgroup$ Mar 10, 2023 at 21:10

2 Answers 2


The delay for Earth-Moon communications is about 1.25 second (distance is ~ 380,000 km, the speed of light is ~300,000 km/s). You'd notice this delay only in conversations: every time ground control says something, it takes 2 seconds for the astronauts to respond.

In videos of the live broadcast (search for 'Apollo 11 live ABC') you can hear the delay: ground control says "go for depressurization", then you hear the echo of that coming back from the Moon, and the astronauts' response.

  • $\begingroup$ yay, thanks!! :-) $\endgroup$
    – uhoh
    Nov 23, 2020 at 4:00

Some modern presentations of the moon landing will edit out the gaps created by the communication delay to make conversation sound more natural, but if you look at the timestamped transcripts, you can verify the 2.5 second round trip delay. Note that the timestamps all refer to the time the Earth-side recording occurred, so the radio delay appears when one of the crew members (CMP, CDR, LMP in the transcript) is responding to the Capcom (CC).


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