“If We Were Supposed to Fly, God Would Have Given Us Wings”
On July 17, 1821, Spain ceded Florida to the United States. From this State, almost exactly 148 years later (July 16 1969), the first men to land on the moon were launched into space from Cape Canaveral, as part of the Apollo 11 Space Program. If you were around at the time, you may even remember it, although your memory may be a little hazy after 54 years.
On the subject of memory, the Apollo Guidance Computer had RAM of just 4KB, and a tiny 32KB hard disk. By way of comparison, half a dozen average emails these days would enough to fill-up the Apollo hard disk, even with no attachments!
The communication time lag (or signal travel time) between Earth and the Moon is determined by the speed of light, which is approximately 186,282 miles per second (299,792 kilometres per second). The average distance from the Earth to the Moon is about 238,855 miles (384,400 kilometres).
Using these values, it takes radio signals — roughly 1.28 seconds to travel from the Earth to the Moon. Therefore, a round trip (from Earth to the Moon and back) takes approximately 2.56 seconds. So, during the Apollo 11 mission, when Mission Control in Houston sent a message to the astronauts on the Moon, there was a delay of about 1.28 seconds before the astronauts received the message. When the astronauts replied, there was an additional delay of 1.28 seconds before their message was received back on Earth. This is why, when you listen to the recordings of the Apollo missions, there are noticeable pauses in the conversations between astronauts and Mission Control.
So much for lag, yet in terms of signal blockages, there were two main times that Houston couldn’t communicate with the astronauts. One of those was during re-entry, when parts of the module’s exterior heated up to around 2,760 degrees Celsius, creating a plasma ‘shell’ which blocked communications. The other time was when they were orbitng the far-side of the moon. Michal Collins (left orbiting in the command module while the other two astronauts went on the surface) described being alone on the dark-side of the moon as the most solitary experience in human history.
Perhaps you might consider that next time you’re struggling to get coverage you get with your mobile phone!
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