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| ▲ | tomrod 44 minutes ago | parent | next [-] |
| It's a semantic saying that misses what people typically mean when we speak about simultaneous events. Someone sends an email or speaks on a voice call on the other side of world and a receiver still gets that note at the speed of light, there is slight latency. It's still completely reasonable to measure that latency as we can effectuate improvements to our machines and networks when it increases. The same as if someone wrote a letter in the 1860s and the horses were sick, causing a delay. Simply because information was received by us, the common understanding is that the notification was sent previously, because that is how cause and effect work. |
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| ▲ | anonzzzies 2 hours ago | parent | prev | next [-] |
| Yes, but we can say it happened in our past. But agreed, we cannot go back 20m years and say it’s simultaneous with the events here. If GP meant that, then agreed. |
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| ▲ | ViktorRay an hour ago | parent | prev [-] |
| Wait then what about events that happen on Pluto? Pluto is around five light hours away from us. If an astronaut goes to Pluto and films herself doing activity A and then broadcasts that back to Earth, it would take around five hours for the broadcast to reach us. So you’re saying that it is not correct to say her recorded activity happened five hours ago? |
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| ▲ | philipov 19 minutes ago | parent | next [-] | | The idea driving this conclusion is called the Relativity of Simultaneity - There is no absolute notion that two events happened "at the same time". You want to say that a distant event occurred at the same time as a nearby event that occurred 5 hours ago. However, a distant third party observing both events would not agree. This becomes painfully apparent when dealing with black holes. Person A falling into a black hole passes through the event horizon normally and reaches the singularity in finite time. However, Person B observing from outside never sees Person A pass through the event horizon. From Person B's perspective, it doesn't make sense to ask what happens simultaneously with Person A reaching the singularity - it takes infinite time just to reach the event horizon. Even asking the question is nonsense. https://en.wikipedia.org/wiki/Relativity_of_simultaneity | |
| ▲ | herbstein 15 minutes ago | parent | prev [-] | | If we imagine a third observer in a space craft traveling close to he speed of light, it's possible to construct the scenario in such a way that the pilot of the space craft would observe the two events happening at the same moment. Time is relative |
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