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I will still have received the message after I had sent it. It seems to me that communication this way does not violate causality. I will receive the laser, however, at year 199,999. The tachyons will arrive 1,000 years earlier than the laser, so for me, I will receive the message at year 199,998. She records a message and releases it at the same time as the laser. So since she got the message at year 99,999, she immediately sends me a reply back going through the same procedure as I did. However, she will only see the laser at year 100,000. From my vantage point, that message will arrive to her at year 99,999 the same would be true for my friend's vantage point. It would arrive, say, a thousand years earlier. If tachyons existed, then the message would arrive to my friend before the photons in the laser. Say it is the year 0 for both of us at the time I did this. I record a message on the tachyon communication device and release the message at exactly the same time as I activate the laser, both of which are directed to the other planet which is one hundred thousand lightyears away. I and my immortal friend on the other planet want to communicate, with a strong laser and a tachyon communication device. Let's say I have two planets that are one hundred thousand lightyears away from each other.