It's funny. Without the Fat Electrician the Youtube algorithm probably wouldn't have recommended me your video. It's nice to hear a reaction from someone who actually knows their stuff.
Fun history fact: the last surviving veteran of the civil war died in 1956. My brain cannot comprehend a civil war soldier witnessing this kind of madness.
The true first man-made item to make it to space was the German V-2 rocket back in 1944. The Germans made up a test to see how high the rocket was able to go straight up, if my recollection serves correct the rocket made it to 175km (109mi) which is well above the established height for reaching space (100km or 62mi).
Thing is, that was the minimum speed for it to have been captured in that single frame. It could have been even higher. The estimate was 41.6 miles per second. If whatever chunk made it out of the atmosphere had 26.16 miles per second velocity remaining, it is currently interstellar and is the furthest manmade object ever and should realistically remain so forever.
Finding this blast as a seismic reading was how America learned to monitor the Soviet Union for when they chose to do underground testing. Which they did, starting in 1963. The seismic waves are different than an earthquake, so were able to be recognized.
Fun Fact: When asked if the plate ever reached space, Dr. Brownlee famously replied, "I have no idea, but I always hoped it did." It remains the fastest man-made object ever recorded relative to Earth's atmosphere.
"Harmless" Nuclear Test - Operation Plumbob - Nuclear Engineer Reacts to the Fat Electrician
https://youtu.be/Komj07wzM5E