I find it interesting that people talk in absolutes ("fusion will never be economical!") when the devices they're using were "impossible" only a few decades ago

I find it interesting that people talk in absolutes ("fusion will never be economical!") when the devices they're using were "impossible" only a few decades ago. Also the difference between a 4:00:00 marathon and a 3:59:59 is less than a 0.007% improvement but it's a huge victory nonetheless. Once someone proves an arbitrary numerical barrier can be overcome humans tend to make a lot of progress shortly thereafter.