Honestly, I can just change what I consider economic growth and the problem immediately goes away. I can make that graph do anything I want, just a matter of convincing enough people to go along with it.
Also:
>Why can't this go on?
>If this holds up, then 8200 years from now
Alright. Well how about we worry about that in 8100 years?
Ultimately an economy has to meet the fundamental physical needs of human beings (at least until we're all Singularitied into Hive Mind Cryostatsis Upload Tanks or equivalent). That's food, clothing, shelter, and the rest of it --- the base of Maslow's Pyramid.
More money can solve some distributional probems, but ultimately not the problem of insufficient production or supply.
The classic "toy economy" example of this is "The Economic Organisation of a P.O.W. Camp", which looks at the use of cigarette-based currency within a World War II prisoner of war camp.
It's not a perfect analogue of a true economy (goods were largely supplied to the camp through the German authorities and Red Cross shipments, there was little actual production or labour). But what was illustrated were both price fluctuations as the currency (cigarettes) increased and decreased in prevalence, subject to an innate destructive demand (habitual smokers). And when the actual supply of goods (food and other items) dried up late in the war, no amount of currency could in fact make the camp economy function.
The point isn't that physical limits will only be a problem in 8200 years, it is to counter the defective idea that such growth can be sustained indefinitely. We don't have access to all the atoms in the galaxy, and can't even make use of most of the ones we have here on earth. We will hit a wall much, much sooner.
Also:
>Why can't this go on?
>If this holds up, then 8200 years from now
Alright. Well how about we worry about that in 8100 years?