Tom Murphy's website occasionally comes up in futurist circles. His general point that unbounded exponential growth is impossible is obviously correct, but I find his condescending attitude tiresome and he often exaggerates the apparent validity of his pessimism through questionable arguments.
For example, he first insists that the conversation about energy consumption be confined to Earth and ignore space exploration, which is reasonably sensible because of the large energy cost of space travel. He moves from there to a thermodynamic bound on energy dissipation from Earth into space via black-body radiation. This argument is self-contradictory: if we were producing so much energy that it were able to heat the atmosphere (>1000x today), we would certainly have enough energy to fly into space. (The linked article "Why not space?" contains no math and few real arguments: https://dothemath.ucsd.edu/2011/10/why-not-space/ )
Also, this paragraph is relatively good evidence he didn't talk to a real economist:
>But if energy became arbitrarily cheap, someone could buy all of it, and suddenly the activities that comprise the economy would grind to a halt. Food would stop arriving at the plate without energy for purchase, so people would pay attention to this. Someone would be willing to pay more for it. Everyone would. There will be a floor to how low energy prices can go as a fraction of GDP.
None of this hemming and hawing about infinity answers the real question: is it possible for the global economy to grow until nobody has to live in mud-huts without air conditioning? The answer is almost certainly yes.
For example to get delta V to go to Mars he adds earth's 11 km/s escape velocity to the 3.6 km/s Mars injection velocity. A freshman aerospace student could tell the speed of a Mars bound ship in a hyperbolic earth orbit is sqrt(11^2 + 3.6^2).
I've done a number of posts calling out Murphy's bad arguments:
I generally agree with him that we live on a fragile, limited planet and need to learn to live within our means.
However I don't see preserving our own planet and opening a new frontier as mutually exclusive. Musk is one of the most passionate space advocates and he's working for a sustainable future (solar panels, electric cars). Some technologies benefit both space development and sustainable comfort here on earth. For example CELSS (Closed Ecological Life Support Systems) technologies needed for space might be used here on earth.
Murphy may be correct that opening a new space frontier is implausible. But he hasn't conclusively demonstrated that's the case.
> is it possible for the global economy to grow until nobody has to live in mud-huts without air conditioning?
I think generally people agree with you that the answer is almost certainly yes. Given that lack of controversy, why would you choose this as "the real question"?
Perhaps more contentious would be something like "how many years into the future will the so-called 4% safe withdrawal rate remain safe?"
I agree that the tone of straw-manning an economist who may or may not exist, but either way cannot elaborate upon or defend their own arguments, is pretty distasteful.
That said, I think you misunderstood the point of dismissing space colonization. That was done to examine the consequences of that assumption, not as an assertion that space colonization can't be economical.
Many people might think exponential growth can continue even without expanding into space, and trying to dispute this opinion without first drawing a line would just result in confusion as the discussion retreats into "but we'll just expand into space then!".
None of this hemming and hawing about infinity answers the real question...
In what world was that the real question? The one where limits to growth are a broadly accepted fact acknowledged by politicians, economists, and business leaders?
It does seem like physicist enjoys spreading the pessimism of that position in a condescending way, which makes me think the allegedly "faithful" write up of the dinner conversation, was in fact compensating for one where the physicist felt they had been beaten, and was so annoyed by that they have re-written the conversation in this more favorable way where it appears they win the argument.
Besides, I think that pessimism (what the physicist probably thinks is realism) rests on one key point, that the price of energy will have a non-zero floor. If you remove that, everything is possible, even assuming steady that energy use, and requiring continued economic growth.
I think the avoidance / supposed maintenance of the "energy price floor" point was too weak. The assumption was that it will still be a purchasable resource ("someone could buy all of it" and hold everyone else hostage), but what if energy becomes unlike that? What if energy in the future is unlimited and no one can buy all of it because everyone can access it? And the only constraint Earth imposes is that no one uses too much so we don't boil off the atmosphere or whatever.
I think that's likely. Zero point energy, free energy from the vacuum. Some whistle-blowers say our secret space program already drives its ships with this kind of power.
What's interesting is that, based on these projections about hitting critical energy output, we won't need this ZPE for another 250 - 600 years. So maybe that's why, if it does exist, it is not going to be released until then. Kind of sad that 40 years ago or so, some bureaucrat planner may have robbed the human race of free energy for the next few centuries because of the projections of an economist and a physicist, not these two, but some other pair tasked with considering the economic and physical implications of then soon-to-be back-engineered alien technology.
There's others ways to restrict access that aren't pricing. you can't marry more than one person, you can't take up all the space on a beach or a public park. it's not about price, is just laws and enforcement.
I wasn't trolling on the rest, just brave. I don't expect you to be able to respond without name calling tho, as I think you'll see free energy as topic you can't seriously touch lest it taint your reputation.
For example, he first insists that the conversation about energy consumption be confined to Earth and ignore space exploration, which is reasonably sensible because of the large energy cost of space travel. He moves from there to a thermodynamic bound on energy dissipation from Earth into space via black-body radiation. This argument is self-contradictory: if we were producing so much energy that it were able to heat the atmosphere (>1000x today), we would certainly have enough energy to fly into space. (The linked article "Why not space?" contains no math and few real arguments: https://dothemath.ucsd.edu/2011/10/why-not-space/ )
Also, this paragraph is relatively good evidence he didn't talk to a real economist:
>But if energy became arbitrarily cheap, someone could buy all of it, and suddenly the activities that comprise the economy would grind to a halt. Food would stop arriving at the plate without energy for purchase, so people would pay attention to this. Someone would be willing to pay more for it. Everyone would. There will be a floor to how low energy prices can go as a fraction of GDP.
None of this hemming and hawing about infinity answers the real question: is it possible for the global economy to grow until nobody has to live in mud-huts without air conditioning? The answer is almost certainly yes.