Aidan,

It is a very long way from the lab to practical applications. A lot of ideas that look promising end up not being useful in practice or take a very long time to become useful. 'Fusion is the energy source of the future and always will be.' You can't just read the hype and assume that it is all going to work somehow. The fact remains that a lot of problems are just plain hard. Just think of all the money that has been pouring into Alzheimers research. There still isn't a cure or a completely reliable method to prevent it. Cancer survival rates have improved a lot for some types, but very little for others. President Nixon's idea was that we would do some research and wipe out cancer.

http://www.cancerresearchuk.org/cancer-info/cancerstats/survival/common-cancers/#Trends

The point about the GPI is that most of us are not much better off in real terms. This wouldn't be the case if population growth were as wonderful as you think it is. Most American men have wages that have stagnated or declined in real terms since 1973. How has population growth helped them?

The problems with congestion, overstretched infrastructure and public services, urban amenity, etc. are obvious. If it were just poor planning, and not an inability to keep up with very rapid population growth, then such problems would not exist in all our major cities.

More people put obvious pressure on the environment. The Australian Conservation Foundation has nominated human population growth in Australia as a Key Threatening Process under the Environmental Protection Act.

http://www.acfonline.org.au/sites/default/files/resources/EPBC_nomination_22-3-10.pdf

It is interesting that our politicians have been unable to come up with tame scientists who will tell them what they want to hear, as they have with demographers and economists. That is why they have to keep ignoring or censoring reports they have commissioned. With all due respect, why do you think people should believe you and not the folks at the CSIRO or Australian Academy of Science who have looked at this issue?

We aren't obsessing about population; you have your head in the sand.

Divergence, it's not a very long way from the lab to getting practical applications commercialised when their advantages are obvious. Fusion is somewhat of an exception because of the extreme difficulty doing it in a lab (as well as the very high setup costs that any practical application would have). I'm not just reading hype and expecting it to work somehow; I'm reading the facts, considering the enormous advantages over the way things are currently done, and expecting engineers to exploit those advantages in a decade or (conservatively) two. Why do you expect them not to?

"The fact remains that a lot of problems are just plain hard. Just think of all the money that has been pouring into Alzheimers research. There still isn't a cure or a completely reliable method to prevent it. "
There's a VERY big difference between commercialising something that's ALREADY been done in the lab and STARTING research on something with the hope of eventually commercialising a product. But the main problem with Alzheimers research was the unchallenged experimental error that led researchers to the false conclusion that it was caused by too much aluminium in the brain, resulting in a huge amount of wasted effort. Now the likeliest cause is thought to be too much copper in the brain, though many researchers dispute this and base their work on alternative hypotheses.

"Cancer survival rates have improved a lot for some types, but very little for others. President Nixon's idea was that we would do some research and wipe out cancer."
Survival rates are improving all the time, and I'd expect to see significant differences between the current rate and what your link reported. Nixon was apparently under the false impression that cancer was one disease with a single cure. We know much better now.

"The point about the GPI is that most of us are not much better off in real terms. This wouldn't be the case if population growth were as wonderful as you think it is."
No, it wouldn't be the case if population growth were as wonderful as you assume I think it is. I think it has advantages and disadvantages, and the advantages (in Australia's case at least) outweigh the disadvantages.

"The problems with congestion, overstretched infrastructure and public services, urban amenity, etc. are obvious. If it were just poor planning, and not an inability to keep up with very rapid population growth, then such problems would not exist in all our major cities"
It's not just poor planning; it's a failure to follow through on the planning that's done. The problem isn't inability; it's unwillingness to commit resources.

"More people put obvious pressure on the environment. The Australian Conservation Foundation has nominated human population growth in Australia as a Key Threatening Process under the Environmental Protection Act."
While we're living unsustainably, more people is always going to put more pressure on the environment. But stopping population growth won't solve the problem; incorporating sustainability into everything will.

Aidan claims that had our politicians "followe[d] through on planning" and had been willing to "commit resources" that the traffic congestion, overcrowding and other problems now being faced by Melburnians could have been prevented.

Would Aidan concede that until our politicians lift their game that further population growth should cease?

Back in August, Denis Napthine, who is thankfully no longer Premier of Victoria, announced plans to increase Melbourne's population from 4.4 million to 7.7 million by 2051! This is discussed on 7.30 Victoria at http://www.abc.net.au/news/2014-05-23/can-melbourne-cope-with-7-million-and-more-/5475094

An article which comprehensively demolishes the case for population growth is: "Is Population Growth a Ponzi Scheme?" (4/3/2010) by Joseph Chamie at http://www.theglobalist.com/is-population-growth-a-ponzi-scheme/.

"Would Aidan concede that until our politicians lift their game that further population growth should cease?"
No. Ceasing population growth would create its own problems, and would probably deter the politicians from lifting their game.

"Back in August, Denis Napthine, who is thankfully no longer Premier of Victoria, announced plans to increase Melbourne's population from 4.4 million to 7.7 million by 2051! This is discussed on 7.30 Victoria at http://www.abc.net.au/news/2014-05-23/can-melbourne-cope-with-7-million-and-more-/5475094 "
Probably just the result of rivalry with Sydney, and it won't make much difference whether the plans are there or not. What are needed are plans for more railways so Melbourne can more easily cope with a bigger population.

As for the article you linked to, it doesn't really demolish anything much, and it assumes the government will mismanage any economic downturn.

Note yet more self-contradiction in Aidan's latest 'contribution' to the debate.

On the one hand Aidan insists that population growth is beneficial for Australia. On the other he proposes measures such as "more railways" and more capable politicians than we now have to "COPE with population growth."

Aidan wrote: "As for the article you linked to, it doesn't really demolish anything much, ..."

Feel welcome to quote from http://www.theglobalist.com/is-population-growth-a-ponzi-scheme/ to illustrate what you mean. I urge others to also read the article for themselves and form their own judgements.