[tzs]

> The total amount of recovereable uranium in the oceans is in the billions of tons. Orders of magnitude more U and Th in the crust. Fusion energy seems possible and the total solar irradiance is astronomical. Self replicating solar system probes, that would turn us into a Kardashev type 2 civilisation, are also conceptually possible, and could use only resources from other planets.

You are greatly underestimating how fast exponential growth gets out of hand.

At 1% annual growth in human energy use starting from where we are now, in around 9300 years our annual energy use would equal all the energy in the Milky Way galaxy. By "all the energy" I mean all the energy including the energy we'd get from converting all the mass into energy (E=mc^2).

12000 years from now, so a mere 2700 years after we are consuming an entire Milky Way per year, our annual consumption would equal all the energy in the entire observable universe.

There are similar limits if we look at population growth. At 1% annual population growth we would need the mass of the observable universe to make all the living humans in about 12300 years.

For population growth another limit 1% hits in 12000 years is space. Assuming no FTL, since every human is close to Earth now in 12000 years every human has to be within 12000 light years of Earth. The volume of a sphere of radius 12000 light years divided by the population after 12000 years of 1% growth gives a volume available per human that is about equal to the volume of one person.

One I've not calculated is what the limit is when you combine 1% energy growth and the speed of light limit on how fast we can expand human space. Long before the earlier limit of 12000 years to needing all the energy in the universe we'd reach a point where the energy density in human occupied space is enough to turn human space into a black hole.

If anyone wants to calculate that limit I'd love to see the results.

[Geisterde]

You are treating the economics of growth like paperclip simulator.

[tzs]

How so?

I believe I'm treating the physics of growth, not the economics of growth.

If you need to use 1% more energy each year starting from what we use now per year, our universe does not contain enough energy to do that for more than 12000 consecutive years.

[Geisterde]

It is that analysis in specific that I object too. Its not obvious energy will increase the way you describe; as ive written elsewhere, the factors involved in current population/birth declines are not related to environmental carrying capacity, they are more closely related to the global monetary system and central planning, and it could have a relationship to high levels of economic development.

Existing political issues aside, an entire industry can die off and we can still call that growth, as we do when its replaced by something that creates more value at a lower cost, like the beginning of the automotive industry ending the reign of horses. We dont know if quantum computers will ever be realized for practical purposes, if they are then maybe we can unlock all the processing power anyone could ever need with much lower power consumption, or maybe we dont but computation simply becomes a less pressing matter after we reach some unknown level of technology (ie. If you are trying to capture a black hole to use as an energy source, you really might only need the computational power of a ti-86.

There is also, in my observation, a type of material ladder that bends ever towards the crystalization (forgive the terminology) of chemicals. Where raw wood rots in weeks to months, treated lumber can last a decade, vinyl can last 2-3, steel for 100+, who knows what comes next? These materials are likely to require lots of energy to create, but require less over their lifespan. There is a similar ladder in energy, starting with humans burning poop and currently sitting somewhere between nuclear and natural gas, where each step up on the ladder requires greater capital investment but produces less pollution and has lower lifetime costs, where nuclear is like the diamond of energy, huge investment to create something that will last this side of forever.