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This paper aims to formalize long-term trajectories of human civilization as a scientific and ethical field of study. The long-term trajectory of human civilization can be defined as the path that human civilization takes during the entire future time period in which human civilization could continue to exist.

This paper focuses on four types of trajectories: status quo trajectories, in which human civilization persists in a state broadly similar to its current state into the distant future; catastrophe trajectories, in which one or more events cause significant harm to human civilization; technological transformation trajectories, in which radical technological breakthroughs put human civilization on a fundamentally different course; and astronomical trajectories, in which human civilization expands beyond its home planet and into the accessible portions of the cosmos.

Status quo trajectories appear unlikely to persist into the distant future, especially in light of long-term astronomical processes. Several catastrophe, technological transformation and astronomical trajectories appear possible.

Some current actions may be able to affect the long-term trajectory. Whether these actions should be pursued depends on a mix of empirical and ethical factors. For some ethical frameworks, these actions may be especially important to pursue.

The purpose of this paper is to communicate a method to perform simultaneous topology optimization of component and support structures considering typical metal additive manufacturing (AM) restrictions and post-print machining requirements.

An integrated topology optimization is proposed using two density fields: one describing the design and another defining the support layout. Using a simplified AM process model, critical overhang angle restrictions are imposed on the design. Through additional load cases and constraints, sufficient stiffness against subtractive machining loads is enforced. In addition, a way to handle non-design regions in an AM setting is introduced.

The proposed approach is found to be effective in producing printable optimized geometries with adequate stiffness against machining loads. It is shown that post-machining requirements can affect optimal support structure layout.

This study uses a simplified AM process model based on geometrical characteristics. A challenge remains to integrate more detailed physical AM process models to have direct control of stress, distortion and overheating.

The presented method can accelerate and enhance the design of high performance parts for AM. The consideration of post-print aspects is expected to reduce the need for design adjustments after optimization.

The developed method is the first to combine AM printability and machining loads in a single topology optimization process. The formulation is general and can be applied to a wide range of performance and manufacturability requirements.

This paper provides a detailed survey of the greatest dangers facing humanity this century. It argues that there are three broad classes of risks – the “Great Challenges” – that deserve our immediate attention, namely, environmental degradation, which includes climate change and global biodiversity loss; the distribution of unprecedented destructive capabilities across society by dual-use emerging technologies; and value-misaligned algorithms that exceed human-level intelligence in every cognitive domain. After examining each of these challenges, the paper then outlines a handful of additional issues that are relevant to understanding our existential predicament and could complicate attempts to overcome the Great Challenges. The central aim of this paper is to constitute an authoritative resource, insofar as this is possible in a scholarly journal, for scholars who are working on or interested in existential risks. In the author’s view, this is precisely the sort of big-picture analysis that humanity needs more of, if we wish to navigate the obstacle course of existential dangers before us.

Comprehensive literature survey that culminates in a novel theoretical framework for thinking about global-scale risks.

If humanity wishes to survive and prosper in the coming centuries, then we must overcome three Great Challenges, each of which is sufficient to cause a significant loss of expected value in the future.

The Great Challenges framework offers a novel scheme that highlights the most pressing global-scale risks to human survival and prosperity. The author argues that the “big-picture” approach of this paper exemplifies the sort of scholarship that humanity needs more of to properly understand the various existential hazards that are unique to the twenty-first century.