Building space-time

The July issue of Scientific American has an interesting article on how our four-dimensional space-time could arise from basic building blocks that self-organize in a quantum superposition. Their approach, called causal dynamical triangulations, is an extension of Euclidean quantum gravity. But instead of just seeing what a superposition of self-organized building blocks that assemble arbitrarily looks like, which turns out to be a bunched up and very messy space-time with plain Euclidean quantum gravity, they imposed causality on each building block so that they can only assemble in specific ways. Their computer simulations show that the result would be a space-time that looks much like our own on large scales.

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Ice or salt?

Has the Mars Phoenix Lander uncovered ice that was buried under the soil? While the blast from its thrusters when it landed may have uncovered ice, it's not reachable by the robotic arm. In a trench dug up by the arm last week, named "Dodo-Goldilocks", the lander may have uncovered ice, which is much more obvious in a color picture than in a black and white photograph. Seeing white on a planet whose most popular color is red is a nice change.

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