Recent content by Ian

Why would you get 'clumps' of dark matter? Normal matter tends to clump because of the electromagnetic forces that dominate their interactions. In the absence of these it is very difficult for particles of any material to shed momentum even if they are drawn to each other by gravity. Instead...

I am also sick of hearing about neolithic mumbo jumbo. Ultimately this planet and its bisophere have a finite lifespan and our prospects in the very long term depend on being able to make some progress in spreading beyond it. Compared to the imperative to progress our spacefaring capabilities...

The issue is that the speed of light in a vacuum is constant in all reference frames. This we do observe. To make it stay constant in all reference frames requires that moving objects experience time-dilation. This we also do observe. The problem with superluminal communication is that- when...

The argument around causality is broadly applicable to anything that permits superluminal travel or communication. Causality itself is not a principle that can be derived from either General Relativity or quantum theory- it is simple a phenomenon we observe in our everyday experience, and as...