Which direction is ‘up’ in space? Without gravity, there’s no real answer, but some spiders have invented a solution.
When golden silk orb weavers create their webs, they place the ‘hub’ (the web’s central point) towards the top, instead of in the exact middle. This is where they sit to hunt, facing downwards and ready to grab anything that lands in their sticky trap.
Scientists think the spiders do this because of gravity – it’s quicker and easier to catch prey you can drop down to, instead of climbing upwards. In 2011, two orb weavers were sent onto the International Space Station to see what webs they’d build in zero gravity.
The researchers who sent them placed lights on one side of the spiders’ boxes, which they switched on and off to simulate day and night. These weren’t supposed to affect the results at all. However, both the orb weavers decided that, like the Sun, these lights must be ‘upwards’ and built their webs to match.
This article was published in Issue 48 of Double Helix magazine (https://www.csiro.au/en/Education/Double-Helix). Copyright for this article is held by CSIRO.
Lachlan Writes Science 