Space
How long would it take to cross the Milky Way?
Crossing the Milky Way at the speed of light would take about 100,000 years.
Source: NASA; galactic disc diameter about 100,000 light-years.
Context
About 100,000 years at the speed of light, which is roughly the diameter of the galaxy's disc. Nothing we have built gets anywhere near that speed.
The Sun sits about halfway out from the centre, so even light from the far side has been travelling for tens of thousands of years when it reaches us.
This fact sits next to the age test. See where you land.
Try the Age test