In special relativity it is impossible to detect one's motion if it is steady, even by measuring the speed of light. (religion-online.org)
I have also included a seed helicopter resource which can be used as a practical to measure the speed at which different sized seeds drop to the ground. (tes.com)
The team has now also confirmed the presence of the black hole by measuring the speed of the gas moving around it. (ras.org.uk)