Gravitational waves are ripples in the fabric of spacetime that travel at the speed of light. They are created by the acceleration of massive objects, such as the swinging of an arm, and carry energy away from the source.
Unlike electromagnetic waves, which can travel through a vacuum, gravitational waves require a medium to propagate through. They also have a much smaller amplitude, making them difficult to detect.
When an object, such as an arm, is accelerated, it creates a disturbance in the fabric of spacetime. This disturbance then propagates outwards as a gravitational wave.
Yes, gravitational waves have been observed and measured by experiments such as LIGO (Laser Interferometer Gravitational-Wave Observatory). They can also be indirectly observed by their effects on massive objects, such as the orbital decay of binary systems.
No, gravitational waves have a very small amplitude and do not interact with matter in the same way as other types of waves, such as electromagnetic waves. They are also very difficult to detect at great distances, so there is no risk of harm from them.