Final answer:
A pebble 'floating' in the International Space Station (ISS) is in a state of continuous free-fall towards Earth. This occurs due to the effect of microgravity in the ISS's orbital path around Earth. This doesn't imply the absence of gravity, but rather the effects of falling at the same rate as the ISS.
Step-by-step explanation:
Within the confines of the International Space Station (ISS), objects, including a hypothetical pebble, do not truly 'float' as one might assume. This seemingly floating effect is a result of the phenomenon known as 'microgravity'. The earth's gravity still pulls objects, like the pebble and the ISS, towards the surface but the station and everything in it is in continuous free fall around the earth causing it to appear as though they are floating.
The station and objects inside it fall towards the earth but also move forward fast enough to constantly miss it due to the curvature of the planet. So, if the pebble is floating in the ISS, it's because the ISS, and everything inside of it, including the pebble, are continuously free-falling towards the Earth.
Learn more about Microgravity