Final answer:
We can't see much smaller detail in the sky than 1 arcsecond because of the small angles involved. The Hubble Space Telescope was launched to obtain even sharper images.
Step-by-step explanation:
The reason we can't see much smaller detail in the sky than 1 arcsecond is due to the small angles involved. One arcsecond is how big a quarter would look when seen from a distance of 5 kilometers. To put it into perspective, the best images obtained from the ground with traditional techniques reveal details as small as several tenths of an arcsecond across, which is remarkably good. The Hubble Space Telescope was launched to escape Earth's atmosphere and obtain even sharper images.