The earth atmosphere extends several tens of km above the earth's surface and contains a wide range of molecule. Each of these molecules has a different absorption spectrum, absorbing radiation of different frequencies. The net effect is to make the earth's atmosphere opaque to ranges of wavelengths as shown below, with the overall absorption illustrated in the bottom graph.

The radiation most dangerous to us – UV and shorter wavelength radiation – is almost completely absorbed. If this were not so, then the earth would be a much more dangerous place to live, since these short wavelengths cause damage cells and cause cancer.

The atmosphere is largely transparent to electromagnetic radiation in the visible part of the electromagnetic spectrum. Our eyes have evolved to see radiation in this range.