The person whose observations seemed to indicate that the heavenly bodies were composed of material substance just like Earth, not pure orbs of light, was Galileo Galilei.

Here's why:

* Telescopic Observations: Galileo was one of the first astronomers to use a telescope for astronomical observations. His observations of the Moon, Sun, and planets revealed details that contradicted the prevailing geocentric view of the universe.

* Lunar Craters and Mountains: Galileo observed mountains and craters on the Moon, indicating that it was not a smooth, perfect sphere as previously believed. This suggested that the Moon was made of material similar to Earth.

* Phases of Venus: Galileo's observations of Venus's phases proved that it orbited the Sun, not the Earth. This was a major blow to the geocentric model and supported the heliocentric model proposed by Copernicus.

* Sunspots: Galileo also observed sunspots, which again contradicted the idea of a perfect, unchanging Sun. These observations implied that the Sun was a physical body like Earth.

Galileo's observations, along with his arguments based on these observations, challenged the prevailing scientific and religious views of the time. His work paved the way for a shift towards a more accurate understanding of the universe and the place of Earth within it.