system
Given the following post, respond as if you're commenting on Reddit:
human
[Valve] What is the relationship between Black Mesa and Aperture Science?

Are they competitors? Why does Gordon Freeman make no mention of Aperture? Do the Combine know of Aperture?
gpt
They competed for grant money for anomalous materials and advanced scientific research back before the Seven Hour War. Ultimately, it was Black Mesa's ability to consistently undercut Aperture Science on price that enabled them to starve out Aperture Science over a period of decades.

Thing is, even with Black Mesa undercutting them they still remained a viable business and a strong competitor due to a heavy emphasis on automation. That worked well until their central testing AI, GladOS, wiped them all out with deadly neuro-toxin. As far as anyone outside the facility knew at the time, the facility had gone into lockdown. Those sent to investigate were both passively and actively deterred from entering the facility. Some were sent home in body bags, others in soup cans, and still others were never seen again at all. More forceful means of entry, such as nuclear weapons, were conceived of as impractical due to both the possibility of international repercussions and the sheer immensity of the facility's fortifications. Further contact with the facility was shelved until either someone from the facility made contact or something horrible started shambling out of it.

With Aperture Science gone seemingly without explanation, observations about it became increasingly speculative and short-lived. Black Mesa may or may not have been aware that it's main competitor had dropped off the face of the map. In the game of highly secretive advanced science research, who can say? But it is more than fair to assume that after several years of inactivity Aperture Science became little more than a memory and certainly nothing to talk about on a daily basis.

As for the Combine, their goals are primarily resource exploitation and secondarily population control. Earth is so far on the periphery of the Empire that no serious attempt has been made to investigate the technological prowess of a race they bested seemingly without effort. Until the destruction of the Citadel, the prospect that Human's might even be capable of surprising the jaded intellects of the Combine Empire was little to none. Since then, however, they may have reconsidered the potential value of such endeavors.