I’ve been thinking about this recently. Light speed is more or less considered to be “The universal speed limit” in a lot of articles. Now, these things are decided upon by smart guys with higher degrees and more experience than I have.
On the other hand, I have also heard of scientists claiming the area outside the observable universe is obscured by a receeding dark energy when a much simpler explination would be that light hasn’t reached there yet to allow us to observe it.
Speaking of observational difficulties though; how would someone observe an object travelling faster than light? If it was moving directly toward the viewer it would outpace its own light and be invisible. If it moved directly away, light from the viewer’s side would never hit it and reflect off.
If it was moving across from the viewer, both the optimal and most likely scenario, there is no telling what might happen. Would it scatter sidelong light waves, making it effectively invisible? Or would it become transparent like when you wave your hand past your eyes, appearing to be a cloud rather than an object?
Without knowing exactly what to look for, the odds seem infinitesmally small that we would accidentally find an object happening to have exceeded light speed. So, I really don’t believe the absence of FTL objects is proof it cant be done.