I'm sure you've heard of the 'Pioneer Anomaly'
when you wrote
Here's a random thought: Maybe the physical laws of the universe we think we know are different outside of the heliosheath of our solar system. How will we really know unless we get there and do some scientific testing?
I was reminded of the Pioneer Anomaly:
The Pioneer anomaly or Pioneer effect refers to the observed deviation from expectations of the trajectories of various unmanned spacecraft visiting the outer solar system, notably Pioneer 10 and 11. As of 2005, there is no universally accepted explanation for this phenomenon; while it is possible that the explanation will be prosaic—such as thrust from gas leakage—the possibility of entirely new physics is also being considered.
which if true, may - or may not - be at odds with ER's point about being able to read and interpret spectra from objects thousands or millions of light years away. Who knows? The Pioneer data is still being analyzed and, I seem to recall, a dedicated mission is being planned ...