[atakan_gurkan]

We may not need a more powerful accelerator. Remember: The cosmic rays contain much more energetic particles than that can be produced in accelerators so far.

It is possible that we will discover new phenomena and new ways to test gravitational theories once we can observe gravitational waves. I expect we will detect gravitational waves in ~10 years and identify a specific source in ~20 years; sooner, if there are some powerful sources that we did not think of yet.

[neutronicus]

As someone who does astrophysics right now, trust me, we want to wring everything we can out of accelerators before we start trying to use cosmic objects to probe the laws of physics.