From the beginning of physics, there have been those who imagined they would be the last generation to face the unknown. Physics has always seemed to… - Lee Smolin

String theory seems to be incompatible with a world in which a cosmological constant has a positive sign, which is what the observations indicate.

We detect light and particles that have traveled billions of light years on their way across the universe to us. During the billions of years of travel, very small effects due to quantum gravity can be amplified to the point that we can detect them.

The hypothesis underlying all approaches to the landscape is that there is a cosmological setting in which different regions or epochs of the universe can have different effective laws. This implies the existence of spacetime regions not directly observable... These regions must either be in the past of our big bang, or far enough away from us to be causally unrelated.