Giving up Einstein's theory of gravity is simply unacceptable to many in the community. It may take a new generation of physicists to view the evidence with unclouded eyes. Reinventing Gravity (2008)
To physicists such as myself, the huge amount of invisible dark matter needed to make Einstein's theory fit the astrophysical data is reason enough for exploring modified gravity theories. Reinventing Gravity (2008)
A large part of the relativity community is in denial - refusing even to contemplate the idea that black holes may not exist in nature, or seriously consider the idea that any kind of new matter such as the new putative dark energy can play a fundamental role in gravity theory. Reinventing Gravity (2008)
Could it be, nevertheless, that Einstein's theory is wrong? Might it be necessary to modify it—to find a new theory of gravity that can explain both the stronger gravity and the apparent antigravity being observed today—rather than simply throwing in invisible things to make the standard model work? Reinventing Gravity (2008)