Why Did Einstein Try to Prove That Gravitational Waves Cannot Exist?

For two interconnected reasons, Albert Einstein fiercely resisted the concept of gravitational waves. These reasons were deeply rooted in his unwavering commitment to time symmetry in physics and the failure of his equations to account for the energy associated with gravitational waves.

Time Symmetry and the Asymmetry of Gravitational Waves

Firstly, Einstein was absolutely committed to the idea that the fundamental equations of physics should look identical in forward and reversed time. This principle underpinned his earlier work on special relativity and the Schwarzschild solution of general relativity. He maintained this stance until the 1930s, when Hubble's observations of redshift led to a broader acceptance of the expanding universe.

In the context of special relativity and inertial physics, the equations remain the same whether time moves forward or backward. For instance, in a collision, the force and energy transfer occur in a specific sequence that resembles a one-way process. However, when time is reversed, the sequence of events seems to lose causality, raising questions about how initial wave fragments could know specific details about future events.

Consider a hammer strike against an anvil. In the forward direction, the abrupt deceleration causes gravitational waves to spread out carrying away energy. In the reverse direction, gravitational waves would need to shrink into a patchwork of causally unconnected wave-fragments that mysteriously converge on the hammer strike, seemingly installed with foreknowledge. Einstein found this notion absurd, as it contradicted the symmetry he held so dear.

Failure of Energy Conservation in General Relativity

Secondly, Einstein's perfectly balanced equations did not account for the energy of gravitational waves. In his 1905 equations for inertial physics, he had assumed flattened spacetime to derive his formulas, largely ignoring gravitational or gravitomagnetic effects. This meant that in a scenario where an atom emits a photon and recoils, there would be a need to distribute this energy via gravitational waves. However, under Einstein's time-symmetric system, there is no source for this energy.

If gravitational waves were to carry no energy, then they would be merely mathematical artifacts with no physical significance. On the other hand, if they did carry energy, it would imply that the basic equations of special relativity had to be fundamentally flawed. Einstein argued that a system of particles constantly accelerating and colliding would lose energy as gravitational waves, which would make his theories lossy with respect to energy conservation.

Conservation of Energy in Gravitational Wave Emission

Einstein also pointed out that a system like a binary star, where two masses orbit each other, should not be emitting energetic gravitational waves. For energy to be conserved, such a system should either not emit gravitational waves or the waves should carry no energy. This view was part of his broader opposition to the idea of Hubble redshifts, a position that seems ironic given the current scientific consensus.

In the face of these challenges, Einstein's skepticism towards gravitational waves was deeply rooted in his belief in a time-symmetric universe and the conservation of energy. His views reflect the complexity of reconciling classical theories with modern observations. The irony of Einstein's skepticism is vividly evident in today's headlines declaring "EINSTEIN WAS RIGHT!" every time a new gravitational wave event is confirmed.

Ultimately, Einstein's resistance to gravitational waves is a testament to his rigorous and meticulous approach to physics. While his skepticism was grounded in a deep understanding of physical principles, the discovery and confirmation of gravitational waves continue to refine our understanding of the universe.