You’re right about time-symmetry. But the key point is that minimal fluctuations are exponentially more probable than large ones.
The most likely Boltzmann brain is one that exists for just an instant—particles briefly converge into a brain configuration then immediately scatter. A fluctuation that maintains a brain for seconds or minutes is exponentially less likely because it requires sustaining an improbable state longer.
So yes, formation and disintegration are time-symmetric, but the most probable Boltzmann brains still form and disintegrate nearly instantly—not because symmetry breaks, but because brief fluctuations vastly outnumber sustained ones.
You’re right about time-symmetry. But the key point is that minimal fluctuations are exponentially more probable than large ones.
The most likely Boltzmann brain is one that exists for just an instant—particles briefly converge into a brain configuration then immediately scatter. A fluctuation that maintains a brain for seconds or minutes is exponentially less likely because it requires sustaining an improbable state longer.
So yes, formation and disintegration are time-symmetric, but the most probable Boltzmann brains still form and disintegrate nearly instantly—not because symmetry breaks, but because brief fluctuations vastly outnumber sustained ones.