Quote · Lex Fridman Podcast
#497 – Biggest Mysteries in Physics: Antimatter, Dark Energy & ToE – Don Lincoln
Where this was said
Theory of everything
At 1:32:33 · chapter starts 1:20:35
The Grand Unified Theory, why the energy gap to test it is 10^15 times current capability, Lincoln's Australopithecus analogy, string theory's failure to make testable predictions, and loop quantum gravity. [1] — Don Lincoln "We need to probe energy scales a quadrillion times higher than our best accelerators to test Grand Unification. That's like a hominid in Ke…" 1:25:22 [2] — Don Lincoln "String theory has been developed since the 1970s and has yet to make a single testable prediction. The energy scale it describes is 10^15 t…" 1:30:40
The energy scale at which Grand Unified Theory effects should appear is roughly 10^15 times higher than the highest-energy accelerators humanity can build today.
Historically, particle accelerator energy has increased by roughly a factor of 7 every 20 years — but even at that rate, reaching the GUT scale would take about 500 years.
We need to probe energy scales a quadrillion times higher than our best accelerators to test Grand Unification. That's like a hominid in Kenya trying to predict Antarctica, sperm whales, and the Alps. Lincoln's prediction: a theory of everything is at minimum 500 years away.
String theory has been developed since the 1970s and has yet to make a single testable prediction. The energy scale it describes is 10^15 times beyond what any accelerator can reach. Lincoln thinks it's almost certainly wrong — not because the people are stupid, but because history guarantees something completely unexpected lies between here and there.
Loop quantum gravity tries to quantize space itself — not to unify all forces, just to make gravity compatible with quantum mechanics. It once predicted the speed of light would vary by wavelength, a prediction killed by gamma-ray burst observations. But Rovelli updated the theory and survived. String theory, by contrast, has been unchanged for decades and still makes no testable predictions.
Gravitational waves and light from two merging neutron stars 140 million light-years away arrived on Earth within just 1.7 seconds of each other, confirming gravity travels at the speed of light.
