Is spacetime fundamental, or does it emerge from something deeper?
Donald Hoffman argues spacetime falls apart at the Planck scale, Annaka Harris explores emergent space-time, and Andrew Strominger and Sean Carroll explain how the holographic principle hints that space is not basic. The convergence from philosophy and physics suggests the stage of reality may itself be a derived thing.
What do the four speakers agree on about spacetime? Show answer
That it is probably not the most basic layer of reality. They disagree on what lies beneath it.
What is Donald Hoffman's Planck-scale argument? Show answer
Probing smaller regions needs more energy, and enough energy in a small region makes a black hole, so smaller distances have no meaning.
What does Hoffman say marks a great theory? Show answer
It gives you the mathematical tools to find its own limits.
What does Hoffman think lies beneath spacetime? Show answer
Consciousness. He compares spacetime to a headset display built for survival, not for showing reality.
What is the holographic principle? Show answer
Roughly, all the information in a volume of spacetime can be stored on the boundary of that region.
What fact about black holes leads to it? Show answer
A black hole's information or entropy is proportional to the area of its surface, not its volume.
What does Andrew Strominger mean by emergent space? Show answer
A plate with fewer dimensions holds the information, and a spatial dimension appears in the image projected from it.
How settled is the holographic principle? Show answer
It is precise for certain black holes and special spaces, but not for a universe like ours, and it is untested.
Why does Sean Carroll reject the word illusion? Show answer
Good predictions track something true about reality whatever the fundamental ingredients turn out to be.
What does Carroll say holography implies about time? Show answer
Nothing dramatic so far. He says we are not close to confident about what is going on.
What is Annaka Harris's middle position? Show answer
Our perceptions map onto a real structure, just not one that looks like what we experience.
Which three claims should be kept separate? Show answer
That spacetime is not fundamental, that it is an illusion, and that consciousness is fundamental.