APOD: 2022 April 24 - Split the Universe

Good morning, Rallypoint, and welcome to an interactive April 24th Astronomy Picture of the Day (APOD): "Split the Universe." Some mysteries (at least for me) are fun to unravel. Are we really about to tear the fabric of the Universe?

If you've dabbled in quantum mechanics, you know about at least one paradox: certain things behave both as a particle and as a wave. Light is a good example: a series of photons (particles) behave collectively like an electromagnetic wave until the external world intrudes. The wave function ceases at this point (it collapses). How can you tell if (or when) the wave function has collapsed?

The answer involves the concept of quantum superposition, where an atom exists in a linear combination of decayed and undecayed states...up to the point that the atom is observed (e.g. measured). At that point, the atom is either decayed or undecayed. Add to this scientific bouillabaisse quantum entanglement, where particles interact in a way such that the quantum state of each particle of the group cannot be described independently of the state of the others. So what is true about a single atom should be true about something larger, correct? Enter Schrödinger's cat.

Suppose a box is created to enclose a cat and a mechanism that releases poison when a single atom decays (a quantum event). The release of poison kills the cat. If the cat is in quantum superposition with the atom, the cat also exists in a combination of decayed (e.g. dead) and undecayed (e.g. alive) states until the box is opened. Now you can observe if the cat is either alive or dead. But the 'measurement problem' of wave function collapse has remained unobserved. Science tells us that it occurs, but we are unable to see it.

Back to the red button. As today's APOD write-up describes, some believe that a personally-initiated quantum decision splits the universe in two, and that both the live-cat and dead-cat universes exist in separate parts of a larger multiverse. Others believe that a click collapses the two possible universes into one -- in a way that could not have been predicted beforehand. Yet others believe that the universe is classically deterministic, and a click just carries out an action predestined since time began. What camp to you fall in?

Did you click it?