Is it possible there are other parallel universes or dimensions or whatever? Anyone knowledgable about physics?

[Griefsucks]

I know it's ridiculous but my mum died and I miss her so desperately tonight and just wish there was parallel universe where she is still alive.

It's obviously not quite that black and white but I have read (in my own crude and uneducated fashion) bits and pieces by physicists that suggest there is so much more to the vastness of the universe that we don't understand, theoretically there could be other dimensions, or other ways of being, that we can't comprehend yet.

If you have read much quantum mechanics or astrophysics or whatever else, what are the most fascinating possibilities out there?

Some Grand Unified Hypotheses of Matter use 11 dimensions (i.e. not proven)

But extra dimensions aren't what you think. It's not like TV science fiction. A dimension is simply a way of defining a physical property of matter. And these dimensions tend to be quite small, the size of atoms.

In terms of Quantum Mechanics, it can be interpreted using the Many-Worlds Hypothesis. It means that every time every single particle in the Universe does something (which happens millions of millions of times a second), a new Universe is created. So we're talking essentially an infinite set of Universes.

Schroedinger's cat is a thought experiment in which a cat is kept in a box, with a detector monitoring the decay of an atom. If the atoms decays, the cat dies. According to QM, the cat is both alive and dead at the same time, and the state of the cat only becomes one or the other on visual inspection. This is a central tenant of QM, but paradoxical to humans. It actually makes sense on the atomic scale, as in order to say see the energy level of an electron, you need a photon (light) to actually interact with it, and their energies are of a similar order of magnitude.

Many-Worlds does solve this paradox, as the Universe splits into two, one in which the cat is dead and one in which it is alive, but it is just a way of interpreting QM though in order to eliminate certain paradoxes, and not universally accepted nor prove-able.

Yes, I think a lot about Schrodinger's cat, and the many worlds theory. And the holographic universe.

Thank you for the informative post, @starfro.

I can't help wondering what happens if the person doing the cat in the box experiment doesn't open the box themselves, but gets a friend to do it but not say what they saw. And so on.

I read a lot about this stuff but in the end no-one really knows.

Just choose to believe it.

Space is 3 dimensional. Which means for example there’s a place where the Eiffel Tower exists even though you’re not there right now and can’t see it. Similarly, space time is 4 dimensional. There’s a time and place where your mother exists even though you’re not there right now and can’t see it. That time and place will always exist. There will always be a part of space time where you’re together.

How about a terrible physics joke?
An officer pulls a speeding car over and asks for ID.
"Mr Heisenberg, are you aware you were travelling at 60mph in a 30 zone?" he asks.
"Great." Heisenberg replies sarcastically. "Now I'm lost."
"May I also ask why there is a cat on the back seat?"
"Ask my friend." Heisenberg points to the man in the passenger seat.
"Sir, why is there a cat in the back of the car? It looks like it's dead."
"Well it is NOW." Schrodinger replies angrily.

Hey, I didn't say it was a good joke!

Well, other dimensions are in the news this week with the ufo/ uap stuff and Grusch talking about higher dimensional planes.