Interesting. I had no idea that the universe would eventually be basically just photons. I wonder if that is why Stephen Baxter had his 'photino birds' as the final form of life in his Xeeleverse?
Interesting. I had no idea that the universe would eventually be basically just photons. I wonder if that is why Stephen Baxter had his 'photino birds' as the final form of life in his Xeeleverse?
The photino birds want the universe to be populated with white dwarfs, because they can feed off their gravity wells without the risk of deadly supernovas and black holes, which can kill them.
After the xelee and humans leave, the universe becomes a cold place dominated by photino birds living in the cold pinpricks of white dwarfs. Eventually matter evaporates into photons, and the photino birds die.
However, it turns out photino birds can always just time travel to a time when the universe still had matter. So they're more or less indifferent to the eventual heat death .
See: https://xeelee.fandom.com/wiki/Photino_Birds
I hypothesize that there is may be only one photino bird. When it appears to die, it is just traveling to another time. When we see multiple photino birds, we're just looking at different segments of the same bird's world line. These are my own speculations, inspired by Wheeler's idea that the universe has only one electron, which travels back in time as a positron, and interacts with itself so many times that it creates the observable universe of matter:
https://en.m.wikipedia.org/wiki/One-electron_universe
One potential hiccup with your one-photino-bird-universe theory (which is quite fun!): I believe I remember a scene in which the ‘birth’ of a photino bird was described. If I remember correctly, it was indeed described as a clone of its parent.
As long as we only see one birth, that's probably fine. It just implies a stable time loop.
> However, Photino Birds carry with them one unassailable advantage the Xeelee could not overcome; they are not bound by time. They can freely exist in and travel to any point in time. The creatures do not age nor die naturally, not even by the end of the universe; they just travel back to the beginning of time, including to points so soon after the Big Bang that baryonic matter (including the Xeelee) could not yet exist.
Where is this described in the books? I don't remember the Photino Birds having this ability.
Roger Penrose has a theory about a cyclical conformal universe, which requires that the universe eventually only contains photons. As photons travel at the speed of light, they do not experience the passage of time, so they also do not experience distance (space). So in the deep remote future, when only photons are left, the difference between the very large and miniscule disappears, and you get all photons in the universe existing at the same point at the same time, which causes a new big bang. At least, that is Penrose's theory. I believe they found some evidence in the CMB supporting it.
https://en.m.wikipedia.org/wiki/Conformal_cyclic_cosmology
It seems the paper made mistakes, using a non-standard model of the CMB that failed upon replication. It's an interesting theory thoughb.
As a non-Physicist, I absolutely love the CCC hypothesis and I really hope it turns out to be true. It seems like such a beautiful alternative to the idea of the heat death of the universe just lasting forever and nothing ever happening again.
This is some absolutely crazy idea. I mean I'm in no position to analyze it critically but that is pretty mind blowing.
I believe proton decay is still considered hypothetical, and the electron is pretty confidently believed to be stable; https://profmattstrassler.com/articles-and-posts/particle-ph... is a good overview.
If protons do decay, their decay product would include a positron that would in turn annihilate with the electron. Leaving a universe with just photons and neutrinos.
If neutrinos are their own antiparticle then they could react with each other and produce ??? Not sure, because you would have to find out of the lepton number is conserved.
> I believe proton decay is still considered hypothetical
Definitely.
> [link] is a good overview
That overview seems to overstate the likelihood of proton decay. In fact, it has it backwards. The default position is that protons are stable, per the standard model, not that they're susceptible to decay.
> The default position is that protons are stable, per the standard model, not that they're susceptible to decay.
It's only the "default" in the sense that the simplest model explaining data gathered to date (the standard model) predicts no decay. However, most physicist do not believe the standard model is the last word (and surely it cannot be when you go to the Planck scale), and many models post-SM models predict proton decay. I would guess if you surveyed high energy physicists, you'd find the majority expect the proton does in fact decay, so it's the "default" in that sense.
Apologies for the late reply -- I just saw your comment now.
I don't think it's the case that many post-SM models predict proton decay. A few do, but even those are now tightly constrained by observations that place the proton's half life at more than 10^34 years. A lot of models that previously predicted proton decay have been empirically falsified on such grounds, and those that remain are looking pretty shaky. So I don't know. If you run that survey, I believe that the average physicist would come out against proton decay. It would be an interesting survey, in any case!!
There is some debate whether this is knowable, some particles are not believed to decay into light at a rate faster than their spontaneous creation from light. (And humanity wont be around to check).
a truly beautiful exploration of that idea is landis's "the melancholy of infinite space": http://www.geoffreylandis.com/infinite.htp