Thermal Death of the Universe

[Zombie Horde]

Just reading then saw your sig .... love it

 

[Aiken_Drumn]

It certainly is one option!

 

[TheMeInTeam]

I do sort of get the vibe multiple universe theories are mostly wishful thinking

it wouldn't change anything about your perceived experience one bit even if it were true, so i'm not sure to what extent that thinking/explanation is "wishful".

i consider it a better "explanation" than continually extending the collapse postulate while failing to ever actually observe collapse of wave function, but i nevertheless agree that it seems more a trick of math than reality. math has a long history of generating singularities because our model of the thing in question wasn't complete. "approaching infinite but technically just ridiculously enormously finite amount of universes" does seem to be a similar interaction offhand. but at least it's similar to other ways we've identified problems in modeling in the past, rather than pretending an explanation is there we can't observe.

as for things science might still uncover on the "big stuff out there" scale:

figuring out what constitutes dark matter/energy (or coming up with/confirming an alternative explanation for the effects we observe and infer these as the source)
black hole information paradox
somehow integrating gravity into quantum theory in a way that doesn't break things (related to above, probably)

there are also questions like anything outside the bounds of planck units, precisely how human brain works/full detailed explanation of the processes that lead to what we call consciousness, or simply reworking present theory based on updated data in fields where there just isn't much information yet.

it is also very difficult to estimate what one doesn't know, even on the scale of humanity. maybe if we stop being able to ask questions we can't answer w/o creating more questions, we can worry about science running out of things to find.

 

[ywhtptgtfo]

Seriously I have been thinking about this a lot for a long time. How many Universes are there?

You should watch Sabine Hossenfelder's youtube channel (https://www.youtube.com/c/SabineHossenfelder). She's a physicist and explores a lot of these questions. Basically, there's a lot of things we just don't know. There are theories that suggest the Big Bang is essentially the result of a white hole. Some other videos (not sure if it's from her), discussed the possibility of some recursive black holes (e.g our universe being inside one already). Then there's also the famous holographic theory that suggests nothing is actually real.

I like Sabine's podcasts because she is a good speaker, slightly light-hearted, but also keep things very factual.

Anton Petrov's podcasts are also good but his accent is a bit flat and harder to parse. He and Sabine do not necessarily overlap too much on topics. Anton's more about astronomy than astrophysics: https://www.youtube.com/results?search_query=anton+petrov

 

[Kaitzilla]

The total amount of energy in the universe is eternally the same. (Right?)

Does the temperature of the universe go down or up every billion years?

 

[El_Machinae]

It's not proven, but it would be mathematically elegant if the total amount of energy in the universe was Zero. It really could be, given the level of precision.

As far as we know, the temperature will just keep decreasing. As space gets bigger, the total number of photons per unit volume goes down. Or, the amount of energy within a unit volume decreases. Blue photons are becoming red. The cosmic microwave background is getting cooler

 

[Kaitzilla]

Hah, the universe is getting hotter!

The Universe is Getting Hotter - Is it Affecting Global Warming?

The universe is getting warmer due to natural activity, astrophysicists report in a new study. Does this have anything to do with global warming?

www.sciencetimes.com

Global warming is not the only temperature increase we need to worry about -- a new study suggests. Due to natural activity in the galaxy, it seems that the entire universe is getting hotter.

A recent paper found in the Astrophysical Journal describes the universe's thermal history over billions of years. The average gas temperature across the universe has increased over 10 times in the last 10 billion years, wrote the researchers. Currently, the temperature of gases closer to the Earth is approximately four million degrees Fahrenheit.

Yi-Kuan Chaing from Ohio State University shared that their work confirms Jim Peeble's research, who won the 2019 Nobel Laureate in Physics. Peeble's theoretical work and calculations were focused on factors of how the universe formed as well as new physical processes such as cosmic background radiation. His results showed that only 5% of the universe's contents are known to matter while the rest is unknown dark matter and dark energy.

 

[El_Machinae]

The cosmic thermal history, quantified by the evolution of the mean thermal energy density in the universe, is driven by the growth of structures as baryons get shock heated in collapsing dark matter halos.

Huh.
This reminds me of the "Vaccine RNA found in breast milk". Our ability to detect very small things is .... astounding.

 

[Thorgalaeg]

Isn't universe going towards a big rip because dark energy is making it expand quicker the bigger it becomes?

 

[TheMeInTeam]

You should watch Sabine Hossenfelder's youtube channel (https://www.youtube.com/c/SabineHossenfelder).

i will back this recommendation, while there are other science-related youtubers i watch imo her videos are the best i've seen so far. both for keeping the explanations reasonable for audience and also quite good for entertainment.

Isn't universe going towards a big rip because dark energy is making it expand quicker the bigger it becomes?

last i heard current models reject a "big rip", in the sense of expansion resulting in smaller and smaller things being torn apart or something. expansion doesn't seem to overcome gravity or the stronger forces at local levels. thus current theory is that universe simply keeps expanding, until eventually we don't see anything outside of local region that's gravitationally bound (assuming we still exist, the time scale for this happening is enormous, so we'd have to survive the sun going red giant).

if nothing else happens, i think our models predict eventually the universe is a 100% dark place of iron balls/similarly inactive matter after black holes decay into hawking radiation unfathomably long from now. i would also not place any real confidence in our current models being correct on those time scales (or even much, much shorter ones, we can't even explain stuff we observe right now in full).

we also don't know what dark matter/energy are; those are effectively placeholder terms for effects we observe but can't yet explain.

 

[Thorgalaeg]

Having not real clue on the (dark) matter i think dark matter is not that big issue. It must be everything we haven't observed yet, be it cosmic dust, not reflective asteroids, black holes, neutrinos, some unknown kind of particle, or all together. Isnt it a bit foolish to think we can observe everything after all? As i see it, the big elephant in the room is dark energy. What the heck is that?

 

[EvaDK]

Dark matter is what we call the phenomenon that allows Galaxys to form in the configurations we can observe.
Dark energy is what we call the phenomenon that accelerates the expansion of the Universe.

Both names are simply an expression of our own ignorance; it's possible they are not matter and not energy either, as we currently understand them.

As for the shape of the Universe, it has no point of origin. No 'crime scene' for the Big Bang that we can point our telescopes at. The topography of the Universe isn't actually a sphere, although that is what it may look like from our POV inside the Universe.

 

[El_Machinae]

Huh.
This reminds me of the "Vaccine RNA found in breast milk". Our ability to detect very small things is .... astounding.

To be clear, this is the average temperature of gas, which will be heated as it falls through gravity. I guess that's what people will mean by 'warmer', so fair enough. I was more thinking about total photonic intensity.