How the Universe Ends

[lpetrich]

As far as we can tell, the Universe is going to keep on expanding and running down, becoming thinner and thinner and colder and colder, making the "Big Freeze". Alternate possibilities are recollapse, the "Big Crunch", and superfast expansion, the "Big Rip".

 The Five Ages of the Universe,  Future of an expanding universe, [astro-ph/9701131] A Dying Universe: The Long Term Fate and Evolution of Astrophysical Objects

Our Universe has aged over a large spread of timescales, and it will continue to do so. Meaning that overall changes happen slower and slower as it ages. Oo it is convenient to use "cosmological decades" for its age at each point:

Age = 10^(dec)

Fred Adams and Gregory Laughlin in their book "The Five Ages of the Universe" divide up the Universe's history into these ages: Primordial, Stelliferous, Degenerate, Black-Hole, and Dark.

The Primordial Era (-50 < dec < 5): quantum gravity - cosmic inflation - freezeout of hadrons - freezeout of electrons and neutrinos - primordial nucleosynthesis - recombination of electrons and nuclei, making the Universe transparent to visible light

The Stelliferous Era (5 < dec < 14): what we are in now, decade 10. Stars form from interstellar dust and gas, then spew much of their substance back into it, often with relatively heavy elements formed by nucleosynthesis in their cores. It will end when there is too little interstellar material to form new stars.

Galaxies form early in this era (dec around 8 or 9), and gradually merge, forming giant elliptical galaxies. The Milky Way and the Andromeda Galaxy will eventually merge, forming a "Milkomeda" galaxy. That galaxy will eventually swallow up all the smaller Local-Group galaxies, like the Magellanic Clouds.

The Degenerate Era (14 < dec < 40): all the stars are burned out, leaving only white dwarfs, neutron stars, and black holes. The first two are composed of forms of degenerate matter, thus the name.

Around decades 15 - 16, planets are either ejected by other stars or else spiral into their stars by gravitational radiation.
G-rad: dec = 19.4 + 4*log10(a/AU) - 3*log10(M/Msun)
Eject: dec = 15.1 - 2*log10(a/AU)

Galaxies gradually evaporate as some of their stars acquire enough velocity to escape them from near-collisions. As they do so, the remaining stars get closer and closer together. Most stars may escape, with the remaining ones falling into the central black hole that most galaxies seem to have. If stars collide, then that may make a new star or even a supernova.

If otherwise-stable nucleons can decay, then at around 100 times their half-life, all the white dwarfs, neutron stars, and other baryonic-matter bodies will all be gone. For a half-life a little above experimental limits, about dec = 36, that disappearance time becomes dec = 38. This is for single-nucleon decay, and nucleons may instead decay in two-nucleon or three-nucleon processes, or even processes involving virtual black holes. However, these processes are expected to be much slower than single-nucleon processes, with half-lives up to dec = 200 or more.

These objects don't disappear right away, of course, but very slowly. Above about Jupiter mass, they slowly expand until they become Jupiter-sized, and then they slowly shrink. Neutron stars have an ordinary-matter crust, and as nucleons decay, that crust expands and the neutronium part shrinks until at about 0.09 solar masses, the neutronium disappears and the star is much like a white dwarf.

The Black-Hole Era (40 < dec < 100): If nucleons have decayed, all that will be left will be black holes. They will glow by the Hawking mechanism, giving them a lifetime of
dec = 65 + 3*log10(M/Msun)

While a solar-mass black hole will decay in dec = 65, a galaxy-mass black hole (10^11 solar masses) will decay in dec = 98.

The Dark Era (100 < dec): all that is left is very-low-density and very-low-energy photons, electrons, and positrons.

What happens next is very speculative. The simplest fate is to continue to expand forever, but other things might happen.

 

[Speakpigeon]

I suspect some idiot will discover something entirely new that will throw the universe off course. Or not but then the universe will be thrown off course nonetheless. And we won't be there to notice anyway. I certainly plan on making a stand but I'm under no illusion. Let's be humble here. If we don't understand the 95 percent of the universe that are dark energy and dark matter, we can't expect things to go according to plan. The future resemble the past only in retrospect.

You can quote me on this.
EB

 

[steve_bank]

In an infinite universe matter and energy change forms and it never ends. That is my vie. In a sense the entire universe becomes a perpetual motion machine.

For there to be a beginning the question of where the initial conditions came from.

We base cosmology on the limit of our ability to detect photons, we declare that the end of the universe. Our observations are over an infinitesimally small amount of cosmic time. Imagine being on a gas molecule in a nuclear explosion trying to deduce what happened making nearby observations over a few seconds. That is the BB.

 

[Loren Pechtel]

In an infinite universe matter and energy change forms and it never ends. That is my vie. In a sense the entire universe becomes a perpetual motion machine.

For there to be a beginning the question of where the initial conditions came from.

We base cosmology on the limit of our ability to detect photons, we declare that the end of the universe. Our observations are over an infinitesimally small amount of cosmic time. Imagine being on a gas molecule in a nuclear explosion trying to deduce what happened making nearby observations over a few seconds. That is the BB.

If the universe is infinite what is your answer to Olber's Paradox? (Given infinite distance all sight lines eventually reach an object, probably a star. Thus the night sky would be as bright as the average star. You might end up at a planet or asteroid, but they would be experiencing the same thing and soon be heated to stellar surface temperatures. Furthermore, stars couldn't radiate away heat--they either shed their mass quickly or they blow up. Soon you end up with a universe consisting of hot gas and degenerate bodies.)

 

[steve_bank]

In an infinite universe matter and energy change forms and it never ends. That is my vie. In a sense the entire universe becomes a perpetual motion machine.

For there to be a beginning the question of where the initial conditions came from.

We base cosmology on the limit of our ability to detect photons, we declare that the end of the universe. Our observations are over an infinitesimally small amount of cosmic time. Imagine being on a gas molecule in a nuclear explosion trying to deduce what happened making nearby observations over a few seconds. That is the BB.

If the universe is infinite what is your answer to Olber's Paradox? (Given infinite distance all sight lines eventually reach an object, probably a star. Thus the night sky would be as bright as the average star. You might end up at a planet or asteroid, but they would be experiencing the same thing and soon be heated to stellar surface temperatures. Furthermore, stars couldn't radiate away heat--they either shed their mass quickly or they blow up. Soon you end up with a universe consisting of hot gas and degenerate bodies.)

I get a tan at night, less crowded on the beach.

The assomption is uniform density of stars over infinity. Stars die and are reborn. The energy density of star on a point on a sphere around the sun decreases 1/r&2.

Do we assume in an infinite universe it is the same everywhere? What we see from observation may be a local phenomena separated from other phenomena by vast distance. I read that if observation is plugged into relativity it would imply we are in a black hole.


Light looses energy through scattering and absorption resulting in heat.

We assume that over infinite time photons will not loose energy.

According to relativity there is no such thing as a straight line in a universe with gravity.

And finally, maybe ET is siphoning off photons to another universe as an energy source.

 

[Jokodo]

In an infinite universe matter and energy change forms and it never ends. That is my vie. In a sense the entire universe becomes a perpetual motion machine.

For there to be a beginning the question of where the initial conditions came from.

We base cosmology on the limit of our ability to detect photons, we declare that the end of the universe. Our observations are over an infinitesimally small amount of cosmic time. Imagine being on a gas molecule in a nuclear explosion trying to deduce what happened making nearby observations over a few seconds. That is the BB.

If the universe is infinite what is your answer to Olber's Paradox? (Given infinite distance all sight lines eventually reach an object, probably a star. Thus the night sky would be as bright as the average star. You might end up at a planet or asteroid, but they would be experiencing the same thing and soon be heated to stellar surface temperatures. Furthermore, stars couldn't radiate away heat--they either shed their mass quickly or they blow up. Soon you end up with a universe consisting of hot gas and degenerate bodies.)

I get a tan at night, less crowded on the beach.

The assomption is uniform density of stars over infinity.

No, that's not the assumption. Any non-zero average density of stars will lead to Olber's paradox in a static universe.

 

[Jobar]

IMO every black hole generates a new universe, differing in properties according to the mass of the collapsed star or galactic core. But that doesn't tell us anything about the fate of this particular universe.

Right now it does look like expansion is accelerating, and thus this particular instantiation will fade to dark and cold near absolute zero. But there may still be things going on we don't know about; so I won't say I'm at all sure of this.

 

[fast]

If we don't understand the 95 percent of the universe that are dark energy and dark matter, we can't expect things to go according to plan.

I don't disagree. My gripe is with something else.

Scientists have said, "we don't understand dark matter and dark energy." I don't disagree with that either, exactly. My gripe is with something else.

They will go on to say that the terms are just placeholders and we might as well have called them "Fred and Wilma." I wouldn't have a gripe with that either if it wasn't for the fact they are mistaken about them having no understanding. They do have an understanding.

So, which is it, they do understand or they don't understand, you might ask me. That's just it, both. They are equivocating and don't even realize it.

When we have at least some understanding of something, we speak about it and say things about it. We may be on shaky ground and realize there's a substantial amount we do not know; in that regard, we don't understand it (I.e. We don't have a thorough intricate intimate working knowledge of it), but this lack of complete understanding does not diminish the few things we can muster to intelligently speak on it, even if our confidence is low. Is our understanding so lacking that there's no justification for the names upon which we have used? No! There is more out there, probably having something to do with matter and energy.

It reminds me of when people say, "we never really truly know anyone" after learning of some horrible thing they've done. They DO know them; what they they don't know is every intimate detail driving their thinking etc.

My gripe is how they diminish what they understand about it in the espousal that they don't understand it.

 

[steve_bank]

I take a differnt approach.

An observationl discrepancy was observed in BB. The mathematical proerties need to bring theory back into alignment witrh observation was defined. There was a missing sorce of gravity.

That was labled drak matter. Thenproprties it should have are known, the form of dark matter is unknown.

When I took astronomy in the 80s the prof took some of us to a presntaion at Yale on 'the missing mass'. As I rember it the total mass dtermined if the BB was one shot out, one shot out and back, or occilatory forever. Point being the question of total mass is not new.

There is a great deal of conjecture and interpretaion of obserservation. With a high temperature singularity at the start and decreasing temperature obseved that sounds like a finite end. The old thermal death idea.

https://en.wikipedia.org/wiki/Big_Bang

 

[Cheerful Charlie]

In an infinite universe matter and energy change forms and it never ends. That is my vie. In a sense the entire universe becomes a perpetual motion machine.

For there to be a beginning the question of where the initial conditions came from.

We base cosmology on the limit of our ability to detect photons, we declare that the end of the universe. Our observations are over an infinitesimally small amount of cosmic time. Imagine being on a gas molecule in a nuclear explosion trying to deduce what happened making nearby observations over a few seconds. That is the BB.

If the universe is infinite what is your answer to Olber's Paradox? (Given infinite distance all sight lines eventually reach an object, probably a star. Thus the night sky would be as bright as the average star. You might end up at a planet or asteroid, but they would be experiencing the same thing and soon be heated to stellar surface temperatures. Furthermore, stars couldn't radiate away heat--they either shed their mass quickly or they blow up. Soon you end up with a universe consisting of hot gas and degenerate bodies.)

The Universe is expanding and by that I mean space is expanding, there is more and more of that. That means at a certain distance, to see beyond would mean that whatever we observe beyond that has to be moving faster than light. So any observer in the Universe has an observational bubble beyond which we can never observe anything. Physicists tell us we are about 1 billion years away from not being able to see anything from our island Universe's earliest beginnings. Olber's paradox is solved.

 

[steve_bank]

I can not accept expanding space, Seems to imply the expansion is creating something out of nothing.

Infinite expansion requires infinite energy?

 

[Jokodo]

I can not accept expanding space, Seems to imply the expansion is creating something out of nothing.

Infinite expansion requires infinite energy?

"Once you eliminate the impossible, whatever remains, no matter how improbable, must be the truth."

A stationary universe that is infinite in space leads to Olber's paradox. *

A stationary universe that is finite in space doesn't age well - it's start to be pulled together by gravity from t0. Also, we'd have to be pretty much at the centre for it to look the same to us in all directions, and how likely is that?




* Technically, if you give up the assumption of conservation of energy, it doesn't have to. But if you give up that, you can't explain that the alternative is "creating something out of nothing". Your model is the one doing it.

 

[Cheerful Charlie]

I can not accept expanding space, Seems to imply the expansion is creating something out of nothing.

Infinite expansion requires infinite energy?

The initial inflation that created our spatial Universe did not end, it only slowed down drastically.

https://en.wikipedia.org/wiki/Inflation_(cosmology)

In physical cosmology, cosmic inflation, cosmological inflation, or just inflation, is a theory of exponential expansion of space in the early universe. The inflationary epoch lasted from 10⁻³⁶ seconds after the conjectured Big Bang singularity to sometime between 10⁻³³ and 10⁻³² seconds after the singularity. Following the inflationary period, the universe continues to expand, but at a less rapid rate.^[1]

----

Yes, there is quite a few questions about the source of inflation, work for physics still to do.

 

[steve_bank]

I can not accept expanding space, Seems to imply the expansion is creating something out of nothing.

Infinite expansion requires infinite energy?

The initial inflation that created our spatial Universe did not end, it only slowed down drastically.

https://en.wikipedia.org/wiki/Inflation_(cosmology)

In physical cosmology, cosmic inflation, cosmological inflation, or just inflation, is a theory of exponential expansion of space in the early universe. The inflationary epoch lasted from 10⁻³⁶ seconds after the conjectured Big Bang singularity to sometime between 10⁻³³ and 10⁻³² seconds after the singularity. Following the inflationary period, the universe continues to expand, but at a less rapid rate.^[1]

----

Yes, there is quite a few questions about the source of inflation, work for physics still to do.

Nice work if you can get it. In the early 70s I hung around mostly with music students. My girlfriend was a ballet student. For classical musicians a lot of good people and few paying jobs. They were intensely competitive. Theoretical physics is probably
worse more competitive, many qualified few jobs.

 

[Loren Pechtel]

If the universe is infinite what is your answer to Olber's Paradox? (Given infinite distance all sight lines eventually reach an object, probably a star. Thus the night sky would be as bright as the average star. You might end up at a planet or asteroid, but they would be experiencing the same thing and soon be heated to stellar surface temperatures. Furthermore, stars couldn't radiate away heat--they either shed their mass quickly or they blow up. Soon you end up with a universe consisting of hot gas and degenerate bodies.)

I get a tan at night, less crowded on the beach.

The assomption is uniform density of stars over infinity. Stars die and are reborn. The energy density of star on a point on a sphere around the sun decreases 1/r&2.

I presume you meant to say r^2. What you're missing is that the number of stars in such a shell goes up at r^2 also.

Do we assume in an infinite universe it is the same everywhere? What we see from observation may be a local phenomena separated from other phenomena by vast distance. I read that if observation is plugged into relativity it would imply we are in a black hole.

The universe is organized into galaxies rather than being uniform but this doesn't matter. Every sight line still ends up on a star or something heated to stellar temperatures except (what I forgot before, as it wasn't known at the time) those that end up at the event horizon of a black hole.

Light looses energy through scattering and absorption resulting in heat.

Scattering doesn't lose energy. Absorption does--but heats up whatever absorbed it. That's why all non-stellar bodies in time get heated to stellar temperatures and thus vaporize.

We assume that over infinite time photons will not loose energy.

True--but you'll have to throw out a lot of physics if that's not true.

According to relativity there is no such thing as a straight line in a universe with gravity.

Note that I said sight line, not straight line.

And finally, maybe ET is siphoning off photons to another universe as an energy source.

Again, Occam's razor.

 

[steve_bank]

Superpostion applies. At the plane of the Earth the enrgy per square meter will be the linear sum of the energy of all stars individualy by inverse square.

Scattering is a loss in terms of the enrgy reaching the Earth. As distance increases nergy at Erath from very distant stars will be below threshold detection.

Hubble Deep Field. Hubble on successive passes on a visually dark region adding up photons. There were a lot of objects. Which is my point, the limit of our ability to detect EM radiation is not neccearily the edge of the universe. A bit like standing on the shore and declaring the horizon is the end of the Earth.

Becasue we don't see it doesn't mean nothing is there.

I'll have to serach for a refernce, I believe I read atoms are changing.

We may not know what the universe will do. We do have a good idea how long before the sun begins to expand incinerating Earth.

 

[Jokodo]

Superpostion applies. At the plane of the Earth the enrgy per square meter will be the linear sum of the energy of all stars individualy by inverse square.

Who said linear? The number of lines of sight not ending in a star decreases asymptotically, not linearly. Some stars will be hiding behind others. Nonetheless, for every shell the lines of sight not ending in a star will diminish by a constant factor (not by a constant absolute value). Say that 0.01% of the lines of sight end in a star within the first 100 million light years. The lines of sight not ending in a star will thus be 0.9999/100 million ly. Over the first 10 billion ly, that's still over 99%: 0.9999^100. Over the first trillion ly, it's down to 37% (that is, 63% do end in a star), and by 10 trillion ly, we're up to 0.99995 of the night sky glaring at us (1 - 0.9999 ** 100000 to be precise). No one notice those few dark spots (if only because we'd long have evaporated). And 10 trillion isn't even scratching infinity.

Scattering is a loss in terms of the enrgy reaching the Earth.

No, it isn't. Not if in all other directions, there are stars too.The light scattering towards us though it originated on a path that would never intercept us, is about the same amount as the light that doesn't reach us through scattering

As distance increases nergy at Erath from very distant stars will be below threshold detection.

Inidividual stars? Sure. The nightsky would still burn doen at us in the color of the average star when there's not just one but literally ininitely many stars in any one direction.

 

[steve_bank]

I worked on radar, electronic countermeasures, and IR systems. One of the first thing I did was verify for myself 1/r^2.

I have done open range testing of antennas. Computing energy at a distance from a source by 1.r^2 is common.

It is not simple line of sight. In radiometry a distant star and the Earth form a frustum with finite areas of the star and Earth at the ends. As an approximation a distant star light years away looks like an isotropic source. It is a theoretical point source radiating equally in all directs over 2PI steradians. Instead of a frustum it becomes a solid angle with a point at the top and the Earth the base of a cone. Near the star there is no defined propagating EM wave at the wavelengths that are radiated, It is called near field. At some distance away called the far field a fully developed transverse electric mode wave develops. The E and H fields are orthogonal. At that point propagation is an expanding sphere. The total energy crossing the surface of the sphere remains constant ignoring losses. At the point at any point on the surface of the sphere the wavefront appears planar, we call that a plane wave. It avoids trig and solid angles in the far field.

When the light from a distant star reaches the plane of the Earth there is it is watts/m^2. At the Earth the sphere is so big the wave front looks flat . The energy from the star is 1/r^2. The energy total is the linear sum of all radiation from all contributing stars adds linear. The linear sum of each star's output reduced by 1/r^2. I suppose tuhat is what you mean.


Aside from 1/r^2 anything that reduces energy between source and observer is considered a loss. Back to LOT. Absorption is a loss to the observer, but in terms off LOT it is converted to heat in the absorber and reradiated as thermal radiation. Scattering also results in some energy transfer. A mirror is not loss free. In some applications mirrors can heat up, like lasers.

 

[DBT]

In the latest edition of New Scientist is a story on Penrose claiming to have found remnants of black holes (B-Modes) from a previous universe, apparently supporting his cyclic model of the universe.

 

[Speakpigeon]

In an infinite universe matter and energy change forms and it never ends. That is my vie. In a sense the entire universe becomes a perpetual motion machine.

For there to be a beginning the question of where the initial conditions came from.

Initial conditions wouldn't need to have come from anywhere. If we assume a beginning to the universe and that there's nothing outside the universe then initial conditions wouldn't somehow come from something else. And there's no logical problem with that.

Of course, if we assume instead that there's something else than our universe then, possibly, its initial conditions could have been determined somehow by something else. But even that is not a necessity because we don't know and there's no reason to assume that there would a have to be a causal relation between this something else and our universe. There might be some other relation, and perhaps none at all.

Logic certainly helps, I think.
EB