<p>There couldn't be a universe where no matter &amp; energy exists;the universe IS matter &amp; energy,so without it,no universe.</p>

CC BY-SA 4.0
2019-05-20T04:30:32.757Z
Can you support this by citing some authoritative sources? Thanks!
uhoh
CC BY-SA 4.0
2019-05-20T08:15:19.423Z
What came out of the singularity which gave birth to the Big Bang? It couldn't by any chance have been matter & energy could it? Without this explosion of energy,some of which later materialised into matter,there couldn't have been a universe. The big mystery is: what became of all the antimatter which must have been created at the same time?
Michael Walsby
CC BY-SA 4.0
2019-05-20T08:49:51.027Z
Stack Exchange is a little different than other sites you may have visited. To post a serious and good quality answer to a question here, you should support your statement with authoritative sources.
uhoh
CC BY-SA 4.0
2019-05-19T14:02:25.083Z
2019-05-19T14:02:25.083Z
Michael Walsby
<blockquote>
  <p>However, due to the Law of Conservation of Energy, I suspect that energy will be all that is left, only in equilibrium meaning no ability for energy to form matter.</p>
</blockquote>

<p>The law of conservation of energy states that energy is conserved <strong>in a closed system</strong>. This means the Universe, which is likely an open system, does not necessarily have to obey that conservation law. Not to mention, scientific laws are <em>not</em> absolute, despite their names; they are entirely empirical, and only apply as far as we've observed. As Edwin Hubble put it, "Beyond the limit of the observations, the form of [a] function, or relation, is speculative. For this reason, [a] law is empirical and it must remain empirical until it is explained by an accepted theory."</p>

<p>Anyway, let's get on with the answer. You've just described the Black Hole Era in the heat death scenario. If Hawking radiation occurs, then the black hole will continue to emit particles. During the last stages of its evaporation, a black hole will emit not only massless particles, but also heavier particles, such as electrons, positrons, protons, and antiprotons.</p>

<p>Once all black holes have evaporated, the Universe will be nearly empty, sans some particles that will almost never interract. Eventually, even the protons and antiprotons emitted by the black holes will decay into photons and leptons. Thus begins the Dark Era, when the Universe will be dominated by dark matter, electrons and positrons.</p>

<p>Electrons and positrons will rarely come together and form <a href="https://en.wikipedia.org/wiki/Positronium" rel="nofollow">positronium atoms</a> (in which the electron and positron are electromagnetically bound). Positronium decays very within nanoseconds, since the two particles annihilate. Thus, over time, the energy levels in the Universe will become lower and lower.</p>

<p>What happens next is a matter of speculation. According to <a href="https://arxiv.org/abs/hep-th/0410270" rel="nofollow">Carroll &amp; Chen (2004)</a>, quantum tunnelling and quantum fluctuations could hypothetically create another Big Bang, approximately $10^{10^{10^{56}}}$ years from now.</p>

<p><a href="https://arxiv.org/abs/astro-ph/9701131" rel="nofollow">Adams &amp; Laughlin (1997)</a> speculates that quantum effects will dominate once all macroscopic matter is gone. Essentially, the laws of "macro-physics" will break down, while quantum mechanical phenomena prevail. As a result, the smallest perturbations would make the biggest difference in this era, so there is no telling what may happen to space or time.</p>

<p>Furthermore, they speculate that if the Universe is a false vacuum, the vacuum may decay into a lower-energy state, creating a new "child universe":</p>

<blockquote>
  <p>It is also possible for the universe to spontaneously create “child
  universes” through a quantum tunneling process roughly analogous to
  that considered above (e.g., Sato et al., 1982; Hawking, 1987; Blau,
  Guendelman, &amp; Guth, 1987). In this situation, a bubble of false vacuum
  energy nucleates in an otherwise empty space-time. If this bubble is
  sufficiently large, it will grow exponentially and will eventually
  become causally disconnected from the original space-time. In this
  sense, the newly created bubble becomes a separate “child universe”.</p>
</blockquote>

<p>So yes, something as small as quantum tunnelling will potentially have an enormous effect on the future of the Universe.</p>

<p>In the end, we really have no idea what will happen after enough time, so there's no definitive answer to your question in the long run.</p>

CC BY-SA 3.0
2016-09-20T20:55:28.933Z
I find a particular elegance to the notion that dead universes give rise to new ones.
called2voyage
CC BY-SA 3.0
2016-09-20T20:56:01.977Z
@called2voyage As do I. I guess we'll just have to be optimistic :)
Sir Cumference
CC BY-SA 3.0
2016-09-20T21:00:41.710Z
Well, I really like the answer. But assuming before a new Big Bang is created, energy and matter levels in fact reach zero and there exists literally nothing, would Universe still be an applicable term? Or is there another term that can classify this scenario? Are we dealing with The Nothing?
El Bromista
CC BY-SA 3.0
2016-09-20T21:01:53.170Z
@ElBromista "Universe" simply means "all that is". There wouldn't be literally nothing because there would still be quantum effects, so there is still something that *is*, thus it would still be called the Universe.
called2voyage
CC BY-SA 3.0
2016-09-20T21:04:37.700Z
@ElBromista Energy and matter levels never reach zero. The Universe reaches a point where there is no more [free energy](https://en.wikipedia.org/wiki/Thermodynamic_free_energy) available for work. What you call the Universe beyond that point is up to you, but since the Universe is defined as "all of space and time and its contents", I'd say "Universe" still works, since time still exists (although not much will necessarily happen).
Sir Cumference
CC BY-SA 3.0
2016-09-20T21:04:47.097Z
Would a question, "What is meant by "quantum events" in the final state of the universe?" be out of scope for this SE? Can I ask that as a separate question?
El Bromista
CC BY-SA 3.0
2016-09-20T21:05:43.623Z
@ElBromista By "quantum events", I refer to quantum tunneling and quantum fluctuations.
Sir Cumference
CC BY-SA 3.0
2016-09-20T21:12:31.133Z
Ah, so that is why they say a new Big Bang could spawn? I'm assuming that this means in the context that a massive fluctuation at the quantum level allows a release of mass and energy, causing a rapid expansion similar to what the original Big Bang was? Is it possible this could happen during our current era of the universe?
El Bromista
CC BY-SA 3.0
2016-09-20T21:14:14.883Z
@ElBromista Roughly speaking, in the quantum world everything is possible, but not everything is likely.
called2voyage
CC BY-SA 3.0
2016-09-20T21:15:04.550Z
@ElBromista It's much more complicated than that. Instead of assuming, I encourage you to read Adams & Laughlin (1997), specifically in page 41.
Sir Cumference
CC BY-SA 3.0
2016-09-20T20:51:36.917Z
2016-09-27T12:56:58.427Z
2016-09-27T12:56:58.427Z
Sir Cumference
<p>In the final energy state of the universe, there exists a hypothesis that all matter will have fallen into black holes and neutron stars. If, through Hawking radiation, after all matter is consumed and black holes eventually do dissipate, what is left of our Universe?</p>

<p>I may be describing Heat Death, but I'm not 100% sure. However, due to the Law of Conservation of Energy, I suspect that energy will be all that is left, only in equilibrium meaning no ability for energy to form matter. </p>

<p>In the event I'm wrong and there exists no matter and no energy, would the term Universe still be applicable here?</p>

CC BY-SA 3.0
2016-09-23T16:15:16.203Z
You may enjoy the famous Asimov short story "The Last Question".  Entertaining articles: [article](https://en.wikipedia.org/wiki/Ultimate_fate_of_the_universe#Theories_about_the_end_of_universe)   And you'll enjoy this one! [article](https://en.wikipedia.org/wiki/Future_of_an_expanding_universe)
Fattie
<cosmology><terminology><fate-of-universe>
What is left of a universe where no matter and energy exist and is there a term for this?
El Bromista
# What is left of a universe where no matter and energy exist and is there a term for this?

(Asked by: username_0 on 2016-09-20)

In the final energy state of the universe, there exists a hypothesis that all matter will have fallen into black holes and neutron stars. If, through Hawking radiation, after all matter is consumed and black holes eventually do dissipate, what is left of our Universe?

I may be describing Heat Death, but I'm not 100% sure. However, due to the Law of Conservation of Energy, I suspect that energy will be all that is left, only in equilibrium meaning no ability for energy to form matter.

In the event I'm wrong and there exists no matter and no energy, would the term Universe still be applicable here?

**Tags:** cosmology, terminology, fate-of-universe
> **Comments:**
> **username_1**: You may enjoy the famous Asimov short story "The Last Question".  Entertaining articles: [article](https://en.wikipedia.org/wiki/Ultimate_fate_of_the_universe#Theories_about_the_end_of_universe)   And you'll enjoy this one! [article](https://en.wikipedia.org/wiki/Future_of_an_expanding_universe)  

---

## 2 answers

### Answer by username_4 on 2016-09-20. Score: 7 | Accepted answer

> However, due to the Law of Conservation of Energy, I suspect that energy will be all that is left, only in equilibrium meaning no ability for energy to form matter.

The law of conservation of energy states that energy is conserved **in a closed system**. This means the Universe, which is likely an open system, does not necessarily have to obey that conservation law. Not to mention, scientific laws are *not* absolute, despite their names; they are entirely empirical, and only apply as far as we've observed. As Edwin Hubble put it, "Beyond the limit of the observations, the form of [a] function, or relation, is speculative. For this reason, [a] law is empirical and it must remain empirical until it is explained by an accepted theory."

Anyway, let's get on with the answer. You've just described the Black Hole Era in the heat death scenario. If Hawking radiation occurs, then the black hole will continue to emit particles. During the last stages of its evaporation, a black hole will emit not only massless particles, but also heavier particles, such as electrons, positrons, protons, and antiprotons.

Once all black holes have evaporated, the Universe will be nearly empty, sans some particles that will almost never interract. Eventually, even the protons and antiprotons emitted by the black holes will decay into photons and leptons. Thus begins the Dark Era, when the Universe will be dominated by dark matter, electrons and positrons.

Electrons and positrons will rarely come together and form [positronium atoms](https://en.wikipedia.org/wiki/Positronium) (in which the electron and positron are electromagnetically bound). Positronium decays very within nanoseconds, since the two particles annihilate. Thus, over time, the energy levels in the Universe will become lower and lower.

What happens next is a matter of speculation. According to [Carroll & Chen (2004)](https://arxiv.org/abs/hep-th/0410270), quantum tunnelling and quantum fluctuations could hypothetically create another Big Bang, approximately $10^{10^{10^{56}}}$ years from now.

[Adams & Laughlin (1997)](https://arxiv.org/abs/astro-ph/9701131) speculates that quantum effects will dominate once all macroscopic matter is gone. Essentially, the laws of "macro-physics" will break down, while quantum mechanical phenomena prevail. As a result, the smallest perturbations would make the biggest difference in this era, so there is no telling what may happen to space or time.

Furthermore, they speculate that if the Universe is a false vacuum, the vacuum may decay into a lower-energy state, creating a new "child universe":

> It is also possible for the universe to spontaneously create “child
> universes” through a quantum tunneling process roughly analogous to
> that considered above (e.g., Sato et al., 1982; Hawking, 1987; Blau,
> Guendelman, & Guth, 1987). In this situation, a bubble of false vacuum
> energy nucleates in an otherwise empty space-time. If this bubble is
> sufficiently large, it will grow exponentially and will eventually
> become causally disconnected from the original space-time. In this
> sense, the newly created bubble becomes a separate “child universe”.

So yes, something as small as quantum tunnelling will potentially have an enormous effect on the future of the Universe.

In the end, we really have no idea what will happen after enough time, so there's no definitive answer to your question in the long run.

> **Comments:**
> **username_5**: I find a particular elegance to the notion that dead universes give rise to new ones.  
> **username_4**: @called2voyage As do I. I guess we'll just have to be optimistic :)  
> **username_0**: Well, I really like the answer. But assuming before a new Big Bang is created, energy and matter levels in fact reach zero and there exists literally nothing, would Universe still be an applicable term? Or is there another term that can classify this scenario? Are we dealing with The Nothing?  
> **username_5**: @ElBromista "Universe" simply means "all that is". There wouldn't be literally nothing because there would still be quantum effects, so there is still something that *is*, thus it would still be called the Universe.  
> **username_4**: @ElBromista Energy and matter levels never reach zero. The Universe reaches a point where there is no more [free energy](https://en.wikipedia.org/wiki/Thermodynamic_free_energy) available for work. What you call the Universe beyond that point is up to you, but since the Universe is defined as "all of space and time and its contents", I'd say "Universe" still works, since time still exists (although not much will necessarily happen).  
> **username_0**: Would a question, "What is meant by "quantum events" in the final state of the universe?" be out of scope for this SE? Can I ask that as a separate question?  
> **username_4**: @ElBromista By "quantum events", I refer to quantum tunneling and quantum fluctuations.  
> **username_0**: Ah, so that is why they say a new Big Bang could spawn? I'm assuming that this means in the context that a massive fluctuation at the quantum level allows a release of mass and energy, causing a rapid expansion similar to what the original Big Bang was? Is it possible this could happen during our current era of the universe?  
> **username_5**: @ElBromista Roughly speaking, in the quantum world everything is possible, but not everything is likely.  
> **username_4**: @ElBromista It's much more complicated than that. Instead of assuming, I encourage you to read Adams & Laughlin (1997), specifically in page 41.  

---

### Answer by username_2 on 2019-05-19. Score: -2

There couldn't be a universe where no matter & energy exists;the universe IS matter & energy,so without it,no universe.

> **Comments:**
> **username_3**: Can you support this by citing some authoritative sources? Thanks!  
> **username_2**: What came out of the singularity which gave birth to the Big Bang? It couldn't by any chance have been matter & energy could it? Without this explosion of energy,some of which later materialised into matter,there couldn't have been a universe. The big mystery is: what became of all the antimatter which must have been created at the same time?  
> **username_3**: Stack Exchange is a little different than other sites you may have visited. To post a serious and good quality answer to a question here, you should support your statement with authoritative sources.  

---

