<p>The universe has a finite age, about 13.7 billion years. So there has not been time enough for infinite events in our past light-cone.</p>
<p>There are rather few events in mainstream physics that are <em>universe</em> ending. Closed universes eventually <a href="https://en.wikipedia.org/wiki/Big_Crunch" rel="nofollow noreferrer">implode</a>, and if certain forms of dark energy exist they can cause a <a href="https://en.wikipedia.org/wiki/Big_Rip" rel="nofollow noreferrer">Big Rip</a> where the universe expands to infinity in a finite time. But obviously observers cannot look back on them in their past. This is also true for other local disasters like <a href="https://en.wikipedia.org/wiki/False_vacuum_decay" rel="nofollow noreferrer">false vacuum decay</a>.</p>

CC BY-SA 4.0
2021-03-13T22:41:47.710Z
If our Big Bang is what follows a Big Rip or implosion, then the universe might be older than 13.7 billion years old, it's just that no evidence survives from back then.
Ryan_L
CC BY-SA 4.0
2021-03-14T09:43:39.753Z
@Ryan_L - You can always add hypothetical, undetectable pasts to any model. After all, the universe *could* be 10 minutes old with fake memories. But it doesn't make for good physics to assume it. Also, I interpret universe-ending as actually ending the universe.
Anders Sandberg
CC BY-SA 4.0
2021-03-13T20:08:53.773Z
2021-03-13T20:08:53.773Z
Anders Sandberg
<p>or is it that the definition of infinity used here excludes such events like there are an infinite number of odd numbers but 2 isn't in that set?</p>

CC BY-SA 4.0
2021-03-14T17:04:15.817Z
Types of infinity: https://math.stackexchange.com/questions/5378/types-of-infinity
Wayfaring Stranger
CC BY-SA 4.0
2021-03-15T07:12:10.540Z
How can you tell that there aren't already an infinite number of "universe ending events", and it's just that none of them have yet reached our (possibly) infinitesimal little pocket of the cosmos in the ridiculously brief 13.8 billion years since the BB? Conversely, what makes you think there's even such a thing as a "universe ending event"? Only a universe-sized singularity could do that.
Chappo Hasn't Forgotten
<universe>
if the universe is infinite shouldn't it have experienced an infinite number of universe ending events?
xaxado2791
# if the universe is infinite shouldn't it have experienced an infinite number of universe ending events?

(Asked by: username_0 on 2021-03-13)

or is it that the definition of infinity used here excludes such events like there are an infinite number of odd numbers but 2 isn't in that set?

**Tags:** universe
> **Comments:**
> **username_1**: Types of infinity: https://math.stackexchange.com/questions/5378/types-of-infinity  
> **username_2**: How can you tell that there aren't already an infinite number of "universe ending events", and it's just that none of them have yet reached our (possibly) infinitesimal little pocket of the cosmos in the ridiculously brief 13.8 billion years since the BB? Conversely, what makes you think there's even such a thing as a "universe ending event"? Only a universe-sized singularity could do that.  

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## 1 answers

### Answer by username_3 on 2021-03-13. Score: 3

The universe has a finite age, about 13.7 billion years. So there has not been time enough for infinite events in our past light-cone.

There are rather few events in mainstream physics that are *universe* ending. Closed universes eventually [implode](https://en.wikipedia.org/wiki/Big_Crunch), and if certain forms of dark energy exist they can cause a [Big Rip](https://en.wikipedia.org/wiki/Big_Rip) where the universe expands to infinity in a finite time. But obviously observers cannot look back on them in their past. This is also true for other local disasters like [false vacuum decay](https://en.wikipedia.org/wiki/False_vacuum_decay).

> **Comments:**
> **username_4**: If our Big Bang is what follows a Big Rip or implosion, then the universe might be older than 13.7 billion years old, it's just that no evidence survives from back then.  
> **username_3**: @Ryan_L - You can always add hypothetical, undetectable pasts to any model. After all, the universe *could* be 10 minutes old with fake memories. But it doesn't make for good physics to assume it. Also, I interpret universe-ending as actually ending the universe.  

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