<p>The truth is we do not have a working or widely accepted "theory of everything" that unifies gravitation with the other fundamental, and quantum, field theories. What we do have is strong evidence that the other field theories - electromagnetic, strong nuclear and weak nuclear - are unified at high energies (indeed the evidence is so strong that I doubt it is widely disputed at all).</p>

<p>We do have a theory of gravitation - general relativity - that appears to work well in "most" circumstances, though it also has a singularity (black holes) and there is a fundamental difference between it and the quantum theories about vacuum energy (the so-called vacuum catastrophe).</p>

<p>What we also know is that gravitation appears to much weaker than the other forces, though it can act over very large distances and so is fundamental in shaping the nature of our universe.</p>

<p>There are various arguments about how/why our universe is able to support life/is the way it is. Perhaps it is just one of many/an infinite number of universes that have a range of physical properties and we just happen to be in one that "works" for life - obviously there could be no life in a universe that had physical properties that didn't support life.</p>

<p>At another extreme perhaps we are all inside a computer simulation.</p>

<p>I'd suggest hunting down works by <a href="http://space.mit.edu/home/tegmark/" rel="nofollow">Max Tegmark</a> or <a href="https://en.wikipedia.org/wiki/The_Hidden_Reality" rel="nofollow">Brian Greene</a> for more information.</p>

CC BY-SA 3.0
2015-10-26T10:28:30.207Z
Maybe OT, but that simulation argument is self defeating. If it is true then we know nothing about physics and cannot know if it is true or not.
LocalFluff
CC BY-SA 3.0
2015-10-26T12:08:33.690Z
Not necessarily - if we detected a fundamental limit/rounding error in the universe then that would suggest a simulation quite strongly.
adrianmcmenamin
CC BY-SA 3.0
2015-10-26T13:02:44.263Z
How could we even know that there exists logic in the physics of the real universe? Logic actually seems like a very convenient software development tool to simplify simulations, as does linear time. What indicates that any of that stuff exists in the real world if we are a simulation?
LocalFluff
CC BY-SA 3.0
2015-11-04T22:27:45.590Z
I get where you are coming from. But your argument also strikes me as saying we could detect no logic in the operation of a computer program. Not true. For sure the idea that we are entities in a simulation borders on metaphysics, but it does not have to be.
adrianmcmenamin
CC BY-SA 3.0
2015-10-26T10:21:07.610Z
2015-10-26T10:21:07.610Z
adrianmcmenamin
<p>I was watching a documentary on the big bang, one of the astronomers said that initially the four fundamental forces were combined as one, they then emerged to become: The strong and weak nuclear forces, the electromagnetic force and the gravitational force. He claimed that the first force to emerge was the gravitational force, he went on to say that had the gravitational force been weaker than it is everything would fly apart so no galaxies would form and if gravity was too large than we would end up with black holes everywhere, so the force of gravity needed to be just right, as it is now. I couldn't find anything backing up this information online or the reasoning behind this information, any help would be appreciated.</p>

CC BY-SA 3.0
2015-10-26T09:53:13.197Z
Sounds a bit like a slight variation of the [fine-tuned universe](https://en.wikipedia.org/wiki/Fine-tuned_Universe) concept (also known as the "perfect universe") to me. "Slight" enough that the linked Wikipedia article should get you started.
user
CC BY-SA 3.0
2015-10-26T14:06:58.653Z
It sounds like there's 2 basic ideas here.  The first, the unification of the forces is a fairly old idea that has been a kind of holy grail in physics.  3 of the 4 forces have been tied together - see https://en.wikipedia.org/wiki/Grand_Unified_Theory, the 4th, gravity, hasn't yet but maybe some day.    The 2nd idea, the ratio of the various strength of each force, I think Michael Kjorling covered that.    In a nutshell, I think both ideas you discuss from the show are pretty much correct.
userLTK
<gravity><big-bang-theory>
Strength of gravity during the big bang?
michael
# Strength of gravity during the big bang?

(Asked by: username_0 on 2015-10-26)

I was watching a documentary on the big bang, one of the astronomers said that initially the four fundamental forces were combined as one, they then emerged to become: The strong and weak nuclear forces, the electromagnetic force and the gravitational force. He claimed that the first force to emerge was the gravitational force, he went on to say that had the gravitational force been weaker than it is everything would fly apart so no galaxies would form and if gravity was too large than we would end up with black holes everywhere, so the force of gravity needed to be just right, as it is now. I couldn't find anything backing up this information online or the reasoning behind this information, any help would be appreciated.

**Tags:** gravity, big-bang-theory
> **Comments:**
> **username_1**: Sounds a bit like a slight variation of the [fine-tuned universe](https://en.wikipedia.org/wiki/Fine-tuned_Universe) concept (also known as the "perfect universe") to me. "Slight" enough that the linked Wikipedia article should get you started.  
> **username_2**: It sounds like there's 2 basic ideas here.  The first, the unification of the forces is a fairly old idea that has been a kind of holy grail in physics.  3 of the 4 forces have been tied together - see https://en.wikipedia.org/wiki/Grand_Unified_Theory, the 4th, gravity, hasn't yet but maybe some day.    The 2nd idea, the ratio of the various strength of each force, I think Michael Kjorling covered that.    In a nutshell, I think both ideas you discuss from the show are pretty much correct.  

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## 1 answers

### Answer by username_3 on 2015-10-26. Score: 1

The truth is we do not have a working or widely accepted "theory of everything" that unifies gravitation with the other fundamental, and quantum, field theories. What we do have is strong evidence that the other field theories - electromagnetic, strong nuclear and weak nuclear - are unified at high energies (indeed the evidence is so strong that I doubt it is widely disputed at all).

We do have a theory of gravitation - general relativity - that appears to work well in "most" circumstances, though it also has a singularity (black holes) and there is a fundamental difference between it and the quantum theories about vacuum energy (the so-called vacuum catastrophe).

What we also know is that gravitation appears to much weaker than the other forces, though it can act over very large distances and so is fundamental in shaping the nature of our universe.

There are various arguments about how/why our universe is able to support life/is the way it is. Perhaps it is just one of many/an infinite number of universes that have a range of physical properties and we just happen to be in one that "works" for life - obviously there could be no life in a universe that had physical properties that didn't support life.

At another extreme perhaps we are all inside a computer simulation.

I'd suggest hunting down works by [Max Tegmark](http://space.mit.edu/home/tegmark/) or [Brian Greene](https://en.wikipedia.org/wiki/The_Hidden_Reality) for more information.

> **Comments:**
> **username_4**: Maybe OT, but that simulation argument is self defeating. If it is true then we know nothing about physics and cannot know if it is true or not.  
> **username_3**: Not necessarily - if we detected a fundamental limit/rounding error in the universe then that would suggest a simulation quite strongly.  
> **username_4**: How could we even know that there exists logic in the physics of the real universe? Logic actually seems like a very convenient software development tool to simplify simulations, as does linear time. What indicates that any of that stuff exists in the real world if we are a simulation?  
> **username_3**: I get where you are coming from. But your argument also strikes me as saying we could detect no logic in the operation of a computer program. Not true. For sure the idea that we are entities in a simulation borders on metaphysics, but it does not have to be.  

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