I am a theoretical physicist and currently Director of 
June 07, 2011
Why a god is not necessary to create the universe
In an article titled Does the Universe Need God?, cosmologist Sean Carroll provides a rejoinder to those who would try to squeeze god in as an answer to what they perceive as unexplained gaps in our knowledge. It is a long article that is worth reading in full but for those who lack the time, I will excerpt some of the key points.
He starts by making the same point that I made in the series Why atheism is winning, that the long-term outlook for religion is extremely bleak because science and its associated modernistic outlook is making it irrelevant in ways that are hard to ignore even by the most determined religionist.
Most modern cosmologists are convinced that conventional scientific progress will ultimately result in a self-contained understanding of the origin and evolution of the universe, without the need to invoke God or any other supernatural involvement. This conviction necessarily falls short of a proof, but it is backed up by good reasons. While we don't have the final answers, I will attempt to explain the rationale behind the belief that science will ultimately understand the universe without involving God in any way.
Those who want to insert god somewhere, to show that he/she/it is necessary in some way, need to realize that they have at most a window of one second just after the Big Bang to work with.
While we don't claim to understand the absolute beginning of the universe, by the time one second has elapsed we enter the realm of empirical testability. That's the era of primordial nucleosynthesis, when protons and neutrons were being converted into helium and other light elements. The theory of nucleosynthesis makes precise predictions for the relative abundance of these elements, which have passed observational muster with flying colors, providing impressive evidence in favor of the Big Bang model. Another important test comes from the cosmic microwave background (CMB), the relic radiation left over from the moment the primordial plasma cooled off and became transparent, about 380,000 years after the Big Bang. Together, observations of primordial element abundances and the CMB provide not only evidence in favor of the basic cosmological picture, but stringent constraints on the parameters describing the composition of our universe.
He then clarifies what it means to talk about the Big Bang event, a singular event in time, as distinct from the Big Bang model that is the working out of the aftermath of that event.
One sometimes hears the claim that the Big Bang was the beginning of both time and space; that to ask about spacetime "before the Big Bang" is like asking about land "north of the North Pole." This may turn out to be true, but it is not an established understanding. The singularity at the Big Bang doesn't indicate a beginning to the universe, only an end to our theoretical comprehension. It may be that this moment does indeed correspond to a beginning, and a complete theory of quantum gravity will eventually explain how the universe started at approximately this time. But it is equally plausible that what we think of as the Big Bang is merely a phase in the history of the universe, which stretches long before that time – perhaps infinitely far in the past. [My italics] The present state of the art is simply insufficient to decide between these alternatives; to do so, we will need to formulate and test a working theory of quantum gravity.
…
The problem with "creation from nothing" is that it conjures an image of a pre-existing "nothingness" out of which the universe spontaneously appeared – not at all what is actually involved in this idea. Partly this is because, as human beings embedded in a universe with an arrow of time, we can't help but try to explain events in terms of earlier events, even when the event we are trying to explain is explicitly stated to be the earliest one. It would be more accurate to characterize these models by saying "there was a time such that there was no earlier time."To make sense of this, it is helpful to think of the present state of the universe and work backwards, rather than succumbing to the temptation to place our imaginations "before" the universe came into being. The beginning cosmologies posit that our mental journey backwards in time will ultimately reach a point past which the concept of "time" is no longer applicable. Alternatively, imagine a universe that collapsed into a Big Crunch, so that there was a future end point to time. We aren't tempted to say that such a universe "transformed into nothing"; it simply has a final moment of its existence. What actually happens at such a boundary point depends, of course, on the correct quantum theory of gravity.
The important point is that we can easily imagine self-contained descriptions of the universe that have an earliest moment of time. There is no logical or metaphysical obstacle to completing the conventional temporal history of the universe by including an atemporal boundary condition at the beginning. Together with the successful post-Big-Bang cosmological model already in our possession, that would constitute a consistent and self-contained description of the history of the universe.
Nothing in the fact that there is a first moment of time, in other words, necessitates that an external something is required to bring the universe about at that moment. [My italics]
The Big Bang event itself does not necessarily imply that the universe had a beginning in time and even if it should turn out that it had, it does not imply a beginner. This strikes at the heart of the arguments of religious apologists who need a beginning to make their claim say that a beginning necessarily implies a beginner. That argument is weak to begin with, but is the main one they have for god.
Religious people know that this conclusion is a devastating one for them. After all, if no god is required to create the universe, then he is truly an unnecessary concept. So they will fight or ignore or obfuscate this point with theological jargon.
Comments
I don't understand this sentence at all (from the article):
"As discussed above, vacuum energy is the leading candidate for the dark energy causing distant galaxies to accelerate; but even if the vacuum energy is exactly zero and the dark energy is something else, we can safely say that the value of the vacuum energy is not greater than that of the dark energy, about 10-8 ergs per cubic centimeter."
It sounds like he is saying the vacuum energy is exactly zero AND it's not greater than that of dark energy. Well, of course not, if it's exactly zero.
What am I misunderstanding?
healthphysicist,
I think that is a typo and that he meant to write "even if the vacuum energy is [not] exactly zero" because otherwise you are right, it does not make sense.
I'm sorry, Professor, but I don't think that's it. Prior to that sentence he is explaining that vacuum energy is the leading "contender" for dark energy. In other words vacuum energy and dark energy are the same thing...a thing which isn't zero.
So I think in the sentence I selected, he meant to say, "even if the vacuum energy is zero and dark energy is something else...". In essence, he is arguing against his prior point (tht vacuum energy and dark energy are the same).
Nowhere above that particular sentence did he argue that the vacuum energy IS zero. So why would he argue against it now, which is what you are suggesting?
I'm still confused.
I see your point. Let me see if I can rewrite this in a way that makes sense.
The measured acceleration of the distant galaxies requires a dark energy of 10^-8 ergs per cubic centimeter. This dark energy may be entirely vacuum energy and zero other forms of dark energy, or zero vacuum energy and entirely other forms of dark energy, or some combination.
Whatever the mix, the total dark energy involved must be 10^-8 ergs per cubic centimeter, which means that the vacuum energy must not exceed this amount.
Does that make sense, irrespective of whether what Carroll wrote is perfectly clear?
Thanks Professor, that clears that up, but raises another question, in regards to this sentence from the same paragraph:
"The fact that the actual value of the vacuum energy is at least 120 orders of magnitude smaller than its natural value is a fine-tuning by anyone's estimation."
When he says "natural" does he mean "calculated" or "expected"?
And if so, how does this "calculational" error imply fine tuning? As I understand "fine tuning", it means a physical constant can't deviate very much without extreme physical consequences in nature. Therefore, "goddidit".
Just because a calculated value deviates from an observed value, doesn't imply fine tuning in and of itself. So I don't understand the linkage he's made.
It also seems worrisome that the deviation is so huge, and that begs for an explanation.
(Sorry to be a pest, but I never learned much about the vacuum in school. I am making my way through this book this week on my own, so your post is timely:
http://www.physics.arizona.edu/~rafelski/Books/StructVacuumE.pdf
I find it odd that the vacuum is the underlying explanation for physics (the book's authors' claim), much like evolution for biology, but it was never presented that way to me.)
What you describe is one form of fine tuning, where if the value of a parameter were to change by even a small amount from its present value, there would be huge consequences that would make the system unstable.
But there is another form of fine tuning that is related to the above. Suppose the value that you need for a parameter to get a stable solution is (say) 2. But when you try and calculate that number, it turns out that you need to calculate two numbers each of which is huge (of the order of trillions) and that you have to subtract one number from the other to get the number 2. The idea that two very large numbers need to be such as to almost (but not exactly) cancel out to give you the required small
value is also considered to be a form of fine tuning, since an extremely tiny change in either of the two large numbers would throw your resultant number completely off.
That is the kind of fine tuning Carroll is referring to. When you try and calculate the vacuum energy using quantum field theory, you get a number of the order of 10^112 ergs/cc. To get the required dark energy density upper limit of 10^-8 ergs/cc, this means that there must be some other term yet to be calculated or another source of dark energy yet to be found which would also give a number of the order of 10^112 ergs/cc, which would almost exactly cancel the first number to give you 10^-8 ergs/cc.
This is what he means by requiring fine tuning to the order of 10^120, since it would require precision to the level of 10^120 significant figures to get the required cancellation.
Mano,
>But it is equally plausible that what we think of as the Big Bang is merely a phase in the history of the universe, which stretches long before that time – perhaps infinitely far in the past.
My understanding of the 2nd law of thermodynamics is that entropy always decreases as you go back in time. Is this decrease asymptotic, or would there be a definite point in time of zero entropy? And what would a zero entropy universe look like, and could a zero entropy universe remain in that state for any amount of time, or would it immediately proceed to a state of greater entropy? It seems logically it could not, and therefore there couldn't be any point of zero entropy in an infinite past, and so entropy must decrease asymptotically into an infinite past. What are your thoughts?
Robert
Robert,
It is true that as you go back in time, the absolute entropy of the universe gets smaller. The formula for the entropy at very early times suggests that it varies as the square of the time. Thus if we set time equal to zero, the entropy becomes zero too.
The catch is that we are not justified in setting time equal to zero or to any value less than what is called the Planck time (which is about 10^-43 seconds), because when we approach that regime, our theories of gravity break down and we need a theory of quantum gravity, which we currently don't have.
So the answer to your question is that we do not really know how entropy varies with time once we get to earlier than the Planck time.
Thanks Professor, that makes sense.
P.S. I see you posted a response at 12:04 p.m. to my 11:33 a.m. "second question". I had checked back here frequently since posting that second question, but saw no update to the website until now (now being about 8:20 p.m.). I am not sure why that is, but hopefully provides an explanation to you as to why I have failed to post since then.
healthphysicist,
Not all pages get refreshed whenever updated. If you don't, then sometimes you get the earlier cached page, even if the page has been updated.
Did you try refreshing the page? If not, that may explain why you did not see the 12:04 update.
This topic will go around in circles for eternity.
It's funny though how many scientific theories border on religion nowadays, kind of like the big bang theory.
Religion will ALWAYS come down to faith, if there is proof of god, what happens to free will?
So what existed before the big bang and before that?
The big bang theory takes just as much faith as believing in god.