Defenders: Excursus on Natural Theology (Part 11): Scientific Confirmation of the Beginning of the Universe

Summary

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Defenders Podcast

Excursus on Natural Theology (Part 11): Scientific Confirmation of the Beginning of the Universe

Host: Dr. William Lane Craig
Date: June 22, 2022

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Overview

In this episode of the Defenders class, Dr. William Lane Craig explores scientific confirmations for the beginning of the universe as support for the second premise of the Kalam Cosmological Argument: "The universe began to exist." He discusses both philosophical and scientific perspectives, focusing particularly on evidence from cosmology, such as the Big Bang model and discoveries like cosmic background radiation. Dr. Craig also addresses alternative models, the limits of science versus metaphysics, and fielded questions from class participants on foundational cosmological theories.

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Key Discussion Points & Insights

Philosophical Foundation (00:19–03:31)

• Dr. Craig and Eric recap two philosophical arguments for why the universe cannot have an infinite past:

  • Impossibility of an Actual Infinite: Forming an actually infinite collection of things (like past events) is impossible.
  • Successive Addition Argument: You cannot form an actually infinite sequence by adding one member at a time, so an infinite series of past events is not possible.

• Simple Explanations:

  • "What is infinity minus infinity? ...You get self-contradictory answers and that shows that infinity is just an idea in your mind, not something that exists in reality." — Bill, (02:26)
  • The dominoes analogy: An infinite line of falling dominoes means the present could never arrive.

• Summary: Philosophy points towards an absolute beginning of the universe in time.

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Transition to Scientific Evidence (03:35–05:57)

• Dr. Craig introduces scientific arguments as confirmations of the philosophical conclusion.
  • "Given the scientific evidence, the statement 'the universe began to exist' is more probable than it would have been without that evidence." — Bill, (04:16)
  • He clarifies science doesn't deal in certainties, but in probabilities, responding to claims that no one "knows" with certainty if the universe had a beginning.

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The Expansion of the Universe & The Big Bang (05:57–14:53)

Historical Background & Expansion Discovery (06:05–08:52)

• The Big Bang model finds its roots in Einstein's 1917 application of general relativity and later mathematical work by Friedman and Lemaitre.
• Edwin Hubble's 1929 discovery of galactic redshifts confirmed that galaxies are moving away, supporting the idea of an expanding universe.

Visualizing the Expansion (09:33–13:13)

• Balloon Analogy: "Imagine a balloon with buttons glued on the surface...as you blow up the balloon, the buttons will get further and further apart because the balloon itself is inflating." — Bill, (09:33)
• Key Point: It’s space itself expanding, not galaxies moving through space.
• Tracing the expansion backward brings every point in space closer together, culminating in a “boundary” where space and time began.

The Cone Analogy & The Absolute Beginning (12:31–13:13)

• Cone Analogy: The expansion of space over time can be represented by a cone—having a boundary “at the bottom” shows there is a finite past.

Important Clarification: "Nothing" Before the Universe (13:36–14:53)

• "When they say there's nothing prior to the Big Bang or nothing prior to the boundary point, what they mean is there was not anything prior..." — Bill, (14:20)
• Point: "Nothing" is not a "something" or a state; it simply means "not anything" existed before.

Implication

• The Standard Model predicts an absolute beginning of space, time, matter, and energy.

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Q&A: Singularity, Oscillating/Alternative Models, and Cause (15:04–21:43)

Singularity as Idealization (15:09–16:24)

• Audience asks if the initial boundary is a real "state":
  • Dr. Craig: It's not an actual physical state, but an ideal mathematical limit (like fractions approaching zero).
  • "There wouldn't be an actual T=0 at the singularity." — Bill, (16:17)

Oscillating and Alternative Universe Models (16:30–19:15)

• Discussion of M-theory and oscillating universe proposals:

  • Russian cosmologists proposed such models in the 1960s to preserve an eternal universe.

  • Stephen Hawking & Roger Penrose's singularity theorems: Showed that a singularity is inevitable in contracted universes, even oscillating ones.

  • Entropy builds with each cycle, so infinite past cycles are impossible.

  • "Based on current entropy levels in the universe, it couldn't have gone through more than about 100 previous oscillations." — Bill, (18:50)

  • "There are all kinds of problems with these oscillating models, as a result of which they haven't really commended themselves to the cosmological community..." — Bill, (19:03)

The Beginning & Causal Explanations (19:15–21:43)

• Science vs. Metaphysics: Science describes up to the beginning; the cause of the universe is a metaphysical, not scientific, question.
  • "The question as to why the universe came into being is really a metaphysical question, not one that lies within the province of science." — Bill, (20:54)
  • Key Point: The Kalam's premise ("the universe began to exist") is a theological-neutral scientific statement; theism is a philosophical extension, not part of the scientific claim.

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Scientific Evidence: Redshift & Cosmic Microwave Background Radiation (CMB) (23:46–26:25)

• CMB Discovery: In 1965, scientists detected faint microwave background radiation everywhere in the universe—a remnant from the hot, dense state following the Big Bang.

  • "The entire universe is permeated by this background microwave radiation. The best explanation...is that this is a vestige of a very hot and very dense state of the early universe." — Bill, (24:20)

• Implications against Oscillating Models:

  • The cosmic background is "extraordinarily evenly distributed...to one part in 100,000." — Bill, (25:28)
  • If the universe had oscillated (multiple cycles), you would see black holes and density fluctuations—but you don't.

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The Status of the Standard Model & Modern Modifications (26:26–29:44)

Need for Modification (27:00–28:16)

• The standard model depends on general relativity, which doesn’t work for the universe at subatomic scales; a quantum theory of gravity is needed (but doesn't exist yet).
• Expansion is not constant: there is acceleration (dark energy) and possibly early inflation.

Fundamental Prediction Stands (28:16–29:44)

• None of these updates undermine the core prediction: the universe had an absolute beginning.
• Alternative models (no-beginning) have failed; viable models (even Hawking’s no-boundary) still imply a finite past.
  • "The only viable non standard models are those that involve an absolute beginning to the universe." — Bill, (28:55)
  • "The history of 20th century cosmology can be seen as a parade of one failed attempt after another to avoid the absolute beginning predicted by the standard model." — Eric, (29:28)

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Notable Quotes & Memorable Moments

• "Infinity is just an idea in your mind, not something that exists in reality." — Bill, (02:37)
• "The best evidence of contemporary science confirms that premise that the universe began to exist. And whether or not that has theistic implications is a further philosophical question." — Bill, (21:25)
• "The only viable non standard models are those that involve an absolute beginning to the universe." — Bill, (28:55)
• "The history of 20th century cosmology can be seen as a parade of one failed attempt after another to avoid the absolute beginning predicted by the standard model." — Eric, (29:28)

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Timestamps for Important Segments

| Topic | Start Time | |------------------------------------------------------------------|:--------------:| | Philosophical Arguments for a Beginning of the Universe | 00:19 | | Simplifying the Arguments (Infinity/Dominoes Analogies) | 02:08 | | Scientific Confirmation: Introduction | 03:35 | | Scientific Evidence: The Big Bang & Expansion | 06:05 | | Red Shift and Hubble's Discovery | 07:46 | | Balloon Analogy for Expansion | 09:33 | | The Cone Analogy & Temporal Boundary | 12:31 | | "Nothing prior" to the Big Bang | 13:36 | | Q&A: Singularity, Oscillating Universe | 15:04 | | Hawking & Penrose Theorems; Problems for Oscillating Models | 17:53 | | The Question of a Cause: Science vs. Metaphysics | 19:15 | | Cosmic Microwave Background Discovery | 24:05 | | Problems for Oscillating Models addressed by CMB | 25:19 | | Current Status: Modifying the Standard Model & Its Prediction | 27:00 | | Failure of Nontemporal/Alternative Models | 28:55 | | Recap/Conclusion | 29:59 |

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Tone & Language

• Dr. Craig maintains an instructive, approachable, and philosophical tone, explaining complex concepts with accessible analogies (balloons, dominoes, fractions).
• Dialogue is interactive, respectful, and clarifies distinctions between scientific observation and philosophical interpretation.

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Conclusion

Dr. Craig concludes that, despite required refinements to the standard cosmological model, modern astronomy and astrophysics strongly confirm the philosophical premise that the universe began to exist. He maintains that while science doesn't claim absolute certainty, the evidence makes this beginning "more probable than not." Alternative models trying to avoid a beginning have failed or remain less plausible.

Next session: The class will continue discussing singularity theorems and their implications for the universe’s origin.

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Transcript

[Dr. William Lane Craig]

Welcome to Defenders, the teaching class of Dr. William Lane Craig. Today An Excursus on Natural Theology, Part 11. For more resources from Dr. Craig, go to reasonablefaith.org We've been looking at philosophical

[Bill]

arguments for the second premise of the Kalam cosmological argument.

[Eric]

And we saw that the impossibility of

[Bill]

forming an actually infinite collection of things,

[Eric]

adding one member after another, implies that

[Bill]

the universe began to exist, which is the second premise of that argument. So we can summarize this argument as follows.

[Eric]

Premise 1, a collection formed by successive

[Bill]

addition cannot be an actual infinite.

[Eric]

Two, the temporal series of events is

[Bill]

a collection formed by successive addition. Three, Therefore, the temporal series of events cannot be an actual infinite.

[Eric]

So now we have two philosophical arguments

[Bill]

for the second premise of the cosmological argument. One based upon the impossibility of the existence of an actually infinite number of things, and the other based upon the impossibility of of forming a collection of actually infinite number of things by successive addition, adding one member after another, one at a time.

[Eric]

Now, lest we lose the forest for the trees, let's just step back a

[Bill]

moment and ask what we've done here.

[Eric]

What we've basically argued is that the idea of an infinite past is absurd,

[Bill]

that the past cannot be infinite and therefore it must have a beginning.

[Eric]

And these arguments, though seemingly very complex and mind stretching, can be shared in a very simple way.

[Bill]

And that's important to understand, lest you

[Eric]

just throw up your hands and say,

[Bill]

oh, all this mathematics is too difficult for me.

[Eric]

The first argument based on the impossibility

[Bill]

of an actual infinite number of things.

[Eric]

What I often do in a debate

[Bill]

situation is to simply say that the existence of an actually infinite number of things is impossible because of the absurdities

[Eric]

that would result if it could exist. For example, what is infinity minus infinity?

[Bill]

That's a simple question. What is infinity minus infinity?

[Eric]

Well, you get self contradictory answers and

[Bill]

that shows that infinity is just an idea in your mind, not something that exists in reality. And so there can't be an actually infinite number of past events. That's a very simple statement of that first argument.

[Eric]

The second argument, you can simply give

[Bill]

an illustration of an infinite series of

[Eric]

dominoes and say, how could the present domino ever fall? If an infinite number of earlier dominoes had to fall first one after another, you'd never get to the present domino. So we know that the past can't be infinite.

[Bill]

It must have had a beginning, it must be finite.

[Eric]

Now there you see, I've shared those two arguments in about 45 seconds. And so even Though there is this wealth of interesting material below the surface, the tip of the iceberg is, can

[Bill]

be shared in a relatively simple and straightforward way.

[Eric]

Now we want to go on to

[Bill]

scientific confirmations of the beginning of the universe.

[Eric]

In one of the most astonishing developments

[Bill]

of modern astronomy and astrophysics, which our

[Eric]

Muslim theologian friend Al Ghazali could never

[Bill]

have anticipated, is that we now have pretty strong evidence scientifically for the beginning of the universe.

[Eric]

And I like to think of these scientific arguments as confirmations of the philosophical arguments. They are confirmation of a conclusion already

[Bill]

reached by philosophical argument.

[Eric]

That is to say, given the scientific evidence, the statement the universe began to exist is more probable than it would

[Bill]

have been without that evidence.

[Eric]

That the evidence confirms the truth of

[Bill]

that premise, that the universe began to exist.

[Eric]

So if someone says to you, as they very often do, well, nobody knows

[Bill]

how the universe began. Nobody knows whether the universe had a beginning or is eternal.

[Eric]

What they're usually thinking of by the word know, there is know with certainty. Nobody knows with certainty. But of course, that's not what we're

[Bill]

claiming here, that somebody knows with certainty.

[Eric]

Science doesn't deal in certainties. What we're saying is that given the scientific evidence that we have, it's more

[Bill]

probable than not that the universe did have a beginning.

[Eric]

And it seems to me that it's

[Bill]

almost undeniable at least, to say that the scientific evidence confirms that the universe began to exist, that that statement is more probable given the scientific evidence we have today than it would have been without it, than it was, say, in the 19th century, before the Big Bang model was ever broached or the expansion of the universe discovered.

[Eric]

So that the evidence at least confirms

[Bill]

the second premise, even if it doesn't render it certain. Certainty is a will of the wisp that we don't need to be concerned about. The question is, is the premise of more probable than not, given the evidence that we have? And I think that it is.

[Eric]

Now, let's look at the first scientific

[Bill]

confirmation, which comes from the expansion of the universe.

[Eric]

All throughout history, men have always assumed that the universe as a whole was unchanging. Now, of course, things in the universe

[Bill]

were moving about in and changing, but

[Eric]

the universe as a whole was just there, so to speak. This was also Albert Einstein's assumption when he first began work on his general theory of relativity in 1917. Einstein applied his gravitational theory, which is called the general theory of relativity. It's really not a theory of relativity, it's a theory of gravitation.

[Bill]

It is the theory of gravitation that is accepted in physics today.

[Eric]

And in 1917, Einstein began to apply his newly discovered gravitational theory to the

[Bill]

universe as a whole.

[Eric]

But he found that something was terribly amiss. His equations described a universe which was either blowing up like a balloon or else collapsing in upon itself. During the 1920s, the Russian mathematician Alexander Friedman and the Belgian astronomer Georges Lemaitre independently discovered models of the universe, which took Einstein's equations at face value. And as a result, they discovered models

[Bill]

of an expanding universe.

[Eric]

In 1929, the American astronomer Edwin Hubble, through tireless observations at Mount Wilson Observatory, confirmed Friedman and Lemaitre's theory. He found that the light coming to us from distant galaxies appears to be redder than expected. And this red shift in the light was most plausibly explained because the galaxies are moving away from us, and therefore the light waves, the wavelengths, are stretched so that they appear to be redder than expected. Wherever Hubble trained his telescope in the night sky, he observed this same red shift in the light from the galaxies. It appeared that we are at the center of a cosmic explosion, that all of the other galaxies are flying away from us at tremendous speeds.

[Bill]

Now, according to the Friedmann Lemaitre model,

[Eric]

we're not really at the center of the universe. Rather, an observer in any galaxy will look out and see the other galaxies flying away from him. This is because, according to the theory, it is really space itself which is expanding. The galaxies are actually at rest with respect to space, but they recede from each other as space itself expands. Now, the best way to visualize this,

[Bill]

I think, is to imagine a balloon

[Eric]

with buttons glued on the surface. The buttons are glued in place so they cannot move across the surface of the balloon. The buttons are stuck and in place. But as you blow up the balloon, the buttons will get further and further apart because the balloon itself is inflating. And those buttons are just like the galaxies in outer space. The galaxies are actually at rest with

[Bill]

respect to expanding space, but they recede from one another as space itself expands.

[Eric]

Now, the Friedmann Lemaitre theory eventually came

[Bill]

to be known as the Big Bang

[Eric]

theory, But that name can be misleading. The Big Bang sounds like an explosion, doesn't it? But thinking of the expansion of the universe as a sort of explosion could mislead us into thinking that the galaxies are moving out into a pre existing

[Bill]

empty space from a central point. And that would be a complete misunderstanding of the theory.

[Eric]

As we've seen, the theory is much

[Bill]

more radical than that. It is space itself, which is Expanding.

[Eric]

Now, as you trace this expansion back in time, the galaxies will get closer and closer and closer together. Eventually, the distance between any two points

[Bill]

in space becomes zero.

[Eric]

You can't get any closer than that. So at that point you have reached the boundary of space and time. Space and time cannot be extended back any farther than that. It is literally the beginning of the universe. Now to imagine this, we can think of our three dimensional space as a two dimensional disk. So we will ignore one spatial dimension

[Bill]

and think of our three dimensional space

[Eric]

as this two dimensional disk. As you go back in time, space shrinks down until the distance between any

[Bill]

two points in space becomes zero.

[Eric]

And that is the beginning of the universe.

[Bill]

So the vertical dimension here represents time. And over time the universe is expanding.

[Eric]

So we can represent the expansion of space geometrically as a cone. Now what's interesting about a cone is that although it can be extended indefinitely in one direction, it has a boundary point in the other direction and cannot

[Bill]

be extended in that direction because this

[Eric]

direction represents time and the boundary point

[Bill]

lies in the past.

[Eric]

That point represents the beginning of the universe. It implies that the past is finite

[Bill]

and that therefore time and the universe began to exist.

[Eric]

And since space time is the arena in which all matter and energy exist, the beginning of space time is the beginning of all the matter and energy in the universe.

[Bill]

It is the beginning of the universe itself.

[Eric]

Now notice that there's simply nothing prior to the initial boundary point.

[Bill]

There's nothing prior to the beginning of the universe.

[Eric]

But here it's very important that we not be misled by words. When scientists say there's nothing prior to the initial boundary, they do not mean that there is something prior to it.

[Bill]

And that is a state of nothingness.

[Eric]

That would be to treat nothing as though it were something. Remember when we talked about what nothing mean?

[Bill]

It's just a term of universal negation, meaning not anything.

[Eric]

So when they say there's nothing prior to the Big Bang or nothing prior

[Bill]

to the boundary point, what they mean

[Eric]

is there was not anything prior to

[Bill]

the boundary point or at that boundary point.

[Eric]

It is false that there is something

[Bill]

prior to this point.

[Eric]

So incredibly, the standard Big Bang model thus predicts an absolute beginning to the universe. And if this model is correct, then we would have amazing scientific confirmation of the second premise of the Kalam cosmological

[Bill]

argument, that the universe began to exist.

[Eric]

Now, is there any question of a comprehension nature about this model and what we've shared so far?

[Bill]

Don has a question here. We'll get you the microphone, Don. So we can hear you, Bill.

[Eric]

Is that zero point also the limit of time?

[Bill]

Yes, yes, both time and space.

[Drew]

Drew, do the cosmologists consider the singularity to be a thing, a being, an actual object?

[Eric]

That's a really good question. Drew is saying when you get to this boundary point, is that an actual physical state of reality?

[Bill]

And my impression, Drew, is that among

[Eric]

many cosmologists, they would say no, that

[Bill]

this is an idealization.

[Eric]

It would be

[Drew]

like an asymptote, then almost like an idealism.

[Eric]

It wouldn't be an astrophysical state. It would be kind of like the series of fractions converging towards zero as a limit.

[Bill]

And so you'd have 1/2, 1/4, 1/8, 1:16.

[Eric]

And there the endpoint is simply an ideal limit that doesn't actually exist, isn't

[Bill]

an actual physical state of affairs.

[Eric]

So in this case, there wouldn't be

[Bill]

an actual T equals zero at the singularity. It would just be like that descending series of fractions.

[Drew]

But that doesn't do anything to avoid a beginning, even if there's no beginning point.

[Bill]

No, exactly. Exactly.

[Drew]

Eric, maybe this is a bit more of an advanced question than what you're looking for, but according to certain models of M theory, scientists have put forth an idea of a variable dark energy that would sometimes be positive, sometimes be negative, and allow for an oscillating universe. What would your response be to something like that?

[Eric]

Yes, I'll raise the question in a

[Bill]

minute about other models than the standard model. I wanted us to first understand, what does the standard Big Bang model say and imply? Now, as Eric says, there have been, over the decades, scores of alternative models

[Eric]

proposed, including oscillating models, where the universe wouldn't actually go down to a singularity. It would kind of be like an hourglass.

[Bill]

And so it would go down, and

[Eric]

then it would expand out again. And that would represent a contracting universe

[Bill]

which then somehow reverses itself and expands.

[Eric]

And. And that contraction was preceded by a

[Bill]

prior expansion and that by a contraction.

[Eric]

So the universe is sort of like

[Bill]

an accordion expanding and contracting from infinity past.

[Eric]

This model was floated during the 1960s

[Bill]

primarily by Russian cosmologists who wanted to restore the eternality of matter and the universe.

[Eric]

And the singularity theorems that were developed

[Bill]

by Stephen Hawking and Roger Penrose that I'll talk about Thursday night and that

[Eric]

are featured in this movie, the Theory

[Bill]

of Everything pretty much put the kibosh

[Eric]

on these oscillating models, because what it

[Bill]

showed was that in a universe that is contracting down like this, a singularity is inevitable. You can't really escape the singularity.

[Eric]

Moreover, even if you could, entropy is conserved from cycle to cycle, which has the effect of making each cycle longer and larger than the previous cycle. So that you still couldn't have an infinite past.

[Bill]

You would still have a beginning prior to the smallest cycle. Joseph Silk, who is an astronomer in his book called the Big Bang, says

[Eric]

that based on current entropy levels in

[Bill]

the universe, it couldn't have gone through more than about 100 previous oscillations.

[Eric]

So there are all kinds of problems

[Bill]

with these oscillating models,

[Eric]

as a result

[Bill]

of which they haven't really commended themselves to the cosmological community at large as more plausible than a more straightforward model. Okay, some other question.

[Cindy]

Yes, Cindy, just want to clarify. At the beginning of space and time, in my understanding, is that God put into place a series of events in time, and starting at that point, there was nothing prior to that point, no energy, nothing Going to a cosmological understanding, what is the difference? In other words, does it state that you have to have a God to start? If you agree that the Big Bang, the collapsing, the coming together space and time did in fact happen, and then how would they address what was the initial cause if you don't have a God that is outside of space and time to create that initial beginning, do they have an answer to that, or does it get into the oscillating universe and all the string theories and that

[Eric]

sort of thing here?

[Bill]

Cindy, it seems to me that the scientist, as a scientist, says that I

[Eric]

will simply offer a description of the

[Bill]

universe back to its beginning.

[Eric]

But beyond that, that's metaphysics, not physics.

[Cindy]

So it's got the gap. In other words, they're saying we don't know, but you know.

[Eric]

No, I think they're saying that that's

[Bill]

not a scientific question unless you're raising an alternative model, like an oscillating model, to avoid the beginning. But once you have an absolute beginning, the question as to why the universe came into being is really a metaphysical question, not one that lies within the province of science.

[Cindy]

Thank you.

[Eric]

It's important to understand that the theist

[Bill]

is not offering here an alternative theory to the Big Bang theory. It's not as though he's offering a theistic creation account or something.

[Eric]

The evidence that I'm appealing to simply confirms the second premise of the cosmological

[Bill]

argument, that the universe began to exist.

[Eric]

And that's a theologically neutral statement that

[Bill]

you can find in any textbook on astronomy and astrophysics.

[Eric]

So it's not God of the Gaps

[Bill]

and God doesn't come into the picture at all. At this point, one is simply saying that the best evidence of contemporary science confirms that premise that the universe began to exist. And whether or not that has theistic implications is a further philosophical question.

[Cindy]

Thank you.

[Eric]

Yes, Ravi.

[Ravi]

Yeah. So is the reason that the scientific arguments are merely confirmations because the Kalam must seek to prove a metaphysical beginning to time and not merely a physical beginning? Because I've heard some stress what is really the importance of even studying the scientific arguments if that doesn't really seek to show the beginning of time that we would need to show in order for the Qalam to be successful?

[Eric]

I think that there is some truth

[Bill]

to what you're saying because you see,

[Eric]

if you just approach the question purely scientifically, then the committed naturalist could just

[Bill]

appeal to unknown natural laws, unknown physics to explain how the universe came into being and resort to a kind of naturalistic metaphysics. For example, someone might say, well maybe our universe just blew up in the laboratory of some sort of mega gigantic scientific study somewhere and we're really just this test universe inside this other greater massive thing. Well, I mean scientifically that's a non starter. How do you even assess something like that?

[Eric]

So in that sense I think it is true to say that the scientific

[Bill]

evidence is confirmatory of an argument that's already reached by philosophical argument, and that it will be the philosophical argument that will exclude these sorts of other metaphysical alternatives.

[Eric]

But again, as one is just doing pure science, if you're just doing pure

[Bill]

science and not speculating metaphysically, it seems to me that it's virtually undeniable that that premise the universe began to exist is more probable than than not given the current state of the evidence, which is all one is claiming.

[Eric]

Yes.

[Bruce]

Bruce, Wouldn't the constancy of the CBR temperature speak against any kind of oscillation or even multi universe? I would think you would see oscillation or perturbation or change in CBR from different directions.

[Bill]

What Bruce is talking about is a discovery made by a couple of Bell Telephone laboratory scientists in 1965 where they

[Eric]

detected a kind of low grade microwave

[Bill]

background radiation in the universe.

[Eric]

The same kind of radiation that is

[Bill]

in your microwave oven at home.

[Eric]

And they found that the entire universe is permeated by this background microwave radiation. And the best explanation of this is that this is a vestige of a very hot and very dense state of the early universe. So this is one of the other

[Bill]

pieces of evidence for the Big Bang

[Eric]

besides the red shift observed by Hubble.

[Bill]

The redshift evidence has been around ever since Hubble in the late 20s. But this cosmic background radiation was only discovered in 1965 and helped put the nails in the coffin of the old steady state model.

[Eric]

Which couldn't explain why this back whether

[Bill]

or not this is compatible with oscillating models.

[Bruce]

No, I would say it disproves oscillating models because of the constancy. The temperature is the same from all directions.

[Eric]

Yeah, right.

[Bill]

What Bruce is pointing out is that this is incredibly homogeneous in every direction

[Eric]

to one part in 100,000.

[Bill]

It does vary. It's extraordinarily evenly distributed. The suggestion is that if the universe

[Eric]

were the result of a prior oscillation, then that contracting phase would create all sorts of black holes and density perturbations

[Bill]

that would then be reflected in the microwave background in the next expansion.

[Eric]

And that is in fact, I think you're right, a huge problem. A contracting universe would be filled with these black holes and other objects that

[Bill]

are formed by gravitational self collapse that

[Eric]

wouldn't just get smoothed out when the

[Bill]

universe starts to expand again. And so that is one of the challenges, I think. Yes. Any other comment on the standard model?

[Eric]

Okay, so the question then is, is the standard model correct? Or I think more importantly, is it

[Bill]

correct in predicting a beginning of the universe?

[Eric]

Well, despite the empirical confirmation from the

[Bill]

redshift, the microwave background radiation and other

[Eric]

evidence, the standard model will need to be modified in various ways. The model is based, as I've mentioned,

[Bill]

on Einstein's gravitational theory, the general theory of relativity.

[Eric]

But the general theory of relativity breaks down when the universe is shrunk down to subatomic proportions. At that point you've got to introduce quantum physics. In order to describe the earliest split second of the universe. You need a theory that would combine general relativity or gravity with quantum physics to have a quantum theory of gravity

[Bill]

to describe the first split second of the universe. The problem is nobody knows how to do this yet. The theory doesn't exist.

[Eric]

Moreover, the expansion of the universe is probably not constant as it is in the standard model. It's probably accelerating, as I think Eric

[Bill]

alluded to, with the dark energy.

[Eric]

The universe is actually speeding up in its expansion. And it may have had a brief

[Bill]

period of super rapid or inflationary expansion very early on in the history of the universe.

[Eric]

So the standard model is going to

[Bill]

need to be modified in various ways if it's to be empirically adequate.

[Eric]

But none of these adjustments need affect the fundamental prediction of the model that

[Bill]

the universe had an absolute beginning.

[Eric]

Indeed, as I've mentioned over the decades,

[Bill]

physicists have proposed scores of alternative models since Friedmann and Lemaitre in order to avoid the absolute beginning of the universe.

[Eric]

And those models that do not feature an absolute beginning have been repeatedly shown to be untenable. Or to put it more positively, the only viable non standard models are those

[Bill]

that involve an absolute beginning to the universe.

[Eric]

Now that beginning may or may not involve beginning point, but even those that

[Bill]

do not have a point like beginning

[Eric]

are still finite in the past.

[Bill]

The past is not infinite, but finite. On these models, like Stephen Hawking's so

[Eric]

called no boundary proposal, the universe has not existed forever.

[Bill]

Rather it came into existence even if it didn't do so at a sharply defined point.

[Eric]

So in one sense, the history of 20th century cosmology can be seen as a parade of one failed attempt after another to avoid the absolute beginning predicted

[Bill]

by the standard model.

[Eric]

That prediction has now stood for nearly 100 years through a period of enormous

[Bill]

advances in observational astronomy and creative theoretical work in astrophysics.

[Eric]

Now, with that, I will bring it to a close today and next week we will continue to discuss the significance of more recently discovered singularity theorems that

[Bill]

also implied that the universe began to exist.

[Eric]

So let's just draw a class to

[Bill]

a close with a word of prayer.

[Eric]

Father, again we give you thanks and

[Bill]

praise that we can meet together in this way to study your creation and the marvelous world in which we live.

[Eric]

As we go out now into the

[Bill]

workaday world this week, we pray that

[Eric]

your Spirit would guide us, that would be conscious of your presence with us,

[Bill]

and that you would fill us and empower us by your Holy Spirit Spirit to be good witnesses for you and to do your will. In Christ's name we pray.

[Eric]

Amen.

[Dr. William Lane Craig]

The copyright for the content of this recording is held by Dr. William Lane Craig. For more go to reasonablefaith.

[Bruce]

Org.