What Could Cause a Big Crunch in the Expansion of the Universe?

[TheIsland24]

In "A Brief History of Time" Hawking questions why the expansion of the universe is accelerating. I must be missing something. If the universe is expanding, its volume is constantly increasing. If its volume is increasing its density is decreasing, so there is more space between bodies/particles and less gravitational force. The farther these particles get from each other, the less resistance there will be on the expansion of the universe...therefore causing it to expand faster and faster. What would have to happen to cause a Big Crunch? Would the rate of the creation of new particles have to be greater than the rate at which the universe was expanding? Help me Out.

 

[sylas]

In "A Brief History of Time" Hawking questions why the expansion of the universe is accelerating. I must be missing something. If the universe is expanding, its volume is constantly increasing. If its volume is increasing its density is decreasing, so there is more space between bodies/particles and less gravitational force. The farther these particles get from each other, the less resistance there will be on the expansion of the universe...therefore causing it to expand faster and faster. What would have to happen to cause a Big Crunch? Would the rate of the creation of new particles have to be greater than the rate at which the universe was expanding? Help me Out.

Expansion is not a force. It's just the movement of things apart from each other. If there was no gravity, then expansion would continue at the same rate... analogous to movement of particles at constant velocity.

With any gravity, expansion tends to slow down, because gravity pulls things together.

But, strangely, things appear to be moving aprt from each other faster, and faster... as if something is giving them an extra boost. The "something" is called "dark energy". And we don't really know anything more about it than it is whatever it is that gives that bit of an extra push to make thing increase in the speed at which they are dispersing.

The Big Crunch is an idea which applies if the force of gravity to pull things together is sufficiently strong to actually slow the expansion, or dispersion, and bring it to a stop, reverse it, and then start everything falling back together again. In terms of just two particles (rather than an entire universe of particles) it is analogous to the particles moving apart at less than escape velocity. They'll eventually stop, reverse, and start moving together. Same with a universe that has a "critical density" of mass and no dark energy.

Cheers -- sylas

 

[negitron]

I must be missing something.

You are.

If the universe is expanding, its volume is constantly increasing. If its volume is increasing its density is decreasing, so there is more space between bodies/particles and less gravitational force. The farther these particles get from each other, the less resistance there will be on the expansion of the universe...therefore causing it to expand faster and faster.

Gravity acts to slow the expansion, that is to say it decelerates it. The decrease in gravity due to the lower density means only that the rate of the acceleration of the expansion will decrease. In order for the acceleration to increase, a force must apparently be at work. We currently call that force "dark energy" but we are really only just beginning to understand it.

 

[negitron]

*shakes fist at fast-typing sylas*

 

[nutgeb]

There are two kinds of expansion:

1. The original expansion left over from the Big Bang (or inflation). This expansion acts like momentum, and is progressively slowed by the gravity of the mass-energy in the universe. This expansion does not act like a force. It cannot cause objects to separate unless the objects were already separating in the initial conditions.

2. The more recent acceleration of expansion over the last 7 Gy or so caused by Lambda, Dark Energy, the cosmological constant, whatever you want to call it. This expansion does act like a force. It can cause objects to begin separating even if they were not separating previously. And if they were already separating (e.g. in the Hubble flow) it will cause the rate of separation to increase.

Lambda is believed to impart sufficient acceleration to the expansion that the universe will never collapse in a Big Crunch. Instead, the expansion will continue accelerating until it asymptotically approaches the acceleration rate of Lambda alone, with the offsetting deceleration effect of gravity having become utterly insignificant, due to the ever-declining density of matter.

Keep in mind that even if there were no Lambda, the universe would not necessarily have collapsed in a Big Crunch. That depends on whether the matter density was sufficiently high compared to the expansion rate (Hubble rate). Such a universe would eventually collapse only if it were "overdense", meaning that it was above critical density. A universe exactly at critical density (and without any Lambda) would expand more and more slowly over time; the Hubble rate would asymptotically approach zero, but would never quite reach zero in finite time. The Hubble rate would never go negative, so such a universe would not collapse. This decreasing rate of deceleration is due to the decreasing effect of gravity, which in turn is due to the decreasing matter density, as you allude to in your OP. But adding Lambda to the mix changes the situation.

 

[TheIsland24]

Thank you Nutgeb! That explained it. So gravity cannot affect the resultant expansion of the big bang. So are you saying that gravity does affect Dark Energy?

 

[sylas]

Thank you Nutgeb! That explained it. So gravity cannot affect the resultant expansion of the big bang. So are you saying that gravity does affect Dark Energy?

Uh... nutgeb described near the end of his post the same effect of gravity on expansion that everyone else did. Gravitation attraction of matter retards, or slows, the rate of expansion.

He also described the critical density case, where which is a case where the density is not quite enough to to reverse the expansion back to contraction.

 

[Chalnoth]

I think that talking about "dark energy" as if it's some force different from gravity is poor use of language.

General Relativity provides a connection between space-time and matter. If you fill the universe with different sorts of matter, the expansion behaves differently. Fill it with normal matter, and it decelerates. Fill it with radiation, and it decelerates even more rapidly. Fill it with one of many types of hypothetical matter now placed under the umbrella term "dark energy", though, and it accelerates. It's still the action of gravity that is affecting the expansion, not some new force. It's just that gravity acts differently depending upon the properties of the underlying matter.

The property in question that is important is the relationship between the density of the matter in question and its pressure. Radiation has positive pressure equal to one third of its energy density, and that positive pressure causes the expansion to slow more rapidly. Normal matter has no pressure (e.g. galaxies don't experience pressure between one another). To get acceleration, you have to have negative pressure that is more negative than minus one third the energy density. A cosmological constant, for instance, has negative pressure equal to the energy density.

 

[sylas]

I think that talking about "dark energy" as if it's some force different from gravity is poor use of language.

General Relativity provides a connection between space-time and matter. If you fill the universe with different sorts of matter, the expansion behaves differently. Fill it with normal matter, and it decelerates. Fill it with radiation, and it decelerates even more rapidly. Fill it with one of many types of hypothetical matter now placed under the umbrella term "dark energy", though, and it accelerates. It's still the action of gravity that is affecting the expansion, not some new force. It's just that gravity acts differently depending upon the properties of the underlying matter.

Yes and no. The term "matter" is more limited than the term "energy". For example, radiation is not a "different form of matter", but you could call it a different form of energy. That's my one quibble here.

The key point is this. As the universe expands and disperses, the density of matter drops. The energy density of radiation (or matter at relativistic speeds, like neutrinos) drops even more quickly, because the cosmological redshift means energy density in a given co-moving region reduces by an additional factor on top of the number density of particles. And finally, the "dark energy" term, also called "cosmological constant", corresponds to an energy associated with the vacuum. The density of this energy remains fixed; it is like a property of empty space.

In general relativity, the crucial quantity is energy... whether it be in the form of matter, or radiation, or some energy associated with the vacuum. So there is indeed a strong sense in which dark energy is not an alternative to gravity at all. It's all still contained in the same relativistic account of gravity as the effects of matter.

What changes is the way energy density varies with the dispersal of expansion of the universe; this is what is different from matter, and from radiation.

Cheers -- sylas

 

[Chalnoth]

Yes and no. The term "matter" is more limited than the term "energy". For example, radiation is not a "different form of matter", but you could call it a different form of energy. That's my one quibble here.

I wouldn't agree with that. Photons are as much matter as electrons. It's just that we mean something specific when we talk about "normal" matter, which means non-relativistic fermions. Basically, I take issue with a definition of matter which excludes things like electrons and protons that are traveling too fast.

The problem with calling these things "energy" is that energy in itself is a property of matter. It isn't something that exists on its own.

And finally, the "dark energy" term, also called "cosmological constant", corresponds to an energy associated with the vacuum. The density of this energy remains fixed; it is like a property of empty space.

This isn't strictly accurate. The cosmological constant is one specific proposal for dark energy. There are others, though they all behave similarly at late times.

For example, so-called "quintessence" models of dark energy track the energy density of the most dominant form of matter at early times (meaning that early in the universe, this "quintessence" matter dilutes just like radiation, later like matter). At very late times, when the universe is sufficiently dilute, it starts to approach a constant energy density.

 

[Ich]

What changes is the way energy density varies with the dispersal of expansion of the universe; this is what is different from matter, and from radiation.

If we call anything with \rho > 0 "matter", as Chalnoth obviously intended, all possible variations follow the same law, dE=-pdV:
\frac{d}{d t}\,(\rho\,a^3) = -p\,\frac{d}{d t}\,(a^3)
So I think it's ok to say that there may be all sorts matter or stuff or something with different equations of state, but all on an equal footing, as far as GR is concerned.
But I think we all agree anyway.

 

[sylas]

I wouldn't agree with that. Photons are as much matter as electrons.

Terminology... I think the standard definition of "matter" is stuff that has non-zero rest mass. This excludes photons. But it is a terminology point.

It's just that we mean something specific when we talk about "normal" matter, which means non-relativistic fermions. Basically, I take issue with a definition of matter which excludes things like electrons and protons that are traveling too fast.

I certainly don't exclude things on the basis of velocity. By my usage, which I think is pretty standard, the term matter excludes photons, but not relativistic protons or other particles with a non-zero rest mas. I noted explicitly that relativistic particles have an equation of state similar to photons.

The problem with calling these things "energy" is that energy in itself is a property of matter. It isn't something that exists on its own.

By normal usage, energy is a property of more than only matter... and dark energy is basically a property of the vacuum.

This isn't strictly accurate. The cosmological constant is one specific proposal for dark energy. There are others, though they all behave similarly at late times.

For example, so-called "quintessence" models of dark energy track the energy density of the most dominant form of matter at early times (meaning that early in the universe, this "quintessence" matter dilutes just like radiation, later like matter). At very late times, when the universe is sufficiently dilute, it starts to approach a constant energy density.

Granted. I was simplifying a bit... deliberately, I confess. But I think we are on the same page. I'm just clearing up how we use terms.

Cheers -- sylas

 

[LtDan]

If the universe has always existed --- is retrospectively infinite --- then there was no "big bang" that started it.

If we hypothesize that is true, then the expansion of the universe which we observe happening is not an expansion outward from a single point of initial explosion. There would have been no such beginning point. Another explanation of the expansion is needed.

Another type of expansion is the expansion that takes place with respect to a rising piece of bread dough.

Visualize a lump of rising dough that has raisins scattered throughout it. As the bread dough expands under the influence of the yeast --- aka dark energy --- the raisins move farther and farther apart from one another. The further any two raisins are located apart from one another in the matrix of the dough, the faster those two raisins will move apart from one another, and their rate of separation will steadily accelerate.

This seems analogous to what we are observing with our powerful telescopes. The farther things are away from us in space, the faster they are moving away from us (and us from them). It is as if the universe is structured very much like the raisinbread model. The "dough" is invisible and expanding "dark matter," and all of the corporeal structures imbedded within the dough --- planets, stars, people, what-have-you --- are the raisins.

The only two differences may be:

(1) that the corporeal "raisins" in the real universe --- what we call "matter" --- also expand at the same rate that the doughy dark matter expands, so that relative near spatial intervals appear to us to be unchanging; and

(2) that there is no limit --- outer edges --- of the universe, it being infinite in size as well as in age.

I expect that the latest expansion of the Hubble telescope's visual accuity has revealed more and more "raisins" out beyond our previous limits of observation. I expect that they are more and more red-shifted toward an ultimate point of invisibility where the separation rate between our planet and those distant bodies attains and exceeds the speed of light. Perhaps we are getting close to the point where we will be able to observe these distant bodies "wink out" of vivibility.

 

[Chalnoth]

If the universe has always existed --- is retrospectively infinite --- then there was no "big bang" that started it.

The big bang theory, properly understood, does not include a beginning. It is generally recognized that the theory breaks down before you go that far back, and a different theory is needed to explain what happens at the earliest times. We don't yet know for certain how our region of the universe began, though the theoretical evidence indicates rather strongly that it had to begin at some point (though possibly from a pre-existing space-time).

If we hypothesize that is true, then the expansion of the universe which we observe happening is not an expansion outward from a single point of initial explosion. There would have been no such beginning point. Another explanation of the expansion is needed.

That's not what the big bang theory says, though.

Another type of expansion is the expansion that takes place with respect to a rising piece of bread dough.

This is a pretty good analogy for what the big bang theory actually says.

(2) that there is no limit --- outer edges --- of the universe, it being infinite in size as well as in age.

Neither is necessarily the case. Our universe may be finite in size. It may be infinite. We don't know. Our region of the universe is almost certainly finite in age, but we don't know how old what it stemmed from is. That may be infinite in age. Or our region of the universe may have been what started it all off. We just don't know.

I expect that the latest expansion of the Hubble telescope's visual accuity has revealed more and more "raisins" out beyond our previous limits of observation. I expect that they are more and more red-shifted toward an ultimate point of invisibility where the separation rate between our planet and those distant bodies attains and exceeds the speed of light. Perhaps we are getting close to the point where we will be able to observe these distant bodies "wink out" of vivibility.

Well, that won't happen. They'll just get gradually more and more redshifted. They only reach zero brightness as time goes to infinity. There's no point where you could say, "after this time, these objects are no longer visible."

 

[LtDan]

If the rate of separation between Earth and a visible far distant object in space eventually reaches and exceeds the speed of light, wouldn't that far distant object become invisible to us?

 

[Chalnoth]

If the rate of separation between Earth and a visible far distant object in space eventually reaches and exceeds the speed of light, wouldn't that far distant object become invisible to us?

We can never see the photons that leave it after a certain time (not simply given by its recession velocity, but instead by the future expansion history of the universe). But this doesn't mean that we cease to see it: we see its after-image forever. It just gets dimmer and dimmer. And, as near as we can tell time slows and slows for this image as time goes forward, and the apparent age of the object in our after image asymptotically approaches the age at which the object crossed our horizon.

Note, however, that this is only true in an accelerating universe. If the universe were not accelerating, or stopped accelerating at some point in the future, then there would be no future horizon, and, given infinite time, we would be able to see the full history of all objects in the universe.

 

[LtDan]

There are two terms I do not understand: "future expansion history" and "asymptotically."

 

[Chalnoth]

There are two terms I do not understand: "future expansion history" and "asymptotically."

future expansion history = the way the universe expands into the future.
asymptotically = behavior that a system approaches out to infinity.

Hopefully future expansion history is understandable. Asymptotically may take a little bit more work. A simple example would be this equation:

f(x) = 1/x.

In the above equation, f(x) approaches zero as x approaches infinity. This is known as asymptotic behavior: there isn't actually any number x for which f(x) = 0. But as x gets bigger and bigger, f(x) gets closer and closer to zero without actually hitting zero.

 

[LtDan]

Is it accurate to refer to our hypothetical infinite-aged and infinite-sized universe, operating in a "rising raisinbread" mode, as an "accelerating universe"?

Since our infinite universe has no outer edges, how can we judge the speed of the universe's expansion. One way would be by calculating expansion speed from the red shift observed in distant objects. Another would be by taking a chunk of the universe --- a chunk with observable edges to it --- and somehow measuring the speed at which that chunk of matter is expanding in size. Since all matter, both visible and invisible, is expanding in size at the same universal rate, it is impossible to measure any universal expansion growth against a constant measuring stick. The measuring stick is also expanding. The only way to discern and measure the expansion of our reference chunk is by referring to what we have been calling "gravity" since Newton's time.

The planet Earth is the handiest corporeal chunk of the universe to use in this exercise. It is expanding at a rate that causes objects located against it to stick to the planet's surface and to display the characteristic we call "weight."

Since the weight of such an object does not change from one second to the next, is it reasonable to assume that the outward movement of the Earth' surface is actually accelerating and not merely moving outward at a steady rate of speed? A steady rate of speed would seem to suffice to keep the planet in contact with its "companion," as long as the companion kept still. But if the companion were to, for instance, jump up in the air, there would seem to be nothing to prevent the companion from simply flying away. There would be no way for the planet's surface to catch up with the companion.

[In an old radio routine, Edgar Bergen was attempting to explain gravity to Mortimer Snerd. He asked Mortimer why, when he jumped up into the air, he returned to earth. Mortimeer replied, "I live there."]

 

[Chalnoth]

Is it accurate to refer to our hypothetical infinite-aged and infinite-sized universe, operating in a "rising raisinbread" mode, as an "accelerating universe"?

Yes, because the measured rate of expansion is accelerating.

Since our infinite universe has no outer edges, how can we judge the speed of the universe's expansion. One way would be by calculating expansion speed from the red shift observed in distant objects. Another would be by taking a chunk of the universe --- a chunk with observable edges to it --- and somehow measuring the speed at which that chunk of matter is expanding in size. Since all matter, both visible and invisible, is expanding in size at the same universal rate, it is impossible to measure any universal expansion growth against a constant measuring stick. The measuring stick is also expanding. The only way to discern and measure the expansion of our reference chunk is by referring to what we have been calling "gravity" since Newton's time.

Well, no, the measurement of the rate of expansion is largely independent of the behavior of gravity.

The planet Earth is the handiest corporeal chunk of the universe to use in this exercise. It is expanding at a rate that causes objects located against it to stick to the planet's surface and to display the characteristic we call "weight."

The Earth isn't expanding.

Since the weight of such an object does not change from one second to the next, is it reasonable to assume that the outward movement of the Earth' surface is actually accelerating and not merely moving outward at a steady rate of speed? A steady rate of speed would seem to suffice to keep the planet in contact with its "companion," as long as the companion kept still. But if the companion were to, for instance, jump up in the air, there would seem to be nothing to prevent the companion from simply flying away. There would be no way for the planet's surface to catch up with the companion.

Ugh. You seem to be confusing the equivalence principle with actual acceleration. While a the existence of a uniform gravitational field is indistinguishable from acceleration, this does not mean that a gravitational field is acceleration. In particular, the gravitational field of a body like the Earth is not uniform at all, but changes from place to place (that is, it gets weaker as you move away from the Earth, and changes in direction as you go around the Earth). Because the gravitational field changes from place to place, there is no acceleration which can mimic the entire gravitational field. So the gravitational field of the Earth cannot be considered an acceleration.

 

[LtDan]

When you say "the Earth is not expanding," you forget that in our hypothetical raisinbread universe all matter expands.

Leaving hypothesis behind for a moment, I believe that the planet does, in many respects, behave as if it is expanding in size. Tectonic movements of the crustal plates, for instance, do not resemble the slight movements seen in the outer skin of a molten metal sphere suspended in a cooling liquid. In the molten sphere there is very little movement to be seen, but if the molten center of the sphere were to be steadily expanding in volume, fractures, spreading and subduction would take place as they take place with our planet's tectonic plates.

 

[sylas]

When you say "the Earth is not expanding," you forget that in our hypothetical raisinbread universe all matter expands.

No... he's TELLING you, correctly, that the expanding universe in cosmology, for which rising raisin bread is a simple analogy, does NOT have all matter expanding. Just like the raisins don't get larger as the break rises; galaxies, stars, and planets all remain the same size.

Cheers -- sylas

 

[LtDan]

Hi Sylas,


Whose raisinbread universe is it, anyway? If I make up a raisinbread hypothetical universe, I'm the one who gets to say whether or not the raisins rise just like the dough.

And I say they rise!

If the univrese is expanding --- and it sure does seem that it is --- then why shouldn't everything in the universe be expanding, including all "matter"?

 

[sylas]

Hi Sylas,


Whose raisinbread universe is it, anyway? If I make up a raisinbread hypothetical universe, I'm the one who gets to say whether or not the raisins rise just like the dough.

And I say they rise!

If the univrese is expanding --- and it sure does seem that it is --- then why shouldn't everything in the universe be expanding, including all "matter"?

Um... check the physicsforums rules, here; and in particular the section on speculative posts.

One of the main goals here is to discuss the current status of physics as practiced by the scientific community. In modern cosmology, the expansion of the universe is not a force driving things apart. One large scales galaxies are dispersing and separating from each other and they continue to do so by the "momentum" of their dispersal. Gravity works to pull them together, and apparently there is a "dark energy" that is pushing things apart; but on small spaces like a galaxy, or a solar system, gravity holds things together. They are gravitationally bound, and not flying apart at all.

If you have a DIFFERENT notion, all of you own, this may not be the best forum for you. Merely asserting things because you say so is not going to be permitted as a basis of discussion anywhere in the forum; though there are designated areas where you can propose some non-standard ideas as long as they are actually worked out with some regard to the realities of physics.

Cheers -- sylas

 

[LtDan]

Well the raisinbread universe theory is certainly speculative, although I think it makes a good bit of sense and isn't, therefore, "overly speculative."

Sylas, regarding "dark energy" driving galaxies apart from one another, do you think that the faint radio signal that seems to come from every direction might be the "sound" that the dark energy makes, and not the echo of a big bang?

 

[sylas]

Well the raisinbread universe theory is certainly speculative, although I think it makes a good bit of sense and isn't, therefore, "overly speculative."

The raisinbread is not a theory at all, but a mental picture than may help understand conventional cosmology. You've mixed up the actual physics with the simple similies used to try and help explain some of the concepts without going into the technical maths of the actual theory.

Sylas, regarding "dark energy" driving galaxies apart from one another, do you think that the faint radio signal that seems to come from every direction might be the "sound" that the dark energy makes, and not the echo of a big bang?

No, it definitely isn't.

Cheers -- sylas

 

[LtDan]

Sylas,

Do you have any notion about what that faint, pervasive radio signal is?

Cheers --- LtDan

 

[sylas]

Sylas,

Do you have any notion about what that faint, pervasive radio signal is?

Cheers --- LtDan

You appear to be speaking of the cosmic microwave background radiation, which is thermal radiation from early stages of the universe when it had cooled enough to form transparent neutral hydrogen., redshifted by a factor of about 1100.

 

[Chalnoth]

You appear to be speaking of the cosmic microwave background radiation, which is thermal radiation from early stages of the universe when it had cooled enough to form transparent neutral hydrogen., redshifted by a factor of about 1100.

Actually, I think he might be talking about this:
http://www.scienceagogo.com/news/20090008190614data_trunc_sys.shtml

We looked over this paper not too long ago, and I think the general conclusion is that it seems more likely this is a case of improper subtraction of the galactic signal than anything.

 

[LtDan]

That is an interesting article about the "new" radiation recently detected, but I was referring to the radiation detected by Penzias and Wilson that so many people believe --- and some say know --- is an echo of the Big Bang. I don't believe it is, but most others disagree. I think --- speculate --- that it's a humming sound or signal created by all matter as it expands in size.

 

[Chalnoth]

That is an interesting article about the "new" radiation recently detected, but I was referring to the radiation detected by Penzias and Wilson that so many people believe --- and some say know --- is an echo of the Big Bang. I don't believe it is, but most others disagree. I think --- speculate --- that it's a humming sound or signal created by all matter as it expands in size.

You would be wrong.

The fact that the cosmic microwave background is the correct explanation for this is held up by the fact that detailed observations of the CMB match up, to an extraordinary degree of accuracy, to a wide variety of other observations. This essay is a good primer on the subject:
http://www.talkorigins.org/faqs/astronomy/bigbang.html

 

[LtDan]

When you say "I would be wrong," how sure are you that I am wrong, on a scale of one to ten, with ten being dead sure?

Thank you for the link to the primer on the Big Bang. I'm sure you know that the term "Big Bang" originated with Fred Hoyle.

 

[Chalnoth]

When you say "I would be wrong," how sure are you that I am wrong, on a scale of one to ten, with ten being dead sure?

10.

Thank you for the link to the primer on the Big Bang. I'm sure you know that the term "Big Bang" originated with Fred Hoyle.

Yes. And as a result, it's a rather misleading term that doesn't accurately represent the theory. But it stuck, and so we live with it.

 

[LtDan]

Dead sure! Wow!

While I have access to your dead sure self, let me ask: Did the universe have a beginning, or has it always existed? Some people have a very difficult time conceiving that something could possibly exist without first being created by someone or something. Creation without a creator? How can that be?

Did the universe begin or didn't it?

Fred Hoyle never had the chance to fully consider the raisinbread idea --- the idea that the entire universe, and everything in it can expand in size without the creation of new matter --- but he was intrigued with the C-field idea and then the idea of "little bangs" happening on an intrermittent basis throughout the universe, creating new matter and thus a form of punctuated equilibrium.

 

[Chalnoth]

Dead sure! Wow!

While I have access to your dead sure self, let me ask: Did the universe have a beginning, or has it always existed?

Unknown currently. Perhaps we will able to tease this out of future observations, but it is not yet clear if this will be possible or not.

Granted, it is absolutely clear that our region had a beginning. But whether it started from some other region of space-time or not is not yet clear.

Some people have a very difficult time conceiving that something could possibly exist without first being created by someone or something. Creation without a creator? How can that be?

An argument from incredulity is not an argument. Perhaps you simply lack the imagination to understand how things might come about without some human-like entity starting them off. Just as people once lacked the imagination to think of a way in which lightning might occur without some human-like being throwing them down from the sky.

While we don't yet know how our region of the universe got its start, we are working towards the answer. And we can be pretty darned near certain that whatever started it off, it almost certainly not was any sort of entity that decided to start it off. Far, far more likely is that it is just a naturalistic process that happens all the time.

 

[LtDan]

My own particular region of the universe --- the region of me --- was started off, I am dead sure, by my father and my mother nearly seventy-two years ago. Whether or not they decided to start it off, I cannot say for certain. They never confided in me about such matters.

I am not lacking in imagination, by the way. I am, after all, the originator of the raisinbread universe idea, and that idea requires belief in an infinite universe --- an infinite sized mass of dough and raisins existing without a pastry chef ever having been involved.

 

[Chalnoth]

I am not lacking in imagination, by the way. I am, after all, the originator of the raisinbread universe idea,

No, you aren't. Not by a long shot. With a very quick online search, for example, I found this:
http://theory.uwinnipeg.ca/mod_tech/node216.html

According to the date on the website, it's nearly 10 years old. I'm sure the raisin bread analogy is much, much older than that. I can't honestly recall where I first heard it. I believe it may have been in Carl Sagan's Cosmos series, which was released back in 1980.

and that idea requires belief in an infinite universe --- an infinite sized mass of dough and raisins existing without a pastry chef ever having been involved.

You're making some very unreasonable conclusions here. First, it is completely unreasonable to extrapolate out to infinity from a local, expanding region. The universe may be infinite. It may not be. We know it's very large, of course, but that doesn't mean it's infinite.

And the claim that there was some intentionality involved in starting off our universe is completely ridiculous and has no place whatsoever in science. I could go on and on about precisely why this is, but I feel I've spent far too long on the topic already.

 

[Atomic Number]

While we don't yet know how our region of the universe got its start, we are working towards the answer. And we can be pretty darned near certain that whatever started it off, it almost certainly not was any sort of entity that decided to start it off. Far, far more likely is that it is just a naturalistic process that happens all the time.

And the claim that there was some intentionality involved in starting off our universe is completely ridiculous and has no place whatsoever in science. I could go on and on about precisely why this is, but I feel I've spent far too long on the topic already.

Chalnoth, you have no problem saying you don't know X, Y, Z about the universe, and it's nice to see that because for whatever reasons a lot of professional scientists, or people who just like science, cannot say that very often.

The exception for you (and many other science-loving folks) is when it comes to the whys and wherefores behind the start the universe. In that case, you know with as close to certainty as possible about something that I would argue is the #1 most unknowable thing for humanity.

There's a lot that science cannot explain, and which does not belong in science, as you correctly point out. But what's truly ridiculous is believing science is the arbiter in such matters, because at that point it's not science, either - it's faith in something that can never be proven, which is the foundation of your criticism.

And, no, this is not an argument for religion, atheism, or anything else outside the realm of science, because everything outside the realm of science runs into the same problem. Feel free to believe whatever you believe, I honestly do not care, nor do I care to argue your beliefs against mine or anyone else's because it's pointless in the grand scheme of things, and, on a much smaller scale, irrelevant to this forum. All I'm saying is that science has its limitations, and I don't understand why it can be so hard to acknowledge that.

 

[Chalnoth]

Except this is a question about what happened, which is most definitely within the domain of science.

 

[Atomic Number]

If we don't know how the universe began, except that it's completely ridiculous to think that some intentionality was involved, that is not a what it is a why. It's also not science.

 

[Fredrik]

And the claim that there was some intentionality involved in starting off our universe is completely ridiculous and has no place whatsoever in science. I could go on and on about precisely why this is, but I feel I've spent far too long on the topic already.

I'll say it then. It's because including gods or other supernatural things in our theories would deprive them of their predictive power. In fact, they wouldn't make any predictions at all, so they wouldn't be scientific theories anymore. They would just be "sets of statements" that can't be falsified, and therefore have nothing to do with science.

...the radiation detected by Penzias and Wilson that so many people believe --- and some say know --- is an echo of the Big Bang. I don't believe it is, but most others disagree. I think --- speculate --- that it's a humming sound or signal created by all matter as it expands in size.

If it was, there would be more of it coming from regions where there is more matter nearby. We would see a lot of it if we look towards the Andromeda galaxy, and even more if we look towards the center of our own galaxy. So your speculation is clearly wrong.

Note that the reason why Chalnoth could be "dead sure" that you were wrong is a good quality of your speculation: that it has observable consequences. Unfortunately those consequences disagree with experiments that have already been performed.

If we don't know how the universe began, except that it's completely ridiculous to think that some intentionality was involved, that is not a what it is a why. It's also not science.

What exactly are you saying is "not science"?

 

[Atomic Number]

What exactly are you saying is "not science"?

The two quotes I pulled from Chalnoth's otherwise excellent reasoning in this whole discussion have zero to do with science. Maybe in 975,600,001 years, if humanity is still around, we might finally have some answers to hard questions. Maybe it will only take 29,487,656 years. Maybe there is absolutely no way intelligent life can fully understand the origins of everything there ever was, is and will be, even if you have \infty years to study the situation. Either we're theoretically capable of knowing this stuff or we aren't. Right now I don't know and neither does anyone else.

As a big fan of science, I prefer science to stick with science and not assume the burdens of theology, philosophy, etc.

 

[Rymer]

Many engineers have a different viewpoint than the 'typical scientist'.

Engineers realize that ANY problem can and will have more than one solution. Generally its an assumed fact of nature.

Many scientists seem to believe that ultimately there is only 'one correct and true' answer. Yes, they do know that the current answer is not complete -- but they still seem to believe in the concept that there exists such an answer.

Sometimes the engineer has trouble telling the difference in the mindset of a scientist and that of a faithful follower of a religion.

 

[LtDan]

Chalnoth,

No one involved in this discussion has so far made a claim that there was "intentionality" involved in the creation of the universe. I do not believe the universe was ever created. I believe it is probably infinitely old and without spatial boundaries. Teleology is not involved in my raisinbread universe.

Fredrik,

That Penzias and Wilson humming noise, I speculate, is the radiation signal given off by all matter in the universe as it expands, including the invisible matter, or dark matter, that makes up the matrix of the universe. It comes from all matter, and not just from the matter we can see, so there would not be an enhancement or concentration of the signal coming from particular areas of the universe.

 

[Chalnoth]

Atomic Number,

You're apparently attempting to put science into a little box which doesn't exist. I don't know precisely why you are attempting to do this, though obviously I have my suspicions. The fact of the matter remains that science is not a static bunch of rules. Science is, at its heart, disciplined inquiry. Nothing more, nothing less. There are no artificial boundaries to science. No rules that are not open to argument.

As a result, because it is entirely possible to engage any hypothesis whatsoever in a reasoned, disciplined manner, there just isn't anything to which science cannot have some say. Now, what science says may be, "That is a bad question," or, "The answer to that is completely arbitrary," but that doesn't mean you can't approach the question, whatever it is, in a reasoned, disciplined manner. And in this case, the question involved isn't even that bad: there most definitely is an answer to what process generated our region of the universe. We don't yet know what that answer is, but it is easy enough to put some very strict bounds upon the possibilities presented by various religious groups: not bloody likely.

 

[Chalnoth]

Many engineers have a different viewpoint than the 'typical scientist'.

Engineers realize that ANY problem can and will have more than one solution. Generally its an assumed fact of nature.

Many scientists seem to believe that ultimately there is only 'one correct and true' answer. Yes, they do know that the current answer is not complete -- but they still seem to believe in the concept that there exists such an answer.

There's a fundamental difference between there existing more than one solution to a problem and more than one correct answer to a question regarding the nature of reality. Scientists are imminently familiar with the concept of their being more than one solution to a problem, as they encounter it all the time in doing their work, work which is, by large, problem solving. This is perhaps most striking in biology, where different organisms find different solutions to the same environmental problems all the time. For example, where whales and seals use blubber for insulation, otters use very thick fur. Same problem (keeping warm in water), different solutions.

But when it comes to a question of the nature of reality, well, it's simply logically impossible for a proposition that is sufficiently specific to be both true and false at the same time. That would be a contradiction. Therefore there can only ever be one correct answer to a sufficiently specific question about the nature of reality. Note that the "sufficiently specific" qualifier is necessary here, and one of the parts of science that takes up quite a lot of time is learning how to word questions specifically enough that there is one and only one answer. It's not always easy. With the above, for instance, the question, "How do mammals who live in the water keep warm?" isn't specific enough: there are multiple ways. "How do otters keep warm?" is, however, a specific question with a specific answer, even if that answer may be a little complex (it's not quite as simple as, "otters use fur," as there are other things involved, but that is definitely part of it).

Sometimes the engineer has trouble telling the difference in the mindset of a scientist and that of a faithful follower of a religion.

This accusation is thrown around all the time by people whose beliefs science challenges, or among those who feel that such beliefs are somehow to be respected regardless of their lack of evidentiary support. It doesn't hold up under any amount of reasoned inquiry, however.

 

[Chalnoth]

Chalnoth,

No one involved in this discussion has so far made a claim that there was "intentionality" involved in the creation of the universe. I do not believe the universe was ever created. I believe it is probably infinitely old and without spatial boundaries. Teleology is not involved in my raisinbread universe.

As I've said, that conclusion is unreasonable at this time. It may be infinitely old and without spatial boundaries (note: it can also be finite without spatial boundaries). But by no means is there good evidence to say it is.

Fredrik,

That Penzias and Wilson humming noise, I speculate, is the radiation signal given off by all matter in the universe as it expands, including the invisible matter, or dark matter, that makes up the matrix of the universe. It comes from all matter, and not just from the matter we can see, so there would not be an enhancement or concentration of the signal coming from particular areas of the universe.

That's not going to work, as dark matter surrounds the normal matter. Or, more accurately, normal matter exists within clumps of dark matter. The statement that Fredrik posted still works.

I should say, though, that I hadn't thought of the point that Fredrik posted, though it's a good one. I was merely thinking of the multitudinous independent tests of the CMB that make it completely unreasonable to conclude it is anything different than the "last light" of the big bang, without really powerful evidence to suggest otherwise. It was clear to me that you had no such evidence, so I feel I was completely justified in being nearly certain that your statement regarding the nature of the CMB was flat wrong.

Of particular interest is the Baryon Acoustic Oscillation data. This analysis takes the CMB data, and our understanding of how matter behaves at those early times, and makes a very specific prediction as to how nearby galaxies should be distributed. Basically, the idea is that most of the time, as you go to larger and larger average separations between galaxies, there are fewer and fewer galaxies. But at a certain distance scale, there is a small increase in the number of galaxies, before dropping off again. Detailed observations of the distribution of galaxies show this 'bump' clear as day, and at precisely the magnitude predicted, to within experimental errors.

 

[Rymer]

That's not going to work, as dark matter surrounds the normal matter. Or, more accurately, normal matter exists within clumps of dark matter. .

If you are referring to non-baryonic dark matter, that has still to be shown.

 

[sylas]

If you are referring to non-baryonic dark matter, that has still to be shown.

... actually, all available evidence does strongly indicate precisely that. As is usual in science, it is not a formal proof. But the evidence for non-baryonic dark matter includes galactic rotation curves and gravitational lensing, and both these lines of evidence do indeed show that normal (baryonic) matter is found within clumps of dark matter.

Cheers -- sylas

 

[Rymer]

... actually, all available evidence does strongly indicate precisely that. As is usual in science, it is not a formal proof. But the evidence for non-baryonic dark matter includes galactic rotation curves and gravitational lensing, and both these lines of evidence do indeed show that normal (baryonic) matter is found within clumps of dark matter.

Cheers -- sylas

sylas, I can actually point to galactic rotation curves and gravitational lensing as 'proof' it DOESN'T exist too. All depends on the model used. And this is NOT MOND.

Amazing stuff 'dark matter' -- has a big gravity effect but hangs around in a halo outside galaxies (but not all of them) and is never seen near baryonic matter in our solar system.
Only 'detectable' when needed to explain anomalies of 'mainstream' models.