Red shift problem?

Graham4C · Feb 10, 2008

wow, id forgotten about this thread for a while

so where was i...
oh yes,
At the beginning of the thread, i gave an Newtonian equation for gravity at the big bang...
I understand that you cannot use the equation to get a figure, BUT what is true is that gravity would still exist in such a situtation, AND an outward force greater than the gravitational force would still need to be provided in all directions in order for the mater to disperse.

I've heard a lot about black holes, and how scientists rekon that the center are very similar to what they think the BB singularity would have been like.
Then, they go on to say how the GRAVITY is so great inside these holes, that not even light can escape (hence "black" hole). Their presence is shown merely by the swirling matter on their fringes.

At the point of the big bang, their would be a great deal more matter at the single point, and hence the gravity would be exponentially larger.

To be honest, ive never heard a decent theory of how this could just explode - or maybe im correct in saying there isnt one??

ArnautDaniel · Feb 11, 2008

Graham4C said:
wow, id forgotten about this thread for a while

so where was i...
oh yes,
At the beginning of the thread, i gave an Newtonian equation for gravity at the big bang...
I understand that you cannot use the equation to get a figure, BUT what is true is that gravity would still exist in such a situtation, AND an outward force greater than the gravitational force would still need to be provided in all directions in order for the mater to disperse.

I've heard a lot about black holes, and how scientists rekon that the center are very similar to what they think the BB singularity would have been like.
Then, they go on to say how the GRAVITY is so great inside these holes, that not even light can escape (hence "black" hole). Their presence is shown merely by the swirling matter on their fringes.

At the point of the big bang, their would be a great deal more matter at the single point, and hence the gravity would be exponentially larger.

To be honest, ive never heard a decent theory of how this could just explode - or maybe im correct in saying there isnt one??

In using Newtonian gravity you are assuming a large dense ball of matter located in some space extending in various directions.

Modern physics would hold that the big bang created space.

It isn't matter exploding in an existing space.

It is space itself expanding, and pulling matter along with it.

Newtonian gravity just doesn't apply.

shernren · Feb 11, 2008

Graham4C said:
At the point of the big bang, their would be a great deal more matter at the single point, and hence the gravity would be exponentially larger.

To be honest, ive never heard a decent theory of how this could just explode - or maybe im correct in saying there isnt one??

Bearing ArnautDaniel's corrective in mind, you actually have a point here. As far as I know, there isn't really a theory that explains how everything started. Here's an example to demonstrate the point.

Someone walks into a convenience store and tries to rob it, but the cashier somehow knocks the erstwhile robber unconscious. You, being a lousy security guard, only notice it on the CCTV after it has all happened, and so you rush down to find the intruder on the floor. Furthermore, on reviewing the security tape, you find that the camera failed at the exact moment that the cashier hit the intruder.

Now, all you have is the tape of the intruder falling to the floor. And you could gain a lot from watching that tape over and over again: you might find out how much force the cashier applied, where the cashier hit, how heavy the intruder is, etc. But you still wouldn't be able to figure out what the cashier hit the intruder with: in other words, how the intruder started falling.

In terms of our astronomical observations, what we have is effectively a tape of the expansion of the universe - that stops just short of the beginning. We have conclusive evidence that the universe is expanding; and it is expanding in such a way that, if you wind the tape back far enough, you must have everything together in one huge singularity right at the start of time. And we can analyze everything on the tape to exquisite detail - an amount of detail that, by the way, precludes an age of anything close to 6,000 years for the universe.

But you can ask: why is the tape even playing? What started the whole shebang? What dislodged the universe into existing, and what kicked everything out of that initial singularity? We don't have a scientific answer for that. We can know that the Big Bang happened, we can even describe many of its effects, many of which we observe exactly as advertised, but we don't know how it happened or why there should even be one.

Which is why, if you look carefully enough, atheistic scientists actually didn't like the Big Bang at first. The beginning of the universe has a scientific gap big enough to drive God through ...

busterdog · Feb 11, 2008

ArnautDaniel said:
In using Newtonian gravity you are assuming a large dense ball of matter located in some space extending in various directions.

Modern physics would hold that the big bang created space.

It isn't matter exploding in an existing space.

It is space itself expanding, and pulling matter along with it.

Newtonian gravity just doesn't apply.

We keep using these words as if they change anything.

ALl you are doing is derailing the question.

They are not precisely the same, but this whole curved space v. gravity thing just distracts from the essential issue being raised. It may play very well in the text books, but the essential question is discussed by Nobel prize winners as if explosion is a more or less workable metaphor.

busterdog · Feb 11, 2008

Graham4C said:
wow, id forgotten about this thread for a while

so where was i...
oh yes,
At the beginning of the thread, i gave an Newtonian equation for gravity at the big bang...
I understand that you cannot use the equation to get a figure, BUT what is true is that gravity would still exist in such a situtation, AND an outward force greater than the gravitational force would still need to be provided in all directions in order for the mater to disperse.

I've heard a lot about black holes, and how scientists rekon that the center are very similar to what they think the BB singularity would have been like.
Then, they go on to say how the GRAVITY is so great inside these holes, that not even light can escape (hence "black" hole). Their presence is shown merely by the swirling matter on their fringes.

At the point of the big bang, their would be a great deal more matter at the single point, and hence the gravity would be exponentially larger.

To be honest, ive never heard a decent theory of how this could just explode - or maybe im correct in saying there isnt one??

Unfortunately, we have to get into the quibbling about words like "explode".

We all know what you mean. And the question is a good one.

Here is an oldy but a goody:

At this moment it seems as though science will never be able to raise the curtain on the mystery of creation. For the scientist who has lived by his faith in the power of reason, the story ends like a bad dream. He has scaled the mountains of ignorance; he is about to conquer the highest peak; as he pulls himself over the final rock, he is greated by a band of theologians who have been sitting there for centuries.

God and the Astronomers (New York: W. W. Norton, 1992), p. 107. (p. 116 in the '78 edition)

Secular science is also miffed at the first cause or the cause behind that, or whatever. I am sure there has been some new ground broken since 1992. But that first cause issue always seems to retreat before man's grasp. I am sure Shernren or someone else can take it back a few milliseconds more, but to what end?

Whether we are talking about the creation of space (gag) or an explosion, the balance of energy allowing this thing to expand in a meaningful way was unimaginably precise, or unlikely, if you are a skeptic:

[FONT=Arial, Helvetica, sans-serif] Dr. Gerald Schroeder, author of "Genesis and the Big Bang" and "The Science of Life" was formerly with the M.I.T. physics department. He adds the following examples:

1) Professor Steven Weinberg, a Nobel laureate in high energy physics (a field of science that deals with the very early universe), writing in the journal "Scientific American", reflects on

how surprising it is that the laws of nature and the initial conditions of the universe should allow for the existence of beings who could observe it. Life as we know it would be impossible if any one of several physical quantities had slightly different values.

Although Weinberg is a self-described agnostic, he cannot but be astounded by the extent of the fine-tuning. He goes on to describe how a beryllium isotope having the minuscule half life of 0.0000000000000001 seconds must find and absorb a helium nucleus in that split of time before decaying. This occurs only because of a totally unexpected, exquisitely precise, energy match between the two nuclei. If this did not occur there would be none of the heavier elements. No carbon, no nitrogen, no life. Our universe would be composed of hydrogen and helium. But this is not the end of Professor Weinberg's wonder at our well-tuned universe. He continues:

One constant does seem to require an incredible fine-tuning -- The existence of life of any kind seems to require a cancellation between different contributions to the vacuum energy, accurate to about 120 decimal places.

This means that if the energies of the Big Bang were, in arbitrary units, not:

100000000000000000000000000000000000000000000000000 000000000000000000000000000000000000000000000000000 000000000000000000,

but instead:
100000000000000000000000000000000000000000000000000 000000000000000000000000000000000000000000000000000 000000000000000001,

there would be no life of any sort in the entire universe because as Weinberg states:

the universe either would go through a complete cycle of expansion and contraction before life could arise, or would expand so rapidly that no galaxies or stars could form.

2) Michael Turner, the widely quoted astrophysicist at the University of Chicago and Fermilab, describes the fine-tuning of the universe with a simile:

The precision is as if one could throw a dart across the entire universe and hit a bulls eye one millimeter in diameter on the other side.

3) Roger Penrose, the Rouse Ball Professor of Mathematics at the University of Oxford, discovers that the likelihood of the universe having usable energy (low entropy) at the creation is even more astounding,

namely, an accuracy of one part out of ten to the power of ten to the power of 123. This is an extraordinary figure. One could not possibly even write the number down in full, in our ordinary denary (power of ten) notation: it would be one followed by ten to the power of 123 successive zeros! (That is a million billion billion billion billion billion billion billion billion billion billion billion billion billion zeros.)

Penrose continues,

Even if we were to write a zero on each separate proton and on each separate neutron in the entire universe -- and we could throw in all the other particles as well for good measure -- we should fall far short of writing down the figure needed. The precision needed to set the universe on its course is to be in no way inferior to all that extraordinary precision that we have already become accustomed to in the superb dynamical equations (Newton's, Maxwell's, Einstein's) which govern the behavior of things from moment to moment. [/FONT]

Now you can pick your flavor about whether that represents a tall tale or extreme serendipity.

birdan · Feb 11, 2008

busterdog said:
Unfortunately, we have to get into the quibbling about words like "explode".

We all know what you mean. And the question is a good one.

Here is an oldy but a goody:

Secular science is also miffed at the first cause or the cause behind that, or whatever. I am sure there has been some new ground broken since 1992. But that first cause issue always seems to retreat before man's grasp. I am sure Shernren or someone else can take it back a few milliseconds more, but to what end?

Quantum Mechanics shows us that many things that happen in the universe are acausal. Thus the basic idea of the 'First Cause' argument is obsolete.

busterdog said:
Whether we are talking about the creation of space (gag) or an explosion, the balance of energy allowing this thing to expand in a meaningful way was unimaginably precise, or unlikely, if you are a skeptic:

Now you can pick your flavor about whether that represents a tall tale or extreme serendipity.

Didn't Guth's inflationary theory show that the inflationary process itself drove the cosmological constant to have the value it does? In other words, its precise value is a direct result of the process and not an arbitrary value. It's been a long time since I've read that, so maybe someone more current can help out here.

Paul365 · Feb 11, 2008

birdan said:
Quantum Mechanics shows us that many things that happen in the universe are acausal. Thus the basic idea of the 'First Cause' argument is obsolete.

Not exactly. Quantum mechanics gives a rather precise description about under which circumstances things that happen are acausal and when they are causal. The beginning of the universe, also called Big Bang, was probably not acausal.

The problem is just to determine what caused it. This seems hard to solve for two reasons. First, we can not observe events outside or before our universe. Second, whatever caused the beginning of our universe must probably be described in terms of String Theory, but we don't have a mathematics foundation for String Theory yet.

The speculation at the moment is that collisions of n-branes in a 10 dimensional space permanently create new universes. This also perfectly explains the fine tuning of our universe. Anyone interested in this can look up "Gabriele Veneziano" in Google, that's the guy who invented String Theory and develops such ideas.

But this is mere speculation, as it is not yet clear if this can ever be verified or falsified with any observation in our universe. We can observe that the Big Bang indeed happened, but we can not observe anything before that moment.

Graham4C · Feb 11, 2008

Here's something else i was going to say...

If space is expanding, then why dont the distances between the planets in our solar syatem increase?
Why don't the distances between the very molecules in the earths crust increase for that matter?

The answer i'm very sure everyone will give is that gravity holds these objects "in position", and together.

So, if that is true, when space first started, and expanded, according to the Big Bang, why should the matter inside that original space also expand?
All assumptions being true, the space would surely expand, while the matter inside the space would be held together by gravity.

Is it just my imgagination, or are there some serious inconsistencies here?

Hnefi · Feb 11, 2008

Graham4C said:
Here's something else i was going to say...

If space is expanding, then why dont the distances between the planets in our solar syatem increase?
Why don't the distances between the very molecules in the earths crust increase for that matter?

IIRC, they do. Which renders your other points moot.

shernren · Feb 11, 2008

busterdog said:
We keep using these words as if they change anything.

ALl you are doing is derailing the question.

They are not precisely the same, but this whole curved space v. gravity thing just distracts from the essential issue being raised. It may play very well in the text books, but the essential question is discussed by Nobel prize winners as if explosion is a more or less workable metaphor.

Nobel Prize winners can get by, when talking to the general media, with using pictures of explosions - but if they talk of explosions to each other then they have no business with the Prize.

It is an important distinction. Let's say you have a grenade in an empty room. Suppose it explodes, and nothing (not even heat) escapes the room. Then the mass-energy density of the room as a whole has not changed.

But let's say that the universe expands to the point that the grenade now takes up the volume of the empty room and that the empty room has expanded proportionately. The difference between this and an explosion is that the mass-energy density of the room has changed (the same mass in a larger volume = less density) and so GR makes different predictions for this.

You can't get by with talk of "explosions". You certainly can't use that to get anywhere near the level of rigor you need to discredit the Big Bang.

busterdog said:
Unfortunately, we have to get into the quibbling about words like "explode".

We all know what you mean. And the question is a good one.

Here is an oldy but a goody:

Secular science is also miffed at the first cause or the cause behind that, or whatever. I am sure there has been some new ground broken since 1992. But that first cause issue always seems to retreat before man's grasp. I am sure Shernren or someone else can take it back a few milliseconds more, but to what end?

Whether we are talking about the creation of space (gag) or an explosion, the balance of energy allowing this thing to expand in a meaningful way was unimaginably precise, or unlikely, if you are a skeptic:

Now you can pick your flavor about whether that represents a tall tale or extreme serendipity.

Quite aside from the merits of the anthropic argument: accepting those numbers entails accepting the math that goes into them. The same math that demonstrates fine-tuning also demonstrates that the universe is observably 14.5 billion years old.

For example, what does this "flatness" of the universe mean? Firstly, flatness doesn't even begin to make sense if we are still talking Newtonian gravity; flat space is a category of curved space. So if the distinction between curved space and gravity as a force doesn't matter, then your numbers don't matter either, and the point you want to make can't be made.

So on to flatness. One of the more recent and accurate measures of this flatness, one that comes from the WMAP data, is based on this: if the universe is curved, things will look different-sized from what they actually are. On a flat piece of paper, a right-angled triangle with short sides of 1m has a long side of about 1.4m; on a sphere with a circumference of 4m, a triangle with a right angle and two sides of 1m also has a third side of 1m. So the scientists calculated the expected size of a particular feature (baryonic acoustic oscillations), compared it to the size they were measuring in the sky, and found out that they were pretty accurately the same - meaning that the universe is pretty much flat.

But consider: scientists assumed that baryonic acoustic oscillations are the size they are by using a conventional Big Bang model. And they calculated the actual size they were measuring by using distance scales which are, again, informed by Big Bang models (and indeed by all of conventional cosmology). Furthermore, the same data that gives the universe's flatness also gives the composition of the universe, the one that tells us that the universe is roughly one-quarter dark matter and three-quarters dark energy. So if the universe is astonishingly flat, it must also be 14.5 billion years old and almost completely incomprehensible - you can't have one without the other.

On the other hand, if you try to stuff the universe into 6,000 years, the evidence completely falls to pieces. It doesn't even begin to make sense to talk about "flatness" from the evidence. The number which was supposedly "fine-tuned" turns out to be just an artifact of a wrong system to understand the universe.

What's the point of saying God fine-tuned the Big Bang if the Big Bang didn't happen?

shernren · Feb 11, 2008

Graham4C said:
Here's something else i was going to say...

If space is expanding, then why dont the distances between the planets in our solar syatem increase?
Why don't the distances between the very molecules in the earths crust increase for that matter?

The answer i'm very sure everyone will give is that gravity holds these objects "in position", and together.

So, if that is true, when space first started, and expanded, according to the Big Bang, why should the matter inside that original space also expand?
All assumptions being true, the space would surely expand, while the matter inside the space would be held together by gravity.

Is it just my imgagination, or are there some serious inconsistencies here?

To answer the first part of your question: within a Newtonian approixmation, the strength of gravitational attraction decreases inversely in proportion to the distance between objects (general relativity doesn't change that significantly). The widest radius of the Milky Way is about 0.1 million light years; the distance from the center of the Milky Way to the next significant galaxy, Andromeda, is about 2.5 million light years - 25 times, meaning a gravitational acceleration that is about 600 times smaller. Thus, while gravity is sufficient to hold the Milky Way together, it barely holds us to Andromeda, and it definitely doesn't suffice to pull us and farther galaxies together.

What about the earth's crust? To find the answer, take a magnet and use it to suspend a nail in the air. Congratulations, your measly magnet has overcome the gravitational pull of the 6x10^24 kg planet we know as Earth. On cosmological scales gravity is the only force that matters (because unlike charges tend to mutually neutralize, and magnetic monopoles generally don't exist), but down here on planet Earth gravity hardly matters. I do a little quantum mechanics, and when we calculate the state of molecules and atoms, we don't even bother to put gravity in - it's just so terribly small. Gravity might not stand a chance against the expansion of the universe, but electromagnetism can hold its own.

So why did everything expand to begin with? It's exactly the inflation that birdan was referring to. You can think of this as kind of a ladder of forces: our current expansion, or "Hubble expansion", beats gravity at very long distance scales; Hubble expansion and gravity are neck-and-neck at small scales, and gravity wins at smaller scales, and electromagnetism wallops gravity, but cosmic inflation beats electromagnetism hands down. And so cosmic inflation could blow things up for the first few microseconds so large that electromagnetism couldn't keep up - but now Hubble expansion has taken over, and gravity can just hold its own on small enough structures, and electromagnetism does wonders holding the planet together.

Does that help?

shernren · Feb 11, 2008

KerrMetric, if you're lurking anywhere near here, it must be obvious to you that I'm almost out of my depth. Help!

Graham4C · Feb 11, 2008

IIRC, they do. Which renders your other points moot.

If you assume both that the solar system has existed for over 4 billion years, and that the space expands between these objects, they would surely be a lot further apart than they are today, given the calculations made concerning size and age of the visible universe

ArnautDaniel · Feb 11, 2008

busterdog said:
We keep using these words as if they change anything.

ALl you are doing is derailing the question.

They are not precisely the same, but this whole curved space v. gravity thing just distracts from the essential issue being raised. It may play very well in the text books, but the essential question is discussed by Nobel prize winners as if explosion is a more or less workable metaphor.

The OP made a point of critiquing a theory using incorrect physics.

This is saying the theory is wrong by using things the theory does not say.

I have no problem with critiquing the theory, but we must do that using things it actually does say.

busterdog · Feb 11, 2008

ArnautDaniel said:
The OP made a point of critiquing a theory using incorrect physics.

This is saying the theory is wrong by using things the theory does not say.

I have no problem with critiquing the theory, but we must do that using things it actually does say.

The correct thing to do is to say, "what you mean by explosion is 'expansion' and indeed during a part of this change there are big issues with the gravitational relationships, though explanations have been offered in some of the more esoteric physics.

I am nitpicking, but lets not indulge in nitpicking that stops the dialogue. The criticism redefined without doing much to address the issue.

busterdog · Feb 11, 2008

birdan said:
Quantum Mechanics shows us that many things that happen in the universe are acausal. Thus the basic idea of the 'First Cause' argument is obsolete.

Lets not let the semantics stop the conversation. We all know what I meant.

busterdog · Feb 11, 2008

shernren said:
Nobel Prize winners can get by, when talking to the general media, with using pictures of explosions - but if they talk of explosions to each other then they have no business with the Prize.

It is an important distinction. Let's say you have a grenade in an empty room. Suppose it explodes, and nothing (not even heat) escapes the room. Then the mass-energy density of the room as a whole has not changed.

But let's say that the universe expands to the point that the grenade now takes up the volume of the empty room and that the empty room has expanded proportionately. The difference between this and an explosion is that the mass-energy density of the room has changed (the same mass in a larger volume = less density) and so GR makes different predictions for this.

You can't get by with talk of "explosions". You certainly can't use that to get anywhere near the level of rigor you need to discredit the Big Bang.

Click to expand...

There is nothing wrong with the correction itself. It just ought to meet the proposal to which it responds. Otherwise we just come to a dead end without any clarity about the OP.

Quite aside from the merits of the anthropic argument: accepting those numbers entails accepting the math that goes into them. The same math that demonstrates fine-tuning also demonstrates that the universe is observably 14.5 billion years old.

For example, what does this "flatness" of the universe mean? Firstly, flatness doesn't even begin to make sense if we are still talking Newtonian gravity; flat space is a category of curved space. So if the distinction between curved space and gravity as a force doesn't matter, then your numbers don't matter either, and the point you want to make can't be made.

So on to flatness. One of the more recent and accurate measures of this flatness, one that comes from the WMAP data, is based on this: if the universe is curved, things will look different-sized from what they actually are. On a flat piece of paper, a right-angled triangle with short sides of 1m has a long side of about 1.4m; on a sphere with a circumference of 4m, a triangle with a right angle and two sides of 1m also has a third side of 1m. So the scientists calculated the expected size of a particular feature (baryonic acoustic oscillations), compared it to the size they were measuring in the sky, and found out that they were pretty accurately the same - meaning that the universe is pretty much flat.

But consider: scientists assumed that baryonic acoustic oscillations are the size they are by using a conventional Big Bang model. And they calculated the actual size they were measuring by using distance scales which are, again, informed by Big Bang models (and indeed by all of conventional cosmology). Furthermore, the same data that gives the universe's flatness also gives the composition of the universe, the one that tells us that the universe is roughly one-quarter dark matter and three-quarters dark energy. So if the universe is astonishingly flat, it must also be 14.5 billion years old and almost completely incomprehensible - you can't have one without the other.

On the other hand, if you try to stuff the universe into 6,000 years, the evidence completely falls to pieces. It doesn't even begin to make sense to talk about "flatness" from the evidence. The number which was supposedly "fine-tuned" turns out to be just an artifact of a wrong system to understand the universe.

What's the point of saying God fine-tuned the Big Bang if the Big Bang didn't happen?

Click to expand...

Understood. That gets us back to our disagreement about whether there is a problem with Bayesian probability.

ArnautDaniel · Feb 11, 2008

busterdog said:
The correct thing to do is to say, "what you mean by explosion is 'expansion' and indeed during a part of this change there are big issues with the gravitational relationships, though explanations have been offered in some of the more esoteric physics.

I am nitpicking, but lets not indulge in nitpicking that stops the dialogue. The criticism redefined without doing much to address the issue.

Okay, what is the central issue then?

When I read the OP, I understood it as saying "such and such doesn't make sense when I take into account Newtonian physics", namely a hypothetical initial escape velocity, and an issue about the Milky Way and Andromeda moving towards each other.

Hnefi · Feb 11, 2008

Graham4C said:
If you assume both that the solar system has existed for over 4 billion years, and that the space expands between these objects, they would surely be a lot further apart than they are today, given the calculations made concerning size and age of the visible universe

Why? Without any numbers, you can't say anything about how far apart they should be. Do the math, then come to the conclusion.

shernren · Feb 11, 2008

busterdog said:
There is nothing wrong with the correction itself. It just ought to meet the proposal to which it responds. Otherwise we just come to a dead end without any clarity about the OP.

And it does - understanding the situation in a Newtonian framework is part of what has gotten Graham4C into this mess. Your talk of fine-tuning, on the other hand, isn't helpful to his OP at all, despite my detailed reply to it.

The OP is asking how the Big Bang can work when gravity is pulling everything together. The response is that you have to factor in the curved nature of spacetime and the fact that spacetime is itself expanding, so that any Newtonian-style calculation is going to go wide of the mark in describing reality.

busterdog said:
Understood. That gets us back to our disagreement about whether there is a problem with Bayesian probability.

No, I don't think you understand.

The numbers that are supposedly fine-tuned fall right out of conventional astrophysics, and don't make any sense outside of it.

If you accept that the universe is flat, you accept that it was formed in a Big Bang 14.5 billion years ago.

If you reject that the universe was formed in a Big Bang 14.5 billion years ago, then the supposed "flatness" of the universe is just a number that doesn't actually describe anything in physical reality.

So which is it? Is the universe old and fine-tuned, or young and less so?

Red shift problem?

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