No need for dark energy , gravity will suffice.

[Peter Watkins]

Thank you for your replies, but this time you've got it wrong. The scenario described in reply #26 applies to on object escaping from a large body such as a planet or star which has a fixed measurement of gravity at anyone particular place, which lessens as the object moves away and leaves the gravity source behind. The expanding universe was entirely different in that it was escaping from itself. With each doubling of the diameter, and these were frequent and fast in the early days, the gravity at anyone point was reduced by a factor of eight. Additionally, the gravity wasn't left behind as in escape from a fixed source, but instead accompanied the outward moving matter and thus was, and is, able to maintain it's advantage in the gravity/kinetic energy battle. You are correct in stating that gravity can be overcome temporarily, a tot can throw a rattle upwards, but not with sufficient energy to escape. And this is state that the universe is in, temporary escape. You will, of course, refer to the increased rate at which galaxies are moving apart, but this is indicative of a slowing in the rate of expansion.
And I would state again that if escape velocity had been reached, gravity would have had no effect. In short, the detectable presence of gravity = collapse. It really is that simple.

 

[Chalnoth]

And I would state again that if escape velocity had been reached, gravity would have had no effect. In short, the detectable presence of gravity = collapse. It really is that simple.

No. It isn't. If you have escape velocity, gravity still has an effect: it slows you down, and, depending upon the motion, deflects that path. If your statement were true, after all, it would mean that gravity can have no effect upon light, because light always has escape velocity (except with a black hole, of course).

 

[PeopleSmoks]

What I am beginning to see is that the "pivot" point in this is dark energy. You see, I am trying to absorb all the information, but I still look at the manner in which the numbers are used in various equations to concur with various theory. My first example of this is Einstein's cosmological constant, which originally confirmed a static universe, until Hubble's obeservations showed expansion. Then, the numbers were modified to coincide with the new data.

Chalnoth is telling us that gravity continues to have an affect, despite excape velocity being obtained. Yes, I understand this. So at what point or what distance would be required for an object to actually escape gravity and it's effects? I also understand that this is relative to the mass of both objects, but what equation proves it and does this equation require dark energy as a positive to make it work?

If positive dark energy is used in this equation, this again brings me full circle in a way as to wondering why dark energy is given a positive value? I read an article that stated dark matter contains equal positive and negative particles, which should make it neutral. Isn't dark energy related to dark matter?

 

[Chalnoth]

Chalnoth is telling us that gravity continues to have an affect, despite excape velocity being obtained. Yes, I understand this. So at what point or what distance would be required for an object to actually escape gravity and it's effects?

You can't. Gravity is an infinite-range force. What is meant by "escape velocity" is not that it escapes the effects of gravity, but rather that the object can escape off to infinity (in infinite time). It will still feel the gravity for its entire travel time.

Gravity is termed an "infinite range force" because it falls off at 1/r^2. By contrast, magnetism is not infinite range because it falls off at 1/r^3 (as there are no magnetic monopoles). And while the range of the electric force is technically infinite as well, as it also falls off as 1/r^2, in reality at large distances it never falls off slower than 1/r^3, because electric charges don't build up in one place due to the strength of the force (so you don't get electric charges building up in anyone area). So gravity is, in effect, the only infinite range force around.

I also understand that this is relative to the mass of both objects, but what equation proves it and does this equation require dark energy as a positive to make it work?

Actually I'd have to go back and look up precisely why this is the case, but I remember that the fundamental quality that makes a force infinite in range is that it falls off at 1/r^2. I could probably figure it out if I thought about it, but I'm too tired for that right now.

If positive dark energy is used in this equation, this again brings me full circle in a way as to wondering why dark energy is given a positive value? I read an article that stated dark matter contains equal positive and negative particles, which should make it neutral. Isn't dark energy related to dark matter?

Well, dark matter is considered very likely to consist of both matter and anti-matter due to its weak interactions (the weak interactions mean it hasn't yet had time for all the dark matter particles to annihilate with their anti-particles). It's all neutrally-charged, though: it has to be, or else it wouldn't be dark.

As for dark energy, we don't know. There are some theorists who have come up with theories that attempt to place dark energy and dark matter into the same framework. I think it'd be neat if one of those theories turned out to be accurate, but I strongly suspect that nothing of the sort is true. The positive value, by the way, is what fits the observed expansion. A negative value would tend to cause the universe to recollapse, not accelerate its expansion.

 

[PeopleSmoks]

Chalnoth, not looking for an answer tonight, but a few more questions. Again, articles I've read, don't refer to dark matter particles as being matter and antimatter, but simply as positively and negatively charged subatomic particles. It was further described as being in a plasma state as opposed to gasious. Is it possible that dark matter is the result of dark energy and not the other way? Kind of switching around E*=*mc2, where mass is created by dividing energy by the speed of light?

Also, once again, not to place a negative value to dark energy, but possibly a neutral or inert energy, how would that affect cosmic expasion? Would this permit the eventual deceleration and future collapse of the universe without undermining the facts of present expansion?

One last thing. Could the acceleration of cosmic expansion and the energy levels be compared to the expansion and energy release of a dying star throwing off hydrogen before it's collapse?

 

[Chalnoth]

Chalnoth, not looking for an answer tonight, but a few more questions. Again, articles I've read, don't refer to dark matter particles as being matter and antimatter, but simply as positively and negatively charged subatomic particles. It was further described as being in a plasma state as opposed to gasious.

Oh, well that's either a misunderstanding, or those articles you've read are entirely wrong. If the dark matter were charged, it wouldn't be dark.

Is it possible that dark matter is the result of dark energy and not the other way? Kind of switching around E*=*mc2, where mass is created by dividing energy by the speed of light?

Dark matter is most likely a result of thermal production in the early universe. That is, when the temperature was high enough, the forces by which the dark matter particles interact were active. When the temperature cooled to the point that those forces were no longer active, the dark matter just stuck around. Due to other constraints (particularly big bang nucleosynthesis), at the time dark energy can't actually have had much effect on the universe.

Also, once again, not to place a negative value to dark energy, but possibly a neutral or inert energy, how would that affect cosmic expasion? Would this permit the eventual deceleration and future collapse of the universe without undermining the facts of present expansion?

Well, it's the interaction with gravity that determines how dark energy affects the expansion. Basically that interaction would have to turn off at some point in the future, such as through the decay of the field that makes up dark energy. And then it would have to turn out that the universe had a positive curvature. The probability that both are the case is, frankly, pretty low, given current observation.

One last thing. Could the acceleration of cosmic expansion and the energy levels be compared to the expansion and energy release of a dying star throwing off hydrogen before it's collapse?

I don't see how they would be in any way related.

 

[Peter Watkins]

Chalnoth, thank you for your time again, but I think that your reply once again refers to escape from a solid body. I doubt that the astronauts were slowed as they departed for the moon. I know that they had a rocket motor to propel them out of orbit, but this only burned for a very short time. And as they weren't headed toward the moon but rather the place where the moon would be, there was no assistance there. There was a probe whose motor malfunctioned and this was placed into an elliptical orbit in order to "wind it up". When this was finally "slung out" I doubt that gravity slowed that either. When I said "no effect whatsoever" I meant that no matter, planets, stars etc. would have formed, so there would have been no light to be deflected.

 

[PeopleSmoks]

Chalnoth, thank you for your time again, but I think that your reply once again refers to escape from a solid body.

I see your point, but as I am trying to understand what Chalnoth is saying about gravitational effects, I think that at great distances, it is like a fly on an elephants back. The weight of the fly is there, but so small that it's affects on the elephant are negligable. Still, I wonder if there is any data showing orbital wobble of venus or Mars when their orbits align with earth.

Oh, well that's either a misunderstanding, or those articles you've read are entirely wrong. If the dark matter were charged, it wouldn't be dark.

I never said that dark matter was charged, but that the particles are, and being of equal number and mass that would mean that dark matter must be a neutral plasma.

Dark matter is most likely a result of thermal production in the early universe. That is, when the temperature was high enough, the forces by which the dark matter particles interact were active. When the temperature cooled to the point that those forces were no longer active, the dark matter just stuck around. Due to other constraints (particularly big bang nucleosynthesis), at the time dark energy can't actually have had much effect on the universe.

You see, this suggests that dark matter was created during the big bang. But, to maintain the balance of mass in the universe as it is now expanding, doesn't more dark matter have to constantly be created? If there is no 'new' dark matter being created, and we have enough today to fill the universe, we would have had too much yesterday, and not enough to fill the universe tomorrow.

 

[Chalnoth]

Actually I'd have to go back and look up precisely why this is the case, but I remember that the fundamental quality that makes a force infinite in range is that it falls off at 1/r^2. I could probably figure it out if I thought about it, but I'm too tired for that right now.

Just fyi, I thought about it some more, and this is the reason:

An infinite range force is one in which Gauss's Law holds. The idea of Gauss's Law with gravity is that when you are some distance away from the center of mass of a source, the force doesn't actually depend upon what the distribution of that mass is, provided it's spherical. That is, it doesn't matter how dense it is. This has a rather neat geometric description in that if you imagine a shell that completely encloses the object, the total flux of the force field through that shell will always be the same, no matter how big that shell is.

By contrast, if you take a force that falls off as 1/r^3 (or any faster than 1/r^2), then the bigger your shell is, the smaller the flux of the force field through that shell. This indicates that the total effects of the force fall off with distance, whereas with 1/r^2 the total effects extend out to infinity.

 

[Chalnoth]

Chalnoth, thank you for your time again, but I think that your reply once again refers to escape from a solid body. I doubt that the astronauts were slowed as they departed for the moon. I know that they had a rocket motor to propel them out of orbit, but this only burned for a very short time.

Of course they were. They just obtained escape velocity (or near enough to it to get as far as the moon, anyway). They had to be slowed by gravity because they kept gaining potential energy as they got further from the Earth. It's just that they had enough velocity once the rocket burn ended to still make the trip.

Think of it like coasting on a car: if you start off with enough speed, you can pop the car in neutral and still get a fair distance. This doesn't mean that friction doesn't continue to slow the car: it does. It just takes a little bit of time to stop it. And if you had enough velocity to start with, you could reach your destination (whatever that might be).

 

[Chalnoth]

I never said that dark matter was charged, but that the particles are, and being of equal number and mass that would mean that dark matter must be a neutral plasma.

No, because in a plasma, the positively and negatively charged particles are separated, so plasmas tend to glow pretty brightly depending upon their temperatures. This is the reason the Sun glows, for instance. It's also the reason why we see galaxy clusters in the X-ray range: they have a plasma trapped in their gravity well that is so hot it emits in the X-ray.

You see, this suggests that dark matter was created during the big bang. But, to maintain the balance of mass in the universe as it is now expanding, doesn't more dark matter have to constantly be created?

No. The universe is just getting less dense. And it has to have formed in the very early universe, because we see its effects as early as the cosmic microwave background.

If there is no 'new' dark matter being created, and we have enough today to fill the universe, we would have had too much yesterday, and not enough to fill the universe tomorrow.

Are you somehow thinking about this curvature issue? The open/closed/flat stuff? That doesn't change with time. The density changes, but the expansion rate changes to compensate. So the overall spatial curvature doesn't change.

 

[PeopleSmoks]

Of course they were. They just obtained escape velocity (or near enough to it to get as far as the moon, anyway). They had to be slowed by gravity because they kept gaining potential energy as they got further from the Earth. It's just that they had enough velocity once the rocket burn ended to still make the trip.

Think of it like coasting on a car: if you start off with enough speed, you can pop the car in neutral and still get a fair distance. This doesn't mean that friction doesn't continue to slow the car: it does. It just takes a little bit of time to stop it. And if you had enough velocity to start with, you could reach your destination (whatever that might be).

It seems a more simplistic way to look at the Earth's gravity as having an affect on travel to the moon is the moon's orbit. It's the combination of the moon's orbital speed and the Earth's gravitational effect that holds the moon in it's present orbit. Although, I have read that the moon's orbit is increasing. I read that the Earth's gravitational effect reaches as far as the Kuiper belt. I find there is may be some confusion between escaping Earth's gravity and escaping the atmosphere.

No, because in a plasma, the positively and negatively charged particles are separated, so plasmas tend to glow pretty brightly depending upon their temperatures. This is the reason the Sun glows, for instance. It's also the reason why we see galaxy clusters in the X-ray range: they have a plasma trapped in their gravity well that is so hot it emits in the X-ray.

There are a few different kinds of plasma that I have read about, including the polar auroras, but I also read that plasma is the base of intergalactic medium, and that not all plasma glows. As you have said, dark matter is called "dark" because we don't know it's true nature. It's also possible that if dark matter glows in some manner, it is beyond the infrared or ultraviolet scales.

No. The universe is just getting less dense. And it has to have formed in the very early universe, because we see its effects as early as the cosmic microwave background.


Are you somehow thinking about this curvature issue? The open/closed/flat stuff? That doesn't change with time. The density changes, but the expansion rate changes to compensate. So the overall spatial curvature doesn't change.

I think I'm beginning to see my misunderstandings regarding the differences between mass of the universe and it's volume density. Which also brings up the question, if the density of the mass is decreased, won't it's gravity decrease proportionately? Remember, we're talking about dark matter being spread across the cosmos and not a star.

 

[Chalnoth]

It seems a more simplistic way to look at the Earth's gravity as having an affect on travel to the moon is the moon's orbit. It's the combination of the moon's orbital speed and the Earth's gravitational effect that holds the moon in it's present orbit. Although, I have read that the moon's orbit is increasing.

The reason the moon's orbit is increasing is basically because the Earth isn't a perfect solid. Because the moon slightly deforms the shape of the Earth (mostly by causing the tides), and because the rotational speed of the Earth is different from the orbital speed of the moon, this causes an additional tidal force between the Earth and the moon. This tidal force has the effect of slowing down the Earth's rotation while at the same time increasing the moon's orbit, and will continue until the Earth and moon always have the same side facing one another.

I read that the Earth's gravitational effect reaches as far as the Kuiper belt.

It's infinite. Gravity is an infinite range force. Now, if you're far enough away from the solar system, you won't be able to distinguish between the Sun's mass and that of the Earth (or other planets, mostly Jupiter). But the amount of mass will still be important, and the Earth makes up some tiny fraction of the mass of the solar system.

I find there is may be some confusion between escaping Earth's gravity and escaping the atmosphere.

Possibly. But I think it's more a confusion between being able to escape Earth's gravity and simply not feeling the effects of it at all. If you have enough velocity, the Earth's gravity won't ever be enough to turn you around. But it still slows you down, the entire way.

There are a few different kinds of plasma that I have read about, including the polar auroras, but I also read that plasma is the base of intergalactic medium, and that not all plasma glows. As you have said, dark matter is called "dark" because we don't know it's true nature. It's also possible that if dark matter glows in some manner, it is beyond the infrared or ultraviolet scales.

The intergalactic medium is made up of normal matter. The word is not used, so far as I am aware, to talk about the much more abundant dark matter. And all plasma most definitely glows, at a range of wavelengths determined by its temperature.

Finally, as far as dark matter emitting in different wavelengths, that's not really possible because then dark matter would interact just as strongly as normal matter, and it wouldn't form dramatically different mass distributions than the normal matter (dark matter tends to be broadly-distributed, while normal matter tends to be stuck in tight clumps).

I think I'm beginning to see my misunderstandings regarding the differences between mass of the universe and it's volume density. Which also brings up the question, if the density of the mass is decreased, won't it's gravity decrease proportionately? Remember, we're talking about dark matter being spread across the cosmos and not a star.

Well, in a way this is so. As the normal and dark matter get spread more thinly, their effect on the rate of expansion diminishes.

 

[Peter Watkins]

Chalnoth, I suppose that what you're saying is pretty much what I was saying, ie. gravity is slowing expansion.

 

[Chalnoth]

Chalnoth, I suppose that what you're saying is pretty much what I was saying, ie. gravity is slowing expansion.

That's only how it works with normal matter. And even if all we had was normal matter, it's still possible for it to never slow expansion enough that it stops and recollapses.

 

[Jorrie]

Are you somehow thinking about this curvature issue? The open/closed/flat stuff? That doesn't change with time. The density changes, but the expansion rate changes to compensate. So the overall spatial curvature doesn't change.

Isn't it so that any spatial curvature present (not precisely flat) will evolve away from flatness as time goes on? It is true that open will always remain open and closed will always remain closed, but not at the same $\Omega$, not so?

 

[Chalnoth]

Isn't it so that any spatial curvature present (not precisely flat) will evolve away from flatness as time goes on? It is true that open will always remain open and closed will always remain closed, but not at the same $\Omega$, not so?

Well, it does depend upon how you write down the parameters. Take a look at the Friedmann equation with curvature:

$$H^2(a) = H^2_0 \left(\frac{\Omega_m}{a^3} + \frac{\Omega_r}{a^4} + \frac{\Omega_k}{a^2} + \Omega_\Lambda \right)$$

Written this way, the curvature parameter $$\Omega_k$$ does not change with a. You can think of this as saying that there's still the same total amount of "k" around, just as there's still the same amount of matter around, no matter how much the universe expands. However, if you look at how the effect of the curvature changes with the scale factor a, it dilutes more slowly than normal matter/dark matter or radiation. This means that even if the density fraction in the early universe was small, it tends to grow very rapidly compared to matter and radiation.

However, if there is a cosmological constant, that doesn't dilute at all, which means that the eventually any amount of cosmological constant will cause the curvature to also dilute away to nothing, leaving the dominant effect the cosmological constant at late times. If there was no cosmological constant (or anything else that acts like one), at late times the curvature would become dominant, as long as it is even slightly non-zero.

This is actually why inflation explains why the curvature was so small in our early universe: inflation behaved very much like a cosmological constant, and so it diluted the curvature away to nearly zero before our region began.

 

[Jorrie]

Well, it does depend upon how you write down the parameters. Take a look at the Friedmann equation with curvature:

$$H^2(a) = H^2_0 \left(\frac{\Omega_m}{a^3} + \frac{\Omega_r}{a^4} + \frac{\Omega_k}{a^2} + \Omega_\Lambda \right)$$

Written this way, the curvature parameter $$\Omega_k$$ does not change with a. You can think of this as saying that there's still the same total amount of "k" around, just as there's still the same amount of matter around, no matter how much the universe expands. However, if you look at how the effect of the curvature changes with the scale factor a, it dilutes more slowly than normal matter/dark matter or radiation...

Thx, that's the way I understood it too: $$\Omega_k$$ is the present curvature parameter and the $$a^2$$ denominator sorts out the evolution of the curvature contribution, if nonzero to start with. But as you said, a dominant $$\Omega_\Lambda$$ can also drive nonzero curvature to zero, so it is not always driven farther away from zero, as I implied...

 

[Naty1]

String theory appears to be the only thing that seems to completely exclude the possibility of cosmic collapse or the cyclic model.

Not sot: Heterotic M theory (Horava and Witten) with two parallel branes leads to the ekpyrotic cyclical model proposed by Paul Steinhardt and Neil Turok and explained in the book the Endless Universe, 2007. I'm reading it now and the main idea is that in the last ten years major ideas have emerged to revive cyclic models, a major one being that dark energy evolves over time. It speeds up the expansion rate, as is now being observed, acts as a shock absorber of the type used on automatic door closers, and also slowly decays over time shutting itself off.
Dark energy is not a constant!

 

[Peter Watkins]

Dark energy could only qualify as a cosmological constant if it existed, and this is very doubtful. When described it is always as an expanding force between galaxies, pushing them apart, much as expanding space is described. But what about galaxies between opposing forces? Picture a single galaxy surrounded by dark energy. Pushed from all sides it would go nowhere. The same would apply equally to a cluster of galaxies or a whole universe of galaxies. The overall effect would be neutral, as it would be with vacuum energy, an earlier attempt to explain galactic movement.

 

[Chalnoth]

Dark energy could only qualify as a cosmological constant if it existed, and this is very doubtful. When described it is always as an expanding force between galaxies, pushing them apart, much as expanding space is described. But what about galaxies between opposing forces? Picture a single galaxy surrounded by dark energy. Pushed from all sides it would go nowhere. The same would apply equally to a cluster of galaxies or a whole universe of galaxies. The overall effect would be neutral, as it would be with vacuum energy, an earlier attempt to explain galactic movement.

By this same logic, nothing could speed up or slow down the expansion. After all, being pushed equally in all directions is identical, in your little thought experiment, to being pulled in all directions. But the expansion rate has changed over time, so obviously something is wrong with your little thought experiment.

 

[Peter Watkins]

Hello Chalnoth. Re above; it is not a thought experiment, it is a simple statement of fact. Cosmologists seem to have forgotten that there is a fundamental law that applies throughout the universe ie., for every action there is an equal and opposite reaction. With regard to nothing to speed up expansion, you are quite right. It is an impossibility. But the rate at which galaxies move apart will increase as the expansion rate is slowed from within. This would resemble acceleration from our viewpoint. You yourself went to great lengths to impress upon me that gravity will always exert a restraining effect, and indeed it is, slowing the rate at which the universe is expanding. It can also cause acceleration, after first slowing the innermost galaxies to a halt, and then pulling them back at an increasing rate. If the universe was made up of layers, like an onion, it is these that are being separated. The outer layers, including us, are still moving outward at a rate that decreases toward the centre, whilst the inner layers are collapsing inward at a rate that increases toward the centre. This picture fits all observations. So, to state that there is no mechanisms to alter expansion rates is incorrect.

 

[Chalnoth]

So, to state that there is no mechanisms to alter expansion rates is incorrect.

You seem to be very confused. The FRW universe is one wherein the universe is modeled as a perfectly uniform fluid. This is known to be not entirely accurate, but works pretty well on large scales. And yes, a perfectly uniform fluid can expand and contract based upon the action of gravity combined with whatever internal pressures this fluid feels.

You can argue in words all you like, but the mathematics is unambiguous and certain: gravity does propel a changing rate of expansion.

 

[Peter Watkins]

Why on Earth is the universe modeled as a perfectly formed fluid? I would have thought that a perfectly formed vacuum would be more appropriate. I agree that gravity can alter he rate of expansion, but only by slowing. Cosmology is a science of observation and reason, not mathematics. I'll wager you that mathematics could not begin to describe our solar system to the un-informed, whilst words and illustrations would quickly convey the message.
Believe me, there is no confusion on my part. I thank you for your time.

 

[Chalnoth]

Why on Earth is the universe modeled as a perfectly formed fluid?

Not perfectly formed. Perfectly uniform. That's the FRW universe, anyway. What cosmologists typically work with is perturbed FRW, where that assumption of uniformity is relaxed.

But regardless, the reason why it's modeled that way is because it's a good approximation.

I agree that gravity can alter he rate of expansion, but only by slowing.

Well, you'd be wrong. It depends upon the matter/energy content of the universe.

 

[chroot]

Cosmology is a science of observation and reason, not mathematics.

Since you're not a cosmologist, it would be wise of you to refrain from telling them how they should conduct their research.

The simple fact is that physics without mathematics is no longer physics. It is philosophy at best, and pointless word games at worst. Physical theories cast in language alone are far too vague and ambiguous to ever make concrete predictions.

Your comments on pictures and words making for better pedagogy are misguided, but even if they were correct, they would be irrelevant. We're not talking about teaching cosmology; we're talking about understanding the universe with a meaningful theory that makes meaningful predictions. Scientists would be enormously handicapped if they chose to only explore theories which are accessible to a lay audience.

- Warren

 

[Peter Watkins]

The universe is essentially a study of the large and the small. Virtually all of the mystery is contained within the atom, how and why they form, interactions, component parts, why there are any forces and so on. And for this mathematics are essential. Then there is the large scale universe. The different types of stars, their life cycles, pulsars, neutron stars, variables etc.. It has taken the finest brains to tease out the secrets of these objects and I don't doubt for a moment that mathematics were involved. But when it comes to large scale movements, what we have is large clumps of matter, inertial or kinetic energy, and gravity. A "lay" person does not need to know how or why gravity works, simply what it does.
This forum constantly denies that the universe expanded from a single point, but we "lay" people have been told for 80 years that the universe is expanding, that is, increasing in size, in all directions, for close to 14 billion years. So, unless I'm living in a crazy alternative reality, this can only mean that the universe was considerably smaller than it now is, probably by a factor of several billions. Regardless of whether this was as small as the volume of our solar system, or our galaxy, or our local group, the fact is that the expansion took place, from that point, against the restraint of gravity. So what is needed is the imagination to picture the manner in which it would expand. For this, a knowledge of mathematics would seem unnecessary. What I don't understand is why this forum is so set against the notion that gravitational restraint from within has, or could have, caused "spreading", ie. the "faster with distance" view, and that this process is continuing, producing the illusion of acceleration. Surely the last thing a cosmologist should possesses is a closed mind.
Re post #60. Matter and energy are two sides of the same coin, the one always resulting only from the other, either from heating or cooling. Which, as an aside, is worth remembering when trying to fathom our origins.

 

[Chalnoth]

So what is needed is the imagination to picture the manner in which it would expand. For this, a knowledge of mathematics would seem unnecessary.

And that's where you're wrong. Only mathematics is precise enough a language to determine what is or is not occurring.

 

[OB 50]

And that's where you're wrong. Only mathematics is precise enough a language to determine what is or is not occurring.

I disagree. Pig Latin has been demonstrated to be a much more efficient and descriptive language for describing the inner workings of the universe.

Ask anyone. It's science.

 

[Chronos]

Science without math is philosophy. Philosophy is not bad, merely incomplete. Math is unforgiving and rigorous. It's what debunks the process of knowledge. Nature does not prohibit an illogical universe. It does prohibit a mathematically inconsistent universe.

 

[Chalnoth]

Nature does not prohibit an illogical universe. It does prohibit a mathematically inconsistent universe.

Only if you use an improper definition of the word "illogical". Formally, illogical = mathematically inconsistent, as formal logic is a type of mathematics. Perhaps "unintuitive" would be a better word: there is no reason why the universe shouldn't be unintuitive.

 

[LostUpNorth]

This whole topic is fascinating. I'm not well versed in field but I appreciate the insight and the references. I'm curious if anyone has explored the idea of something at the edge of the universe pulling things apart. In effect, a "big rip" instead of a "big bang." That same force could still be there today exerting gravitational pull and causing the increasing speed of separation that leads us to this whole dark energy idea.

 

[Atomic Number]

This whole topic is fascinating. I'm not well versed in field but I appreciate the insight and the references. I'm curious if anyone has explored the idea of something at the edge of the universe pulling things apart. In effect, a "big rip" instead of a "big bang." That same force could still be there today exerting gravitational pull and causing the increasing speed of separation that leads us to this whole dark energy idea.

I've thought about this, too. Is there any reason the universe can be pulled out, instead of pushed out?

 

[Chronos]

Assuming there is nothing 'outside' the universe, pushing is the only apparent option.

 

[LostUpNorth]

Assuming there is nothing 'outside' the universe, pushing is the only apparent option.

Interesting point. I'd be very interested in any work that analyzes whether or not there could be something at the edge or outside of the universe. That analysis may prove or disprove dark energy quite well.

As I said, I'm not well versed in the field, but to me it's simple. If dark energy is acting as some sort of cosmic wind that pushes things in a direction away from a point, then our orbiting galaxies and planets should show some measure of change as they head "into" the wind. Imagine trying to fly an airplane in a circle on a windy day. On the down wind side the plane will go faster and on the upwind side it goes slower. To get a true circle you must constantly adjust the rate of turn. If you keep the same rate of turn your plane will spiral along in ellipses as the wind pushes you farther and farther along.

If indeed there is dark energy pushing our galaxy away from some location at an ever increasing speed, we should be able to measure acceleration AND deceleration within the galaxy as well. Quite simply, the up wind stuff should be going slower than the down wind stuff.