Universe Expansion Accelerating in Real Time?

I'm looking forward to what's coming on this one. Einstein had some good ideas. Unfortunately, I'm not quite smart enough to reply inellegenty during my grandsons kindergarten graduation bar-b-que. Cheers!

Farther objects are moving faster than nearer objects; that's how they got farther.

Whether everything is accelerating or decelerating is a somewhat separate, though related, question. (I studied physics too long ago to be up to speed on the more recent ideas about dark matter and energy.)

Consider an ordinary explosion:Maximum acceleration and velocity at first, with velocity decreasing(decelerating) as time goes forward.This is a normal explosion.

Scientists claim that our universe, on the other hand, is continuously accelerating and expanding, furthermore, that the acceleration rate is increasing .They arrive at this conclusion because the objects at a distance are moving away at a faster rate than closer objects.

The problem as I see it is when we look farther away, we are also looking back in time, to an earlier time in the history of the universe.

It would be nice to know the current state of the universe, but that is forbidden by the speed of light.

"Consider an ordinary explosion:Maximum acceleration and velocity at first, with velocity decreasing(decelerating) as time goes forward.This is a normal explosion."

Why (in your opinion) do the fragments decelerate?

_{I have my own ideas, but I'm holding them back for now.}

They decelerate when the expanding gas ceases to expand and the gasses begin to cool.

Even in space, when a star explodes, the gasses cool and begin to slow down with distance.

Consider one of the particles, or fragments, moving away from the center of the event. Say it's a lump of schrapnel the size of a sugar-cube (about 1cm³), rather than an atom/molecule of gas. It's ballistic - why should cooling have any effect on its velocity?

I can see that it would decelerate because (in Newtonian speak) it would be affected by the gravitity of the entire collection of particles (which is centered at the point where the explosion occured), but I can't see that it has anything to do with the gas laws.

Jus' thinkin'.

This still seems to be confusing velocity, constant acceleration, and increasing acceleration. Even with no acceleration, distant objects would move faster away than nearer objects.

Actually, there is know way to know for sure whether our "neighborhood" of the universe is shrinking, or whether the rest of the universe is expanding. One would get exactly the same measurements either way.

Were we accelerating towards the Black Hole that appears to exist at the center of the Milky Way Galaxy, to which we seem to be attached gravitationally, we would measure the exact same phenomena on which scientists base their theory that the expansion of the universe is accelerating.

I haven't yet figured out why they prefer the "accelerated expansion" model over falling into a black hole model. Maybe the math is more elegant?

We had a lengthy discussion in one of my classes about this. There is one measurable difference. For the case of the collapse, in certain areas the doppler effect from some neighboring stars would show a blue shift. Since we pick up only red shifts in our neck of the woods, to prove a collapse we would need to see blue shift information from another part of the universe.

So as I understand it, to believe expansion we need only the info we have, to believe in collapse we need to believe in information we don't have (yet).

There was one other thing we discussed. Why does it have to be one or the other? It could be both expansion and collapse happening simultaneously. The expansion at the periphery and a point of collapse somewhere within.

We discussed what you called "blink out" too. There was a reference in our book that gave us an actual estimate for the distance and how it changes. It basically said that the rate at which two celestial objects move away from each other is related to their separation distance, the further they are apart the faster they move apart (as someone stated already). The theory said that it isn't actually so much that the objects are moving so much as the space between was becoming larger (a subtle but important difference). It allowed them to expand faster than light. Essentially, if we could sit on the earth and look out for a very very long time, we would slowly watch more and more stars disappear from the sky until the sky was void of stars. It was kind of scary.

One of the reasons I like the idea of us accelerating away from the rest of the universe rather than the universe expanding away from us is that we don't need dark energy to explain the observations. The concept of Dark Energy is derived from a need to adjust the models to fit the data. It has never been detected directly.

There are several models out there that offer alternatives to the Standard Model. The Standard Model is constantly being tweaked to account for new data from new observations.

You are right about getting Jorrie and Roger Pink involved in this discussion- they are our resident Gurus on this subject.

Astronomers use various yardsticks to measure distance. Within a few lightyears, parallax caused by the earth's orbit can be used. Further out, variable stars whose brightness can be linked to their period of variation are used. At much further distances, supernova are used for calibration. These other methods are compared with the expansion of the universe. This expansion is determined by measuring the amount of doppler shift in the spectral lines of rarified gases. If the expansion is constant over time, the lines will be shifted proportional to the distance. (Think of a balloon with spots drawn on it being inflated. The farther away the spots are, the faster they will move apart.)

If the lines are shifted more than this, the expansion was greater in the past and the expansion is slowing down. Likewise, a lesser shift, which appears to be the case now, indicates that the expansion is speeding up. It all boils down to comparing one yardstick with another.

When you look up at the night sky you're seeing many things. What's close to you (like the moon or Mars) is what is current. Right next to these objects you might see what "was". To your eyes they both look the same but in fact many of the little bright lights you see may have exploded or burned out thousands or even millions of years ago. What you see now is a record of what that light looked like when it left that star a long time ago. If you haven't already you might want to Google "Doppler shift", or red shift to get a better idea on how you can understand the things moving away from you. What you see in the sky isn't really there, It's a time record of what WAS there when the light left its source. That can defiantly play tricks on your mind!

Our knowledge and understanding are limited based on known theories and laws. May be in future we may discover that it is just contrary to what we think today.

Seems like every day a new announcement re surprising astronomical observations are being published ..an amazing amount of discovery happening nowadays due to computers capacity to analyze raw data ..and the sheer number of fellow travelers on our spaceship earth having the time/employment opportunities to spend on these sorts of questions..Re the premise of your question that the farther away one sees the further back in time one sees and its obverse that objects closer to us are slowing down here while those further away are speeding up here are my quick thoughts on this always fascinating subject..

It has something to do with gravity...Objects on the edges of our universe (that is visible in some sort of electromagnetic spectrum wavelength or other) have been ejected from the primordial mass at the start of what we cal time(10 to the minus 10th of a second or less after the initial event horizon say) along with everything else...Not being an explosives expert but doing a little thought experiment means everything was ejected perhaps symmetrically at 360 deg...Items of mass at the edges would over time get further and further away from items near the core of that explosion and the combined gravitational effect on the edge units would decrease more quickly than the gravitational effects on items closer to the core of the event horizon...Assuming everything started at the same outward rate of speed and with no frictional forces involved at the very outermost edges this combined with the relative increasing communal gravitational effect nearer the core of the event horizon would see these outer bodies continuing to distance themselves and at a certain distance perhaps freeing themselves from the communal core gravitational effect while the central core remnants would over time slow and perhaps reverse due to gravity giving the distant observer trapped in the coalescing core a sense of slowing .

An interesting question is where do these speeding remnants end up going?? A vast place this universe of ours..and is time a measure of speed relative to an observers location..??

Something to consider with respects to time here. We are not at the center of the universe. So relative to the center of the universe we can see objects closer to us that are on both sides closer and farther from the center of the universe (and both closer in time to us). We can then look out further away from us (but possibly closer or further from the center of the universe) and see further back in time. So if you look at object closer to us and measure the redshift (nearer in time), then look for a position similar distance from the center of the universe and measure the redshift (further back in time), we can see the acceleration away from us and estimate the acceleration away from the center of the universe relative to the universe time. So consider the comparison of near and far object more in a sense of those in the past and those much closer in time.

As far as dark matter and energy go, well those were just cheats invented to account for the mathematical failings in theories that astonomers did not want to have to throw out.

Well, suppose space is curved in its essence... not just by gravitational warpage. That's a vague and incorrect way, maybe to pose the question. But what if it is somehow "folded" or "shaped" in such a way, that at some point in time light traveling "back" to our observation point is the reverse Doppler effect? Now there is no way to state the question without it being related to concepts our mind can grasp.

Suppose space itself is distorted in such a way that it can be compared to a sphere. (Spherical tendencies exist in nature. Bubbles for instance.) And consider that "observation" is a fixed point on the edge of that sphere. Now consider that light only travels on the outer surface of the sphere and always seeks the shortest route to the observation point. Observation is perceiving the light as going away only until it reaches the farthest side of the sphere. Once the light travels through the space beyond the farthest point the "red shift" would change due to it's path. In which case, "red shift" might have to be qualified.

In the same way that Newtonian physics doesn't work for atomic events, maybe our understanding of "space" works at "short" distances, but not at distances like the furthest reaches of the universe. We do NOT understand space. We've gone from aether to nothingness, to a sea of virtual particles, which may be back to a better version of aether, all over again. Like Newtonian mechanics, there is something still missing in our understanding of space.

How's that for some gibberish?

If light were accelerating away from you how would you ever detect it. Reflected light would be influenced by the structure reflecting it plus the light would then be accelerating towards you.

The doppler effect has to do with the object that emitting the light moving in a reference frame relative to the observer. So even if space was warped, the object emitting the light is always moving in reference to the observer. Since C is a constant and it is space-time that warps, the doppler effect reflect the change in frequency correlating to the movement of the observed object (towards or away) relative to the observer. So assuming a spherical space then light would travel in all directions around the sphere, thus there would be a multiple observations of the object. Such that if the object was moving on the sphere relative to the observer, you could find an occurence where the object was red-shifted and one where it was blue-shifted by the exact same amount when observed in the opposite direction from the red-shifted observations, though due to effects in the media on which it travels (space-time) the light may not arrive at the same time and could arrive at differing angles from 180 degrees opposite.

Well, that's why I said we don't understand space. It was a poor attempt at posing an idea, using the example of a sphere. Sometimes I make that kind of mistake just to participate. I was only thinking that space might have qualities, such that, we might use properties of a sphere to describe it. There is a fine distinction. Clearly stating it is being used as an analogy is probably preferred. But analogies don't serve well in the microscopic world. And space is explained as full of microscopic virtualities. After all, saying a photon or electron has both wave and particle properties conjures up what in our minds? How do we visualize that?

All of our sense experience is with macro particles and waves. And we consider waves as propagating through a medium. With current physical theory how does a light beam travel through a vacuum? A modern physicist might say excitation of virtual photons along a path. Or he might not. I don't know.

After centuries of man trying to understand time and space he still is dependent on whatever "consciousness" is for the context, analysis, and meaning of it all. We can't perceive atomic phenomena directly with our senses. We have to devise ways to do this with "instruments" which use the very phenomena we can't experience to bring it into our awareness. Atomic phenomena happens all the time all around us. But our senses don't see phenomena (such as electrons), just the results and after-effects, so to speak.

I would suggest that without understanding what consciousness is, we may never understand the rest of it. If we ever get to a point where we can reproduce consciousness from scratch (not the Turing kind; and other than through biological reproduction), then almost by definition we will have understood everything. Will we get there? Talk about a catch-22... how do you reproduce something you don't understand? By accident, maybe. Like other accidental inventions? I'd bet not -- certainly not in our lifetime.

(Just for RP, since he's been invoked: Here is one discussion musing about such things. And I couldn't help noting one of the section headings refers to an "Existential Risk!!??" Others relevant links are here and here. What I find funny about these kinds of musings is that the possibility is beyond our lifetimes and highly improbable, yet we comment as if we think that our discussion of these things will be preserved and consulted by those so far, far in the future. As if our opinions matter much. First, we have to survive our mistakes as a species.)

Besides, RCE, the post was labeled as gibberish, wasn't it?

Aren't the waves propigating through electric and magnetic fields as a medium?

Maybe that's the current thinking. Similar to what I was saying, about photons arising and disappearing out of virtualness to "reality" back to virtualness; i.e., electromagnetic fields propagating along a path, but not moving themselves. That is similar to wave action on the ocean.

I'm just now in the process of updating my Physics. I majored in college, then left after 2½ years. Then left off for 10-15 years. I read some about 20 years ago, but have forgotten it all. I know enough to already think in some ways it is futile.

But still, as conscious beings we naturally try to "visualize" whatever we're talking about. With quantum physics that's hard.

As far as the electromagnetic fields, our minds STILL wish to try to visualize a medium because that's our experience at the macro scale, sense level. If the fields are arising like photons along a path, the concept of a "path" signifies something to our minds. That's 3D. If that goes away, then all the new TVs and movies are going to be exposed for what they are, nothing!

What that something is is what all the hoopla is about. Some physicists, no doubt, think it can be reduced to mathematical equations or expression. But what does THAT mean??

Is your answer supports my view at #10?

The following link should clear up a lot of misconceptions about this subject:http://www.astro.ucla.edu/~wright/cosmology_faq.html

Thanks for the link... I made it through FAQ #3 before I disagreed, although I'm no physicist and perhaps I'm misunderstanding... The question was "Why do we think that the expansion of the Universe is accelerating?" ... in the answer... "...But if the expansion is decelerating, it was faster in the past and the distance NOW is smaller."

In simple mechanics deceleration does not necessarily mean two objects are closing the gap between them, it can also imply they're simply moving apart with less velocity. ie.. the distance NOW can be larger.

I'll keep reading... in the meantime, am I misunderstanding?

Maybe the following link will help for a simple explanation:

http://www.ebtx.com/ntx/snap2001.htm

For a thorough one see this link:

http://www.spacetelescope.org/static/archives/releases/science_papers/heic1005_sciencepaper.pdf

Thanks. I think I'm starting to grok this (a little anyhow).

To really confuse the issue, Science News (http://www.sciencenews.org) recently published a report from some researchers in Sweden where they created visible photons from "virtual photons" in a vacuum utilizing the Casimir effect. The original paper is available on line here.

Read "A Brief History of Time", written by Stephen Hawking and published in 1988. Basically, it's a universe-for-dummies kind of thing. I'm not suggesting you're a dummy, but I had to read it three times.

That was standard reading for one of my courses! I'd also recommend it (although it is a little dry, so have some coffee at the ready).

Oh dear, I wish I could stay away from threads like this one.

Consider the model of the universe that is a rice pudding with raisins spread uniformly within it. As it cooks it expands and the raisins are moved further apart. If this movement is recorded from any given raisin against time, those furthest away will be be seen to move away more quickly than those nearby. This is true whether the expansion of the pudding is accelerating or decelerating.

However, in the universe, more of the distant raisins become visible (the light has had time to reach us). If we see them at an early stage of the universe, you would think they would be close together.

The problem is further complicated because there is the "redshift" of expanding space as well as of relative motion. So when it comes to considering a body moving through an expanding or contracting space, I move to the sidelines and watch the brainy people figure it out.

Even worse, measuring rods get shorter and hours get longer on moving objects observed by us, especially if they move through a heavy gravitation area.

Although I appreciate the endorsements I've been getting in this thread, I have to say that Jorrie is far superior to me in matters or Special or General Relativity. There are others that are pretty good too, if you look at Jorrie's blog you'll see them there discussing things with Jorrie. That said, I will give my understanding.

It's space that is expanding. All space. The matter that sits in space is swept along (except when held in place by local gravity. The reason objects further away are accelerating faster is because there is more expanding space between us and them. The more space in between us and the object that is expanding, the faster it will appear to recede from us. This happens even if the spatial expansion rate is constant, which up until the last decade or so we thought was.

Other unrelated factors made us realize that that spatial expansion wasn't constant at all but in fact increasing. I won't get into that here though you can read about why here: http://en.wikipedia.org/wiki/Dark_energy

I hope that helps.