Posted on 06/04/2008 11:07:19 AM PDT by LibWhacker
BALTIMORE — Mario Livio tossed his car keys in the air.
They rose ever more slowly, paused, shining, at the top of their arc, and then in accordance with everything our Galilean ape brains have ever learned to expect, crashed back down into his hand.
That was the whole problem, explained Dr. Livio, a theorist at the Space Telescope Science Institute here on the Johns Hopkins campus.
A decade ago, astronomers discovered that what is true for your car keys is not true for the galaxies. Having been impelled apart by the force of the Big Bang, the galaxies, in defiance of cosmic gravity, are picking up speed on a dash toward eternity. If they were keys, they would be shooting for the ceiling.
“That is how shocking this was,” Dr. Livio said.
It is still shocking. Although cosmologists have adopted a cute name, dark energy, for whatever is driving this apparently antigravitational behavior on the part of the universe, nobody claims to understand why it is happening, or its implications for the future of the universe and of the life within it, despite thousands of learned papers, scores of conferences and millions of dollars’ worth of telescope time. It has led some cosmologists to the verge of abandoning their fondest dream: a theory that can account for the universe and everything about it in a single breath.
“The discovery of dark energy has greatly changed how we think about the laws of nature,” said Edward Witten, a theorist at the Institute for Advanced Study in Princeton, N.J.
(Excerpt) Read more at nytimes.com ...
That must be the stuff that keeps the Obama campaign going.
“It has led some cosmologists to the verge of abandoning their fondest dream: a theory that can account for the universe and everything about it in a single breath.”
In the beginning God...
No, no, that's just too easy. We'll never get paid for that idea.
This cosmological expansion...
Is it only happening on very large scales, or are the galaxies in our local group also sliding farther away from us?
Are distances between stars within the same galaxy also increasing?
What about the distance between atoms on my computer screen? Is the screen expanding, along with my eyeballs?
No, it’s long been known that all the galaxies are moving away from each other (well, almost all - at the more local scale some are getting closer to each other). The surprising find was that they are actually accelerating away from each other - that analogy would be your keys “falling” upwards, getting faster and faster the higher they go.
It seems to me that this idea must pretty much blow away Hubble’s idea, which was that you can tell how far away a galaxy (or other object) is by how fast it is moving away (commonly determined by the redshift of light from those objects). If galaxies are actually accelerating away from each other, it means that they’re probably not as far away as they seem, and the universe is younger and smaller than we thought.
Not necessarily.
At different points in the arc the keys will be accelerating away from you at different rates of speed. Sometimes faster, sometimes slower, to the point where the top of the arc is reached.
At different points in the arc the keys WILL be accelerating faster and faster away from you to a point where they are still accelerating away from you but not quite as fast as they were before.
Maybe, just maybe, we haven't reached the point where the acceleration slows down.
No, no, we won't get paid for that idea.
Never mind, go about your business.
You don’t know the power of the Dark Side of The Force!
Perzackly!
What I think he is doing is confusing acceleration with velocity. You can have an object, with an acceleration towards you that is also moving away from you. But, you cannot have an object ultimately move toward you that has both a velocity and acceleration away from you.
Viewed by an outside observer they will be decelerating at different speeds until they reach the top of the arc.
Viewed from your hand? With all the distances involved being proportionate? Are we really sure that the other galaxies aren't decelerating, but still at such a huge speed that we can't tell?
As Dr. Amit Goswami puts it, “consciousness is the ground of all being” and “the Universe is self-aware through us.”
It’s simple, really. So many factors hd to come into alignment in a particular way against odds so huge that they might as well have been zero that the simplest explanation that covers all teh facts is that some entity, some foce, some being must have driven it to this particular expression.
There it is without the religious language. Simple science.
That’s the WHY. . .
Science is about the HOW, and to how many decimal places. . .
It would just mean that it took less time for the galaxies to have reached their present positions, not that the universe is any smaller. The distance to their present positions is based on "standard candle" indicators. SCs are relatively rare cosmic objects of known brightness. When a remote object's actual brightness is known, the distance to it can be determined by how bright it appears as we view it on earth. Fortunately for us, light intensity diminishes with distance according to a very simple rule known as the 'inverse square law'. ie, 1 over r squared, r being distance. Once a distance to an object is established, a redshift measurement is taken on its light signal. A specific redshift is then associated with that particular distance and subsequent distances can be estimated based solely on redshift alone. Redshifts are comparatively easy to measure.
“At different points in the arc the keys will be accelerating away from you at different rates of speed. Sometimes faster, sometimes slower, to the point where the top of the arc is reached.”
Not to get pedantic, but you’re confusing velocity and acceleration. The acceleration of the keys (neglecting air resistance) will be the same all the way through their arc -32.2 ft/s/s - the constant acceleration of gravity. The velocity is constant decreasing from the time they leave your hand, going to zero at the top of the arc, and then picking up speed all the way back to your hand - again, neglecting air resistance, ending up back in your hand with the same velocity you threw them up with in the first place.
What they expected to find was that two objects attracted to each other by gravity (like your keys and good old terra firma), whatever their initial velocity towards each other, that velocity would be constantly decreasing (if moving apart) or increasing (if moving closer to each other). What they found is that
I guess they don’t really know the answers, eh?
Are distances between stars within the same galaxy also increasing?
What about the distance between atoms on my computer screen? Is the screen expanding, along with my eyeballs?
On local scales, the four fundamental forces apparently fight the expansion (gravity, electromagnetic, strong and weak forces).
By all means, get pedantic.
Hell, I have no idea what I'm talking about.
But I DID stay in a Holiday Inn Express last night. ;^)
Seriously, you folks seem to know what you're talking about a lot more than I do.
I'm just not so sure that with the distances and speeds involved we can state anything about it for certain.
The problem is that the Hubble constant is not very exactly known - the range in its accepted values is quite large. Also, measuring distances by redshift, which is how the distance of most very distant objects in the universe have been measured, assumes that their distance from us IS proportional to their speed away from us. If everything in the universe is actually accelerating away from everything else, I’m thinking that would really throw a spanner in the computed distances, and possibly to Hubble’s theory altogether.
What God has torn asunder, let no man put together.
***Viewed by an outside observer they will be decelerating at different speeds until they reach the top of the arc.***
The problem is that there is no justification that your point of reference changes anything. In fact, it is easy to demonstrate that your point of reference doesn’t matter. It is like having a bungee chord with balls on it. As the chord is stretched (the universe expands) all balls on it move away from each other. Pick a ball, any ball for your point of reference.
BTW, there is no such thing as an outside observer, i.e. outside of the universe, but supposing there were, you would still observe things accelerating away from each other.
***Are we really sure that the other galaxies aren’t decelerating, but still at such a huge speed that we can’t tell?***
Astronomy is pretty settled that things are accelerating away.
Except the way you see something.
An example, admittedly crude since I can't post a drawing that will do, -
You see a square with lines radiating to the four corners from a point in the center of the square.
From 180 degrees out of phase you see a square, no lines radiating from the center.
From 90 degrees out of phase you see a triangle
What are you looking at? - A pyramid.
I tend to understand the theory in a general way however I still think the point of view matters and still am not sure that considering the distances and speeds involved that we can state anything with certainty.
Your analogy of a FIXED object has nothing to do with relational motion. My example with the balls on the bungee chord is accurate. All balls move away from each other and you can’t tell which ball is the center ball, even if you are on the center ball. No matter which ball you pick, you observe all balls moving away.
This is like picking any galactic cluster from which to make your observation. You will observe all clusters moving away from you.
Even if you step outside the universe, the proper analogy would be dropping a stone in a still lake 10 feet away. Some of the ripple will move toward you; some away. But, you will clearly see that the ripple expands and moves away from itself.
You have to pick the right analogy or you will get a warped view of what you are tring to describe and using a fixed an stationary object that you observe from different angles has nothing to do with what we are discussing.
Your analogy of a pebble dropping in the pool of water.
The event would look different depending on whether you were above the pool or on one of the ripples.
It wouldn't BE different but it would LOOK different.
Uh, maybe the big bang is wrong. Maybe there were lots of
little bangs all over the place where just supposedly like at the
supposed “cosmic egg” point in the universe, matter and
energy just came into being supposedly....so these mini-bangettes
go their merry way not having to all come from one point,
and don’t need to obey gravitational “laws” cause they
were formed at different times in different places and have
different trajectories.
Or maybe the present is NOT the key to the past. Hmmmm?
I like simple science, uh 2+2 = 4...oh, sorry, that’s in
decimal system...might not explain quarks,strings or leptons,
I need imaginary numbers and imaginary time to do that.
“The discovery of dark energy has greatly changed how we think about the laws of nature,”
Technically speaking of course, they haven’t actually discovered “dark energy”, they have hypothesized “dark energy” to explain the discrepancies between what they thought they knew, and what they measured. Gotta parse the sentences.
Interestingly, the cosmic microwave background does seem to act as sort of a universal referrence frame for determining absolute motion. Within it we can detect the motion of our own Milky Way galaxy. If you ever see a MBG map in it's initial state, you'll see that one half of it has slightly more blue blotches while the other half is slightly more red (blue means moving towards, red, moving away). These blotches are often subtracted out later.
I'm not sure if the map below shows this effect or not.
Sure hope current theory is wrong.It's not all that different than looking forward towards the Big Crunch. Though I guess that would be a lot more spectacular towards the end, with the sky getting brighter millenia by millenia and all the new contacts popping up on the radio.
Either way, though, we're talking about a length of time at least as long as the universe has currently existed, which is something like 30 times the length of time since multi-celled life has been on earth.
Or look at it another way.
Our journey from cave-dweller to rocket-man has taken about 10,000 years. Before the end of the universe we have time to make that same-length journey ten million more times.
Thanks for the link. Inside the article are several more links. All of them are VERY interesting reading.
Thanks again.
LOL!
On local scales, the four fundamental forces apparently fight the expansion (gravity, electromagnetic, strong and weak forces).That's what I was hoping. Seems not, though. Follow the link in post#12.
But that's a big "if" that the expansion acceleration *rate* will not only increase but continue to increase, although it is something that I've wondered about as well. Below is an excerpt from the article you referred to. A very interesting one I should add.
"The question Caldwell and his colleagues posed is, what would happen if the rate of acceleration increased? Their answer is that the eventual, phenomenal pace would overwhelm the normal, trusted effects of gravity right down to the local level. Even the nuclear forces that bind things in the subatomic world will cease to be effective.
'The expansion becomes so fast that it literally rips apart all bound objects,' Caldwell explained in a telephone interview. 'It rips apart clusters of galaxies. It rips apart stars. It rips apart planets and solar systems. And it eventually rips apart all matter.'"
He calls it, as you might guess, the Big Rip."
Actually, that’s sort of what happens, they think, when matters falls into a black hole.
42!
That sounds really gay.
Not a very pretty picture.
The first, and biggest problem is that scientists refer to things like the Hubble Constant, to be used to calculate distance, when the constant is actually a wide-ranging variable.
The concept appears to be one in which we assume an answer, then use a fudge factor to make the math work out to match our predetermined answer.
Is that a fair description?
“you cannot have an object ultimately move toward you that has both a velocity and acceleration away from you.”
According to the curved space theory, any object that has a velocity and acceleration away from you will eventually sneak up behind you.
I think we have a long way to go in our learning, before we have a truer understanding of the universe.
We are basing estimates of distance, vector,velocity, and throwing in acceleration(which is total BS), based on straight line trajectories.
Nothing could be further from the truth.
Nothing in the universe, that we have ever observed, actually moves in a straight line, not even light.
From the largest scales, down to the smallest, it’s the same.
Thank you for posting the article.
Isn’t the ‘dark energy’ theory just another ‘fudge factor’?
We are saying that something undetectable, invisible to any and all of our instruments, exists, and that it explains the gaps in our theories.
“If everything in the universe is actually accelerating away from everything else,”
If we accept gravitational attraction, then everything in the universe is in a constant state of change with respect to vector, velocity, and acceleration due to interactions with each other.
“On local scales, the four fundamental forces apparently fight the expansion (gravity, electromagnetic, strong and weak forces).”
On universal scales, it would seem that the four fundamental forces are the methods by which the universe expands (if it truly is expanding.)
But those (local) accelerations are small in comparison and wouldn’t appear to be centered around our position (or, theoretically, any other point in the universe) as is the supposed expansionary acceleration.
How do you figure that?
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