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).
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