Posted on 03/28/2003 5:49:29 PM PST by vannrox
Huntsville - Mar 28, 2003
For the second time in as many months, images gathered by the Hubble Space Telescope (HST) are raising questions about the structures of time and gravity, and the fabric of space.Using two HST images, astronomers from Italy and Germany looked for but did not find evidence supporting a prevailing scientific theory that says time, space and gravity are composed of tiny quantum bits.
Using existing theories, the team led by Dr. Roberto Ragazzoni from the Astrophysical Observatory of Arcetri, Italy, and the Max Planck Institute for Astronomy in Heidelberg, Germany, calculated that infinitesimally small quantum-scale variations in space time would blur images of galaxies seen from vast distances across the universe.
Instead, when they looked at both diffraction patterns from a supernova and the raw image of a second galaxy more than five billion light years from Earth, they saw images much sharper than should be possible if quantum-scale phenomenon operated as previously supposed. Their research is scheduled to be published in the April 10, 2003, edition of Astrophysical Research - Letters.
"The basic idea is that space time should fluctuate," said Ragazzoni. "If you are looking at light from a huge distance, this light passing through space time would be subject to this fluctuation in space time. They should give a distorted image of the far universe, like a blurring.
"But you don't see a universe that is blurred. If you take any Hubble Space Telescope deep field image you see sharp images, which is enough to tell us that the light has not been distorted or perturbed by fluctuations in space time from the source to the observer. This observation is enough to rule out this effect on the quantum scale.
"You can say," said Ragazzoni, "that this measurement constrains the quantum gravity theory to certain parameters."
This report comes a month after physicists at The University of Alabama in Huntsville (UAH) announced their unsuccessful attempt to use an image from an HST interferometer to find evidence of Planck-scale effects. Taken together, the independent research findings might force physicists to reexamine the scientific underpinnings of the quantum theories of gravity, time and space.
To look for the quantum blurring effect the European team used a parameter from optics, the Strehl ratio, to calculate how sharply the telescope should be able to resolve an image of the distant light source and its first Airy ring - a signature of the interference of the rays of light entering a telescope.
If the popular quantum theories were correct, space-time effects should blur light from distant sources beyond the telescope's ability to resolve them.
They didn't.
"Without a theory to describe this, I think it's hard not to agree that it is time to start to consider theories that do not require this Planck scale, at least not like it is now," said Ragazzoni. "From an experimental point of view, there is no establishment. We are proud to have established in as rigorous a manner as possible the parameters of this quantum effect."
The Planck-scale quantum theories of time, space and gravity were derived from attempts to calculate the theoretical limits to electromagnetic energy, according to a UAH physicist, Dr. Richard Lieu.
By inverting Albert Einstein's theory of relativity (E=mc2 becomes m=E/c2), physicists could calculate how much mass should be added to a photon as it gains energy. Using that, they calculated a theoretical limit to how much energy a photon might contain before gaining so much mass it would collapse into a photon-sized black hole.
That theoretical upper limit was then used to set theoretical limits on time. One cycle of a photon carrying that much energy would last 5 x 10-44 seconds, an interval called Planck time. As the shortest potentially-measurable interval of time, theorists speculated that time moves is Planck time-sized quantum bits.
In his theory of general relativity, Einstein theorized that time, space and gravity are different manifestations of the same phenomenon, much as light and thunder are signatures of the electrical discharge in lightning. If time is made up of quantum bits, that would also mean space and gravity should also be composed of quantum units.
Since the expected blurring "signature" of quantum space time isn't seen, however, it might mean that time isn't made of quantum bits, and neither are space or gravity.
Dost thou love life? Then do not squander time, for that is the stuff life is made of.
-- Poor Richard's Almanac, Benjamin Franklin
Note that I said that time was "variable" and not "a variable." By this I meant that time is not independant of space (i.e. cannot be measured in absolute terms, regardless of motion and/or position). I can see where the term might have expressed a connotation I did not intend; sorry about that!
As for time "flow," imagine growing up on a spaceship which constantly accelerated from zero to lightspeed and back. Time would certainly "flow" (or ripple) if measured under those conditions, as it would move faster or slower depending on the velocity of your ship at any moment. Besides, time does "flow" normally, as a dropped ball shows the direct flow of time (the ball doesn't hover or reverse directions)...
Is space "active" or "passive"? It' is a coordinate system, too. Think carefully, because space-time curves due to the presence of mass/gravity...
Besides, active or passive is a term you have invented to describe what ever it is you have in your head. Please describe the meaning of those two terms and the theoretical consequences of them. For example, how would I tell experimentally if I am dealing with an active or passive phenomenon? Is an electormagnetic field active or passive? Why?
If space/time is curved due to gravity then it is passive as it is being acted upon. I'd say that gravity is the cause and therefore active, but it is matter/energy that holds the cards here.
Matter/energy is the substance of all things. Time and space only exist in the attempt to rationalize our perceptions and limitations.
No it would not. Referring to any clock on board your ship would reveal no changes. You would conclude that time was 'flowing' in a perfectly normal manner--one second per second. Only by reference to an external clock could you 'perceive' a change in the "rate of flow" (whatever that is) of time. Furthermore, you would reasonably conclude that it was the external clock that was speeding up or slowing down, since manifestly things are normal aboard ship.
"Besides, time does "flow" normally, as a dropped ball shows the direct flow of time (the ball doesn't hover or reverse directions)..."
The laws of physics are time-symmetric. You cannot distinguish a film of a ball bouncing up from the pavement from one of the ball dropping to the pavement and played backward. Entropy provides an 'arrow' of time but this is not an explanation; it is an observation. It is perfectly possible, e.g., for a glass of water at 70F to spontaneously freeze, or all the air in a room to collect in one corner. The second law is empirical, a statement that we rarely see such phenomena--indeed that they are so improbable as to require more than the age of the Universe to be likely to happen.
Exactly. Just like in your example: only by referencing the ground outside of the train could you see space "flow" by. Space-time is a four coordinate system. Our only problem is that we can't displace back in time, nor control our personal perception of time. Just like we are always "here," but need an outside referent in order to make "here" a meaningful statement...
You have that backwards. Gravity is due to space-time curvature. The curvature of space-time might be due to mass, but the force of gravity is itself the "active" component of space-time curvature. This is why gravity curves the path of light when light has no mass for the gravity to act upon.
Yes. But causality is always a one-way street, flowing from cause to consequence. I have no support on this in any of the physics literature, nor do any of the truly knowledgeable people on this board agree with me, but I regard causality as the principle "arrow" of time, and the only one which gives time what we perceive as its direction -- from past to future.
So the apple falls due to space/time curature?
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