Tackling the big questions -- approaching a revolution in our understanding of gravity

Nov 05, 2008

(PhysOrg.com) -- The way galaxies move through the cosmos has recently begun to baffle scientists. Even when the gravitational theories of Newton and Einstein are taken into account, the universe is expanding and galaxies are rotating in ways that do not comply with our current knowledge and predictions.

Now theoretical physicists at The University of Nottingham are examining possible solutions to the 'dark energy' and 'dark matter' problems — tackling the potential theories that would explain why the universe is evolving as it is today.

We are now able to see deep into the universe using satellite telescopes, but ever more powerful technology raises more questions. The rotational curves of galaxies cannot be explained by Newtonian dynamics or Einstein's theories of General Relativity without assuming the existence of some mysterious unseen form of matter — often referred to as 'dark matter'. But dark matter has an even more mysterious cousin, dubbed dark energy — the effects of which can be seen by observing distant supernova. Observations show that this unseen force is speeding up the expansion of the universe, overpowering the gravitational attraction present between stars and galaxies.

Funded by a new grant from the Royal Society, Dr Tony Padilla of the University's School of Physics and Astronomy will examine the potential candidates to explain dark matter and dark energy. These include:

Vacuum energy
Vacuum energy — or the cosmological constant — is the energy left over when all the matter is removed from the universe. It has a special property, negative pressure, which results in the accelerated expansion of the universe. However, current theories suggest that vacuum energy in the universe is huge, while observations suggest it is tiny. How can we reconcile this theory with observation? String theory offers a vast number of vacuum energy solutions — states in which different kinds of universes could exist depending on the level of vacuum energy in each string vacua. In some the vacuum energy may be too large, leading to a collapsing universe or one that expands too fast for stars to form. Some theories suggest that our universe has been selected anthropically from limitless possibilities — the universe has to have a tiny vacuum energy, or humans wouldn't be here to ask questions about it.

Dr Padilla will take a different approach, exploring transitions between different universes. He thinks that we may have ended up where we are today after cascading through a series of different universes, tunnelling quickly from one to another.

In a separate study, Dr Padilla will also explore the concept of degravitation — which suggests that the vacuum energy could actually be huge, but just appears small when observed on large scales as gravity becomes weaker.

Quintessence
This theory suggests that cosmic acceleration could be driven by quintessence — a quantum field with an extremely low mass. The field, which oscillates extremely slowly over very large scales, behaves much like a cosmological constant, exerting negative pressure on the universe and causing the acceleration we see today.

Extra dimensions
Inspired by string theory, this proposes that cosmic acceleration is due to large extra dimensions, beyond the three observable dimensions of space and one of time. This theory poses the idea that we live on a 'brane' — an island universe marooned in a sea of large extra dimensions. Ideas such as degravitation can be realised by allowing gravity to leak into these extra dimensions, making it appear weaker than expected in our island universe. We can also think of dark matter as being hidden in these extra dimensions, observable by us only through the effect of its gravitational field.

“Whether we are excited by old problems like how to model the interior geometry of a rotating star in General Relativity, or newer ones like dark energy, there can be little doubt that we seem to be approaching a revolution in our understanding of gravity,” said Dr Padilla. “And it is not all speculation and theory — experiment is catching up. When the Large Hadron Collider begins producing results at CERN, there is a chance that black holes will form in the accelerator and that extra dimensions will start to open up. It sounds scary, but from a physicist's point of view it is enormously exciting!”

Provided by University of Nottingham

Explore further: Linear accelerator could improve X-rays, particle colliders

add to favorites email to friend print save as pdf

Related Stories

Recommended for you

Backpack physics: Smaller hikers carry heavier loads

20 hours ago

Hikers are generally advised that the weight of the packs they carry should correspond to their own size, with smaller individuals carrying lighter loads. Although petite backpackers might appreciate the ...

Extremely high-resolution magnetic resonance imaging

20 hours ago

For the first time, researchers have succeeded to detect a single hydrogen atom using magnetic resonance imaging, which signifies a huge increase in the technology's spatial resolution. In the future, single-atom ...

User comments : 11

Adjust slider to filter visible comments by rank

Display comments: newest first

Traveler
3.1 / 5 (14) Nov 05, 2008
"Even when the gravitational theories of Newton and Einstein are taken into account, the universe is expanding and galaxies are rotating in ways that do not comply with our current knowledge and predictions."

When observation does not agree with prediction, it is time to revise one's theories and hypotheses. In other words, why invent all sorts of weird explanations (dark matter, dark energy, extra dimensions, etc.) when the most obvious culprit is the theory itself? And if the theory is suspect, so are all the conclusions (big bang, accelerated expansion) that are derived from it.
Question
2.9 / 5 (8) Nov 05, 2008
We need new ideas and ways of looking at the basics of science. For example, can we even be sure our view of light is correct? Maybe the source of the red-shift can be explained in different way without violating any of the laws of classical physics?
http://www.iunive...00037539
Quantum_Conundrum
3 / 5 (14) Nov 05, 2008
When observation does not agree with prediction, it is time to revise one's theories and hypotheses. In other words, why invent all sorts of weird explanations (dark matter, dark energy, extra dimensions, etc.) when the most obvious culprit is the theory itself? And if the theory is suspect, so are all the conclusions (big bang, accelerated expansion) that are derived from it.


Such an obvious conclusion comes too high for the modern "scientist".

They would rather cling to their failing formulae and try to add yet another patch to it, instead of discarding the entire nonsense and starting over from scratch.


The galaxy problem is this, in a nut shell.

According to both Newton and Einstein, the gravity needed to hold a galaxy together is insanely high.

However, if the center of the galaxy has that much mass to make so much gravity, the all the stars at the center of the galaxy should have been pulled into an SMBH by now, according to newton and einsteins gravity theories.

Thus the paradox. There is not enough mass to explain how to hold the outter bands of a galaxy together, and the galaxies already have too much mass in their center to explain why stars don't collapse into the SMBH in the center...

Thus, the formulae predict stronger gravity at the center of a galaxy than what appears to be there, and weaker gravity at the edges of a galaxy than what appears to be there, a paradox.

But moreover, gravity certainly cannot explain any possible interpretation of an "acceleration" of the expansion of the universe (that is, if the universe is expanding at all.)

Among all current theories of gravity, this gravity SHOULD act to slow any expansion that is taking place, not speed it up.

Personally, I believe distances and red shifts are being misinterpreted based on faulty reasoning. This is one of the key problems in cosmology. If objects really are so far away, pinpointing there exact distance is utterly impossible, and moreover, pinpointing their mass or composition is also not reliable. Predicting what the gravitation effects of such an object so very far away "should be" is unreliable. You do not know how fast the object is actually moving away in "local" time nor in the greater scheme of things, and you do not know the actual mass of that object or other objects it may have encountered in the eons since the light you are looking at left that object.
Alizee
Nov 05, 2008
This comment has been removed by a moderator.
Quantum_Conundrum
2.7 / 5 (9) Nov 05, 2008
Therefore, the Red shift and the big bang theory are essentially a circular reasoning.

Q: "How do you know the big bang happened?"

A: "Well, because everything shows red shift."

Q: "How do you know it is red shifted?"

A: "Because all elements emitt a certain color spectral line and we can guesstimate how much that has been altered in the freguency of light and see how much the line shifted in color..."

Q: "Uh huh...how do you know the line hasn't been changed due to some other means beside space-time expansion?"

A: "we don't, we just assume it hasn't..."


"Tired C" was supposedly disproven, and yet, I've never actually "seen" a formal proof against it.


in fact, Red shift should be explainable by the mere propagation of light through vaccum over long distances. Why? Because light propagates into 3 space dimensions, which means it is "stretched" into a surface perpendicular to its direction of motion. This stretching should naturally reduce the frequency of the light and increase its wavelengths(red shift). This works much like tossing a stone into a pond. The farther the ripples spread, the more energy they lose, until at last they are no longer ripples at all.

Thus, Red shift is not necessarily a result of expanding space time, but rather a result of energy of the light waves being "spread out" and stretched into vast regions of space. On a local scale, this change would be too small to be detected, but if you were trying to describe objects very far away, the inverse square law of forces quickly takes over.

For an object 1000Ly distant, if you moved that same object to 100,000Ly distant, it would be spreading its light waves over 10,000 times the surface of space that intersects the viewer.

For the same object being 1 million LY distant, the number goes up to one million times as much surface area intersecting the same viewer.

When we spread a wave over a larger area, that wave must lose energy levels per unit surface area, just as the ripple in the pond. This is manifest in the form of Red Shift.

Thus distant objects are potentially quadratically closer and younger than they have been calculated to be, and they are not moving away (at least universally.)

Alizee
Nov 05, 2008
This comment has been removed by a moderator.
jeffsaunders
1 / 5 (4) Nov 06, 2008
I am most with you on this one Quantum_Conundrum.
Atomsview
3 / 5 (1) Nov 06, 2008
Antimatter gravity is not known. Repulsion or attraction by earth's gravity will be tested soon,see GOOGLE: antihydrogen gravity ALPHA DAPNIA CERN
QubitTamer
1.8 / 5 (6) Nov 06, 2008
As long as we stupidly believe that the entire universe is homogenous in composition, density, gravitational interaction, etc then we will never find mathematical models to explain it. As soon as we realize that the universe is 'lumpy' and our planet happens to be in some kind of 'bubble' of physical laws and there are billions of other bubbles / knobs / protrusions where physical laws like the speed of light vary then we will begin making progress.

Think: If you accept the big bang, nevermind the mystery of what could have been going on before it or what caused it, would an explosion of that magnitude REALLY remain spherical for long with a uniform distribution of quantum matter and effects or would there be islands / bubbles of coalesced particles which would make these laws and constants we rely on nothing more than variables which change over time and distance...
Noumenon
5 / 5 (1) Nov 06, 2008
....This stretching should naturally reduce the frequency of the light and increase its wavelengths(red shift).
@Quantum,

Are you confusing intensity with frequency?
Yes
5 / 5 (3) Nov 09, 2008
This stretching should naturally reduce the frequency of the light and increase its wavelengths(red shift).

Where would the disappearing energy of the photon packets go? Would that be radiated off in heat somehow? I find it quite unlikely.
Noumenon
5 / 5 (1) Nov 11, 2008
The frequency would not decrease because of the spreading out into space. It would only decrease (increase in wavelength) as a result of the relative difference in velocity between observer and oscillator. The observed frequency would be;

w=(w0*sqrt(1-v^2/c^2)/(1-v/c), where w0 is the natural frequency.
HenisDov
1 / 5 (2) Apr 20, 2009
Gravity Limits Link Ultracold And Superhot,

Our Inability To Create Singularity





A. From "Strings Link the Ultracold with the Superhot"

http://http://www.scienc...Superhot



A new truth always has to contend with many difficulties,%u201D the German physicist Max Planck said decades ago. %u201CIf it were not so, it would have been discovered much sooner.%u201D





B. IMO gravity is attempted reversal of inflation



To me, a simple uninformed one, E=mc^2 is a derived formula, whereas E=Total[m(1 plus D)] is a commonsensical descriptive concept.



I intuitively regard both the ultracold and superhot liquids as being in a confined space and "striving but unable" to overcome D, to render D=0.



I also intuitively regard accelerated collisions smashups as attempted "reverse inflations" in the sense that Newton's law of universal gravitation seems to me as "reverse inflation".





Dov Henis

(Comments From The 22nd Century)