By Jon Lackman Posted 10.12.2010 at 5:11 pm 21 Comments

Waning Influence iStock

No one has ever quite nailed down gravity. Newton saw that bodies appeared to attract each other even at a great distance, and from this observation was able to construct a mathematical formula that predicted the motion of the planets with astonishing accuracy. Einstein improved on that definition by stating that massive objects attract lesser ones by bending the space around them—like how a bowling ball deforms the surface of a trampoline so that a marble will roll toward it—and based on this insight was able to construct his theory of general relativity, which proved to be even more elegant and predictive.

Erik Verlinde: Erik Verlinde says gravity isn’t a force at all.  Erik P. Verlinde
But not perfect. Einstein’s theory posits that the universe is expanding such that each object is moving away from everything else, which Hubble Space Telescope observations have confirmed. Yet for this theory to hold, it requires a far more complicated conclusion: If everything is moving apart as it goes forward in time, then at some moment everything in the universe must have been gathered into a single point.

The problem, which has challenged theorists for nearly a century, is that Einstein constructed several specific mathematical formulas from his general theory, and they have proved accurate in describing nearly everything—except the proposed origins of the universe itself. When mathematicians reverse the theory to repackage the universe as it was before the big bang, the math produces something infinitely small and dense. This “singularity” is a common sign that something in the equation is amiss. “Physicists don’t like infinite numbers because they imply a solution that isn’t very physical,” says Nikodem Poplawski, a gravitational theorist at Indiana University. But this summer, two physicists may have figured out how to bring order to Einstein’s universe.

Pedro Ferreira: Pedro Ferreira proposes modifying Einstein’s theory of relativity by limiting gravity’s pull.  Oxford University
Astrophysicists Maximo Bañados and Pedro Ferreira of the University of Oxford replaced the Einstein-Hilbert action—the equation from which all of general relativity’s other equations are derived—with a modified Born-Infeld action, which describes electromagnetism. With Born-Infeld conditions in place, Ferreira and Bañados were able to replicate Einsteinian gravity in normal situations, and they were also consistent with the conditions scientists have observed about the origins of the universe.

According to Ferreira and Bañados, gravity is not strong enough to crumple the universe’s mass into an infinitely dense point, but with the limit they placed on gravity, it could have compressed the universe into an extremely small ball.

Rather than emerging from a point, that ball may have been the densest part of an ongoing process, in which a previous universe had collapsed in on itself, “bounced” against the limits of density, and then expanded again to become our current universe. Or, after its initial growth, the universe may have paused before expanding as it does today. Future analysis of gravitational waves left over from the early universe could validate the work, Ferreira says. “Einstein’s theory is simpler,” he admits. “But sometimes the simplest idea isn’t the best one.”

“It’s a good step toward improving our understanding of gravity,” Poplawski says. But as it stands, the theory is less developed than other alternatives to Einstein’s gravity. There’s gravity in higher dimensions, gravity with extra curvature terms, and gravity coupled to a ‘chameleon field’ that makes the strength of gravity different near matter than in a vacuum. The recent appearance of so many theories may be a sign of a field on the verge of a breakthrough. Indeed, Erik Verlinde of the University of Amsterdam argues that gravity is not a force at all but rather an “emerging condition.” As he told the New York Times in July, “For me, gravity doesn’t exist.”

21 Comments

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sheblindedmewit...
10/12/10 at 6:25 pm

A ball made from a previous Universe? Doesnt that just push the problem back a level? ie. how did THAT Universe get it's start. Eventually you have to explain the "ex nihilo".

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Dirk Mcbratney
10/12/10 at 6:26 pm

Ferreira and Bañados wouldn't need M (or string) theory, then? The whole point of string theory as I'd understood it was making EM and the nuclear forces work in the same universe as gravity, but they're saying that the equations work across the board after all and all the string theory folks were just kind of wasting their time?

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ScottieD
10/12/10 at 6:55 pm

Are these people just barking or is there some science behind what they say?

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trireme
10/12/10 at 7:24 pm

There is no science here until they can make some physical predictions with this new theory. Without something to test experimentally, all these theories are just mathematical models.

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speedoflight
10/12/10 at 7:49 pm

I agree with Erik, gravity is an emerging condition, not an actual force. Gravity that we feel or observe is a by product of mass of an object and curve of space around it. The higher the axial rotation of a mass object in space, the higher gravitational value physicist observe. On the contrary, the rotation of an object combined with it's mass, create sort of a slide effect in space itself, therefore anything inside the slide effect comes crashing down, and outside that boundry seems orbiting. Simple expirement would be to a put a Watermelon and Orange in a vaccum box. Create a axial rotation of the Watermelon as the Earth and Orange as the moon. SEE WHAT IT DOES at different variations.

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Siromar
10/12/10 at 7:58 pm

@speedoflight, both melon and orange would fall to the ground due to earth's gravity... Or do you mean doing this experiment in space? Watermelons do not have enough mass to induce a gravitational force.

And this article is not news. There are dozens of different hypotheses that try to solve the problem of gravity. Does this theory offer unique predictions that can be tested? Can you at least provide a link with some basic SCIENTIFIC information regarding this idea? Is there any reason this is worth mention?

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tertertert
10/12/10 at 9:59 pm

Ferreira says. “Einstein’s theory is simpler,” he admits. “But sometimes the simplest idea isn’t the best one.”
See Occam's Razor.

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Mycellium
10/12/10 at 10:50 pm

Someone said what the hey let's throw in this EM equation and see what happens. Hey it doesn't completely blow up, Einsteins wrong again for the first time hurrah. Someone get these boys a nobel peace prize or err that other one.

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SteveMcQwark
10/12/10 at 11:22 pm

@speedoflight — Axial rotation has no impact on gravitational attraction. There is no positional boundary between falling and not falling. An object could orbit a metre above the surface of the Earth, assuming the Earth were a perfect sphere without atmosphere ;).

@Siromar — All massive objects generate a gravitational field. In the case of the watermelon and the orange, it would be very small, but it would (under ideal conditions) gradually have an effect.

@tertertert — Occam's razor states "entities must not be multiplied beyond necessity", meaning that, in formulating a theory, don't postulate the existence of things for which you don't have evidence, unless you have to. It doesn't apply to mathematical or logical complexity. It also does not serve as a way to conclusively choose between theories — this is what empirical evidence is for.

I agree that this isn't really significant unless their model works for empirical results where general relativity does not. Otherwise, back of the line, there's umpteen contenders ahead of you.

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tcolguin
10/13/10 at 12:06 am

I disagree with this statement "Einstein improved on that definition by stating that massive objects attract lesser ones by bending the space around them"

I'm pretty sure Einstein didn't say that because it is not just massive to lesser. If that was true then they wouldn't be finding planets by watching the wobble of the Sun.

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tcolguin
10/13/10 at 12:07 am

Opps. Meant "wobble of the star".

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poopshoop
10/13/10 at 10:35 am

gravity isnt strong enough to compress all the star stuff into a tiny ball?

what about black holes?

imagine the universe slowly imploding and galaxies colliding, getting bigger and denser. the more massive, the stronger the pull. is it the cause or is there just a correlation? who knows? but if gravity isn't the force behind this, then Verlinde is saying there's another force at work. then we'll discover that it's pretty much similar to, if not the same as, our old classical definition of gravity with a cherry on top.

AND YOU KNOW WHAT? i bet we'll just call THAT gravity.

unless he's got proof, he's no different from a medieval priest

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Ivan Malagurski
10/13/10 at 11:38 am

Good read, but I think gravity still has a chance...
Ivan Malagurski

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gizmowiz
10/13/10 at 12:09 pm

Space is comprised of an infinite number of universes, each of which is a product of a black hole. Our rapidly expanding universe is a case in point having exited a black hole as a 'singularity' and is now expanding within the 'time clock' of OUR universe which is separate from each and every other universe out there.

As black holes suck in matter to a singularity it's spit back out into new universes such as our own that we can 'see'.

The dark matter we can't find? It's other universes close by that we cannot see because they exist in another universe but which do have some affect via the weak gravitational force. So scientists will have to find a way to tap into adjacent universes if they ever hope to find the real source of dark matter.

Of course, that's only my theory ha.

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friedguy
10/13/10 at 12:50 pm

Question:
Could the Big Bang have caused particles to move away from the point of impact at speeds very near or at the speed of light?

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Tode
10/13/10 at 2:18 pm

@poopshoop They said that using Einstein's theory all matter would have come from a single point infinitely small. But with this new equation, it begins as a small ball of super dense matter. Read before posting imo.

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V3RTIGO
10/13/10 at 8:20 pm

XD, after hearing something about the guy who believed "gravity" doesn't exist, and finally hearing the truth on PopSci makes me laugh, i wonder where they received their exaggerated and proportionate information, oh, yeah, the 5 O'clock news :P

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bunkertank
10/14/10 at 5:33 am

Maybe there was no beginning... maybe we have been swinging back and forth from one limit to the other small ball to big ball, forever... http://www.bieres-et-vin.com

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Moezart
10/14/10 at 1:55 pm

Ok question,

What happens when you feed the three body problem into the equation?

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samir12
10/24/10 at 10:33 pm

Thanks for sharing. Nice article post. Really enjoyed reading. www.homewebjobs.com



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