A ‘Fifth Force’ May Alter Gravity at Cosmic Scales

Radical new research is attempting to characterize the properties of a fifth force that disrupts the predictions general relativity makes outside our own galaxy, on cosmic-length scales. University of Pennsylvania astrophysicist Bhuvnesh Jain, says the nature of gravity is the question of a lifetime. As scientists have been able to see farther and deeper into the universe, the laws of gravity have been revealed to be under the influence of an unexplained force.

Two branches of theories have sprung up, each trying to fill its gaps in a different way. One branch — dark energy — suggests that the vacuum of space has an energy associated with it and that energy causes the observed acceleration. The other falls under the umbrella of “scalar-tensor” gravity theories, which effectively posits a fifth force (beyond gravity, electromagnetism and the strong and weak nuclear forces) that alters gravity on cosmologically large scales.

“These two possibilities are both radical in their own way,” Jain said. “One is saying that general relativity is correct, but we have this strange new form of energy. The other is saying we don’t have a new form of energy, but gravity is not described by general relativity everywhere.”

Jain’s research is focused on the latter possibility; he is attempting to characterize the properties of this fifth force that disrupts the predictions general relativity makes outside our own galaxy, on cosmic length scales.

via A ‘Fifth Force’ May Alter Gravity at Cosmic Scales.

Does Antimatter Fall Up or Down?

The atoms that make up ordinary matter fall down, so do antimatter atoms fall up? Do they experience gravity the same way as ordinary atoms, or is there such a thing as antigravity?

These questions have long intrigued physicists, says Joel Fajans of the U.S. Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab), because “in the unlikely event that antimatter falls upwards, we’d have to fundamentally revise our view of physics and rethink how the universe works.”

So far, all the evidence that gravity is the same for matter and antimatter is indirect, so Fajans and his colleague Jonathan Wurtele, both staff scientists with Berkeley Lab’s Accelerator and Fusion Research Division and professors of physics at the University of California at Berkeley – as well as leading members of CERN’s international ALPHA experiment – decided to use their ongoing antihydrogen research to tackle the question directly. If gravity’s interaction with anti-atoms is unexpectedly strong, they realized, the anomaly would be noticeable in ALPHA’s existing data on 434 anti-atoms.

The first results, which measured the ratio of antihydrogen’s unknown gravitational mass to its known inertial mass, did not settle the matter. Far from it. If an antihydrogen atom falls downward, its gravitational mass is no more than 110 times greater than its inertial mass. If it falls upward, its gravitational mass is at most 65 times greater.

What the results do show is that measuring antimatter gravity is possible, using an experimental method that points toward much greater precision in future. They describe their technique in the April 30, 2013 edition of Nature Communications.

How to measure a falling anti-atom

ALPHA creates antihydrogen atoms by uniting single antiprotons with single positrons (antielectrons), holding them in a strong magnetic trap. When the magnets are turned off, the anti-atoms soon touch the ordinary matter of the trap’s walls and annihilate in flashes of energy, pinpointing when and where they hit. In principle, if the experimenters knew an anti-atom’s precise location and velocity when the trap is turned off, all they’d have to do is measure how long it takes to fall to the wall.

ALPHA’s magnetic fields don’t turn off instantly, however; almost 30-thousandths of a second pass before the fields decay to near zero. Meanwhile flashes occur all over the trap walls at times and places that depend on the anti-atoms’ detailed but unknown initial locations, velocities, and energies.

Wurtele says, “Late-escaping particles have very low energy, so gravity’s influence is more apparent on them. But there were very few late escaping anti-atoms; only 23 of the 434 escaped after the field had been turned off for 20-thousandths of a second.”

Fajans and Wurtele worked with their ALPHA colleagues and with Berkeley Lab associates, UC Berkeley lecturer Andrew Charman and postdoc Andre Zhmoginov, to compare simulations with their data and separate gravity’s effects from those of magnetic field strength and particle energy. Much statistical uncertainty remained.

“Is there such a thing as antigravity? Based on free-fall tests so far, we can’t say yes or no, ” says Fajans. “This is the first word, however, not the last.”

ALPHA is being upgraded to ALPHA-2, and precision tests may be possible in one to five years. The anti-atoms will be laser-cooled to reduce their energy while still in the trap, and the magnetic fields will decay more slowly when the trap is turned off, increasing the number of low-energy events. Questions physicists and nonphysicists have been wondering about for more than 50 years will be subject to tests that are not only direct but could be definitive.

via Does Antimatter Fall Up or Down? « Berkeley Lab News Center.

How Fat is Schrödinger’s Cat?

In recent years physicists have been placing ever-larger objects into states of quantum superposition – the curious state that Schrödinger’s cat finds itself in. Now, researchers in Germany have devised a way of quantifying just how macroscopic those objects are and how much ground still needs to be made up before cats and other familiar items can be held in two or more quantum states at the same time.

Check it out here on the IOP Physics News site

The Importance of Science Fiction for Science Fact


Over the last few years, it has become overwhelmingly obvious to me, that the majority of the Scientific community, has become somewhat “jaded” towards any suggestion that is not 100% scientifically provable TODAY. By no means does this cover all science folk, but It worries me that a number of ‘eminently public’ scientists shun and mock any speculative suggestion made as rubbish.

Now, before we continue, let me just assert. As a budding member of the scientific world, I am fully aware of the need for any scientific theory to have results to back it up. BUT, lets just be a little realistic here. Without “speculation” there would be very few of the scientific discoveries that we have today.

As I stated before, we cannot tar the entire community with the same brush. For instance, the greatly eminent physicists Michio Kaku (one of the great heavy weights in physics today) along with Stephen Hawking (possibly THE heavy weight) are both prolific dreamers. Michio has written a whole library of books, where the “Physics of Tomorrow” are considered. From tri-corders to time travel. Without this sci-fi, head in the clouds approach to physics, the field would be a deadly boring world of mundane calculations and repetitive observation.

Stephen Hawking recorded a whole series based on physics principals that he dreams about, to the extent where he supposedly set up a dinner party for time travellers. Sending out invitations so that they might, in distant time be found by time travellers. Who would appear, at that the set time and date for this temporal gathering with canapés.

One of my most loved topics of thought, dream and conversation is time travel. Something that is greatly studied at this point in time. There are a great number of theories, papers and books all on this fascinating topic. The possibilities are endless. From time dilation at the event horizon of a black hole, to the microscopic wormholes of the quantum foam at Plank scales.1 Conversation of paradox and loopholes (the most famous of the time travel paradox is the grandfather paradox which postulates that, you travel back in time to kill your own grandfather, so that you were never born. However, that very action means that you do not exist too travel back to make the kill…..and therefore time is stuck in what becomes known as a causal loop) I have spent hours of my life, trying to unpick causal loops and paradox to see what effect specific actions would have on the overall temporal outcome. Needless to say, its normally the same outcome.

That was somewhat of a wormhole digression, so back to the original geodesic.

From the very earliest days of the science fiction genre, those of Jules Verne and his 1865 novel From the Earth to the Moon humanity has dreamt of things that were (at that point) technologically impossible. THIS WILL NOT ALWAYS BE THE CASE, as Joules proved (well, you know what I mean). He was a man far before his time. Yet, over a century on, people HAVE walked on the moon, and we are well on the way to walking on Mars. The Star Trek franchise is yet another science fiction series, from which we are now taking inspiration. Walk into the medical bay on the Enterprise and you would be sure to spot a tri-corder. Well, now there is such a device, being trialed in the US. Warp Drive is yet another of the Trek Tech which is taking on a physical presence in today’s physics research. (For more on this see the Wiki for Alcubierre Drive )

Scientists in the public eye, especially, need to actually get the younger generations to dream, to speculate. For only then, will the scientific field progress and grow.

  1. I note here that the use of wormholes doesn’t technically relate to “time travel” in the same sense of the time dilation of black hole theory. However, the use of the highly speculative wormhole would effectively cut journey times from one side of the universe to the other. So it’s more of a time saving, than a time travel.

Astrophysics: Fire in the hole! : Nature News & Comment

In March 2012, Joseph Polchinski began to contemplate suicide — at least in mathematical form. A string theorist at the Kavli Institute for Theoretical Physics in Santa Barbara, California, Polchinski was pondering what would happen to an astronaut who dived into a black hole. Obviously, he would die. But how?

According to the then-accepted account, he wouldn’t feel anything special at first, even when his fall took him through the black hole’s event horizon: the invisible boundary beyond which nothing can escape. But eventually — after hours, days or even weeks if the black hole was big enough — he would begin to notice that gravity was tugging at his feet more strongly than at his head. As his plunge carried him inexorably downwards, the difference in forces would quickly increase and rip him apart, before finally crushing his remnants into the black hole’s infinitely dense core.

via Astrophysics: Fire in the hole! : Nature News & Comment.