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Physicist advances a radical theory of gravity

Erik Verlinde has been compared to Einstein for completely rethinking the nature of gravity.

Erik Verlinde

Photo by Willeke Duijvekam
  • The Dutch physicist Erik Verlinde's hypothesis describes gravity as an "emergent" force not fundamental.
  • The scientist thinks his ideas describe the universe better than existing models, without resorting to "dark matter".
  • While some question his previous papers, Verlinde is reworking his ideas as a full-fledged theory.


The Dutch theoretical physicist Erik Verlinde is no stranger to big ideas. His 2009 hypothesis about gravity earned him comparisons to Einstein for its complete rethinking of what gravity could be. Verlinde proposed that gravity was not a fundamental force of nature but rather emerged out of the interactions of information that fills the universe. He also didn't think there was such a thing as "dark matter" – a useful construct which is supposedly taking up 27% of the known universe (but is yet to be observed). Now, in a new interview, Verlinde reveals he is taking steps towards conceptualizing his groundbreaking ideas in a full-fledged theory.

As reported by the Netherlands Organization for Scientific Research (NWO), Verlinde understands why many had trouble accepting his original proposal. After all, the previous leading explanations of gravity have been by Newton, who saw it as an invisible pulling force, and Einstein, who conceived of it as a curvature of space-time by mass and energy.

In Verlinde's view, based on string theory, quantum information theory and the physics of black holes, gravity is an "entropic" force that comes into existence as a result of "information associated with the positions of material bodies," as he wrote in his 2011 paper. What drives gravity is the quantum entanglement of tiny bits of spacetime information.

Ten years after publishing his ideas in a paper that caused much discussion, both from admirers and critics, Verlinde shares that he is still fleshing them out, based on the research and advancements that have taken place since then.

"Over the past ten years, we have gradually learned a lot more about how you should talk about space and time information," said Verlinde to NWO. "I am seriously considering rewriting my story from 2009, but now formulated much more precisely. I think that could remove some of the scepticism that still exists.'­­

Verlinde: Gravity Doesn't Exist

In 2016, Verlinde's ideas were tested by a team from Leiden Observatory, which found that a key prediction of the physicist held up. They studied the lensing effect of gravitational fields that are far away from the centers of more than 33,000 galaxies and found the numbers to be consistent with what the Dutch scientist's theory showed. The only way to get these calculations to match under the prevalent gravitational theory would have been to invoke dark matter – a potential fudge factor more than fact at this point.

A 2017 study from Princeton University found against Verlinde's ideas, however, showing that they are not consistent with the observed data on the rotation velocities of dwarf galaxies.

While some have accused of Verlinde of publishing his thoughts too early, before they are packaged in a theory that explains all of the implications, the scientist thinks such naysayers don't really understand the way theoretical physics works. "You need to elaborate and test a new idea step-by-step," he explains, adding "We must find the correct formulations and techniques.'

Scientists like the theoretician Koenraad Schalm from Leiden University defend Verlinde, saying that "Contrary to the sceptics' opinions, Verlinde's work is definitely taken seriously". In fact, Verlinde, who is the winner of the Spinoza Prize, has been cited over 700 times by other scientists.

The physicist himself feels his overall thesis that information is the fundamental building mechanism of the universe is becoming more accepted. Perhaps his long-awaited new paper on the subject can bring it to an even stronger position amidst the main physics ideas of our time.

Dark matter and dark energy explained | Erik Verlinde

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What if Middle-earth was in Pakistan?

Iranian Tolkien scholar finds intriguing parallels between subcontinental geography and famous map of Middle-earth

Could this former river island in the Indus have inspired Tolkien to create Cair Andros, the ship-shaped island in the Anduin river?

Image: Mohammad Reza Kamali, reproduced with kind permission
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  • J.R.R. Tolkien himself hinted that his stories are set in a really ancient version of Europe.
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Giant whale sharks have teeth on their eyeballs

The ocean's largest shark relies on vision more than previously believed.

An eight-metre-long Whale shark swims with other fish at the Okinawa Churaumi Aquarium on February 26, 2010 in Motobu, Okinawa, Japan.

Photo by Koichi Kamoshida/Getty Images
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  • Japanese researchers discovered that the whale shark has "tiny teeth"—dermal denticles—protecting its eyes from abrasion.
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A massive star has mysteriously vanished, confusing astronomers

A gigantic star makes off during an eight-year gap in observations.

Image source: ESO/L. Calçada
Surprising Science
  • The massive star in the Kinsman Dwarf Galaxy seems to have disappeared between 2011 and 2019.
  • It's likely that it erupted, but could it have collapsed into a black hole without a supernova?
  • Maybe it's still there, but much less luminous and/or covered by dust.

A "very massive star" in the Kinman Dwarf galaxy caught the attention of astronomers in the early years of the 2000s: It seemed to be reaching a late-ish chapter in its life story and offered a rare chance to observe the death of a large star in a region low in metallicity. However, by the time scientists had the chance to turn the European Southern Observatory's (ESO) Very Large Telescope (VLT) in Paranal, Chile back around to it in 2019 — it's not a slow-turner, just an in-demand device — it was utterly gone without a trace. But how?

The two leading theories about what happened are that either it's still there, still erupting its way through its death throes, with less luminosity and perhaps obscured by dust, or it just up and collapsed into a black hole without going through a supernova stage. "If true, this would be the first direct detection of such a monster star ending its life in this manner," says Andrew Allan of Trinity College Dublin, Ireland, leader of the observation team whose study is published in Monthly Notices of the Royal Astronomical Society.

So, em...

Between astronomers' last look in 2011 and 2019 is a large enough interval of time for something to happen. Not that 2001 (when it was first observed) or 2019 have much meaning, since we're always watching the past out there and the Kinman Dwarf Galaxy is 75 million light years away. We often think of cosmic events as slow-moving phenomena because so often their follow-on effects are massive and unfold to us over time. But things happen just as fast big as small. The number of things that happened in the first 10 millionth of a trillionth of a trillionth of a trillionth of a second after the Big Bang, for example, is insane.

In any event, the Kinsman Dwarf Galaxy, or PHL 293B, is far way, too far for astronomers to directly observe its stars. Their presence can be inferred from spectroscopic signatures — specifically, PHL 293B between 2001 and 2011 consistently featured strong signatures of hydrogen that indicated the presence of a massive "luminous blue variable" (LBV) star about 2.5 times more brilliant than our Sun. Astronomers suspect that some very large stars may spend their final years as LBVs.

Though LBVs are known to experience radical shifts in spectra and brightness, they reliably leave specific traces that help confirm their ongoing presence. In 2019 the hydrogen signatures, and such traces, were gone. Allan says, "It would be highly unusual for such a massive star to disappear without producing a bright supernova explosion."

The Kinsman Dwarf Galaxy, or PHL 293B, is one of the most metal-poor galaxies known. Explosive, massive, Wolf-Rayet stars are seldom seen in such environments — NASA refers to such stars as those that "live fast, die hard." Red supergiants are also rare to low Z environments. The now-missing star was looked to as a rare opportunity to observe a massive star's late stages in such an environment.

Celestial sleuthing

In August 2019, the team pointed the four eight-meter telescopes of ESO's ESPRESSO array simultaneously toward the LBV's former location: nothing. They also gave the VLT's X-shooter instrument a shot a few months later: also nothing.

Still pursuing the missing star, the scientists acquired access to older data for comparison to what they already felt they knew. "The ESO Science Archive Facility enabled us to find and use data of the same object obtained in 2002 and 2009," says Andrea Mehner, an ESO staff member who worked on the study. "The comparison of the 2002 high-resolution UVES spectra with our observations obtained in 2019 with ESO's newest high-resolution spectrograph ESPRESSO was especially revealing, from both an astronomical and an instrumentation point of view."

Examination of this data suggested that the LBV may have indeed been winding up to a grand final sometime after 2011.

Team member Jose Groh, also of Trinity College, says "We may have detected one of the most massive stars of the local Universe going gently into the night. Our discovery would not have been made without using the powerful ESO 8-meter telescopes, their unique instrumentation, and the prompt access to those capabilities following the recent agreement of Ireland to join ESO."

Combining the 2019 data with contemporaneous Hubble Space Telescope (HST) imagery leaves the authors of the reports with the sense that "the LBV was in an eruptive state at least between 2001 and 2011, which then ended, and may have been followed by a collapse into a massive BH without the production of an SN. This scenario is consistent with the available HST and ground-based photometry."

Or...

A star collapsing into a black hole without a supernova would be a rare event, and that argues against the idea. The paper also notes that we may simply have missed the star's supernova during the eight-year observation gap.

LBVs are known to be highly unstable, so the star dropping to a state of less luminosity or producing a dust cover would be much more in the realm of expected behavior.

Says the paper: "A combination of a slightly reduced luminosity and a thick dusty shell could result in the star being obscured. While the lack of variability between the 2009 and 2019 near-infrared continuum from our X-shooter spectra eliminates the possibility of formation of hot dust (⪆1500 K), mid-infrared observations are necessary to rule out a slowly expanding cooler dust shell."

The authors of the report are pretty confident the star experienced a dramatic eruption after 2011. Beyond that, though:

"Based on our observations and models, we suggest that PHL 293B hosted an LBV with an eruption that ended sometime after 2011. This could have been followed by
(1) a surviving star or
(2) a collapse of the LBV to a BH [black hole] without the production of a bright SN, but possibly with a weak transient."

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