Category: signal

Could DAMA’s ‘Dark Matter Signal’ Simply Be Poorly Analyzed Noise?

“To date, DAMA has shown that a non-constant signal exists with 13-sigma significance. (5-sigma is normally the gold standard for experimental physics.) If they made their overall event rate publicly available, it would be easy to check — even just by eye — whether the modulation is real or whether there’s a noise floor that’s changing over time. Until they release their data, we cannot have any confidence that they haven’t fallen through this loophole.

As Nicola Rossi pointed out, “if the background is either increasing or decreasing an artificial modulation is introduced in the residual rate and it interferes with a possible real modulation.” Whether DAMA’s signal is real, and how strong it is if it is real, cannot be established without independently checking this very basic piece of raw data. If the data shows an annual growth in their noise of even just a few percent, their signal will vanish entirely.”

For around 20 years now, one and only one experiment has claimed to have directly detected a signal that would be consistent with dark matter: the DAMA collaboration. By looking for collisions with their targets that yield a specific amount of energy in their detector, they run similarly to a large number of complementary detectors. But only DAMA has seen a signal, and they have steadfastly refused to release either their raw data or their analysis pipeline, making independent verification difficult. Two attempts at verification, COSINE and ANAIS, have failed to reproduce their signal.

Earlier this month, a new paper came out contending that simply a poor analysis of their noise could mimic this signal at the full 13-sigma significance. Is DAMA too good to be true?

Hubble Catches Asteroids Photobombing Ultra-Distant Galaxies

“There are a total of 20 objects seen in these fields, corresponding to 7 unique asteroids, most of which are imaged multiple times. Only 2 of them were previously known; the remainder were serendipitously discovered by Hubble. Approximately 10-to-20 hours of observing time leads to the discovery of a new asteroid, telling us something interesting about the density of asteroids at the level that Hubble’s imaging capabilities are sensitive to. As long as you’re observing a target close to the plane of the Solar System’s ecliptic, you’re bound to be polluted by these interlopers.”

There’s an old saying among astronomers: one astronomer’s noise is another astronomer’s data. If you’re trying to view the galactic center, then the interstellar medium is “noise,” but if you’re studying the interstellar medium, then that’s exactly the data you want! Well, a team studying the massive galaxy cluster Abell 370 got to do a very long, deep-exposure image of both that cluster and its parallel field, accumulating a total of nearly 100 hours of observing time. As it so happens, this cluster happens to lie very close to the Solar System’s ecliptic plane, meaning that objects in the asteroid belt occasionally cross through Hubble’s field-of-view. Although it would take tens of millions of Hubble images to cover the entire sky, there are millions of asteroids bright enough for Hubble to see, and a few of them “photobombed” both the galaxy cluster and its parallel field.

We can produce cleaned images without them in the end, but the extragalactic astronomer’s noise is the asteroid hunter’s data! Come get the story, and see the remarkable photos, today!

How Uncertain Are LIGO’s First Gravitational Wave Detections?

“What’s vital to understand is that no one is claiming LIGO is wrong, but rather that one team is claiming that perhaps LIGO has room for improvement in their analysis. And this is a very real danger that has plagued experimental physicists and astronomical observers for as long as those scientific fields have existed. The issue is not that LIGO’s results are in doubt, but rather that LIGO’s analysis may be imperfect.”

Three times now, the LIGO collaboration has produced very strong evidence that black hole pairs, from across the Universe, inspiraled and merged, producing gravitational waves. The twin LIGO detectors in Hanford, WA and Livingston, LA each detected these signals, and the signals were correlated between both detectors. For the first time ever (and the second, and the third), we had directly detected gravitational waves. But last month, a team of independent scientists from Denmark attempted to reproduce LIGO’s analysis, and noticed something that shouldn’t be there: noise correlations between the two detectors. Noise is supposed to be uncorrelated, and yet the noise correlations peaked at the moment of the inspiral-and-merger event. It doesn’t mean that gravitational waves aren’t real, but it does mean that LIGO, perhaps, has room for improvement.

This has been a very controversial topic over the past few weeks; come learn where we are in this saga of science playing out in real-time!