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Category: cosmology – Page 66

The expansion of the universe has been a well-established fact of physics for almost a century. By the turn of the millennium the rate of this expansion, referred to as the Hubble constant (H 0), had converged to a value of around 70 km s –1 Mpc –1. However, more recent measurements have given rise to a tension: whereas those derived from the cosmic microwave background (CMB) cluster around a value of 67 km s –1 Mpc –1, direct measurements using a local distance-ladder (such as those based on Cepheids) mostly prefer larger values around 73 km s –1 Mpc –1. This disagreement between early-and late-universe measurements, respectively, stands at the 4–5 σ level, thereby calling for novel measurements.

One such source of new information are large galaxy surveys, such as the one currently being performed by the Dark Energy Spectroscopic Instrument (DESI). This Arizona-based instrument uses 5,000 individual robots that optimise the focal plane of the detector to allow it to measure 5,000 galaxies at the same time. The goal of the survey is to provide a detailed 3D map, which can be used to study the evolution of the universe by focussing on the distance between galaxies. During its first year of observation, the results of which have now been released, DESI has provided a catalogue of millions of objects.

Small fluctuations in the density of the early universe resulted not only in signatures in the CMB, as measured for example by the Planck probe, but also left imprints in the distribution of baryonic matter. Each over-dense region is thought to contain dark matter, baryonic matter and photons. The gravitational force from dark matter on the baryons is countered by radiation pressure from the photons. From the small over-densities, baryons are dragged along by photon pressure until these two types of particles decoupled during the recombination era. The original location of the over-density is surrounded by a sphere of baryonic matter, which typically is at a distance referred to as the sound horizon. The sound horizon at the moment of decoupling, denoted r d, leaves an imprint that has since evolved to produce the density fluctuations in the universe that seeded large-scale structures.

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“… living systems evolve to exploit any aspect of physics that enables exploration of all possible ‘fitness landscapes’.”

Indeed!

In 1990, within the intellectual haven of Haverford College, I embarked on a transformative academic journey into biophysics – the captivating intersection of physics and biology.

It was during this time that I delved into the tantalising notion of quantum mechanics operating within living organisms.

Continue reading “This bold new theory of ‘quantum weirdness’ could rewrite the story of evolution” | >

It’s possible that our universe is the antimatter counterpart of an antimatter universe that existed earlier in time than the Big Bang. So claim physicists in Canada, who have devised a new cosmological model positing the existence of a “antiuniverse” which, paired to our own, preserves a fundamental rule of physics called CPT symmetry. Though many details in their theory still need to be worked out, the researchers claim that it naturally explains the existence of dark matter.

According to standard cosmological models, the universe—which consists of space, time, and mass/energy—exploded into being about 14 billion years ago. Since then, it has expanded and cooled, causing subatomic particles, atoms, stars, and planets to gradually form.

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Nvidia CEO Jensen Huang has unveiled plans to build a next-generation AI platform called Rubin — named after astronomer Vera Rubin.

Huang made the announcement at an address ahead of the COMPUTEX technology convention in Taipei, which starts on June 4.

According to the company’s blog, Huang spoke to nearly 6,500 industry executives, reporters, entrepreneurs, gamers, inventors, and AI fans who had congregated at the glass-domed National Taiwan University Sports Center in Taipei.

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To use the Instagram Chandra experience, search for the “NASAChandraXray” account. Select the effects options (the tab that looks like three four-pointed stars) and select the one you want. Then, you can either save the effect to your camera and apply it to your stories, or you can select the “Try it” button for instant access.

Related: Peer inside remnants of an 800-year-old supernova and see a ‘zombie’ star

“We are excited to bring data from the universe down to Earth in this way,” Kimberly Arcand, Chandra X-ray Center visualization and emerging technology scientist, said in a statement. “Enabling people to access cosmic data on their phones and through AR brings Chandra’s amazing discoveries literally right to your fingertips.”

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The Dark Energy Spectroscopic Instrument (DESI) is a robotic instrument and spectrograph mounted on the Mayall Telescope in Kitt Peak, Arizona. The DESI collaboration aims primarily to understand the elusive Dark Energy. This is an energy of unknown source causing the Universe to accelerate in its expansion; this accelerating expansion is not predicted to occur for a universe that is filled with just ordinary matter and radiation (some more detail can be seen in this Astrobite). Since we still know so little about Dark Energy, a large galaxy survey can allow us to explore the history of the expansion of the Universe in more detail. The DESI instrument has 5,000 individual optical fibres controlled by robots that allow it to measure individual spectra of up to 5,000 galaxies in just a mere 20 minutes! Due to this design, and an observing program that optimises targets in the sky based on observing conditions, the survey will measure spectra of up to 35 million galaxies over 5 years. This will allow DESI to perform precise cosmological measurements, as a great volume of space and number of galaxies can be probed, and noise in the data products is reduced. This bite looks at the cosmology results from the collaboration’s analysis of the recently released Year 1 Data (YR1), in particular, via a signal that can be seen in the data known as Baryon Acoustic Oscillations.

DESI tracers

For the cosmological results in this work DESI uses information from various different ‘tracers’ – galaxies that trace the Large Scale Structure of the Universe. These consist of low redshift bright galaxies (BGS) that are measured when the moon lights the sky (and thus dimmer galaxies are less visible), and higher redshift galaxies measured during the dark time. The dimmer objects include luminous red galaxies (LRGs) which are elliptical galaxies that are extremely bright, emission line galaxies (ELGs) which are younger galaxies with emission line features in their spectra, and quasars (QSOs) which are very distant and bright galaxies that contain active galactic nuclei. The sample used also includes QSOs detected using Lyman-alpha forest measurements, or a method of tracing matter that utilises a series of absorption lines detected due to light from distant QSOs passing through neutral hydrogen in the space between us and the distant galaxies.

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The accelerated expansion of the present universe, believed to be driven by a mysterious dark energy, is one of the greatest puzzles in our understanding of the cosmos. The standard model of cosmology called Lambda-CDM, explains this expansion as a cosmological constant in Einstein’s field equations. However, the cosmological constant itself lacks a complete theoretical understanding, particularly regarding its very small positive value.

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