Chapter 1: Unveiling the New Dark Matter Map

Recent advancements have led to the creation of a groundbreaking mass map that reinforces Einstein’s theories, potentially intensifying the ongoing "crisis in cosmology."

This innovative map, while primarily a mass representation, is being referred to as the "new dark matter map" because around 80% of the universe's mass remains invisible. In this depiction, the orange areas indicate regions of higher mass density, whereas the purple areas signify lower density. The lighter band illustrates the interference from dust within our Milky Way, which has been measured by the Planck satellite, obscuring deeper cosmic observations. Credit: ACT Collaboration.

"The iconic blue and yellow image of the cosmic microwave background (CMB) captures a moment from the universe approximately 13 billion years ago, providing insights into all subsequent epochs," explains Suzanne Staggs, director of ACT and Princeton's Henry DeWolf Smyth Professor of Physics.

The Atacama Cosmology Telescope was instrumental in producing this map, which outlines the mass situated between us and the Big Bang, using the CMB as a "backlight."

To clarify, the CMB represents the universe's first light emitted during a pivotal moment of rapid expansion post-Big Bang. This residual radiation has traveled for billions of years, allowing us to witness the formation of stars, galaxies, and clusters. The gravitational influence of these colossal entities bends the path of CMB light, akin to how light would pass through a textured fabric with uneven surfaces.

"The effect is reminiscent of a silhouette, but rather than just a flat outline, we see textures and structures of dark matter, as if light were filtering through a fabric with numerous lumps," states Staggs.

At the lower left corner, we see the latest dark matter visualization created by the ACT team, illustrating all matter along the CMB light's path. Credit: Lucy Reading-Ikkanda, Simons Foundation.

"We have utilized light distortions resulting from the Big Bang to create this new mass map," remarks Mathew Madhavacheril, a former Princeton postdoc and current assistant professor in physics and astronomy at the University of Pennsylvania.

The data gathered from the Atacama Cosmology Telescope focused on light emitted when the universe was merely 380,000 years old (CMB). This analysis reveals how dark matter formations along the path to the Big Bang have influenced the CMB's journey over 13.8 billion years.

The warps and distortions observed in the CMB are indicative of the "clumpiness" of dark matter and lend support to the standard cosmological model (ΛCDM) derived from Einstein’s theory of general relativity. However, alternative theories like Modified Newtonian Dynamics (MoND) challenge the dark matter hypothesis. The absence of a definitive dark matter candidate raises questions about the existence of this phenomenon, meaning that indirect mappings of dark matter do not necessarily signify a seismic shift in physics.

"Our findings contribute new perspectives to an ongoing debate dubbed 'The Crisis in Cosmology,'" comments co-author Blake Sherwin, a Ph.D. graduate from Princeton and professor of cosmology at the University of Cambridge, where he leads a substantial team of ACT researchers.

Chapter 2: The Crisis in Cosmology

The first video titled "Dark Matter Physics in the Sky - Dr. Ethan Nadler" explores the implications of dark matter mapping on our understanding of the universe and addresses the associated challenges.

The new mass map is poised to significantly contribute to the ongoing discourse surrounding the "crisis in cosmology," particularly concerning the universe's age. Determining the universe's age requires an understanding of its expansion history, which can be quantified using the Hubble constant (H0). There exist two methodologies for measuring this constant: the "distance ladder" method, which examines standard candles and redshift, and the "early universe" method, which interprets data from the CMB. The discrepancy between these methods, which results in a 5.6 (km/s)/Mpc difference, is referred to as Hubble tension, leading to conflicting age estimates of the universe.

H0 = 73.24 ± 1.74 (km/s)/Mpc (distance ladder method)

H0 = 67.4 ± 0.5 (km/s)/Mpc (early universe method)

The CMB is renowned for its precise measurements of the universe's primordial state. These lensing maps, which detail the universe's subsequent evolution, provide an abundance of data. "We now possess a second primordial map of the universe, offering an extraordinary opportunity to synthesize these diverse data sets," Staggs states. "Our map encompasses all dark matter from the Big Bang, while other maps focus on a later epoch, allowing for a comparative analysis of structural growth in the universe."

This intriguing aspect of the study reveals that while the new map includes all dark matter up to the Big Bang, its results pose an alternative to the early universe method. The true implications of this dark matter map will unfold over time, potentially corroborating or contrasting with existing interpretations of the CMB.

Recent studies have bolstered the late universe method, which was elaborated in a 2023 Astronomy & Astrophysics publication. This research yielded a highly accurate calibration using Cepheid stars, refining the measurement of cosmic expansion to within ±0.9%, thereby lending strong support to the late universe methodology.

While the team anticipates that this new dark matter map may help mitigate the "crisis in cosmology," each method yielding differing measurements reaffirms its validity independently. This raises the question: which measurement is correct?

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The second video, "Mapping the Universe: Dark Energy, Black Holes, and Gravity – with Chris Clarkson," delves into the complexities of cosmic structures and their implications for our understanding of the universe.