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[A]n unseen ‘mirror world’ of particles that interacts with our world only via gravity might be the key to solving a major puzzle in cosmology today – the Hubble constant problem. The Hubble constant is the current rate of expansion of the universe. Predictions for this rate — from cosmology’s standard model — are significantly slower than the rate found by our most precise local measurements. This discrepancy is one that many cosmologists have been attempting to solve by changing our current cosmological model. The challenge is to do so without ruining the agreement between standard model predictions and many...

Dark Matter Still Missing After Many Decades ... "Big Bang theory in trouble". November 22, 2019 | Jerry Bergman All the proposed candidates for mysterious, unknown stuff have failed to materialize, putting Big Bang theory in trouble. by Jerry Bergman, PhD The cover story of the November 16-22 New Scientist announced prominently on the cover: “DARK MATTER: We still haven’t found it. Our theories are falling apart. Is it time to rethink the universe?” [1] Dan Hooper, author of the cover story, is worried, because Dark Matter theory is a necessary support for the Big Bang. Thus, the Big Bang...

These galaxies are selected from a Hubble Space Telescope program to measure the expansion rate of the universe, called the Hubble constant. The value is calculated by comparing the galaxies' distances to the apparent rate of recession away from Earth (due to the relativistic effects of expanding space). By comparing the apparent brightnesses of the galaxies' red giant stars with nearby red giants, whose distances were measured with other methods, astronomers are able to determine how far away each of the host galaxies are. This is possible because red giants are reliable milepost markers because they all reach the same...

There’s a crisis brewing in the cosmos. Measurements over the past few years of the distances and velocities of faraway galaxies don’t agree with the increasingly controversial “standard model” of the cosmos that has prevailed for the past two decades. Astronomers think that a 9 percent discrepancy in the value of a long-sought number called the Hubble Constant, which describes how fast the universe is expanding, might be revealing something new and astounding about the universe. The cosmos has been expanding for 13.8 billion years and its present rate of expansion, known as the Hubble constant, gives the time elapsed...

Measurements of gravitational waves from approximately 50 binary neutron stars over the next decade will definitively resolve an intense debate about how quickly our universe is expanding, according to findings from an international team that includes University College London (UCL) and Flatiron Institute cosmologists. When neutron stars collide, they emit light and gravitational waves, as seen in this artist's illustration. By comparing the timing of the two emissions from many different neutron star mergers, researchers can measure how fast the universe is expanding. Credit: R. Hurt/Caltech-JPL The cosmos has been expanding for 13.8 billion years. Its present rate of expansion,...

It's been nearly a century since scientists first theorized that the Universe was expanding, and that the farther away a galaxy was from us, the faster it appears to recede. This isn't because galaxies are physically moving away from us, but rather because the Universe is full of gravitationally-bound objects, and the fabric of space that those objects reside in is expanding. But this picture, which held sway from the 1920s onward, has been recently revised. It's been only 20 years since we first realized that this expansion was speeding up, and that as time goes on, individual galaxies will...

Next time you eat a blueberry (or chocolate chip) muffin consider what happened to the blueberries in the batter as it was baked. The blueberries started off all squished together, but as the muffin expanded they started to move away from each other. If you could sit on one blueberry you would see all the others moving away from you, but the same would be true for any blueberry you chose. In this sense galaxies are a lot like blueberries. Since the Big Bang, the universe has been expanding. The strange fact is that there is no single place from...

Our universe's rate of expansion keeps getting stranger. New data continues to show a discrepancy in how fast the universe expands in nearby realms and more distant locations.  The study's researchers said this "tension" could mean we need to revise our understanding of the physics structuring the universe, which could include exotic elements such as dark matter and dark energy. New measurements from the Hubble Space Telescope and the Gaia space telescope together showed that the rate of expansion nearby is 45.6 miles per second per megaparsec. This means that for every 3.3 million light-years a galaxy is farther away from...

Once we discovered that the Universe was expanding, the next scientific step was to determine what the rate of expansion was. Despite the fact that it's been more than 80 years, we still don't have agreement on how fast that rate actually is. By looking at the largest cosmic scales and the oldest signals -- the leftover radiation from the Big Bang and the largest-scale galaxy correlations -- we get one number for the rate: 67 km/s/Mpc. But if we look at individual stars, galaxies, supernovae and other direct indicators, we get another number: 74 km/s/Mpc. The uncertainties are very...

Explanation: Well over a thousand galaxies are known members of the Virgo Cluster, the closest large cluster of galaxies to our own local group. In fact, the galaxy cluster is difficult to appreciate all at once because it covers such a large area on the sky. This careful wide-field mosaic of telescopic images clearly records the central region of the Virgo Cluster through faint foreground dust clouds lingering above the plane of our own Milky Way galaxy. The cluster's dominant giant elliptical galaxy M87, is just below and to the left of the frame center. To the right of M87...

In a few months I'll be teaching my high-school students about cosmology and, in particular, how Edwin Hubble discovered that the universe is expanding. That's how most of us learned it, anyway, but it's not the whole story. In fact, it's not even correct. During the 1920s, astronomers Edwin Hubble (left) and Georges Lemaître both came o the realization that the universe is expanding. Carnegie Inst. of Washington / Catholic Univ. Louvain Hubble came to his game-changing revelation when he compared his distance measurements of a few dozen galaxies (or "spiral nebulae," as they were then called) with prior observations...

Explanation: What does the universe nearby look like? This plot shows nearly 50,000 galaxies in the nearby universe detected by the Two Micron All Sky Survey (2MASS) in infrared light. The resulting image is anincredible tapestry of galaxies that provides limits on how the universe formed and evolved. The dark band across the image center is blocked by dust in the plane of our own Milky Way Galaxy. Away from the Galactic plane, however, each dot represents a galaxy, color coded to indicate distance. Bluer dots represent the nearer galaxies in the 2MASS survey, while redder dots indicating the more...