“People often ask about this, and simulating these difficult-to-imagine processes helps me connect the mathematics of relativity to actual consequences in the real universe,” said Jeremy Schnittman, an astrophysicist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, who created the visualizations. “So I simulated two different scenarios, one where a camera — a stand-in for a daring astronaut — just misses the event horizon and slingshots back out, and one where it crosses the boundary, sealing its fate.”
Category: cosmology – Page 142
Astronomers inspect population of young stellar objects in open cluster NGC 346
Using the James Webb Space Telescope (JWST), an international team of astronomers has explored young stellar objects (YSOs) in an open cluster known as NGC 346. The study, published April 24 on the preprint server arXiv, yields crucial information about the properties of YSO population in this cluster.
Deep space collision 650 million light-years away sends gravitational-wave signal
Astronomers have picked up a gravitational-wave signal originating from a dramatic collision deep in the cosmos. The event, dubbed GW230529, was recorded by the LIGO Livingston detector in May 2023.
Gravitational waves are caused by the acceleration of massive objects, such as merging black holes or neutron stars. According to Albert Einstein’s theory of general relativity, massive objects like planets, stars, and black holes distort the fabric of spacetime around them.
When these massive objects accelerate or change speed, they create waves that propagate outward at the speed of light. The detection of gravitational waves opens up a new window for observing the universe, allowing scientists to study phenomena that were previously inaccessible, such as the mergers of black holes and neutron stars, as well as the nature of gravity itself.
Physicists Say They May Have Found a Powerful Glitch in the Universe
Researchers have discovered what they’re calling a “cosmic glitch” in gravity, which could potentially help explain the universe’s strange behavior on a cosmic scale.
As detailed in a new paper published in the Journal of Cosmology and Astroparticle Physics, the team from the University of Waterloo and the University of British Columbia in Canada posit that Albert Einstein’s theory of general relativity may not be sufficient to explain the accelerating expansion of the universe.
Einstein’s “model of gravity has been essential for everything from theorizing the Big Bang to photographing black holes,” said lead author and Waterloo mathematical physics graduate Robin Wen in a statement about the research. “But when we try to understand gravity on a cosmic scale, at the scale of galaxy clusters and beyond, we encounter apparent inconsistencies with the predictions of general relativity.”
‘Cosmic glitch’ discovered in gravity’s behavior challenges Einstein’s general relativity theory
Researchers have stumbled upon a phenomenon that could rewrite our understanding of the universe’s gravitational forces. Known as the “cosmic glitch,” this discovery highlights anomalies in gravity’s behavior on an immense scale, challenging the established norms set by Albert Einstein’s theory of general relativity.
For over a century, general relativity has served as the backbone for our understanding of cosmic phenomena, ranging from the dynamics of the Big Bang to the intricacies of black holes. The theory posits that gravity influences not only the three spatial dimensions but also time itself.
Validated through numerous tests and observations, general relativity has been a robust model that physicists and astronomers worldwide rely on.
Why is it ok for people to be saying that dark matter makes up x amount of the universe when we don’t know what it is?
It strikes me as contradictory that the scientific community will say that we don’t know what dark matter is, but be happy to state things like “dark matter makes up about 85% of the cosmos” (source: phys.org)
Is there something wrong with the way I’m thinking about this? If MOND is correct for example, which seems to be a possibility still, wouldn’t this mean that the statement about dark matter making up a certain percentage of the universe be false?
The Big Bang, as Simple as Possible
The big bang is the model that describes the birth and evolution of the universe. But where did the term come from? What does it actually mean?
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Element Origins:
• Not all your Atoms are Stardust.
New Scientific Data Shows That Dark Matter Is Even Stranger Than We Thought
Recently more careful examination of the structure of the universe has thrown up fresh reasons to doubt cold dark matter. Its concept may work well at the largest scales, but on the scale of individual galaxies, something seems incomplete.
According to the cold dark matter model, dark matter sub-halos of all sizes, right down to Earth-scale masses, should exist. This would be a lot of invisible cannonballs to be floating around the Milky Way and interacting with star streams, yet hardly any evidence has been found, besides in 2018, when Adrian Price-Whelan and Ana Bonaca found that one particular star stream, better known as GD-1, has gaps along its length, as if it has been hit multiple times.
Another more recent doubt about the cold matter concept is that simulations show halos should get denser towards the center of the galaxy: the closer you get to the center, the more dark matter per unit volume should be. However, when astronomers look at the way galaxies move, this isn’t what they see: the dark matter appears evenly distributed across the halo of our galaxy, especially in the core regions. Which could be a hint that something more complex is going on.