Flagship NASA space telescope faces a penny-pinching death
Starts With A Bang!
by Ethan Siegel
2d ago
The Bullet Cluster, the aftermath of a galaxy cluster collision that occurred 3.8 billion years ago in a region of space located ~3.7 billion light-years away, represents very strong evidence for the existence of dark matter. The separation of the gravitational effects (blue, reconstructed through gravitational lensing) from the location of the majority of the normal matter (pink, revealed by Chandra’s X-ray capabilities) is very difficult to explain without dark matter’s presence. (Credit: NASA/CXC/M. Weiss)NASA’s only flagship X-ray telescope ever, Chandra, still works and has no planned suc ..read more
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Why “incompleteness” matters in theoretical physics
Starts With A Bang!
by Ethan Siegel
3d ago
Quantum gravity attempts to combine Einstein’s general theory of relativity with quantum mechanics. Quantum corrections to classical gravity are visualized as loop diagrams, as the one shown here in white. Alternatively, it’s possible that gravity is always classical and continuous, and that quantum field theory, not general relativity, needs to be modified. (Credit: SLAC National Accelerator Laboratory)Physicists just can’t leave an incomplete theory alone; they try and repair it. When nature is kind, it can lead to the next major breakthrough. In physics, many of our greatest advances aren’t ..read more
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March 25, 2024’s full moon portends April 8th’s solar eclipse
Starts With A Bang!
by Ethan Siegel
3d ago
On March 25, 2024, a full moon will coincide with a penumbral lunar eclipse, causing one portion of the Moon to experience limb-darkening as seen from Earth over approximately a ~2 hour duration. Here, a similar penumbral eclipse during a full moon is showcased from 2012, as viewed from Hong Kong. (Credit: Hong Kong Space Museum)The least exciting of all eclipses, a penumbral lunar eclipse, foreshadows the spectacular show that April 8th’s total eclipse will bring. On April 8, 2024, a spectacular total solar eclipse arrives. This photograph, taken the 2017 total solar eclipse, s ..read more
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Ask Ethan: How did matter come to exist in our Universe?
Starts With A Bang!
by Ethan Siegel
1w ago
In the very early Universe, there were tremendous numbers of quarks, leptons, anti-quarks, and anti-leptons of all species. After only a tiny fraction-of-a-second has elapsed since the hot Big Bang, most of these matter-antimatter pairs annihilate away, leaving a very tiny excess of matter over antimatter. How that excess came about is a puzzle known as baryogenesis, and is one of the greatest unsolved problems in modern physics. (Credit: E. Siegel/Beyond the Galaxy)You can only create or destroy matter by creating or destroying equal amounts of antimatter. So how did we become a matter-r ..read more
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When will the Earth meet its demise?
Starts With A Bang!
by Ethan Siegel
1w ago
If the Earth had the misfortune to either encounter a black hole or simply have one get too close to it, our planet would be irrevocably destroyed. This is an extremely unlikely scenario, however, as there are much more likely, and much more seemingly inevitable ways, for our planet to meet its demise. (Credit: ESO/M. Kornmesser)No matter how you define the end, including the demise of humanity, all life, or even the planet itself, our ultimate destruction awaits. If you have ever read the news, you’ve likely seen stories that announce our impending doom, usually brought on by some apocalyptic ..read more
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The humiliating truth behind Harvard astronomer’s alien spherules
Starts With A Bang!
by Ethan Siegel
1w ago
One of the very first spherules collected off of the ocean floor by Avi Loeb’s expedition to try to recover fragments of a suspected interstellar meteor. The actual nature of these spherules is almost certainly terrestrial, not extraterrestrial, and has nothing to do with the alleged meteor Loeb is chasing. (Credit: The Galileo Project)Harvard astronomer Avi Loeb claimed to track down and find alien spherules on the ocean bottom. The sober truth is an utter embarrassment. One of the most common, and unfortunately well-deserved, tropes is that of an arrogant physicist who shamelessly wande ..read more
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JWST’s mysterious young galaxy: dead, or just sleeping?
Starts With A Bang!
by Ethan Siegel
1w ago
The “dead” galaxy JADES-GS-z7–01-QU, whose light comes to us from just 700 million years after the Big Bang, is low in mass and small in size. We do not yet know whether star-formation has temporarily turned off in this galaxy about 10–20 million years ago, or whether it has ended completely and permanently. Either way, this is now the youngest, earliest “dead” galaxy ever discovered, but it may merely be sleeping. (Credit: JADES Collaboration)Given enough time, all galaxies will expel their star-forming material and wind up dead. Is this the earliest one, or is it just asleep? All across ..read more
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Ask Ethan: How do symmetries work in physics?
Starts With A Bang!
by Ethan Siegel
1w ago
We can imagine that there’s a mirror Universe to ours where the same rules apply. If the big red particle pictured above is a particle with an orientation with its momentum in one direction, and it decays (white indicators) through either the strong, electromagnetic, or weak interactions, producing ‘daughter’ particles when they do, that is the same as the mirror process of its antiparticle with its momentum reversed (i.e., moving backward in time). If the mirror reflection under all three (C, P, and T) symmetries behaves the same as the particle in our Universe, then CPT symmetry is conserved ..read more
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The future of US astronomy just dimmed by half
Starts With A Bang!
by Ethan Siegel
2w ago
The 25-meter Giant Magellan Telescope is currently under construction, and will be the greatest new ground-based observatory on Earth. The spider arms, seen holding the secondary mirror in place, are specially designed so that their line-of-sight falls directly between the narrow gaps in the GMT mirrors, creating a view of the Universe without sharp corners to its mirrors or diffraction spikes around its stars. As one of the two US Extremely Large Telescopes proposed by astronomers and currently in development, it is an essential part of bringing about a new generation in cutting-edge ground-b ..read more
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Why scientists think the Multiverse isn’t just fiction
Starts With A Bang!
by Ethan Siegel
2w ago
How likely or unlikely was our Universe to produce a world like Earth? And how plausible would those odds be if the fundamental constants or laws governing our Universe were different? Most Universes that we can imagine would not give rise to potential observers, like human beings. A Fortunate Universe, from whose cover this image was taken, is one such book that explores these issues, along with the likelihood of a Universe like ours arising within a Multiverse. (Credit: Geraint Lewis and Luke Barnes)The Multiverse fuels some of the 21st century’s best fiction stories. But its supporting ..read more
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