Starts With A Bang podcast #104 — The magnetized galactic center
Starts With A Bang!
by Ethan Siegel
10h ago
This image shows the magnetized galactic center, with various features highlighted, as imaged by the SOFIA/HAWC+ FIREPLACE survey team. The giant bubble at the left of the image is some 30 light-years wide, several times larger than any other supernova-blown bubble ever discovered. (Credit: D. Paré et al., arXiv:2401.05317v2, 2024)Starts With A Bang podcast #104 — The magnetized galactic center The center of the galaxy doesn’t just host stars and a black hole, but an enormous set of rich gassy and dusty features. Find out more! Have you ever wondered what the full story with the gala ..read more
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What was it like when human beings transformed the Earth?
Starts With A Bang!
by Ethan Siegel
1d ago
The original “blue Marble” image, from Apollo 17, was actually snapped in the orientation shown here: where south is at the top and north is (invisibly) on the other side of the world. This image is now more than 50 years old, as humanity has transformed our planet in a myriad of ways both leading up to, and since, this image was obtained. (Credit: NASA/Lunar and Planetary Institute)Although human beings arrived on Earth just ~300,000 years ago, we’ve transformed the entire planet completely. Here’s how we did it. When each of us is first born into this world, it might feel like the world ..read more
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What was it like when humans first arose on planet Earth?
Starts With A Bang!
by Ethan Siegel
2d ago
70,000 years ago, a brown dwarf pair known as Scholz’s Star, right on the precipice of igniting hydrogen fusion in its core, passed through the Solar System’s Oort cloud. Stars, failed stars, and stellar remnants pass through our Solar System multiple times every million years. Both modern humans and Neanderthals were likely around to see this event. Unlike the illustration, however, it’s so intrinsically faint that it still wouldn’t have been visible to human eyes; today, it’s approximately 22 light-years away. (Credit: José A. Peñas/SINC)Despite billions of years of life on Earth, humans fir ..read more
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What was it like when mammals appeared and thrived?
Starts With A Bang!
by Ethan Siegel
3d ago
During the Cambrian explosion, some 550–600 million years ago, the first complex, differentiated, macroscopic, multicellular, sexually-reproducing animals came to dominate the oceans. Over the next half a billion years, evolution would take life in many different directions. By the time the asteroid eliminating the dinosaurs arrived, 65 million years ago, mammals had diversified in a number of directions, with the earliest primates splitting off just before that great event. Modern lemurs, shown here, likely bear a strong resemblance to those early primates. (Credit: Bas Czerwinski/AFP/Getty I ..read more
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What was it like when life on Earth became complex?
Starts With A Bang!
by Ethan Siegel
4d ago
Somewhere around 550 million years ago, an enormous abundance and diversity of large plants and animals begins showing up in the fossil record: an event known as the Cambrian Explosion. Roughly around this time, life became enormously complex and differentiated on Earth: a sharp contrast to the prior 4 billion years of terrestrial history. (Credit: James St. John/flickr)For billions of years on Earth, life was limited to simple unicellular, non-differentiated organisms. In a mere flash, that changed forever. A single look at Earth today, with enormous plants, animals, and fungi dominating ..read more
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Ask Ethan: How do symmetries lead to conservation laws?
Starts With A Bang!
by Ethan Siegel
1w ago
Emmy Noether, the person who proved Noether’s theorem, which connects symmetries and invariances of a theory with an associated conserved quantity. At right, the illustration of conservation of linear momentum, a consequence of spatial-translation invariance, is shown. (Credit: Mathematical Association of America (L)/R Nave (R))First derived by Emmy Noether, for every symmetry a theory possesses, there’s an associated conserved quantity. Here’s the profound link. In this Universe, there are certain physical quantities that are — quite importantly — always conserved. Laws like the “co ..read more
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Particle physics finally charts a healthy path forward
Starts With A Bang!
by Ethan Siegel
1w ago
On the right, the gauge bosons, which mediate the three fundamental quantum forces of our Universe, are illustrated. There is only one photon to mediate the electromagnetic force, there are three bosons mediating the weak force, and eight mediating the strong force. This suggests that the Standard Model is a combination of three groups: U(1), SU(2), and SU(3), whose interactions and particles combine to make up everything known in existence. Despite the success of this picture, many puzzles still remain. (Credit: Daniel Domingues/CERN)A great many cosmic puzzles still remain unsolved. By embra ..read more
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How to measure a lunar month during the solar eclipse
Starts With A Bang!
by Ethan Siegel
1w ago
This partial solar eclipse, captured over Arlington, VA in 2021, shows the Moon’s disk partially blotting out the Sun. The Moon’s motion across the Sun’s disk corresponds to a portion of the Moon’s 360 degree revolution around the Earth, and extrapolating what we observe during an eclipse to a full lunar month enables us to estimate the duration of a lunar month. (Credit: NASA/Bill Ingalls)Even if you aren’t in the path of totality, you can still use the solar eclipse to measure how long it takes the Moon to orbit Earth. A solar eclipse is a very special physical phenomenon. The Moon orbi ..read more
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5 total mistakes to avoid at the April 8, 2024 solar eclipse
Starts With A Bang!
by Ethan Siegel
1w ago
This image, of the Sun’s inner corona and prominences on the Sun, was taken during the April 20, 2023 total solar eclipse. Exquisite views of what’s occurring just off of the Sun’s disk are best captured during a total solar eclipse. (Credit: Phil Hart)There are only a precious few minutes of totality during even the best solar eclipses. Don’t waste yours making these avoidable mistakes. On April 8, 2024, millions of North Americans will enjoy a spectacular total solar eclipse. The path of totality of the April 8, 2024 total solar eclipse cuts from southwest Mexico up through Texas ..read more
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Ask Ethan: Has a new study disproven dark matter and dark energy?
Starts With A Bang!
by Ethan Siegel
2w ago
The full-field image of MACSJ0717.5+3745 shows many thousands of galaxies in four separate sub-clusters within the large cluster. The blue contours show the inferred mass distribution from the gravitational lensing effects on background objects. Not shown in this diagram is the X-ray data, which shows an offset between the X-ray emitting gas, which traces the normal matter distribution, and these blue contours, which map out the total mass, including dark matter. (Credit: NASA, ESA, D. Harvey (École Polytechnique Fédérale de Lausanne, Switzerland), R. Massey (Durham University, UK), Harald Ebe ..read more
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