If you look farther and farther away, you also look farther and farther into the past. If the number of galaxies, the densities and properties of those galaxies, and other cosmic properties like the temperature and expansion rate of the Universe didn’t appear to change, you’d have evidence of a Universe that was constant in time; that is not what we see. (Credit: NASA/ESA/STScI/A. Feild)The Universe is 13.8 billion years old, going back to the hot Big Bang. But was that truly the beginning, and is that truly its age? According to the theory of the hot Big Bang, the Universe had a beginnin ..read more

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

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

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

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

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

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

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

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

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