A solar flare, visible at the right of the image, occurs when magnetic field lines split apart and reconnect. When the flare is accompanied by a coronal mass ejection, and the magnetic field of the particles in the flare is anti-aligned with the magnetic field of Earth, a geomagnetic storm can occur, with grave potential for a natural disaster. (Credit: NASA/Solar Dynamics Observatory)

From the 1600s through the mid-1800s, solar astronomy was a very simple science. If you wanted to study the sun, you simply looked at the light from it. You could pass that light through a prism, breaking it up into its component wavelengths: from ultraviolet through the various colors…

Distant galaxies, like those found in the Hercules galaxy cluster, are not only redshifted and receding away from us, but their apparent recession speed is accelerating. Many of the most distant galaxies in this image are receding from us at speeds that appear to exceed the speed of light. We will never be able to reach any of the ones presently located more than 18 billion light-years away. (Credit: ESO/INAF-VST/OmegaCAM. Acknowledgement: OmegaCen/Astro-WISE/Kapteyn Institute.)

Our universe, everywhere and in all directions, is filled with stars and galaxies.

William Shatner, shown here immediately after leaving the Blue Origin capsule that took him into space and back, cannot hold back his tears or his emotions as he begins to recount his experience. (Credit: Global News TV)

In all of human history, only a few thousand people have ever reached the final frontier: breaking the gravitational bonds of Earth and experiencing the wonders of being present in space. On October 13, 2021, William Shatner — best known as Star Trek’s Captain Kirk — became the oldest person…

The modern cosmic picture of our universe’s history begins not with a singularity that we identify with the Big Bang, but rather with a period of cosmic inflation that stretches the universe to enormous scales, with uniform properties and spatial flatness. The end of inflation signifies the onset of the hot Big Bang. (Credit: Nicole Rager Fuller/National Science Foundation)

Where did all this come from? In every direction we care to observe, we find stars, galaxies, clouds of gas and dust, tenuous plasmas, and radiation spanning the gamut of wavelengths: from radio to infrared to visible light to gamma rays. No matter where we look or how we look…

The NEXIS Ion Thruster, at Jet Propulsion Laboratories, is a prototype for a long-term thruster that could move large-mass objects over very long timescales. (Credit: NASA/JPL)

One of the most steady, unchanging properties in our cosmic history is Earth’s orbit. For the past 4.5 billion years, even as a whole slew of fantastic events have occurred — giant impacts, the formation of moons, the continued slowing of our planet’s rotation, and even the emergence of life…

This artist’s illustration shows an electron orbiting an atomic nucleus, where the electron is a fundamental particle but the nucleus can be broken up into still smaller, more fundamental constituents. (Credit: Nicole Rager Fuller/NSF)

The humble atom is the fundamental building block of all normal matter.

The expanding Universe, full of galaxies and the complex structure we observe today, arose from a smaller, hotter, denser, more uniform state. But even that initial state had its origins, with cosmic inflation as the leading candidate for where that all came from. (Credit: C.-A. Faucher-Giguere, A. Lidz, and L. Hernquist, Science, 2008)

For as long as humans have been around, our innate sense of curiosity compels us to ask questions about the universe. Why are things the way they are? How did they get to be this way? Were the outcomes that we observe inevitable, or could things have turned out differently…

Atomic and molecular configurations come in a near-infinite number of possible combinations, but the specific combinations found in any material determine its properties. Graphene, which is an individual, single-atom sheet of the material shown here, is the hardest material known to humanity, but with even more fascinating properties that will revolutionize electronics later this century. (Credit: Max Pixel)

Almost everything we encounter in our modern world relies, in some way, on electronics. Ever since we first discovered how to harness the power of electricity to generate mechanical work, we’ve generated devices large and small to technologically improve our lives. From electric lighting to telephones to computers and much…

The difference between a disordered, amorphous solid (glass, left) and an ordered, crystalline/lattice-like solid (quartz, right). Note that even made from the same materials with the same bond structure, one of these materials offers more complexity, and more possible configurations, than the other. (Credit: Jdrewitt/Wikipedia, public domain)

One of the oldest jokes in physics is that you should begin by imagining a spherical cow. No, physicists don’t think that cows are spherical; we know this is a ridiculous approximation. However, there are cases where it’s a useful approximation, as it’s much easier to predict the behavior of…

The two-toned Iapetus is the strangest known moon in all the solar system. The combination of its color, shape, equatorial ridge, and orbital parameters eludes a cohesive, compelling explanation some 350 years after its original discovery. (Credit: NASA/JPL-Caltech/Space Science Institute/Cassini)

After having no superior tools to our naked eyes to explore the universe, the 17th century ushered in a revolution with the adoption of the telescope. With larger apertures and the power to gather more light at once, objects beyond the limits of human visibility — both in terms of…

Ethan Siegel

The Universe is: Expanding, cooling, and dark. It starts with a bang! #Cosmology Science writer, astrophysicist, science communicator & NASA columnist.

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