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)

Many contrarians dispute that cosmic inflation occurred. The evidence says otherwise.

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)

Graphene, microsensors, supercapacitors, and other innovations promise to weave tech into the fabric of our lives

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)

It’s not for climate science and condensed matter physics. It’s for advancing our understanding beyond spherical cows.

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)

Saturn’s Iapetus, discovered way back in 1671, has three bizarre features that science still can’t fully explain.

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…

When lower-mass, sun-like stars run out of fuel, they blow off their outer layers in a planetary nebula, but the center contracts down to form a white dwarf, which takes a very long time to fade to darkness. Over time, any remaining planets will lose gravitational radiation, where they’ll eventually merge with our sun’s stellar remnant. (Credit: Mark Garlick/University of Warwick)

The last ~4 billion years have been an incredibly successful, unbroken run for life on Earth. The future won’t be nearly so bright.

For over 4 billion years, terrestrial life has survived and thrived.

(Image credit: ESA/Hubble and NASA, H. Ebling)

The largest collections of mass in the universe have so much to teach us.

In the science of astronomy, it’s important to see both the forest and the trees. Galaxy clusters, in many ways, serve as both. They’re rich environments with stars, gas, dust, dark matter, black holes and more. The diversity of stars and stellar populations found within them, as well as found…

The farther away we look, the closer in time we’re seeing towards the Big Bang. In the far future, there will be an enormous distance separating even the closest galaxies from the local group, but with enough motivation and a little luck, even a far-future civilization, in a universe dominated by dark energy, could still uncover the Big Bang origin of the universe. (Credit: Robin Dienel/Carnegie Institution for Science)

If we were born trillions of years in the future, could we even figure out our cosmic history?

13.8 billion years ago, the universe as we know it ⁠ — full of matter and radiation, expanding and cooling and gravitating ⁠ — came into existence with the onset of the hot Big Bang. Today, we can see for enormous cosmic distances, measuring the signals that come to us…

This artist’s depiction shows what the sky might look like around the moon of a giant planet in a trinary system. Although numerous planets in trinary systems have been discovered, the characterization of GW Orionis indicates that it may be the first known system where planets orbit around all three members of a trinary system. (Credit: NASA/JPL-Caltech)

Move over, Tattooine, and instead feast your eyes on GW Orionis.

How many stars can a planet successfully orbit? For a long time, we had only our own solar system to look to, as we were the only star we knew of with planets around it at all. It wasn’t until the 1990s that we found planets orbiting other star systems…

The multiverse idea states that there are large, possibly infinite numbers of Universes like our own, and large, possibly infinite numbers of universes with differences. It all depends on the duration that inflation persisted for prior to the onset of our hot Big Bang. (Credit: Lee Davy/flickr/cc by 2.0)

If there really is another version of you out there in a parallel universe, what can that teach us about reality?

One of the most compelling ideas out there in all of physics sounds like pure fiction, but could actually describe our reality: the idea of a multiverse. In the multiverse scenario, what we know of as our universe is just one of many universes that independently and simultaneously exist in…

Artist’s logarithmic scale conception of the observable universe. Galaxies give way to large-scale structure and the hot, dense plasma of the Big Bang at the outskirts. This ‘edge’ is a boundary only in time. (Credit: Pablo Carlos Budassi; Unmismoobjetivo/Wikimedia Commons)

The Universe is only 13.8 billion years old, but we can see back 46.1 billion light years. Here’s how the expanding universe does it.

No matter where you look in the Universe, in any direction, your line-of-sight will eventually run into some type of matter or radiation. The Earth is embedded in the solar system, with planets, moons, rocky and icy bodies, dust, and plasma particles permeating our environment. Beyond our own backyard are…

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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