When describing any object that’s acted upon by an outside force, Newton’s famous F = ma is the equation that describes how its motion will evolve with time. Although it’s a seemingly simple statement and a seemingly simple equation, there’s an entire Universe to explore encoded in this seemingly straightforward relationship. (Credit: Dieterich01/Pixabay)

If there’s one equation that people learn about physics — and no, not Einstein’s E = mc² — it’s Newton’s F = ma. Despite the fact that it’s been in widespread use for some ~350 years now, since Newton first put it forth in the late 17th century, it rarely…

Illustration of cosmic rays striking Earth’s atmosphere, where they produce particle showers. By building large ground-based arrays of detectors, the original energy and charge of the incoming cosmic ray can frequently be reconstructed, with observatories like Pierre Auger leading the way. (Credit: Asimmetrie/INFN)

If you want to travel as fast as you can through the Universe, your best bet is to pump as much energy into as small a mass as you can. As you add progressively more kinetic energy and momentum to your particle, it will travel through space more quickly, approaching…

When we look back at the Universe through cosmic time, we see too few galaxies at the greatest distances to account for the Universe becoming transparent to light. The newest discovery, going beyond what Hubble can see, discovered the low-mass, low-brightness early galaxies that had been missing up until now. (Credit: NASA, ESA, P. Oesch (University of Geneva), and M. Montes (University of New South Wales))

Back in the Universe’s early days, starlight couldn’t travel very far at all.

The process of unfurling and tensioning the 5-layer sunshield, as seen during a recent test. NASA’s James Webb Space Telescope is now fully launch-ready, with the sunshield having been adequately tested previously. It is now stowed for launch, and the telescope only awaits the final few milestones before a launch scheduled for late 2021. (Credit: NASA/JWST Team)

At present, as we near the end of 2021, many events seem to be shaking the foundations of our society. The combination of social unrest, widespread injustices, political polarization, and a still-raging global pandemic seem to be afflicting humanity on a worldwide, global scale. Meanwhile, global problems such as a…

The exoplanetary system TOI-178 has multiple known planets orbiting a central star. The star and all of the planets should be in hydrostatic equilibrium, with their round shape determined by gravity and rotation. This should be true of all planets. (Credit: ESA)

For more than 2,000 years, humanity has known that our planet, Earth, is round in shape. Just as the Moon and Sun appear round, so does not only Earth, but every planet in our Solar System. Even non-planets get in on the “round” action as well. Earth’s moon, Jupiter’s four…

A visual history of the expanding Universe includes the hot, dense state known as the Big Bang and the growth and formation of structure subsequently. The full suite of data, including the observations of the light elements and the cosmic microwave background, leaves only the Big Bang as a valid explanation for all we see. (Credit: NASA/CXC/M. Weiss)

If there’s one rule that most people know about the Universe, it’s that there’s an ultimate speed limit that nothing can exceed: the speed of light in a vacuum. If you’re a massive particle, not only can’t you exceed that speed, but you’ll never reach it; you can only approach…

If other inhabited planets exist in our galaxy, near-future technology that will be at our disposal within this century, or perhaps even this decade, may be able to first uncover it. (Credit: NASA Ames/JPL-Caltech/T. Pyle)

Since humans first gazed upwards, we’ve wondered whether extraterrestrial life exists.

Although science has revealed much about our Universe, life beyond Earth remains elusive.

Axions, one of the leading candidates for dark matter, may be able to be converted to photons (and vice versa) under the right conditions. If we can cause and control their conversion, we might discover our first particle beyond the Standard Model, and possibly solve the dark matter and strong CP problems as well. (Credit: Sandbox Studio, Chicago, Symmetry Magazine/Fermilab and SLAC)

Astrophysically, even with all the different forms that normal matter can take, it simply can’t explain the Universe we observe on its own. Beyond all the stars, planets, gas, dust, plasma, black holes, neutrinos, photons and more, there’s an overwhelming suite of evidence that the Universe contains two ingredients whose…

This artist’s impression shows the cigar-shaped interpretation of ‘Oumuamua. Although it was initially suspected to be rocky in nature, the lack of observed outgassing combined with its anomalous acceleration instead suggests that it may be made of nitrogen ice. That remains the leading hypothesis, even after a recent analysis (faultily) suggested otherwise. (Credit: ESO/M. Kornmesser; nagualdesign)

In 2017, scientists discovered an object in our Solar System that was unlike anything else we’d ever seen before. Whereas all the other bodies in our own cosmic backyard — planets, moons, comets, asteroids, Kuiper belt objects and more — had properties that indicated they originated from within our own…

The lunar horizon glow, shown here as imaged by the Clementine Spacecraft in the 1990s, had actually been seen numerous times during the Apollo mission, but its existence was treated as dubious until an explanation for the lunar atmosphere was fully developed. This didn’t occur until 1998, when the sodium Moon spot, and a sodium tail extending from the Moon, were discovered. (Credit: NASA)

For a number of very good reasons, you wouldn’t expect the Moon to have an atmosphere at all. Compared to planets that do have substantial atmospheres — like Earth, Venus, and even Mars — the Moon is tremendously low in mass. At just 1.2% the mass of the Earth, it…

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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