The Earth, moving in its orbit around the Sun and spinning on its axis, appears to make a closed, unchanging, elliptical orbit. If we look to a high-enough precision, however, we’ll find that our planet is actually spiraling away from the Sun, while the rotation period of our planet is slowing down over time. The same calendar that we use today won’t apply to the distant past or future. (LARRY MCNISH, RASC CALGARY)

Leap years will only get us through the next few thousand years before we have to fix it.


Many people, despite the overwhelming evidence supporting the safety and efficacy of vaccines, refuse them for themselves and their children. The resistance that many people have to accepting vaccinations is presently the top public health problem in the fight against the COVID-19 pandemic. (Smith Collection/Gado/Getty Images)

Ignoring a scientific truth doesn’t change it, even when the consequences are deadly.

  • underdressed for the cold winter weather,
  • with your jeans below your buttocks instead of above them,
  • or with holes or rips deliberately put into your clothes,


The Moon, Venus, and faint Mars, together in the July 12, 2021 night sky. The close proximity of Venus to Mars is the result of a planetary conjunction, while the thin crescent Moon just happened to be relatively nearby. Venus, the brightest planet in Earth’s night sky, easily outshines all the stars, and is some ~200 times brighter than Mars at the moment this photo was taken. (CHRISTOPHER BECKE / @BECKEPHYSICS)

And why, even at its faintest, it always outshines every other star and planet.


This artist’s impression of the Nu2 Lupi planetary system shows three exoplanets. If we wanted to observe an Earth-sized planet at an Earth-like distance from a Sun-like star, we would need to block out the Sun-like star’s light to about 1 part in 10-to-100 billion. This is a difficult, but not impossible, task for modern technology. (ESA / CHEOPS COLLABORATION)

If our nearest star has an Earth-like planet, here’s how we’ll see it.


When two orbiting stars come into contact with one another, they can exchange mass, interact, or merge, with the potential of leading to a luminous red nova if the right conditions are met. In between the brightness of a classical nova and a supernova, we expect one in our galaxy every few years. (DAVID A. AGUILAR (HARVARD-SMITHSONIAN CENTER FOR ASTROPHYSICS))

The contact binary system KIC 9832227 is worth another look.


Light is well known to exhibit both wave-like and particle-like properties, as imaged here in this 2015 photograph. What’s less well appreciated is that matter particles also exhibit those wave-like properties. Even something as massive as a human being should have wave properties as well, although measuring them will be difficult. (FABRIZIO CARBONE/EPFL (2015))

Hidden variables aren’t ruled out, but they can’t get rid of quantum weirdness.


On November 18, 2019, approximately 19 Starlink satellites passed over Cerro Tololo Inter-American Observatory, disrupting astronomical observations and hindering the science being undertaken in a real, measurable way. If the current plans of SpaceX, OneWeb, and other satellite providers unfold as laid out, the consequences for astronomy will be extraordinary. (CLARAE MARTÍNEZ-VÁZQUEZ / CTIO)

Over the coming decades, over 100,000 new satellites are expected.


When cooled to low enough temperatures, certain materials will superconduct: the electrical resistance inside them will drop to zero. When exposed to a strong magnetic field, some superconductors will exhibit levitation effects, as flux pinning and flux expulsion can overcome the force of gravity for even weakly magnetic materials. (PETER NUSSBAUMER / WIKIMEDIA COMMONS)

The dream of zero resistance is closer than you may think.


Physicist and best-selling author Stephen Hawking presents a program in Seattle in 2012. Note his (outdated) assertion that a singularity, and the Big Bang, precedes the epoch of cosmic inflation, which is the earliest epoch we have any certainty about. (AP PHOTO / TED S. WARREN)

Yes, the Big Bang is real, but what about what came before?


The planet Mercury, as imaged here with a special filter, has a detectable sodium tail. The Moon, despite being three times as far away from the Sun as Mercury and receiving only one-ninth the flux, has a similar, but much weaker, sodium tail as well. Despite their ‘airless’ appearance, both Mercury and the Moon have thin, tenuous atmospheres. (ANDREA ALESSANDRINI)

With sodium-sensitive eyes, we’d see it every new Moon.

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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