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Ethan Siegel
Theoretical astrophysicist and science writer
Ethan Siegel is a Ph.D. astrophysicist and author of "Starts with a Bang!" He is a science communicator, who professes physics and astronomy at various colleges. He has won numerous awards for science writing since 2008 for his blog, including the award for best science blog by the Institute of Physics. His two books "Treknology: The Science of Star Trek from Tricorders to Warp Drive" and "Beyond the Galaxy: How humanity looked beyond our Milky Way and discovered the entire Universe" are available for purchase at Amazon. Follow him on Twitter @startswithabang.
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We've long known we can't go back to infinite temperatures and densities. But the hottest part of the hot Big Bang remains a cosmic mystery.
Red dwarfs are the Universe's most common star type. Their flaring now makes potentially Earth-like worlds uninhabitable, but just you wait.
Found by Hubble before JWST's launch, GNz7q looked like a mix of a galaxy and a quasar. Was it actually our first known "little red dot"?
Observations with the Hubble space telescope helped cement dark energy and reveal the Hubble tension. How are these two things so different?
The whole isn't greater than the sum of its parts; that's a flaw in our thinking. Non-reductionism requires magic, not merely science.
Solar power has the disadvantage that there's no Sun at night. Satellite startup Reflect Orbital wants to change that, but at what cost?
Inflation's two main criticisms, that it can predict anything and that the "measure problem" remains unsolved, can't erase its successes.
The Orionids meteor shower peaks October 20th/21st here in 2025, coinciding with a new Moon. See the brightest shooting stars of the year!
To learn how our Universe grew up, we have to look at large numbers of galaxies at all distances to find out. Good thing we have JWST!
Our Sun only arose after 9.2 billion years of cosmic history: with many stars living and dying first. How many prior generations were there?
Since the time of Galileo, Saturn's rings have remained an unexplained mystery. A new idea may have finally solved the longstanding puzzle.
Quantum mechanics was first discovered on small, microscopic scales. 2025's Nobel Prize brings the quantum and large-scale worlds together.
In 2025, Earth remains the only planet where life is known to exist. Without a second example, "The Stand" has a vital lesson to teach us.
By deeply imaging a large volume of space, COSMOS-Web provides JWST's widest cosmic views. Its gravitational lenses reveal a big surprise.
As the Universe ages, it continues to gravitate, form stars, and expand. And yet, all this will someday end. Do we finally understand how?
From here on Earth, looking farther away in space means looking farther back in time. So what are distant Earth-watchers seeing right now?
As October begins, thousands of longtime NASA employees are leaving the agency. 4000+ will exit by January 9, 2026, changing NASA forever.
Proposed over 2000 years ago by Democritus, the word atom literally means uncuttable. Revived in 1803, today's "atoms" can indeed be split.
From the Big Bang to a prior period of cosmic inflation, our cosmic origins are clearer than ever. Yet these 5 big mysteries still remain.
If you think of the Big Bang as an explosion, we can trace it back to a single point-of-origin. But what if it happened everywhere at once?