Ethan Siegel

Ethan Siegel

A theoretical astrophysicist and science writer, host of popular podcast “Starts with a Bang!”

Ethan Siegel Starts with a Bang!

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.

A healthcare worker wearing blue gloves gently inserts an IV into a man's hand as he lies on a hospital bed, battling lung cancer.
Here in 2025, many of us claim to come to our own conclusions by doing our own research. Here's why we're mostly deluding ourselves.
Two side-by-side images of a galaxy cluster in space, captured by JWST, showcase numerous bright galaxies and stars on a dark background—highlighting one of the most extreme gravitational lens effects ever observed.
Massive galaxy cluster Abell S1063, 4.5 billion light-years away, bends and distorts the space nearby. Here's what a JWST deep field shows.
Infographic illustrating three steps to measure the Hubble Constant, showing Cepheid variable stars, supernovae, and galaxies at increasing distances with redshifted light—highlighting how these methods reveal that the hubble tension is real.
Is the Universe's expansion rate 67 km/s/Mpc, 73 km/s/Mpc, or somewhere in between? The Hubble tension is real and not so easy to resolve.
parallel universe
The ANITA experiment found cosmic rays shooting out of Antarctica. One interpretation claims "parallel Universes," but is that right?
A composite image showing a galaxy with red circles marking stars on the left and multicolored expanding rings with Earth on the right, all set against a grid background, illustrating concepts like Hubble tension studied by Wendy Freedman.
Different methods of measuring the Universe's expansion rate yield high-precision, incompatible answers. But is the problem robustly real?
Circular astronomical image showing constellations and celestial objects labeled against a dark sky, reminiscent of a NASA PUNCH video sun corona visualization, with a timestamp of 2025-06-03 01:52 at the bottom left.
Launched in March, the PUNCH mission has viewed two incredible coronal mass ejections, tracking them farther from the Sun than ever before.
The tiniest galaxies of all are the most severely dominated by dark matter. Could black holes be the cause of the extra gravity instead?
A digital illustration showing a glowing blue particle on the left, evoking cosmic inflation, transitioning into a geometric, grid-like structure on a purple background on the right.
A few physical quantities, in all laboratory experiments, are always conserved: including energy. But for the entire Universe? Not so much.
Timeline of the universe from the Big Bang, as described in cosmology, showing inflation, formation of atoms, stars, galaxies, and expansion to the present day over 13.8 billion years.
If you want to understand the Universe, cosmologically, you just can't do it without the Friedmann equation. With it, the cosmos is yours.
entanglement across space
If all massive objects emit Hawking radiation, not just black holes alone, then everything is unstable, even the Universe. Can that be true?
Two bright, irregularly shaped nebula clouds with blue, purple, and pink gases dominate the dark space background, where dazzling stars twinkle—reminding us that in space, appearances can deceive.
There's an old saying that "what you see is what you get." When it comes to the Universe, however, there's often more to the full story.
mars
The surface and atmosphere is colored by ferric oxides. Beneath a very thin layer, mere millimeters deep in places, it's not red anymore.
Abstract illustration of a figure reaching for a yellow sphere on the left, with colored overlapping circles and concentric arcs—evoking themes of physics and consciousness—set against a vibrant multicolored gradient background.
Many, from neuroscientists to philosophers to anesthesiologists, have claimed to understand consciousness. Do physicists? Does anyone?
Scatter plot with dark blue data points and black dashed elliptical contours centered on the origin, with axes labeled ξ (') horizontally and vertically—similar to plots used by astronomers in studies of the smallest galaxy ever discovered.
With stars, gas, and dark matter, galaxies come in a great array of sizes. This new one, Ursa Major III/UNIONS 1, is the smallest by far.
Astro2020
NASA astrophysics, which gave us Hubble, JWST, and so much more, faces its greatest budget cut in history. All future missions are at risk.
Diagram of the solar system with gravitational waves emanating from a distant bright source, and a triangular spacecraft array detecting the waves in space.
Just 10 years ago, humanity had never directly detected a single gravitational wave. We're closing in on 300 now, with so much more to come!
dark energy accelerated expansion
The fact that our Universe's expansion is accelerating implies that dark energy exists. But could it be even weirder than we've imagined?
symmetry
The laws of physics obey certain symmetries and defy others. It's theoretically tempting to add new ones, but reality doesn't agree.
A healthcare worker wearing gloves administers an injection with a syringe into a person's upper arm, reminding us that when it comes to vaccines, do your own research and stay informed.
For centuries, vaccines have been the top life-saving, expert medical intervention known to humans. How can individuals make the right call?
baryon acoustic oscillations
It took nearly 400,000 years, after the Big Bang, to first form neutral atoms. The imprints from that early time can now be seen everywhere.