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 graph depicting projectile motion with displacement on the vertical axis and time on the horizontal axis. The projectile's trajectory forms a perfect parabola, with initial velocity u and angle θ clearly indicated.
Taught in every introductory physics class for centuries, the parabola is only an imperfect approximation for the true path of a projectile.
A person is giving a presentation at a podium with a large abstract, colorful light pattern displayed on a screen behind them.
Inflation, dark matter, and string theory are all proposed extensions to the prior consensus picture. But what does the evidence say?
A satellite orbits Earth against a backdrop of space. Below, the Earth's curvature and cloud formations are visible, making our planet seem even bigger.
The observation that everything we know is made out of matter and not antimatter is one of nature's greatest puzzles. Will we ever solve it?
zero gravity flight stephen hawking
The mass that gravitates and the mass that resists motion are, somehow, the same mass. But even Einstein didn't know why this is so.
Interior of a particle physics laboratory showing a complex particle accelerator setup with multiple cables, detectors, and machinery designed to study glueball particles.
Scientific surprises, driven by experiment, are often how science advances. But more often than not, they’re just bad science.
JWST deep field vs hubble
The "little red dots" were touted as being too massive, too early, for cosmology to explain. With new knowledge, everything adds up.
Comparison of weight on Earth and Mars for a 1 kg mass. On Earth: gravity = 9.81 m/s², weight = 9.81 N. On Mars: gravity = 3.72 m/s², weight = 3.72 N; demonstrating that weight and mass are not the same across different planets due to varying gravitational forces.
Here on Earth, we commonly use terms like weight (in pounds) and mass (in kilograms) as though they're interchangeable. They're not.
So far, Earth is the only planet that we're certain possesses active life processes. Here's what we shouldn't assume about life elsewhere.
cosmic inflation
The Universe isn't just expansion, but the expansion itself is accelerating. So why can't we feel it in any measurable way?
A colorful, abstract scientific illustration with a central glowing sphere, circular patterns, and various lines and circles suggesting quantum connections or uncertainty data points, on a dark background with blue accents.
No matter how good our measurement devices get, certain quantum properties always possess an inherent uncertainty. Can we figure out why?
first contact
Life arose on Earth early on, eventually giving rise to us: intelligent and technologically advanced. "First contact" still remains elusive.
A circular illustration depicting the observable universe with various galaxies, stars, and cosmic structures emanating from a central point, symbolizing the solar system and hinting at how far away the Big Bang occurred.
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?
every square degree
The Universe is 13.8 billion years old, going back to the hot Big Bang. But was that truly the beginning, and is that truly its age?
cosmic inflation
Many contrarians dispute that cosmic inflation occurred. The evidence says otherwise.
pulse light quantum tunnel barrier
In all the Universe, only a few particles are eternally stable. The photon, the quantum of light, has an infinite lifetime. Or does it?
Raisin bread expanding Universe
The big question isn't whether the Universe is expanding at 67 or 73 km/s/Mpc. It's why different methods yield such different answers.
A painting of a group of people standing in front of a church.
The original principle of relativity, proposed by Galileo way back in the early 1600s, remains true in its unchanged form even today.
A vast expanse of outer space densely populated with numerous stars, including the typical star, and celestial objects of varying brightness against a dark background.
Most stars in the Universe are located in big, massive, Milky Way-like galaxies. But most galaxies aren't like ours at all.
A worker in a hard hat and safety vest adjusts equipment in a facility alongside large red machinery labeled "Jefferson Lab." The scene fades into concentric circles, as if drawn by the powerful collider, leading to a bright light.
The largest particle accelerator and collider ever built is the Large Hadron Collider at CERN. Why not go much, much bigger?
Einstein
More than any other equation in physics, E = mc² is recognizable and profound. But what do we actually learn about reality from it?