Ethan Siegel

The Universe is: Expanding, cooling, and dark. It starts with a bang! #Cosmology Science writer, astrophysicist, science communicator & NASA columnist.


The Physics of the Death Star

How to destroy an Alderaan-sized planet.

“What’s that star?
It’s the Death Star.
What does it do?
It does Death. It does Death

Ask Ethan #90: Muons, relativity & a new record?

How one of the first tests of special relativity might lead to the greatest particle accelerator of all-time.


Throwback Thursday: When We Changed The Laws Of Gravity

How the Solar Eclipse of 1919 spelled the end for Newton.

“Oh leave the Wise our measures to collate…

Throwback Thursday: The Legacy of Sally Ride

What the first American woman in space meant for people everywhere.

“Each generation goes further than the generation

Publications edited by Ethan Siegel

The Universe is out there, waiting for you to discover it.


Jupiter, Io, and a Cosmic Zamboni

How tides, gravity and lava give Io the youngest surface in the Solar System.

“The crust, being so thin, must bend, if, over wide

Mostly Mute Monday: The Largest Eruption In The Known Universe

A galaxy cluster that’s been actively devouring matter for hundreds of millions of years blows all the records away.


Weekend Diversion: The Logic That Stumped Brooklyn Nine Nine

The most famous logic puzzle from the best police comedy on television, and how to (finally) solve it!


Ask Ethan #89: The Universe’s Dark Ages

After the CMB, before the first stars, there was nothing to see. Or was there?

“[I]f there were no light in the universe…

Throwback Thursday: Are asteroids dangerous?

Sure, they wiped out the dinosaurs, but do they really pose a risk to humans?

“The oldest and strongest emotion of

The Invisible Mountains of Earth

How gravity teaches us that the mountains we see extend far underground.

“Journalists often ask me when I go to the field, ‘What

What’s causing Ceres’ white spots?

A series of mysterious white features lurk at the bottom of one of its most massive craters. Here’s what they could be, and how we’ll find out!