Ethan Siegel

Ethan Siegel

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Astrophysicist; cosmology education

Unification Attempts May Be Fundamentally Misguided, Always Needing New Ingredients
SocialApr 23, 2026

Unification Attempts May Be Fundamentally Misguided, Always Needing New Ingredients

The idea of “theories of everything” may be fundamentally wrong All attempts at "unification" or "theories of everything" necessarily add new particles and new ingredients to the theory. Is this a fundamentally flawed approach? https://t.co/Khl3XWnF9s

By Ethan Siegel
Antimatter: Humanity’s Only Viable Interstellar Fuel
SocialApr 22, 2026

Antimatter: Humanity’s Only Viable Interstellar Fuel

Only antimatter provides the energy we need for interstellar travel This Earth Day, some dream of saving the Earth, while others dream of leaving it. Here's why using antimatter as fuel is humanity's best bet for interstellar travel. https://t.co/ZBs6y8YGTm

By Ethan Siegel
Dark Matter Passes New Cosmic Test, MOND Fails
SocialApr 21, 2026

Dark Matter Passes New Cosmic Test, MOND Fails

Dark matter passes a new cosmic test, while MOND fails A new cosmic test has finally, with CMB and large-scale structure data, become realistic: using the kinetic Sunyaev-Zel'dovich effect to test dark matter vs. MOND. Guess who wins? https://t.co/jja8ObZ5OQ

By Ethan Siegel
Stars Are Born when Equilibrium, Not Ignition, Occurs
SocialApr 20, 2026

Stars Are Born when Equilibrium, Not Ignition, Occurs

Star birth doesn’t come from ignition, but from equilibrium In astronomy, "a star is born" happens when nuclear fusion ignites in its core, according to the internet. That's not the scientific standard, though: equilibrium is. https://t.co/9OP0xyy5xL

By Ethan Siegel
Planet Formation Timeline Finally Solved After 35 Years
SocialApr 17, 2026

Planet Formation Timeline Finally Solved After 35 Years

Ask Ethan: How long does it take planets to form? Just 35 years ago, we knew so little about how planets formed, or how long the process took. Here in 2026, we now have a complete end-to-end story: validated by actual data. https://t.co/coJPyFNQW0

By Ethan Siegel
Strong Force Explained Simply, No Color Charge Needed
SocialApr 16, 2026

Strong Force Explained Simply, No Color Charge Needed

Can you explain the strong nuclear force without colors? The idea of a "color charge" confuses a lot of people, and the analogy certainly has its flaws. Here's how to understand the strong force without colors, and without group theory, too. https://t.co/4qKBpVpZCI

By Ethan Siegel
Viral Saturn Image Is AI Fake, Here's Proof
SocialApr 15, 2026

Viral Saturn Image Is AI Fake, Here's Proof

This viral image of Saturn isn’t real; it’s AI slop A new image of "Saturn's North Pole" has gone viral. Too bad it's an AI fake. Here's what the real things look like, and how you can tell for yourself. https://t.co/r5kz9pGCZM

By Ethan Siegel
Mass Alone Determines Planets, Stars, and Brown Dwarfs
SocialApr 14, 2026

Mass Alone Determines Planets, Stars, and Brown Dwarfs

Everything in the Universe changes by adding enough mass What sets the dividing line between rocky planets, gas giants, brown dwarfs, and stars of different colors and lifetimes? One parameter alone, mass, explains almost all of it. https://t.co/I3pkaf2lX7

By Ethan Siegel
Bad Measurement Cannot Explain Hubble Tension, Study Shows
SocialApr 13, 2026

Bad Measurement Cannot Explain Hubble Tension, Study Shows

“One bad measurement” ruled out as Hubble tension explanation When thinking about the Hubble tension, many fault "one bad measurement," somewhere, as the ultimate culprit. Astronomers just showed this cannot be the case. https://t.co/e3cdhUyAZT

By Ethan Siegel
Scientists Spot First Ever Proto‑Protoplanet, Pre‑Planetary Stage
SocialApr 11, 2026

Scientists Spot First Ever Proto‑Protoplanet, Pre‑Planetary Stage

Starts With A Bang #128 – Planet formation and proto-protoplanets You've heard of planets, exoplanets, and protoplanets. Now, for the first time, we've discovered something more primitive than any of them: a proto-protoplanet. Here's what it means. https://t.co/1HEVsXDCDp

By Ethan Siegel
Three Factors That Let Artemis II Surpass Apollo’s Record
SocialApr 10, 2026

Three Factors That Let Artemis II Surpass Apollo’s Record

How did Artemis II break Apollo’s distance record? #AskEthan If you ask google how Artemis II broke Apollo 13's distance record, it'll lie and say "because the rocket was more powerful." But these three reasons, combined, are how it really happened. https://t.co/lqbj3u00kP

By Ethan Siegel
Inflation Explains Universe’s Low‑entropy Big Bang
SocialApr 9, 2026

Inflation Explains Universe’s Low‑entropy Big Bang

Cosmic inflation explains the Universe’s low entropy at birth The "past hypothesis" problem questions why, if entropy always increases, the hot Big Bang began with such a low amount of it. That's another puzzle solved by cosmic inflation. https://t.co/WYVdSHxPx9

By Ethan Siegel
Discovery of Ultra‑pristine Star Reshapes Early Star Formation
SocialApr 7, 2026

Discovery of Ultra‑pristine Star Reshapes Early Star Formation

Astronomers just found the most pristine star of all-time The most pristine star of all-time has been found: J0715-7334, with just 0.005% of the heavy element content of the Sun. Here's what it teaches us about how stars grow up. https://t.co/3FEBKLH6g8

By Ethan Siegel
Artemis II Moon Return Sparks Hope for Humanity
SocialApr 6, 2026

Artemis II Moon Return Sparks Hope for Humanity

Something special is happening in space right now As Artemis II astronauts reach the Moon for the first time in 54 years, it gives humanity something we've been missing for decades: hope that we can become something great. https://t.co/wdFUF4tfOB

By Ethan Siegel
Gravitational Waves Also Experience Cosmic Redshift
SocialApr 3, 2026

Gravitational Waves Also Experience Cosmic Redshift

Ask Ethan: Do gravitational waves redshift like light does? Light redshifts as it travels through the expanding Universe, and is affected by a host of other phenomena. But not everything is the same for gravitational waves. https://t.co/x7HvhjGPU5

By Ethan Siegel
Evolving Dark Energy Claims Remain Weak, Puzzles Persist
SocialApr 1, 2026

Evolving Dark Energy Claims Remain Weak, Puzzles Persist

The flimsy case for evolving dark energy There's been a lot of talk about evolving dark energy, and how DESI data demands it. But the case for this remains somewhat weak, while the true underlying puzzles remain unsolved. https://t.co/Xh1dgGu3kI

By Ethan Siegel
Space Megaconstellations Threaten Near-Earth Environment, Urge Resilience
SocialMar 31, 2026

Space Megaconstellations Threaten Near-Earth Environment, Urge Resilience

The new Big Think print issue just dropped: on the Roots of Resilience. Here's how we can avoid a space megaconstellation mega-disaster. The current situation, where companies do nothing, is a recipe for destroying our one & only near-Earth environment. https://t.co/FycTO9j4QD

By Ethan Siegel
Even a Three‑second Pause Reshapes the Universe
SocialMar 31, 2026

Even a Three‑second Pause Reshapes the Universe

The Universe has changed by the time you finish this sentence It takes just over three seconds to read a typical sentence. In that tiny flash of time, the Universe has changed in tiny but mighty ways. On cosmic timescales, that really adds...

By Ethan Siegel
Peculiar Galaxies Reveal Cosmic Violence Behind Galaxy Formation
SocialMar 30, 2026

Peculiar Galaxies Reveal Cosmic Violence Behind Galaxy Formation

Peculiar galaxies showcase the beauty of cosmic violence Most galaxies are spirals, with ellipticals and lenticulars making up the next most common types. But peculiar galaxies reveal the in-between steps, showing how modern galaxies are made. https://t.co/IDAhiX1sEr

By Ethan Siegel
Dark Energy Keeps Universe Flat Despite Dilution
SocialMar 27, 2026

Dark Energy Keeps Universe Flat Despite Dilution

Ask Ethan: Does dark energy curve the Universe over time? Our Universe was once ruled by radiation and matter, but those densities eventually dilute. Would spatial curvature appear? Even if it did, dark energy now flattens the Universe once again. https://t.co/zF67EySaRB

By Ethan Siegel
No Cosmic Hole Exists; Nebula Image Is Misused
SocialMar 26, 2026

No Cosmic Hole Exists; Nebula Image Is Misused

The widely reported “hole in the Universe” is a lie It's 2026. There still isn't a hole in the Universe, and the famous nebula they always show when describing it doesn't have anything to do with the Universe at all. https://t.co/91kWOrNZTD

By Ethan Siegel
AI Use Stunts Skills at Any Age, Keep Learning
SocialMar 25, 2026

AI Use Stunts Skills at Any Age, Keep Learning

BrainMaxxing: the road less traveled in the age of AI For older people, AI overuse leads to skill erosion. For younger people, AI leads to you never developing those skills in the first place. It's never too late to grow your mind instead. https://t.co/1DY5Eyi0sm

By Ethan Siegel
Why Does the Universe Follow Universal Laws?
SocialMar 20, 2026

Why Does the Universe Follow Universal Laws?

Ask Ethan: Does nature need to obey laws at all? One of the most profound facts about the Universe is that it obeys the same laws in all places and at all times. But why are there laws that govern it...

By Ethan Siegel
A Fifth Force May Exist, Yet Detection Remains Elusive
SocialMar 19, 2026

A Fifth Force May Exist, Yet Detection Remains Elusive

The case for and against a 5th fundamental force of nature Looking for a fifth fundamental force of nature? It might be out there. But finding one is a much bigger challenge than any experiment or observation is up to, at least, so...

By Ethan Siegel
CPT Symmetry: Nature’s Truly Unbreakable Rule
SocialMar 18, 2026

CPT Symmetry: Nature’s Truly Unbreakable Rule

Why “CPT” is the Universe’s most unbreakable symmetry Some symmetries are always preserved, although things could be different if they weren't. But particle physics's CPT symmetry may truly be unbreakable. https://t.co/tcGehBgNs7

By Ethan Siegel
Observations Show Universe Is Flat Despite Einstein’s Curvature Possibilities
SocialMar 17, 2026

Observations Show Universe Is Flat Despite Einstein’s Curvature Possibilities

Einstein showed space can curve, but data reveals a flat Universe According to Einstein, space can take on any curvature depending on what's in it: positive curvature, negative curvature, or zero (flat) curvature. So why is our Universe so flat? https://t.co/fyjYOnXs1d

By Ethan Siegel
Future Universe: Darkness Fades, New Light Awaits
SocialMar 13, 2026

Future Universe: Darkness Fades, New Light Awaits

How dark will the Universe become? #AskEthan Sure, dark energy will empty out the Universe and galaxies will run out of fuel to form new stars. But that doesn't mean our sky will only get darker. Look forward to the brightness ahead. https://t.co/huqNduzpjh

By Ethan Siegel
Relativity Lets You Jump Ahead, Not Live Longer
SocialMar 12, 2026

Relativity Lets You Jump Ahead, Not Live Longer

A quirk of relativity is the closest thing to achieving immortality Even relativity, with all the power of time dilation, won't increase the span of your lived life. But it can take you far into the future, and even to the ends...

By Ethan Siegel
NASA's AXIS X-Ray Mission Canceled After 2025 Cuts
SocialMar 11, 2026

NASA's AXIS X-Ray Mission Canceled After 2025 Cuts

NASA’s next X-ray mission, AXIS, has been killed Did you think that the cuts to NASA made in 2025 had all been reversed, and everything is now fine? Think again. NASA's AXIS mission, on account of that 2025 bloodbath, is now dead. https://t.co/gdFHBnGzRJ

By Ethan Siegel