Ethan Siegel

Ethan Siegel

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Astrophysicist; cosmology education

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