Ethan Siegel

How far back in time can the naked eye see? Every observation out into deep space is also a look back in time.

How far back in time can the naked eye see?

To see back in the Universe farther than ever before, we need large, powerful telescopes.

But the naked eye, if you look just right, can take you impressively far.

bigthink.com/starts-with-...

#space #astro #cosmology

Ask Ethan: Is there really a "dark side" of the Moon? One side of the Moon always faces us: the near side. The "dark side" of the Moon began as a mere metaphor, but today, science can weigh in.

Is there really a “dark side” of the Moon?

#AskEthan

The phrase "dark side of the Moon" used to refer to the Moon's unseen, away-facing side: the far side.

But there is a "dark side" after all, just not where you'd expect.

bigthink.com/starts-with-...
#space #astro #moon

YouTube video by Rose City Astronomers RCA General Meeting November 17, 2025

Ethan, can you make a one hour presentation about The Grand Cosmic Story, and can we watch it irrespective of whether we buy your newest book or not?

www.youtube.com/watch?v=loCt...

Thanks to OMSI and the Rose City Astronomers for hosting me and letting me give this epic talk!
#space #astro

Either let us scan your private emails for AI training or we'll revert to hotmail circa 2000.

Enshittification of everything that was once good intensifies.

A scientific life is like a video game.

The fact that you are encountering new enemies is a sign that you're moving in the right direction.

Keep going!

The 6th grade question I'd have wanted to know was:

How did birds come from dinosaurs, and why did they survive when all the rest of the dinosaurs went extinct?

Ring galaxies, the rarest galaxy type of all, are finally understood Spirals, ellipticals, and irregulars are all more common than ring galaxies. At last, we know how these ultra-rare objects are made.

Ring galaxies, the rarest galaxy type of all, are finally understood

Only about 1-in-10,000 galaxies are ring galaxies, with an old, red nucleus and a young, blue ring surrounding it.

The mystery of their formation has finally been solved.
bigthink.com/starts-with-...
#space #astro #galaxies #ring

Request solved!

Thanks to all who liked and reshared!

Yay that's awesome!

Bluesky for #physics seems like the right place to make this ask, so...

Does anyone have (or can get) and want to send me a PDF copy of John Ralston's 2018 book on Quantum Mechanics: iopscience.iop.org/book/mono/97...

Thank you!

How are redshift, temperature, distance and time related? Wavelengths stretch, distances grow, and temperatures cool as the Universe expands with time. How are the various cosmic parameters related?

How are redshift, temperature, distance and time related?

As the Universe expands, the relationship between redshift, distance, and time becomes anything but trivial.

Here in the 21st century, though, we've finally figured it out.
bigthink.com/starts-with-...
#space #astro #cosmology

Ugh, I hate that I'm in here.

I don't even want the money.

I want the slop and the plagiarism to stop.

Jellyfish and bunny ear galaxies have cosmic consequences Weird-looking galaxies, with tentacle-like tails or prominent dual streams, appear like jellyfish or bunny ears. But that’s just the start.

Jellyfish and bunny ear galaxies have cosmic consequences

Some galaxies have jellyfish-like tentacles, and some have two prominent "bunny ears" attached to the main disk.

They aren't just fascinating; they create the intracluster light.
bigthink.com/starts-with-...
#space #astronomy #astro

The decline and fall of stars in the Universe For over 10 billion years, the cosmic star-formation rate has been dropping and dropping. Someday, the final star in the Universe will die.

The decline and fall of stars in the Universe

The cosmic star-formation rate rose and rose for billions of years, peaking about 10-11 billion years ago.

Today, it's slowed to a trickle, and someday, will cease altogether.
bigthink.com/starts-with-...
#space #astro #astronomy #stars

That is not good.

It hasn't lasted, but EC96's class theme was "I Stole Patt" because we stole Brian Patt's picture from EC95.

A few people from our graduating class in 2000 "fixed it" (made it PG) before our graduation.

That combination of immaturity plus creative brilliance is the ISP hallmark.

Insane Science Posse represent!

Ask Ethan: How can we better measure G, the gravitational constant? We first measured G, the gravitational constant, back in the 18th century. As the least well-known fundamental constant, can it be improved?

How can we better measure G, the gravitational constant?

#AskEthan

The universal gravitational constant, G, is one of the oldest fundamental constant of all, and yet, one of the least well-measured.

Can measuring it from space help?

bigthink.com/starts-with-...
#space #physics #astro

Light and gravity travel at the same speed, but don't arrive together In 2017, a kilonova sent light and gravitational waves across the Universe. Here on Earth, there was a 1.7 second signal arrival delay. Why?

Light and gravity travel at the same speed, but don’t arrive together

Yes, light waves and gravitational waves travel at exactly the same speed.

But when cosmic events create both at the same time, they don't arrive together.

Here's why.
bigthink.com/starts-with-...
#astro #space #gravity #light

Same. News to me; just finding out.

The devious trick behind the most sensational science headlines Dark matter, dark energy, and the Big Bang are all part of a solid scientific foundation. Here's why popular media often claims otherwise.

The devious trick behind the most sensational science headlines

Sick of sensationalistic science headlines that promise revolutions, but that don't pan out?

Here's what's wrong with science news, and why you keep seeing those dubious stories.
bigthink.com/starts-with-...
#space #physics #news

Astronomy's first gap-clearing planet fills in our "missing link" Planets grow from protostellar material in disks, leading to full-grown planetary systems in time. At last, the final gap has been filled.

Astronomy’s first gap-clearing planet fills in our “missing link”

We've seen protoplanetary disks with gaps, and fully mature systems with directly imaged planets.

For the first time, we've found them together: a disk-gap with an exoplanet inside.
bigthink.com/starts-with-...
#space #astro #planet

You probably haven't said this in 30 years but...

Damn you wasted no time breaking out the fist-shaking and off-my-lawn-getting did you?

How the "meter" came to be exactly one meter long Until the late 20th century, there wasn't a truly universal standard. Under our current definition, everyone agrees on what "one meter" is.

How the “meter” came to be exactly one meter long

In the search for a universal standard of distance, scientists have defined and redefined the meter over and over again.

After centuries of change, this 1983 definition should last forever.
bigthink.com/starts-with-...
#physics #measure #meter

Starts With A Bang podcast #123 - Alien physics Do aliens speak the same physics that we do, with similar laws, observables, and underlying mathematics. Maybe not, argues Daniel Whiteson.

Starts With A Bang podcast #123 – Alien physics

Do aliens speak the same physics that we do?

@danielwhiteson.bsky.social argues, in his new book and in this fascinating episode, that no, they probably don't.

I disagree; listen to the intense interview here!
bigthink.com/starts-with-...
#aliens

I mean that is an end-to-end problem.

This is the only type of scicomm people are paid by universities/research institutes to do: advertising the work at the institute, regardless of quality, accuracy, or merit, and often oversold atop that.

And then journos pick it up and try to maximize clicks.

Ask Ethan: Can Weber bars detect gravitational waves? We've now detected hundreds of gravitational waves with LIGO, Virgo, and KAGRA. What if we tried Weber's original method in the modern day?

Can Weber bars detect gravitational waves?

#AskEthan

Starting with 2015's first gravitational wave detection, LIGO/Virgo/KAGRA have now seen hundreds of gravitational waves.

Could the original detector design, Weber bars, work today?

bigthink.com/starts-with-...
#space #astro #physics #weber

Ask Ethan: What is the true purpose of scientific peer review? Just because a paper passes peer review doesn't mean that what's written, or what the author asserts, is true. Here's why it still matters.

Well, sure, that's true: assuming you are too young in your career to understand what peer review is and how it works and what it means to pass peer review.

But that's not you, because you know all of this:

bigthink.com/starts-with-...

To be sure, some get it "less wrong" than others (space dot com's reporting was egregious), but I wish that trying to play whack-a-mole after the fact wasn't the only tool I had to fight the Sisyphean battle.

It's lonely out here!

How is this "fair" in any way other than noting, "yeah, this is a flaw in the system of how we do journalism so don't blame the journalists for the flaws in the system?"

It's not fair to the reader who, you know, tends to expect reporters to report truthful things.