with Ethan Siegel • March 1, 2025
Greetings readers,
Here we are: all the way through February. It may have been the shortest month of the year, but there was no shortage of incredible science to learn and incredibly rich topics to think about, even as many events in the world have unfolded to place our scientific concerns on the back burner. Still, science and all it has to show us about the world (and beyond) remain a universal source of joy and knowledge, and no political concerns will ever change that. After all, we're in the business of exploring and understanding reality, and no matter what we do, nature will continue to obey the fundamental rules that govern it. It's up to us to figure out what those rules are and how to apply them.
This week, I've jumped all over, topic-wise. The largest galactic mosaic ever taken with the Hubble Space Telescope, of the Andromeda galaxy, was just completed, with an incredible number of science discoveries already uncovered within it. A new mission just launched yesterday: SphereX, which will perform large-scale galaxy mapping and teach us cosmic lessons that even the CMB cannot. The Universe around us may seem arbitrary in terms of the different scales that objects form on, but it isn't. It's determined by the charges and masses of what is in the Universe. Plus, if you wanted the USA to become a scientific nation, what changes would our country need to make? I've got four key steps we can all take. And finally, there's our weekly Ask Ethan column, devoted to the question of what it is that increases as we near the speed of light: mass or energy, and how do we know?
As we head into March, I'm very excited to tease that we'll soon have our first big video: of me explaining the Universe right here in a giant and compelling Big Think interview. Don't miss it!
All the best,
Ethan
HUBBA HUBBLE
Hubble completes the largest galactic mosaic of all-time
Ten years ago, Hubble released their results from PHAT, the Panchromatic Hubble Andromeda Treasury. It stitches together 394 hours of observations, containing over 100 million stars, into one glorious mosaic. Now, in 2025, they’ve extended that survey to the southern half of Andromeda and completed our largest galactic mosaic ever, with more than 600 overlapping snapshots in a 2.5+ billion pixel image. Check it out.
CAPTURING THE COSMOS
How mapping galaxies can teach us what the CMB can’t
The CMB gives us critical information about our cosmic past. While an enormous amount of cosmic information comes from the Big Bang’s leftover glow, the CMB can’t teach us everything about the Universe. That’s where mapping galaxies can come in; here’s why it’s so critical.
ASK ETHAN
Ask Ethan: Does mass or energy increase near the speed of light?
Perhaps the most well-known equation in all physics is Einstein’s E = mc². Does mass or energy increase, then, near the speed of light? Different interpretations have confused many, even physicists, for a long time. Let’s bring some clarity to our physical reality.
If you have a burning question about the Universe, send me an email.
ITS WHY WE EXIST
How charges and masses create the Universe around us
It’s hard to believe, but the incredibly rich, varied world and Universe we see around us is composed, at its core, of just a few different species of fundamental particles. Everything that exists, from the tiniest subatomic scales to the grandest cosmic structures, depends on two things: charge and mass.
WORKING TOGETHER
4 key steps to transform the USA back into a scientific nation
Any prosperous society must commit to working collectively for the common good of all of us, including investing resources in endeavors that benefit everyone. It might seem that we’re a long way away from that, and it might seem like we’re heading in the wrong direction, but these four key steps, if all taken together, can put us back on the right track.
Ethan Siegel, Ph.D., is an award-winning theoretical astrophysicist who's been writing Starts With a Bang since 2008. You can follow him on Twitter @StartsWithABang.