All posts tagged: Ethan

Ask Ethan: What do surveys of physicists actually reveal?

Ask Ethan: What do surveys of physicists actually reveal?

Published by Jenni Sidey

Out there in the Universe, there’s so much that we’ve learned and discovered. We know all about the normal matter present in the Universe: the full suite of Standard Model particles and how they interact all throughout cosmic history. We know about the laws that govern reality extremely well, including the fundamental forces and how they behave under a wide variety of cosmic and quantum conditions. We’ve reconstructed most of the history of the Universe in extraordinary detail, and from a variety of different approaches — observationally, theoretically, and experimentally — we’re gathering more and more evidence every day to peel back the curtains that obscure what’s beyond the currently understood frontiers governing reality. But what lies beyond what we’re already certain about? If we don’t already know, what do the greatest minds who ponder these problems think, and can their intuitions, educated guesses, or even hunches help drive the field forward? In one of the largest surveys of physicists about fundamental physics ever conducted, solicited by Physics magazine in 2025 and published online in …

Ask Ethan: Do gravitational waves redshift like light does?

Ask Ethan: Do gravitational waves redshift like light does?

Published by Jenni Sidey

Here in our Universe, the light that gets emitted from objects isn’t necessarily the same as the light that arrives in either our eyes or our instruments. Not only are there many intervening effects that can alter a signal on the way — by interacting with fields, by passing through neutral and ionized matter, and by having to compete with sources of noise — but there are kinetic (motion-based) and gravitational (spacetime-based) effects that alter those signals while in transit as well. In particular, three main effects all can systematically shift light of any wavelength toward either redder or bluer wavelengths: the relative motion of the emitting source and the receiving observer, the changes in the gravitational field that the traveling signal experiences during its journey, and the effects of either expansion or contraction of the spacetime through which the signal travels. These three effects can lead to redshifts or blueshifts, depending on which direction they occur in, and it was long expected that they’d affect all waves, not just light waves, in a similar …

Ask Ethan: Will anything persist when the Universe dies?

Ask Ethan: Will anything persist when the Universe dies?

Published by Jenni Sidey

If we’re willing to think about the future, the farther ahead we extrapolate, the farther along the inevitable path toward our thermodynamic end state: the heat death of the Universe. Star-formation will eventually end, and then the last shining stars will burn out. Galaxies will dissociate due to gravitational interactions, ejecting all masses and leaving only supermassive black holes behind. And then those black holes will decay via Hawking radiation, leaving only cold, stable, isolated bodies, from which no further energy can be extracted, all accelerating away from us within our dark energy-dominated Universe. At least, that’s what will happen in our far future based on our current cosmic picture: the best one we’ve figured out as of 2026. But this troubles a great many people, including our reader Mary Luce, who writes in to inquire: “I know I’ll be long dead and the Earth long gone, but it still makes me sad to think the Universe will die. That there will arise a time when everything that came before is meaningless. Instead of our …

Ask Ethan: How long can the longest-lived star shine?

Ask Ethan: How long can the longest-lived star shine?

Published by Jenni Sidey

If there’s one thing we can be certain of when we look out at the glittering canopy of the night sky, it’s this: that someday, all of those luminous points of light, including every star and every galaxy, will someday fade away and cease to shine. The stars and stellar remnants, the primary sources of light and heat and energy that propagate throughout the Universe, are only powered by finite sources of fuel: whether through nuclear fusion, gravitation, or any other mechanism. At some point, those fuel sources will be exhausted, no further energy will be naturally extracted from what remains within them, and those once-brilliant objects will fade away into darkness. Some stars live only briefly, others will continue to shine long into the future, with lifetimes far exceeding our Universe’s current 13.8 billion year age. That brings us to the question of James D, who was curious about the longest-lived stars of all, and wrote in to ask: “I was reading one of your articles about the lifespan of red dwarf stars, with …

From self-erasure to self-mastery: Ethan Suplee’s second act

From self-erasure to self-mastery: Ethan Suplee’s second act

Published by Jenni Sidey

Ethan Suplee is half the man he used to be. Literally. At his heaviest, the Hollywood actor weighed about 550 pounds. That’s large enough that it maxed out most standard scales, so Suplee stood on one used for weighing shipping containers instead. Today, at 250 pounds, he’s regularly described as “unrecognizable” by people once they realize that the bearded, muscular man making the fitness podcast rounds was once Frankie, the chubby bully on Boy Meets World, and lovable Louie from Remember the Titans. Suplee has spent the past several years documenting his transformation on his podcast, American Glutton, and across social media, where his second career as a fitness influencer has taken on a life of its own. But Suplee’s story isn’t just some feel-good redemption arc — it’s the account of a man who spent the first half of his life unaware that the hardest role to master would be being himself. The art of disappearing For Suplee, being someone else was easy. The man who has acted alongside the likes of Leonardo DiCaprio, …

Ask Ethan: Where are all the blueshifted galaxies?

Ask Ethan: Where are all the blueshifted galaxies?

Published by Jenni Sidey

Sign up for the Starts With a Bang newsletter Travel the universe with Dr. Ethan Siegel as he answers the biggest questions of all. Here in the Universe, there’s a fascinating property that nearly every galaxy beyond our own Milky Way seems to possess: the light that we observe from it seems to be shifted towards redder, longer wavelengths than the light that’s emitted from within our own galaxy. Within the context of General Relativity, there are a number of possible explanations for an observed redshift: it could be due to the relative motion of the source and the observer, it could be due to a different in the curvature of space between the source and the observer, or it could be due to the fabric of space itself stretching and expanding as light travels through it. Yet, if it were the effects of gravitational masses (like galaxies) tugging on other masses (like other galaxies) that dominated the Universe, you’d expect that there would be equal numbers of galaxies that are redshifted as compared to …

Ask Ethan: Why do gravitational lenses make crosses, not rings?

Ask Ethan: Why do gravitational lenses make crosses, not rings?

Published by Jenni Sidey

Sign up for the Starts With a Bang newsletter Travel the universe with Dr. Ethan Siegel as he answers the biggest questions of all. One of the most amazing properties of gravity in the context of Einstein’s General Relativity is that mass, wherever it’s concentrated, is capable of curving the very fabric of space. This leads to a number of vital effects: other nearby objects, from gas to galaxies, get attracted to and drawn into those massive clumps, all particles in motion, including massless particles, get gravitationally attracted to that region when they pass by it, and the light from background objects gets deflected, bent, magnified, and distorted by that curved space as it passes through it. That last effect is known as gravitational lensing, and it plays many important roles on cosmological scales. You might think, then, that a large, massive clump of matter — one that behaves as a gravitational lens — would commonly bend the light from background objects into a geometrically perfect shape: a ring. In fact, that very shape was …

Ask Ethan: Why is there no such thing as antigravity?

Ask Ethan: Why is there no such thing as antigravity?

Published by Jenni Sidey

Sign up for the Starts With a Bang newsletter Travel the universe with Dr. Ethan Siegel as he answers the biggest questions of all. Although there are four known fundamental forces to the Universe, there’s only one that matters on the largest cosmic scales of all: gravitation. The other three fundamental forces: the strong nuclear force, which holds protons and neutrons together, the weak nuclear force, responsible for radioactive decays and any “species change” among quarks and leptons, and the electromagnetic force, which causes neutral atoms to form, are all largely irrelevant on cosmic scales. The reason why is simple: the other forces, when you gather large sets of particles together, all balance out at large distances. Matter, under those three forces, appears “neutral” at large scales, and no net force exists. But not so with gravitation. In fact, gravitation is unique in this sense. With gravitation, there are only “positive” charges: things with positive amounts of mass and/or energy. Between those things, the gravitational force is only attractive, and so cumulatively, it can really …

Ask Ethan: Why does something exist instead of nothing?

Ask Ethan: Why does something exist instead of nothing?

Published by Jenni Sidey

Sign up for the Starts With a Bang newsletter Travel the universe with Dr. Ethan Siegel as he answers the biggest questions of all. Perhaps the most remarkable fact about the Universe, if you think about it on a truly fundamental level, is that it exists at all. And yet, not only does it exist, but there’s matter within it, which obeys the same rules everywhere and at all times, and assembles according to the physical laws governing reality to create, among other things: atomic nuclei, neutral atoms, molecules, stars and planets, galaxies, and a large-scale cosmic web. Not only that, but in at least one relatively unremarkable corner of this Universe, a planet arose some 4.5 billion years ago where life survived and thrived, eventually giving rise to an intelligent, self-aware species that can ask deep questions about the Universe they inhabit. In doing so, we’re also asking fundamental, deep questions about our own selves, as we’re just as much a part of this Universe as any inanimate objects that exist. That’s what led …