ask Ethan
esiegel | March 7, 2015“It followed from the special theory of relativity that mass and energy are both but different manifestations of the same thing — a somewhat unfamiliar conception for the average mind.” -Albert Einstein
On the one hand, we have matter -- things with mass -- in the Universe, ranging all the way from planets, stars and galaxies on the largest scales to molecules, atoms and fundamental particles on the smallest.
Image credit: Jenny Mottar.
But then, on the other hand, there are particles without mass at all: photons, for example. They still carry energy and momentum, but of all the…
esiegel | February 27, 2015“A vacuum is a hell of a lot better than some of the stuff that nature replaces it with.” -Tennessee Williams
The depiction of dying in space -- by exposure to its terrifying vacuum -- is incredibly varied, from freezing to swelling and bulging to simply exploding.
Image credit: Mike Tyson Mysteries / Adult Swim. Uh oh, looks like I killed another astronaut!
For this week's Ask Ethan, we take on the question of Kerrie Pinkney, who wants to know:
[W]ill you explode if exposed to the vacuum of space? I’ve gone down the “water boils in a vacuum then freezes” road, others have gone down the “…
esiegel | February 20, 2015“It followed from the special theory of relativity that mass and energy are both but different manifestations of the same thing — a somewhat unfamiliar conception for the average mind.” -Albert Einstein
In physics, we're always on that quest for the next frontier: the next order of magnitude higher in energy, the next order of magnitude closer to absolute zero, the next extra decimal place in our quest towards the speed of light. As far as we've come in terms of pushing the frontiers, we're always striving to go a little bit farther.
Image credit: RHIC collaboration, Brookhaven, viahttp://…
esiegel | February 6, 2015“Henceforth space by itself, and time by itself, are doomed to fade away into mere shadows, and only a kind of union of the two will preserve an independent reality.” -Hermann Minkowski
When you think of waves, chances are you think of some type of pressure wave moving through a medium, like sound or water waves, or you think of light, which is an electromagnetic wave that requires no medium to move through. But there's another type of wave that exists, that no one expected before Einstein came along: gravitational waves.
Image credit: Wikimedia Commons user MOBle.
It's very…
esiegel | January 30, 2015“Go then, there are other worlds than these.” -Stephen King, The Dark Tower
Ever since quantum mechanics first came along, we've recognized how tenuous our perception of reality is, and how -- in many ways -- what we perceive is just a very small subset of what's going on at the quantum level in our Universe.
Image credit: Wikimedia commons user Christian Schirm.
Then, along came cosmic inflation, teaching us that our observable Universe is just a tiny, tiny fraction of the matter-and-radiation filled space out there, with possibilities including Universes with different fundamental laws…
esiegel | January 23, 2015“The only reason for time is so that everything doesn’t happen at once.” -Albert Einstein
And yet, this is a very good reason! We need things to happen in stages: you can't form human beings before you form planets (that would be bad); you can't form stars before you form atoms (also bad); you can't form atomic nuclei before you get rid of antimatter (still bad).
Image credit: Addison Wesley.
But somehow, despite having very little direct evidence for what happened in the early Universe, we tend to give timelines of precisely when various events happened. For this week's Ask Ethan, we take…
esiegel | January 17, 2015“The single most powerful element of youth is our inability to know what’s impossible.” -Adam Braun
"I'm going to be a star," says every clump of matter in a molecular cloud, as it prepares to collapse under the tremendous pull of gravitation. But try as they might, only a small fraction of that gas and of those clumps -- the largest and earliest, preferentially -- will ever get there.
Image credit: Tom O’Donoghue, via http://www.flickr.com/photos/28192200@N02/8528939580/in/photostream.
This week's Ask Ethan question is one of the shortest and sweetest out there, and comes from Greg Rogers…
esiegel | January 10, 2015“I want to stand as close to the edge as I can without going over. Out on the edge you see all the kinds of things you can’t see from the center.” -Kurt Vonnegut
The Universe is expanding and cooling, with all but a few of the closest galaxies receding from our view. In fact, the farther away an object is, the faster it appears to recede.
Image credit: E. Siegel.
This may sound an awful lot like an explosion to you, and the name "the Big Bang" sure gives that same implication, doesn't it? Yet despite these facts, it turns out that the idea that the Universe has a center is completely false…
esiegel | January 2, 2015“What is that feeling when you’re driving away from people and they recede on the plain till you see their specks dispersing? — it’s the too-huge world vaulting us, and it’s good-bye. But we lean forward to the next crazy venture beneath the skies.” -Jack Kerouac
But how do you say goodbye to a galaxy that will never receive your message? As it turns out, that's 97% of the galaxies in our Universe!
Image credit: NASA; ESA; G. Illingworth, D. Magee, and P. Oesch, University of California, Santa Cruz; R. Bouwens, Leiden University; and the HUDF09 Team.
While we might still be able to see the…
esiegel | December 26, 2014“Be miserable. Or motivate yourself. Whatever has to be done, it’s always your choice.” -Wayne Dyer
We all can think back to that moment that happened where we knew our lives would be forever different, right? To that one moment in our past where we suddenly knew what it was that we wanted to be, what we wanted to do, what that special career move defining us would wind up becoming.
Image credit: My Little Pony: Friendship Is Magic, Season 1 Episode 23.
You know, that moment where you figure out what your special talent/passion is.
Only, that isn't how real life works! It's actually a…
esiegel | December 19, 2014“We are incredibly heedless in the formation of our beliefs, but find ourselves filled with an illicit passion for them when anyone proposed to rob us of their companionship.” -James Harvey Robinson
The Universe seems to be full of contradictions. On one hand, everywhere we look -- in all directions and at all locations -- we find that it's full of stars, galaxies and clusters. There are regions pretty much everywhere where, in the great cosmic struggle between all the pulls and pushes, gravitation has won.
Image credit: NASA; ESA; G. Illingworth, UCO/Lick Observatory and the University of…
esiegel | December 12, 2014“Time takes it all whether you want it to or not, time takes it all. Time bares it away, and in the end there is only darkness.” -Stephen King
This story seems to come up every few months. Someone detects a possibly unexpected signal somewhere in the sky -- normally correlated to the centers of galaxies or galaxy clusters -- and says: that's it, I found dark matter!
Image credit: European Space Agency, NASA and Jean-Paul Kneib (Observatoire Midi-Pyrénées, France/Caltech, USA), via http://www.spacetelescope.org/images/heic0309a/.
Did you, though? The evidence has panned out to be a …
esiegel | December 5, 2014“Nothing is too wonderful to be true, if it be consistent with the laws of nature.” -Michael Faraday
And yet, it's often incredibly difficult to use those laws of nature -- even if they're as simple as can be -- to actually measure and quantitatively understand the Universe around us. Perhaps one of the most glaring examples is magnetism.
Image credit: Alexander Wilmer Duff, 1916.
Sure, it's easy to visualize a magnetic field if you've got a set of iron filings and a laboratory to experiment in, but what about the distant stars? What of entire galaxies? They're thought to have magnetic…
esiegel | November 28, 2014“The trees that are slow to grow bear the best fruit.” -Molière
So if the Universe is expanding and cooling, what does that mean for the matter in it? Sure, it's easy to visualize how radiation cools: it has a wavelength, space expands, and so as the wavelength gets stretched, the energy drops.
Image credit: James Imamura of University of Oregon, viahttp://hendrix2.uoregon.edu/~imamura/123cs/lecture-5/lecture-5.html.
But the energy must have dropped for matter as well, otherwise it wouldn't have lost enough kinetic energy to become gravitationally bound into gas clumps, stars and galaxies…
esiegel | November 22, 2014“You can try to lie to yourself. You can try to tell yourself that you put in the time. But you know — and so do I.” -J.J. Watt
Before there was the Universe we know and love today, there were many epochs and eras that came before, including one before there were galaxies and stars, one before there were atoms, one before there were nuclei, and even one where matter and antimatter were spontaneously created at ultra-high energies.
Image credit: ESA and the Planck collaboration, modified by me.
But throughout all those eras, spacetime has been a constant companion. Given that we had an…
esiegel | November 14, 2014“Sometimes, I sit alone under the stars
and think of the galaxies inside my
heart, and truly wonder if anyone will
ever want to make sense of all that
I am.” -Testy McTesterson
The largest galaxies in the Universe all have a few things in common: they all contain many trillions of stars, they all contain many times their stellar mass in the form of dark matter, and they're all found towards the centers of great galactic clusters.
Image credit: ESO and Digitized Sky Survey 2. Acknowledgment: Davide De Martin. Via http://www.eso.org/public/images/eso0949m/.
Oh, and one more thing: none of…
esiegel | November 7, 2014“In my dreams and visions, I seemed to see a line, and on the other side of that line were green fields, and lovely flowers, and beautiful white ladies, who stretched out their arms to me over the line, but I couldn’t reach them no-how. I always fell before I got to the line.” -Harriet Tubman
One of the things we learn about the gravitational force is that it has an "infinite range" to it. Because it's a ~1/r^2 force, and because as you move radially away from the source, a sphere spreads out (in surface area) as ~r^2, you don't lose anything as you move farther and farther away. So long as…
esiegel | November 1, 2014“I think one of the coolest things you can do is disappear for a while, because it gives you the chance to re-emerge.” -Josh Homme
The Big Bang -- and General Relativity in general -- teaches us that in an expanding Universe, it's the fabric of space itself that evolves over time. One of the consequences of this is a bit puzzling: that since the Universe was denser in the past, it must have been hotter in the past as well.
Image credit: NASA / GSFC.
But if each individual photon has redshifted to longer wavelengths, and the energy of every photon is inversely proportional to that…
esiegel | October 25, 2014“The light that burns twice as bright burns half as long — and you have burned so very, very brightly, Roy. Look at you: you’re the Prodigal Son; you’re quite a prize!” -Dr. Eldon Tyrell, Blade Runner
Some questions that we look at are fun to consider because of how far outside our own experience they are, but others are fun for the exact opposite reason: because they ask about a very common phenomenon whose explanation isn't so simple!
Image credit: James Brittin.
Think about fire, for example, and why a campfire with a single large log on it takes a certain amount of time to burn, but…
esiegel | October 17, 2014“I must choose between despair and Energy —— I choose the latter.” -John Keats
Yes, we know that the fabric of the Universe is not made up of space and time but rather a unified spacetime; that the spacetime isn't static but rather expands as the Universe goes on; and that the expansion isn't slowing down but is rather accelerating as we continue. The term we give to this phenomenon is dark energy, and we arrive at it via multiple, independent lines of evidence.
Image credit: Supernova Cosmology Project / Amanullah et al., Ap.J. (2010).
But with all of that, just what exactly is dark…