How Can We Still See The Disappearing Universe?
“In fact, we can even think about what you’d see if you were to look at a galaxy whose light hasn’t arrived at our eyes yet. The most distant object we can see, 13.8 billion years after the Big Bang, is presently 46 billion light-years away from us. But any object that’s presently within 61 billion light-years of us will someday have that light eventually reach us.
That light was already emitted, and is already on its way to us. In fact, that light is already most of the way there; it’s closer than the 15 billion light-year limit of what we could possibly reach if we left for it at the speed of light. Even though the Universe is expanding, and even though the expansion is accelerating, that journeying light will someday arrive at our eyes, giving us, in the far future, the ability to see even more galaxies than we can today.”
Dark energy seems to present a paradox. On the one hand, galaxies are receding from us as the Universe expands, meaning we can never reach them once they’re beyond a certain point, and that the light being emitted by them can also no longer reach us. But even though these galaxies are a part of our dark energy-dominated Universe, we’ll always be able to see them in the future once they become visible to us.
If the Universe is disappearing, how can we still see the galaxies in it? Come get the answer to one of cosmology’s biggest (misconception-related) puzzles today!
New Podcast: Black Holes And Gravitation
So, you want to know about black holes, including how we’re seeing them, what happens when you fall into them, what our future plans for direct and indirect detection are, and how scientists are answering some of the biggest questions about them today?
It’s a fascinating story about some of the most mind-blowing objects in the Universe. Please welcome Assistant Professor of Astronomy and Physics at the University of Mississippi, Dr. Leo C. Stein, to the show, and enjoy a 1 hour+ conversation where we explore some of the deepest concepts in cutting-edge physics and gravitational wave astronomy!
Go hear the whole thing on Soundcloud today!
What Would The Milky Way Look Like If You Could See All Of Its Light?
“When you look at the Milky Way in visible light, you might see billions of stars, but you miss so much more. The human eye is only sensitive to a tiny fraction of the entire electromagnetic (light) spectrum. Each wavelength range showcases a novel view of all that’s out there.”
If you looked out at our galaxy with your eyes and the wavelengths they’re sensitive to alone, there’s an incredible amount of information you’d miss no matter how powerful you became at gathering light or resolving individual objects. That’s because visible light only occupies a narrow range of electromagnetic wavelengths, meaning that what you can see is limited to what emits visible light (stars and some reflective clouds) and constrained by dust, which can absorb all the visible light behind it.
But there are other wavelengths than these, and they reveal a series of fascinating details. What do they all look like? Come get a fuller picture today!
Ask Ethan: Why Haven’t We Found Gravitational Waves In Our Own Galaxy?
“Why are all the known gravitational wave sources (coalescing binaries) in the distant universe? Why none has been detected in our neighborhood? […] My guess (which is most probably wrong) is that the detectors need to be precisely aligned for any detection. Hence all the detection until now are serendipitous.”
On September 14, 2015, our view of the Universe changed forever with the first direct detection of gravitational waves. Since then, we’ve detected a variety of black hole and neutron star binaries in the final, end-stages of coalescence, culminating in a spectacular merger. But they’re all hundreds of millions or even billions of light-years away!
Simultaneously, we know that we have neutron stars and black holes in binary systems here in our own galaxy. But of all the gravitational waves that LIGO and Virgo have detected, none of these objects are among them. This remains true, even though we can identify many of them from their electromagnetic signatures.
Why haven’t we found gravitational waves in our own galaxy? Give us a better observatory and we will! Here’s the full scientific story on that.
One Of These Four Missions Will Be Selected As NASA’s Next Flagship For Astrophysics
“Choosing which of these missions to build and fly will, in many ways, inform our plans for the next 30 years (or more) of astronomy. NASA is the pre-eminent space agency in the world. This is where science, research, development, discovery, and innovation all come together. The spinoff technologies alone justify the investment, but that’s not why we do it. We are here to discover the Universe. We are here to learn all that we can about the cosmos and our place within it. We are here to find out what the Universe looks like and how it came to be the way it is today.
People will always argue over budgets — the penny-pinchers are always happy to propose something that’s faster, cheaper, and worse — but the reality is this: the budget for NASA Astrophysics as a whole is just $1.35 billion per year: less than 0.1% of the federal discretionary budget and less than 0.03% of the total federal budget. And still, for that tiny amount, NASA has steadily built a flagship program that’s the envy of the free world.”
Every 10 years, NASA performs a decadal survey, where it outlines its highest mission priorities for the next 10 years. The 2020 decadal is happening imminently, and once the recommendations are submitted to the National Resource Council at the National Academies of Science, the four flagship finalists will be ranked. This will determine NASA astrophysics’ direction for the 2030s.
James Webb is the flagship for the 2010s; WFIRST is it for the 2020s. What will we choose for the 2030s? It will be one of these four finalists! Dream big, everyone.
No, Quantum Tunneling Didn’t Break The Speed Of Light; Nothing Does
“You might think, based on what you just read about the speed of quantum tunneling being instantaneous, that this means that particles can travel infinitely fast, breaking the speed of light, through a quantum mechanical barrier of finite, non-zero thickness. That’s the misinterpretation that always crops up, and how people fool themselves (and unscrupulous news organizations try to fool you) into thinking they’re breaking the speed of light.
But all that’s happening here is a portion of the quantum particles found in the pulse tunnels through the barrier, while the majority of the particles does what tennis balls do: they bounce back, failing to arrive at the destination. If you can front-load which particles make it through the barrier, preferentially cutting off the particles in the back of the pulse, you’ll falsely measure a faster-than-light speed, even though no individual particle actually breaks the speed of light.”
For the first time, researchers have measured what the speed of quantum tunneling is, and found that it was consistent with an instantaneous transition. If you’re in a quantum configuration that keeps you bound, or on one side of a barrier, tunneling can enable you to become unbound, or arrive on the other side of the barrier. But that doesn’t mean you can physically travel a finite distance through that barrier instantaneously, or faster-than-light. You can’t.
Here’s the real story, with an extra bonus of how this story (and ones like it) get mis-reported all the time.
What Was It Like When Oxygen Appeared And Almost Murdered All Life On Earth?
“This might be a simple biological scenario, but its results are nearly universal. In the presence of virtually no competitors or predators, and given practically unlimited resources, a living population will grow at an exponential rate. It will consume the available resources, produce whatever metabolism products it produces, and then reproduce in greater-than-replacement-level numbers.
The next generation will then consume more, produce more of its metabolites, and reproduce even greater numbers. So long as resources are freely available, this process will continue. Until, that it, the metabolic processes it has been undergoing build up to a critical level where it poisons its environment. If this sounds like what the yeast did — or what modern humans are doing with CO2 — you’ve put the pieces together correctly. Organisms, if left unchecked, will poison their habitat with the waste products of their own success.”
Approximately 2.5 billion years ago (but maybe more), a key development occurred in life on Earth: some unicellular creatures that were capable of photosynthesis began producing oxygen as an end-product of their metabolic processes. For hundreds of millions of years, these early cyanobacteria succeeded tremendously, but their success had a by-product: the oxygen poisoned the other organisms around them, as well as the environment as a whole. In short order, Earth was transformed into a giant snowball, leading to perhaps the greatest mass extinction in history: the Huronian Glaciation.
There are lessons to learn here, about ourselves, our environment, and how fragile our climate is. Come get the story of Snowball Earth today.
This Is What’s Special About A Full Supermoon Occurring On The Equinox This Year
“You may remember that two months ago, in January, we received a total lunar eclipse: where the Sun, Earth, and full Moon were perfectly aligned. Now that it’s two months later, the full Moon is misaligned, because the plane that the Moon orbits the Earth in is tilted with respect to the Sun.
This is incredible for science! On any old equinox, you can measure your latitude on Earth; on any solstice, you can measure the axial tilt of the Earth. Well, on an equinox that coincides with a full Moon, you can measure how far out of the Sun-Earth plane the Moon actually is at this particular moment in time. And if you know when the last eclipse was and the next eclipse will be, you can actually determine the tilt of the Moon’s orbit. Here’s how.”
If you had a perfectly vertical stick on the day of the equinox, by measuring the shadow it casts when the Sun reaches its highest point above the horizon, you can measure your latitude. Yet that very night, when we have a full Moon, measuring the same shadow on the same object will give you a very different answer, by a little more than 4 degrees.
The reason is because the Moon’s orbit is tilted with respect to the Earth-Sun plane.
This is brilliant! Make that measurement yourself, and you can calculate the Moon’s orbital tilt for yourself. Here’s how.
5 Killer Events From Space That Could Wipe Out Human Life On Earth
“4.) A supernova: these have affected Earth many times, but we have endured without significant harm.
A Type II supernova must occur within <25 light-years of Earth to endanger us, an extremely uncommon occurrence.”
When we look ahead to the challenges we face as a species, our survival seems largely threatened by terrestrial causes, such as problems of our own making. But don’t count the Universe out yet! There are many ways that events from outside our own planet could cause catastrophe and even extinction for humanity, and asteroid/comet strikes are only one of them.
Here are 5 killer events from space that definitely occur, and they could wipe humanity out. One possibility may be just a few thousand years away!
Ask Ethan: Could ‘Cosmic Redshift’ Be Caused By Galactic Motion, Rather Than Expanding Space?
“When we observe a distant galaxy, the light coming from the galaxy is redshifted either due to expansion of space or actually the galaxy is moving away from us. How do we differentiate between the cosmological redshift and Doppler redshift? I have searched the internet for answers but could not get any reasonable answer.”
It’s true: the farther away we look, the greater we find a galaxy’s redshift to be. But why is that? You may have heard the (correct) answer: because space is expanding. But how do we know that? Couldn’t something else be causing this redshift?
The answer is yes, there are actually four other explanations for cosmic redshift that all make sense. But the beauty of science is that there are observational tests we can perform to tell these various scenarios apart! We’ve done those tests, of course, and concluded the Universe is expanding, but wouldn’t you like to know how?
I bet you would! Come and find out how we know that cosmic redshift is caused by the expansion of the Universe, and learn where the alternatives fall apart.