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Ethan Siegel
44,103 followers -
Science writer, professor and theoretical astrophysicist
Science writer, professor and theoretical astrophysicist

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“We like to extrapolate our Universe back to a singularity, but inflation takes the need for that completely away. Instead, it replaces it with a period of exponential expansion of indeterminate length to the past, and it comes to an end by giving rise to a hot, dense, expanding state we identify as the start of the Universe we know. We are connected to the last tiny fraction of a second of inflation, somewhere between 10^(-30) and 10^(-35) seconds worth of it. Whenever that time happens to be, where inflation ends and the Big Bang begins, that’s when we need to know the size of the Universe.”

13.8 billion years ago, the Universe as we know it came into existence. Today, the part we can observe is 46 billion light years in radius, having grown tremendously thanks to the expansion of the Universe. But if we extrapolate that backwards, we find that the Universe couldn’t have been infinitely small at the moment of its birth, but rather was a finite size at all finite times. We know an awful lot about the moment the Universe can first be described by the hot Big Bang thanks to the last 50 years of modern cosmology. People used to think the Universe could be contained in a volume no bigger than a marble, or that the part accessible to us could have been the size of the Solar System at birth. No more!

Between the size of a soccer ball and a skyscraper-filled city block is the only range left, and the more we learn about inflation, the smaller that range will get. Find out the science behind it today!

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"How much money will we save by cutting funding to the EPA? To NASA Earth Science? To the National Institutes for Health? Take all those numbers for all those organizations that the proposed federal budget would slash and add them up. Now, do the math on the other side. What's the cost of environmental pollution? Of unclean, unsafe water? Of air that puts us at risk of health problems like asthma, lung disease and COPD? Of a loss of Earth monitoring for extreme weather, climate change, sea level rise, droughts, and natural disasters? Of the cessation of medical research, working to fight preventable diseases, and working to cure some of society's greatest afflictions such as cancer, heart disease, alzheimers and more?"

The President of the United States just released his proposed budget for the next fiscal year, and there are some big losers in the scientific world. The EPA, the NIH, NASA Earth Science and many other organizations that exist for the benefit of America and all of humanity are poised to lose a significant amount of federal funding. This doesn't simply affect the scientists who lose their jobs. If we take as a given that the projects that these organizations invest in are vital at some level, and that they will need to be accomplished at some point, we're actually making it far more expensive in the long run. The loss of expertise, the cessation of production and the exodus of the team that would provide scientific continuity are all extremely costly, and will make all of these projects cost us more than they would have overall.

We saw this lesson firsthand just a few years ago with James Webb. Are we really willing to throw away so much money and time now just to shave a tiny bit off the deficit for the short-term?

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"How much money will we save by cutting funding to the EPA? To NASA Earth Science? To the National Institutes for Health? Take all those numbers for all those organizations that the proposed federal budget would slash and add them up. Now, do the math on the other side. What's the cost of environmental pollution? Of unclean, unsafe water? Of air that puts us at risk of health problems like asthma, lung disease and COPD? Of a loss of Earth monitoring for extreme weather, climate change, sea level rise, droughts, and natural disasters? Of the cessation of medical research, working to fight preventable diseases, and working to cure some of society's greatest afflictions such as cancer, heart disease, alzheimers and more?"

The President of the United States just released his proposed budget for the next fiscal year, and there are some big losers in the scientific world. The EPA, the NIH, NASA Earth Science and many other organizations that exist for the benefit of America and all of humanity are poised to lose a significant amount of federal funding. This doesn't simply affect the scientists who lose their jobs. If we take as a given that the projects that these organizations invest in are vital at some level, and that they will need to be accomplished at some point, we're actually making it far more expensive in the long run. The loss of expertise, the cessation of production and the exodus of the team that would provide scientific continuity are all extremely costly, and will make all of these projects cost us more than they would have overall.

We saw this lesson firsthand just a few years ago with James Webb. Are we really willing to throw away so much money and time now just to shave a tiny bit off the deficit for the short-term?

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“Every star will someday run out of fuel in its core, bringing an end to its run as natural source of nuclear fusion in the Universe. While stars like our Sun will fuse hydrogen into helium and then – swelling into a red giant – helium into carbon, there are other, more massive stars which can achieve hot enough temperatures to further fuse carbon into even heavier elements. Under those intense conditions, the star will swell into a red supergiant, destined for an eventual supernova after around 100,000 years or so. And the brightest red supergiant in our entire night sky? That’s Betelgeuse, which could go supernova at any time.”

One of the most sobering cosmic truths is that every star in the Universe will someday run out of fuel and die. Once its core fuel is exhausted, all it can do is contract under its own gravitational pull, fusing heavier and heavier elements until it can go no further. Only the most massive stars, capable of continuing to fuse carbon (and even heavier elements) will ever create the Universe’s ultimate cataclysmic event: a Type II, or core collapse, supernova. Stars that are fusing carbon (and up) appear to us today as red supergiants, and the brightest red supergiant as seen from Earth is Betelgeuse. Sometime in the next 100,000 years or so, Betelgeuse will go supernova. When it does, it will emit incredible amounts of radiation, become intrinsically brighter than a billion suns and and be easily visible from Earth during the day. But that’s not all.

What’s the full story on what will happen when Betelgeuse goes supernova? Come get the science today!

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“If this result holds up with more and better data, this may provide a window into galactic evolution that finally allows us to discriminate between dark matter and modified gravity in a clear and robust way. These types of observations, to measure the rotation curves of galaxies many of billions of light years away, will be a prime science goal for new telescopes in the 2020s like GMT, E-ELT and WFIRST. Both sides will continue to argue for their interpretation of the data, but in the end, it will be the full suite of data that reveals how nature truly behaves. Will Einstein be superseded? Or will we all wind up joining the dark side? By time another decade goes by, the answer may finally be known.”

The dark matter wars rage on and on, with both sides – those in favor of modifying gravity and those in favor of adding an additional mass component to the Universe – claiming victories for their own side and defeat for the other. But one piece of evidence, hitherto elusive, might finally hold the key to distinguishing one from the other: early, young, less-evolved galaxies. Billions of years ago, not as much dark matter had fallen into the inner portions of galaxies, meaning that the outer portions of rotating spirals should display less dark matter in the past than they do today. Instead of flat rotation curves, the galaxies in the distant Universe should exhibit falling rotation curves. In a series of new papers, a team was able to observe 101 distant galaxies at relatively high redshifts, and what they found presented compelling evidence for exactly this phenomenon. As always, more and better data is needed, as it’s only a three-sigma effect so far.

But as the first hint of this long-anticipated effect, it’s a compelling preview of what the telescopes of the 2020s will offer! Come get the scientific story today.

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“Visible light can reveal the wispy tendrils of evaporating gas, the presence of various elements and light-blocking dust. But to see the location of stars and the density of the heated, star-forming material, an infrared telescope is necessary.”

Want to identify where stars are forming (or about to form) in the Universe? We’ve got no problem using visible light, which reveals unambiguous signatures associated with newborn stars. But if you want to view those stars themselves, or the processes occurring within the nebula where they’re being born? You have to go to infrared light. Right now, the sharpest, highest-resolution views of the Universe in the infrared are revealed by Hubble, which can only go out to 1.6 microns, or barely twice the wavelength limit of visible light. But when the James Webb Space Telescope launches next year, it will not only be more powerful and higher-resolution than Hubble, it will go out to wavelengths of 30 microns: nearly twenty times redder than Hubble.

What will be revealed? These five visible/infrared image comparisons showcase what we’ve seen so far. How can you not be excited for what comes next?

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"Recently, I have seen a few of you who disagree get engaged in name-calling wars, baiting each other and generally engaging in “poking the bear.” I can think of nothing better to do than to try and make peace. We all have different ways of interacting with the world, different perspectives and different opinions. Some of them are downright incorrect, but I would encourage and implore you to be good to each other, always, even when you observe bad behavior. It’s only through our goodness to each other that existence becomes bearable."

There's plenty of science afoot, from climate science to the solar system to deep space and beyond, but there's also a good chance to remind one another that we're all on this same world for a limited amount of time, and it's up to us to make it a good one for as long as we're here.

Please be a part of the solution!

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“What would be brighter: a full moon or a full earth from the moon? Would the brightness remain constant?”

The full Moon is undoubtedly bright. As viewed from the Earth’s surface, it’s the second brightest object of all, after the Sun, and is more than 1,500 times brighter than Venus. In fact, the full Moon is over 40 times brighter than the entire rest of the night sky combined, and can outshine even a big city when seen right next to one. But the Earth has the Moon beat on the only two intrinsic properties that matter: size and reflectivity. The much larger size of Earth means that a “full Earth” as seen from the Moon has 13 times the surface area as the full Moon as seen from Earth. But on top of that, the Moon, as bright as it appears in the sky, is actually a relatively dull grey in color, more similar to charcoal than it is to a snowy white. The Earth, on the other hand, has icecaps, clouds, and highly reflective continents, particularly where deserts are involved.

So how bright is the Earth as seen from the Moon by comparison, and what does this tell us about these worlds? Find out on this edition of Ask Ethan!

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“So the CMB isn’t the end of the Universe, but rather the limit of what we can see, both distance-wise (as far as we can go) and time-wise (as far back as we can go). Until we can directly detect the signatures of what was released earlier – the cosmic neutrino background, gravitational waves from inflation, etc. – the CMB will be our window into the earliest time we can observe: 380,000 years after the Big Bang.”

The farther away in space we look, the farther back in time we’re seeing. Light arriving from a star ten light years away is ten years old; light that took a billion-year journey from a distant galaxy is a billion years old. If we look out today at the most distant light we can see, we discover that it originates from the Big Bang itself: the Cosmic Microwave Background, or CMB. But this doesn’t mean the light has never interacted with anything since the birth of the observable Universe. In fact, many arose from matter/antimatter annihilations, all of them have scattered off of charged particles, and the CMB photons we detect today were all released when the Universe was a few hundred thousand years old. Because of the way the Big Bang works, the particles are literally everywhere, all at once, including right here.

Come get the full story on where the CMB actually is, and what it means when we state its age and distance!

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“Still, time crystals as Wilczek originally envisioned them – in systems in thermal equilibrium – really do appear to be impossible. You have to have an open system, and the system needs to be driven at a periodic frequency with imperfections that aren’t too large. Over-drive it, and the crystal will “melt,” losing the properties that made it so interesting in a periodic fashion. We still haven’t crystallized time, and likely never will. But the ability to make a system, that when all you do is pulse it in a particular way, returns, periodically, to a uniform state over and over again, is truly remarkable.”

When you think of crystals, you likely think of an interlocked, repeating lattice of atoms or molecules. That’s exactly what a conventional crystal is. But recently, there’s been an exciting new idea, first proposed by Frank Wilczek in 2012: that it would be possible to create a time crystal, an entirely new class of system. You might think that this means that time – rather than atoms or molecules – are crystallized, but that’s not quite right. Instead, particles that are coupled together would spontaneously return to the same state, breaking the symmetry known as time-translation invariance. A method for building one was proposed just last year, and already two independent teams have made it work!

Come get the story on time crystals, including what they are, how they work and what it might mean not just for physics, but for our future.
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