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Ethan Siegel
43,991 followers -
Science writer, professor and theoretical astrophysicist
Science writer, professor and theoretical astrophysicist

43,991 followers
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5 Questions You Were Too Embarrassed To Ask About The Expanding Universe

“5.) Are there galaxies moving away faster than the speed of light, and isn’t that forbidden? From our point of view, the space in between us and any distant point is expanding. The farther away something is, the faster it appears to recede from us. Even if the expansion rate were tiny, an object far enough away would eventually cross that threshold of any finite speed, since an expansion rate (a speed-per-distance) multiplied by a great enough distance will give you a speed as fast as you want. But this is okay in General Relativity! The law that nothing can travel faster than the speed of light only applies to an object’s motion through space, not to the expansion of space itself. In reality, the galaxies themselves only move around at speeds that are hundreds or thousands of km/s, much lower than the 300,000 km/s speed limit set by the speed of light. It’s the expansion of the Universe that causes this recession and the redshift, not a true galactic motion.”

The idea that the spatial fabric of the Universe itself is expanding, and that’s what’s behind the observed relationship between redshift and distance has long been controversial, and also long-misunderstood. After all, if more distant objects appear to recede more quickly, couldn’t there be a different explanation, like an explosion that flung many things outward? As it turns out, this isn’t a mere difference in interpretation, there are observations we can make that tell us the answer! The Universe is not expanding ‘into’ anything, despite what your intuition might tell you. The Hubble ‘constant’ isn’t actually a constant, but is rather decreasing as time goes on. The Universe looks like it’s going to expand forever, but even that scientific conclusion is subject to revision depending on what data shows in the future. And although 97% of the galaxies in the Universe are already unreachable, it isn’t a violation of relativity or a faster-than-light phenomenon that’s to blame.

Come learn the answers to five questions about the expanding Universe that many are too embarrassed to ask!
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The Big Bang Wasn’t The Beginning, After All

“The Universe began not with a whimper, but with a bang! At least, that’s what you’re commonly told: the Universe and everything in it came into existence at the moment of the Big Bang. Space, time, and all the matter and energy within began from a singular point, and then expanded and cooled, giving rise over billions of years to the atoms, stars, galaxies, and clusters of galaxies spread out across the billions of light years that make up our observable Universe. It’s a compelling, beautiful picture that explains so much of what we see, from the present large-scale structure of the Universe’s two trillion galaxies to the leftover glow of radiation permeating all of existence. Unfortunately, it’s also wrong, and scientists have known this for almost 40 years.”

Did the Universe begin with the Big Bang? When we discovered the cosmic microwave background, and its properties matched exactly the prediction of the Big Bang theory, it was a watershed moment for cosmology. For the first time, we had uncovered the origins to the entire Universe, having learned where all of this came from at long last. Emerging from a hot, dense, expanding, and cooling state, the matter-and-radiation-filled early Universe gave rise to everything we see today. Except there were a few pesky problems that the Big Bang couldn’t explain. If the Universe truly emerged from an arbitrarily hot, dense state, and if space and time themselves were born at that exact moment, the Universe would have signatures that we simply don’t see. Instead, theorists came up with an alternative beginning: cosmic inflation. Inflation made a bold prediction about the scale and magnitude of the fluctuations that should arise from this early state, and when our technology finally caught up to our imaginations, we measured them.

It turns out that the Universe didn’t begin from the Big Bang at all. It happened, but it wasn’t the beginning! Find out what came before, and how we know.
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We did another interview for Treknology, and Seattle Astronomy wrote up a great piece about it. http://www.seattleastronomy.com/blog1/2017/09/treknology-looks-at-star-trek-gizmos/

Also, they have a podcast: https://soundcloud.com/user-242847938/interview-with-ethan-siegel-author-of-treknology

And you can pick up the book here: http://amzn.to/2xo44BX
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“On Earth, we’re currently burning more than ten billion tonnes of fossil fuels per year worldwide, supplying some 80% of our energy needs through those methods. Unfortunately, air-and-water pollution, along with vast atmospheric changes, have arisen from this. Renewable sources of energy are one potential (although, arguably only a partial) solution, but nuclear power — if it can be done safely — could solve our fossil fuel problem today, with current technology alone. With the amount of fuel it presently takes to power the world, the cost of doing nothing is not only far too high, but will be borne by humanity for generations to come.”

Arguably the greatest advance of humanity — and the cause of the greatest increase in our quality of life — in the past few centuries has been the widespread availability of electrical energy. It powers our homes, our industries, our automobiles, our places of business and more. Our world runs on energy, with the world using upwards of 155,000 TeraWatt-hours annually. That’s a huge amount of energy, and it requires a huge amount of fuel. But must it? If we were to power the world entirely with coal, oil, or natural gas, it would take billions of tonnes of fuel each year to make it happen. If we switched to nuclear, those “billions” drop to thousands. And if we could switch to nuclear fusion or even antimatter, the amount of fuel plummets even further. Looking at the numbers, it makes no sense not to switch. Is it only our fears of nuclear disaster that prevents us from using our current technology to better the world for humanity for generations to come?

I’m not 100% sure, but at least get the answer to how much fuel it takes to power the world today!
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“But these potential discoveries are what we know we’re going to be looking for. With every new major technological leap forward we’ve ever taken in astronomy and astrophysics, the greatest achievements of all have been the ones we could not have anticipated in advance. The great unknowns of the Universe, including what it looks like in the faintest regimes, how the most distant stars, galaxies, gas clouds, and the intergalactic medium behaved at early times, and what it looks like beyond anything we’ve ever seen will all be exposed for the first time. It’s possible that we’ll learn we were quite arrogant and wrongheaded in a great multitude of arenas, but we’ll need this new, high-quality data to show us the way.”

If you were an observational astronomer, what would your dream telescope look like? It would have to be huge, with an incredible amount of light-gathering power. The quality of the optics would have to be pristine, and higher-precision than anything ever created before. It would have to have multispectral capabilities, extending beyond both sides of the visible light spectrum. And it would have to be in space, with no interference from our atmosphere. If we could build a telescope like that, so many things would immediately become possible. We’d be able to directly image perhaps 100 exo-Earths around nearby stars, including spectra of their atmospheres. We’d take images of Jupiter of the same quality that JUNO can, but from Earth’s orbit. We’d be able to measure the star clusters inside and gas halos surrounding every galaxy in the Universe to just a few hundred light year-precision. And we’d be able to take high-resolution images of the faintest, most distant galaxies of all, in just a tiny fraction of the time it’s taken Hubble to do it.

There’s a 15.1-meter space telescope that’s in design right now: LUVOIR. If everything goes well, it could be NASA’s flagship mission of the 2030s. Want to learn more? Here’s what it’s all about!
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"It's incredibly difficult to even make the effort to understand those with different experiences, different priorities, or even different values from ourselves. Yet Star Trek is at its best when it gives us the opportunity to confront our worst impulses. Unless we are willing to consider the validity of perspectives other than our own, often including ones far outside our own experience, we may be doomed to dividing, rather than uniting, the world. With political issues like nationalism, sovereignty, autonomy, secession, racism, misogyny, police brutality, immigration and more in the spotlight right now, Star Trek has the unique capacity to confront these issues with the distance of the far future but with the intimacy of humanity. It is with this in mind that I most look forward to Star Trek: Discovery."

When you think about Star Trek, a whole variety of things might come to mind. It might conjure images of space exploration, feelings of optimism about the future of humanity, the inextricable link between prosperity and technology, or the fear of the unknown. But what has always set Star Trek apart from any other sci-fi or fantasy show has been its ability to hold a mirror up to humanity, and force us to confront our greatest moral and ethical quandries. We inhabit a world today rife with "othering," where we look at those who we see as different from ourselves, and are quick to condemn them as being inferior to those we see as more like us. This extends not just to physical traits, but ideological ones as well. Yet each of the Star Trek series in the past has embraced this conflict, and with five stunning examples from Star Trek's past, I'm happy to elucidate my great hopes for what Star Trek: Discovery just might bring to the world.

Starting next week, we'll once again have a Star Trek series on the air, for the first time in over a decade. What's in store? Here's what I'm looking forward to!
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"What’s remarkable about our theories isn’t how intuitive or simple they are, but how well they describe the Universe that we inhabit. How successful their quantitative predictions are, and what a wide range of phenomena they apply to. There’s nothing else in the Universe quite like the fundamental laws of physics, and perhaps that’s what it was that made me fall in love with the subject all those years ago. It’s a love that countless others have shared throughout history, and that many will continue to share for generations to come. You’re always welcome to share in it with me, and hopefully there will be even more to come in the days, weeks, months and years ahead."

Science is a lot of things to a lot of people, but the big thing we should all agree on is that it is our best description of and explanation for the natural world. Yes, in the best case scenario science will explain what something is, why it happens and how large/impactful its effects will be, but even when it fails to rise past the descriptive stages, science still matters. As the climate continues to change and the world continues to feel its impact, many still continue to deny that humans are responsible, or that we should do anything about it.

The science -- and I -- strongly disagree. Get the story on this and so much more bonus topics on this edition of our comments of the week!
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“Many sources state that quarks are point particles… so one would think that objects composed of them — in this instance, neutrons — would also be points. Is my logic flawed? Or would they be bound to each other in such a way that they would cause the resulting neutron to have angular size?”

When we consider things like molecules, atoms, or even protons and neutrons, they all have finite, measurable sizes. Yet the fundamental particles that they’re made out of, like quarks, electrons, and gluons, are all inherently points, with no physical size to them at all. Why, then, does every composite particle not only have a size, but some of them, like atoms, grow to be relatively huge almost immediately, even with only a few fundamental particles involved? It’s due to three factors that all work together: forces, the quantum properties of the particles themselves, and energy. Since the strong and electromagnetic forces work against each other, quarks and gluons can form finite-sized protons; protons and neutrons assemble into nuclei larger than the protons and neutrons combined would make; electrons, with their low mass and high zero-point energy, orbit around nuclei only at great (relative) distances.

Matter doesn’t need to be made of finite-sized particles to wind up creating the macroscopic Universe we know and love. Find out how on this week’s Ask Ethan!
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Proof Of ‘God Playing Dice With The Universe’ Found In The Sun’s Interior

“If it weren’t for the quantum nature of every particle in the Universe, and the fact that their positions are described by wavefunctions with an inherent quantum uncertainty to their position, this overlap that enables nuclear fusion to occur would never have happened. The overwhelming majority of today’s stars in the Universe would never have ignited, including our own. Rather than a world and a sky alight with the nuclear fires burning across the cosmos, our Universe would be desolate and frozen, with the vast majority of stars and solar systems unlit by anything other than a cold, rare, distant starlight.

It’s the power of quantum mechanics that allows the Sun to shine. In a fundamental way, if God didn’t play dice with the Universe, the nuclear flame that powers the stars would never light, and the life-giving fusion that occurs in our Sun’s core would never come to be. Yet with this randomness, we win the cosmic lottery all the time, to the continuous tune of hundreds of Yottawatts of power. Thanks to the fundamental quantum uncertainty inherent in the Universe, we’ve achieved a chance at existence. Fiat lux.”

Inside the nuclear furnace of the Sun, protons and other atomic nuclei are compressed together into a tiny region of space, where the incredible temperatures and energies try to overcome the repulsive forces of their electric charges. At a maximum temperature of 15 million K, and with a long-tailed (Poisson) distribution of energies at the highest end, we can compute how many protons are energetic enough to overcome the Coulomb barrier, interact with one another, and wind up in a more tightly-bound, fused state. That number, if you do that calculation, turns out to be exactly zero. When you consider that 95% of stars are less massive and reach lower core temperatures than our Sun, the situation appears to be even more dire. If there were no quantum mechanics, nuclear fusion would be an impossibility. Yet we’re saved by a feature of quantum indeterminism, where spread-out wavefunctions can overlap, and nuclear fusion as we know it can proceed.

If Einstein and Bohr knew how the Sun worked, they could have settled the question of whether “God plays dice” with the Universe once and for all. Find out the answer today!
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Successfully Predicting The Future Requires Theoretical Science

“In science, as in all things, not knowing everything doesn’t mean that there’s nothing valid about what we already know. Instead, the failure of a theory to accurately predict what’s going to happen in a given situation is often an omen of advancing our understanding, where the door is open for the creation of a better model in the future. What we already know is important, substantial, and provides the foundation for predicting what comes next. If you want to know what’s going to happen in the future, looking to the predictions of our best scientific theories are far and away the most successful pathway humanity has ever discovered. It only gets better from here.”

It’s all too easy to take a look at a prediction that’s about something yet unproven and dismiss it as mere speculation. But in science, it’s the ability to predict the unknown accurately that’s at the core of what it means to have a successful scientific theory. Our best theoretical frameworks, laws, and models enable us to not only predict what should happen in familiar circumstances, but in unfamiliar ones as well. When we first looked into the distant Universe, at a patch of pure darkness, many were uncertain of whether we’d find anything at all. When we were rewarded with thousands of galaxies in the Hubble Deep Field, it was no surprise; it was a consequence of well-established theories like the Big Bang and General Relativity. Signals from merging black holes, the discovery of the Higgs boson, and many other instances across many scientific fields validate this approach. And when a theoretical model makes failed predictions, that doesn’t necessarily mean the theory is a failure, but rather that there’s another important contributing factor to include in the future.

In science, a theory is the most powerful thing you can invoke to help predict the future. It may not always be 100% correct, but it’s the best option humanity has ever discovered thus far.
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