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Ethan Siegel
Science writer, professor and theoretical astrophysicist
Science writer, professor and theoretical astrophysicist

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“Most neutron stars don’t appear as pulsars to us, simply because their “pulses” aren’t lined up with planet Earth. But over time, pulsars can newly appear or disappear, which we’ve actually seen happen since the Voyager probes were launched. As objects rotate and orbit in space, their relative orientations change, so the pulsars that are pointing at us today won’t be pointing at us millions of years in the future. Additionally, pulsars that aren’t pointing at us today will be pointing at us in millions of years. Compound that with the fact that neutron stars adjust their rotation periods over time (via starquakes and pulsar speedup), and it’s clear that both the periods and orientations of these pulsars change dramatically over millions of years. By the time any alien picks up our pulsar map, it will be woefully out-of-date.”

When the Voyager and Pioneer spacecraft were launched, they contained a message emblazoned on them: a map of 14 pulsars, showing the location of Earth relative to them. This was a brilliant idea: showcase bright, unique identifiers, complete with their observed periods and distances from our world, and people would be able to find Earth. If we wanted to be found, it was the best idea 1977 had to offer. But 40 years later, the idea is fundamentally flawed. There are up to a billion pulsars in the Milky Way, their periods change long-term, and their orientations are variable over time, meaning they won’t be pointing at Earth in the future. If we wanted to be detected, we’d be much better off sending the same information we use to detect exoplanetary systems today!

Although it was a very clever idea presented just 10 years after the discovery of pulsars, we now know that Voyager’s cosmic map to find Earth will be hopelessly wrong by the time an alien civilization finds it.

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“There are some astronomical observations, even with a powerful telescope, that can only be made with the help of photography. To gather enough light to stand out against the brightness of other objects is something that goes beyond what human eyes can deliver. Thankfully, that technology is widespread today, and enables us to enjoy a whole slew of sights our eyes cannot deliver. It may be dark during the eclipse, but darkness, as we perceive it, is relative. Our Sun’s corona, during totality, will become the brightest thing in the sky, and is the reason the Moon, to human eyes, will be completely invisible.”

During those moments of totality, the Sun is eclipsed by a new Moon, with the latter’s shadow falling onto Earth. From within that shadow, the Sun’s disk is blocked entirely, revealing a slew of fainter objects: stars, planets, and the Sun’s corona, all of which cannot normally be seen during the day. Yet one object even brighter than all the stars – the new Moon – will remain invisible throughout the eclipse. Despite the Moon acting as the ultimate coronagraph, blocking out 100% of the Sun’s light, and despite the full Earth reflecting its light back onto the Moon, you won’t be able to see the lunar surface at all. Why is that? It’s the relative brightness of something very close by: the solar corona. Even though the Sun’s corona is some 400,000 times less bright than the Sun, it’s still ~10,000 times brighter than the new Moon, enough to render it totally invisible to human eyes. It’s like trying to see a firefly an inch away from a shining light bulb, when you’re standing 20 feet away.

In short: the corona is too close and too bright, and that’s why the Moon is only visible in photographs.

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“Either life began on Earth with a complexity on the order of 100,000 base pairs in the first organism, or life began billions of years earlier in a much simpler form. That could have been on a pre-existing world, whose contents migrated into space and eventually came to Earth in a great panspermic event, which is certainly possible. But it also could have been in the depths of interstellar space, where the energy from the galaxy’s stars and cataclysms provided an environment for molecular assembly. It may not necessarily have been life in the form of a cell, but a molecule that can collect energy from its environment, perform a function, and reproduce itself, encoding the information essential to its existence in the reproduced molecule, just might qualify as life.”

We talk about the origin of life on Earth with bated breath, wondering all the time how things occurred to make our planet unique. But within that big question lies an assumption that may not be true: that life on Earth originated on Earth itself. It’s entirely possible, based on what we’ve seen out there in the Universe, that life didn’t originate here at all. Rather, it could have come from a primitive, pre-existing world, or even from the depths of interstellar space itself. If it’s the latter case – interstellar space – then perhaps we don’t even require a planet at all to create the more primitive forms of life itself. Perhaps all you need is a molecule that encodes information, reproduces itself, and converts external energy for use in biological processes. And if that’s the case, the origin of life may bear very little resemblance to what life has evolved into today.

Could pretty much all places in the Universe, by the present time, have these ingredients that qualify as life? Let’s look at the evidence!

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"3.) Stop viewing the Sun through binoculars/telescopes before totality ends. Looking at direct Sun for even a split second through binoculars/telescopes can blind you forever.

Putting your eclipse glasses back on as soon as totality ends for your naked eyes is fine."

For most of us heading to the path of totality, we're in for an incredible experience. If we get clear skies, it will take roughly an hour for the Moon to pass in front of the Sun's disk completely, and after that we'll get just over two minutes of totality: an experience like no other. Yet if you're not careful -- or if you get too excited about one particular thing -- you might miss the best parts. A lot of photography enthusiasts are planning to capture the eclipse on film (or digitally), but that may be a very poor decision. Others are planning on using binoculars to get a better view of the corona, but that has extreme dangers. Others aren't sure whether they need their eclipse glasses or what all the things they should look for and try to experience are. But there are too many scientists passionate about getting the right information out there to let this event go by without sharing that knowledge and wonder with the world.

There will be an awful lot to take in during those moments of total darkness, and there's no substitute for knowing what to expect. Here are five pitfalls you must avoid.

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“We live in a country where a black man will be criticized and even blacklisted from his job for taking a knee during the national anthem because he’s making a statement about equal right and protections under the law, but the rights of neo-nazi murderers to hatch terrorism plots and violently attack counter-protesters (two pretty illegal things, by the way) are not even addressed by our country’s leadership. In 2017, more than 70 years after the world united to defeat fascism and white supremacy and oppression, actions like these are not condemned by the president. My grandfathers fought those Nazis, alongside the rest of the free world. It is up to every one of us – whether we’re white or persons of color; whether we’re men, women, or non-binary; whether we’re Christian or not; whether we’re cis or straight or citizens or not – to recognize that we’re all human beings, and that we have every right to demand those same human rights: life, liberty, and the pursuit of happiness. That is what America is about.”

So the eclipse is coming up, the Perseids just peaked, and we’ve got so much else going on in the world and the Universe. We’re making progress learning about black holes; we’re experiencing some pretty nasty wildfires; we’re learning about life on other worlds (and contamination from Earth); plus the usual topics of relativity, climate science, right-and-wrong, and even some bonus science on junk science, politics and rocket fuel. But we also just had one of the most awful events in the 21st century just happen, right here in our own nation, and people are saying nothing. It’s time we all spoke out.

There is no place for silence now. Come get your weekly dose of bonus science, plus some ethics, on our Comments of the Week!

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“Explain to me what information is gained from the quantum mechanical commutation relation. There’s more to it than, “we just can’t measure both properties at the same time."”

It’s absolutely true that, in quantum mechanics, there are certain pairs of properties that we simply can’t measure simultaneously. Measure the position of an object really well, and its momentum becomes more uncertain. Measure its energy, and its time becomes more uncertain. And measure its voltage, and the free charge becomes more uncertain. Although this is disconcerting to some, it’s a fundamental part of the quantum nature of the Universe. But there’s also more to it than that! Not only are pairs inherently uncertain, but each component has some built-in uncertainty that you can never take away. Moreover, it arises from a simple fact that isn’t true classically: the order of operations – whether you measure position or momentum first – makes a fundamental difference in what you get out. This quantum commutation relation is where so much of the fundamental quantum weirdness in our Universe comes from.

It’s also why we have technologies like atomic clocks, hydrogen masers, and MRI machines! Come find out where quantum uncertainty arises from, and why it matters, on this week’s Ask Ethan!

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“Every object in our Solar System that takes the plunge from out beyond Neptune to our inner reaches, where the rocky planets lie, will become a comet. As it nears the Sun, its ices melt, creating the tails we associate with them, and also creating a debris path that can create meteor showers if they cross Earth’s orbit. For thousands of years, the most consistent, spectacular meteor shower has been the Perseids, created by Comet 109P/Swift-Tuttle.

At its incredibly large size (26 kilometers across) and speed, it contains nearly 30 times the energy of the asteroid strike that wiped out the dinosaurs. Over the next few thousand years, it will come perilously close to Earth. If Jupiter — which it also passes by — gives it just the slightest gravitational kick, it could be flung into the Sun, ejected from the Solar System, or hurtled directly into our world. If this were to happen, and it’s a real possibility some 2400 years from now, it would mark the largest mass extinction our world has seen in hundreds of millions of years.”

Enjoying the Perseid meteor shower this year, as perhaps you do every August? As you look up, the great cosmic show might have a lot more to offer than mere streaks of light, due to cometary debris brightly burning up in the Earth’s atmosphere. This year, Jupiter has slightly disturbed the debris stream, resulting in an increase in the number of meteors-per-hour, as the stream passes quite centrally through Earth’s location. Someday, unless we continue to get lucky, Jupiter just might have that same effect on the comet that spawned the Perseids: comet Swift-Tuttle. Only, instead of an enhanced shower, we’d get struck by this comet. With a top speed of 60 km/s and a size of 26 km in diameter, this would result in an impact 28 times more energetic than the impactor that wiped out the dinosaurs.

Comet Swift-Tuttle is the single most dangerous object known to humanity. Come enjoy our continued existence and learn about our possible future demise, while you still can!

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“Yet that doesn’t stop some people, who’ve convinced themselves that such a link is there, from promoting that claim with every small study that supports it, regardless of what the total evidence adds up to. Even if you’re a scientist, unless you yourself are an expert in the particular field (or sub-field) in question, it’s very likely that you’re not wholly aware of exactly what the full suite of evidence is. Unless you’re willing to put in an extraordinary amount of legwork — and to do it in a scientifically unbiased way — you’re going to wind up with only a partial picture of what we actually know, setting yourself up for the possibility of deceiving yourself, no matter how earnest you are. It’s with that pitfall in mind that the American Center for Science and Health published their Little Black Book of Junk Science.”

When it comes to health, safety, and how we interact with the world around us, pretty much everyone recognizes the importance of making our decisions based on sound science. Yet even when presented with the same evidence, many people will draw different conclusions. Why? Because once we’ve made up our minds that something is either good or bad for us, we cherry-pick the remaining data to support our previously-held positions. Humans are notoriously bad at distinguishing legitimate science from junk science. In a new mini-book from the American Council on Science and Health, author Alex Berezow runs us through hundreds of arenas, personalities, and health claims where junk science is prevalent. No matter where you are on the political or scientific spectrum, there are sure to be some entries in there that cause you to bristle, and that’s a good thing. If you can challenge your assumptions and preconceptions, you just might wind up doing the most important thing one can do in this world: learning something new.

I fell victim to some of those things myself, and am not ashamed to admit it. Take a look inside, and see if you can tell junk science from actual science today!

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“How many black holes are there in the Milky Way? This straightforward question has proven extremely difficult to answer, since black holes are so difficult to directly detect. However, scientists not only have developed indirect methods for locating and even weighing them, we also understand how the Universe forms them: from stars and stellar remnants. If we can understand the different stars that existed at all different times in our galaxy’s history, we should be able to infer exactly how many black holes — and of what mass — exist in our galaxy today. Thanks to a comprehensive study by a trio of researchers from UC Irvine, the first accurate estimates of the number of black holes found in Milky Way-like galaxy have now been made. Not only is our galaxy filled with hundreds of billions of stars, but we also are home to up to 100 million black holes.”

When LIGO announced their first discovery of a black hole-black hole merger, it came as a surprise to almost everyone. The shocking part wasn’t that LIGO had seen merging black holes, but that they were discovered to be so massive. At right around ~30 solar masses each, these were black holes that were much larger than expected, forcing astronomers to confront the fact that they didn’t have a good, comprehensive model for how many black holes – and what mass they should be – were in the Universe. To help this, a trio of researchers from UC Irvine just used the best information we have to simulate galaxy growth and formation, along with stellar evolution, to figure this out. The results they found were that a Milky Way-sized galaxy should have up to 100 million black holes in it, mostly around 10 solar masses each, with a few percent of them being significantly higher in mass. Meanwhile, smaller, lower-mass (and lower-metallicity) galaxies would have fewer black holes that were more massive on average.

This remarkable result gives us our first-ever precise estimate of how many black holes should be in our galaxy, and paves the way for understanding what LIGO (and other gravitational wave observatories) should see in the future!

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“Is there life on other worlds? On other planets in our Solar System; on moons around gas giants; on asteroids or Kuiper belt objects? Was there once a thriving colony of life, but no longer, on some of those worlds? Are there pieces of evidence that organic material is present there, wholly unlike anything we’ve yet found on Earth?

These tantalizing possibilities are real, and can teach us so much about how ubiquitous life might be, in the galaxy and Universe at large. But if we contaminate those worlds, unnaturally, with Earth-based life, we may never get the chance to find out. That’s the primary role NASA’s Planetary Protection Officer plays: in securing the pristine nature of these other worlds. When the time comes that our technology is sufficiently advanced and implemented, it will be the long-term success of that office that determines whether we learn that answer or not.”

Sure, you probably laughed about it when you first heard that NASA had a Planetary Protection Officer, as though Earth actually needed protection from non-existent alien invasions. Perhaps, you thought, this might have been relevant back in the 1960s, before we realized how barren the Moon was, or how woefully insufficient the Solar System is for harboring some type of doomsday, Andromeda-strain-like bacterium. Although that NASA office is responsible for external biological threats to Earth, the main function of planetary protection is quite different: protecting other worlds from Earth. Which is to say, every time we launch a mission into deep space, we need to ensure that Earth-based life doesn’t compromise an otherwise pristine environment. There are big questions about the Solar System that we can only answer if we don’t contaminate those other worlds; one screw-up can override billions of years of natural history.

What is the big deal with NASA’s Planetary Protection Office (and officer)? Find out, and get the facts instead of just some vainglorious headlines!
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