0 comments on “Unexplainable astronomy? Part 2: Of pigeons and cosmic uniformity”

Unexplainable astronomy? Part 2: Of pigeons and cosmic uniformity

By Sam Jarman

Ask just about any scientist, and they will tell you that the very best discoveries they can make are the ones which force us to change how we think about the world completely. That’s exactly what happened in 1923, when Edwin Hubble looked out at a small, hazy nebula from his mountaintop telescope in California.

Without Henrietta Leavitt’s work, we might still think of galaxies like Andromeda as funny-looking nebulae which don’t make any sense | Image: NASA

Based on previous research by Henrietta Leavitt, Hubble was looking for Cepheid variable stars in the nebula, which would tell him exactly how far away it was. He managed to find a variable star easily enough, but it revealed a pretty big problem. The star showed Hubble that the nebula he was looking at was not even a nebula after all, but a vast cluster of stars situated very, very far away.

The distance was greater than any we had thought possible for thousands of years. For scientists, that meant that we needed to completely rethink our model for the structure of the universe. With the discovery of the Andromeda galaxy, the fundamental idea of billions of galaxies occupying a vast, ever-expanding universe was born. It was a lot for the world of astronomy to take in.

In the decades following Hubble’s discovery, theoretical physicists struggled to discern the scientific rules which could possibly govern such a newly colossal, mysterious universe. Some of their theories seemed promising, but In the meantime, the imaginations of the media and the public ran wild. If our understanding of the universe could be so shaken by one discovery like Hubble’s, they reasoned, what other revelations could be hiding in plain sight? And, of course, the biggest question: could intelligent life be out there somewhere?

Apprehension had grown strong by the 60s. Theoretical physicists had some convincing ideas about the nature of the universe, but at the time, technology just wasn’t sophisticated enough to prove experimentally which were correct, and which were misguided. Their ideas so often disagreed with each other that it seemed like no-one had really got anywhere at all. But change was coming. Improved telescopes meant that by 1964, mysterious signals, the likes of which would make or break previously speculative cosmological theories, began to come in.

A dodgy radio receiver? 

Pigeons. It had to be. Since making their home in the cosy hovel that was the Holmdel Horn Antenna, the birds had been busy and painting the walls with the remains of their dinner, which was giving off who knows what kind of radiation. How else could radio astronomers Arno Penzias and Robert Woodrow Wilson explain the uniform, unwanted microwave signal, which wouldn’t go away no matter where in the sky they pointed the telescope?

Whenever you’re feeling down, just remember that a sad metal toilet in New Jersey once became one of the most important telescopes of the 20th century| Image: NASA

The pair cleared out the avian intruders, and scrubbed the inner surface of the antenna clean. They checked the equipment thoroughly yet again, making sure the receiver was still cooled to just above absolute zero, minimising any interference from within the telescope. But still, the low, intense noise hindering their experiment persisted. Clearly, the radiation was originating from something more interesting than pigeon droppings. Something, they realised, beyond our own galaxy.

Coinciding with Penzias and Wilson’s predicament, a group of astrophysicists at Princeton University were working on a theory they believed could explain what was happening in the earliest moments of the universe’s existence. Based on earlier work by cosmologist Ralph Alpher, their idea hinged on the concept that the universe had all started with a rapid, high-energy expansion from a single point: a Big Bang. They proposed that if the Big Bang had really happened, it must have released a colossal surge of radiation, still observable to this day with the right equipment. The radiation would have cooled significantly by now, but if its remnants were detected, it would be definitive proof that the scientists’ notion was correct.

The idea was in direct conflict with the earlier-proposed Steady State theory, which suggested that the universe had no beginning, meaning no Big Bang, at all. Instead, the universe had existed for an eternity beforehand, and had never changed significantly. The two theories were radically different, and both appeared to have equal weight. But without any hard evidence, neither could be validated over the other. That all changed in 1964, when Penzias and Wilson caught word of the Princeton scientists’ research.

The Colossal Clang and Tremendous Toot were also considered, but never really caught on| Image: NASA/WMAP Science Team

Through a friend, Penzias got access to a preview of the Princeton paper. What he read astounded him: using first principles, the astrophysicists had argued that a surge of electromagnetic radiation had permeated the entire universe following the Big Bang. As the universe expanded, so too did the wavelength of the radiation, until reaching its current wavelength of 7.35 cm. That was the very same radiation Penzias and Wilson had attributed to pigeon poop – almost exactly. The pair got in touch with the Princeton scientists as soon as they could.

The rest of the story is history. The two groups teamed up to publish not only a theory of how the Big Bang could have hypothetically played out, but indisputable experimental proof of the Big Bang itself on top of it. The Steady State theory had been disproved, and was consigned to history. In 1975, Penzias and Wilson earned a Nobel Prize for their ground-breaking discovery.

Decades later, the radiation observed for the first time by Penzias and Wilson – now known as Cosmic Background Radiation – has been studied in meticulous detail. It has been found to be incredibly uniform, but not perfectly so. In the very earliest moments of the universe, some regions emerged where matter was densely clumped together, whereas it was sparser in others. As the regions formed, the surge of radiation created by the Big Bang was slightly distorted by the clumps of matter.

Of all the scientific results which were first thought to be literally crap, the Cosmic Microwave Background has got to be the most impressive | Image: NASA

Billions of years later, the denser regions have become areas abundant in galaxies, while the sparser regions are now vast, empty voids in space. The Cosmic Microwave Background has retained the distortion it underwent at the very start. By picking up the subtle variations in the radiation, we can now create maps of the structure of the universe with detail which must have been unthinkable just a few decades ago.

So from a mysterious error first attributed to pigeons with poor housekeeping skills, came another fundamental theory in cosmology. But the 60s weren’t over, and there were yet to be more discoveries which would prove to shake up our understanding of how the universe works. In 1967 came another bizarre signal, this time with a somewhat more exciting misguided idea about where it came from.

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G is for Gravity

By Siobhan Fairgreaves

“Gravity pulls everything down”

Wrong!

Now we know what gravity doesn’t do- let’s take a look at what it does.

If it helps, you can think of the force of gravity as ‘falling’ into this thing – a gravity potential. If you’re ever floating in the void of space and you’ve lost your keys again, simply having mass would be a good way to get them back | Image: AllenMcC

Before I get too stuck in I’m going to clarify- we’ve all heard of gravity right? Just in case you missed that class here is a quick reminder. Gravity is one of the many invisible forces acting upon us and our environment every minute of every day. We learn about it in the early days of school, but gravity is still hugely important to physicists. The famous Sir Isaac Newton had a ‘eureka!’ moment concerning the force – more on that later though.

Every object with mass has some gravitational pull (that includes you!) That means your own body is exerting its own force, however tiny, both on the clothes you are wearing, and on distant stars. But for gravity, a bigger mass means a bigger force. So you never need to worry about walking around with lots of small objects stuck to you simply because the gravitational pull created by the Earth is much, much stronger.

For humans, animals and absolutely everything we share our planet with, gravity pulls us towards the centre of Earth. It might seem pedantic but there is an important difference between pulling towards the centre of the Earth and pulling ‘down’. An important law in physics, called Newton’s Third Law, states that “for every action, there is an equal and opposite reaction”.

Not to be pedantic, but the gravitational pull of Earth isn’t the same everywhere: this image from NASA’s GRACE mission shows the subtle differences across the Earth’s surface | Image: NASA

Applying the law to gravity; the force you exert on the Earth (pulling the Earth towards your body), and the force the Earth exerts on you (pulling your body to the Earth’s centre), are equal and opposite, keeping you firmly in place on the planet’s surface. Understanding this principle helps us understand how gravity works when we scale things up.

So how does this come into play for the rest of the Solar System? Well, the Earth has a bigger mass than our moon – just as all the other planets have bigger masses than their moons. But the circular orbits the bodies make around each other mean that gravity doesn’t simply cause the bodies to crash into each other. Instead, the force of gravity maintains the circular paths.

Another one of Newton’s laws – the second this time – states that the acceleration of an object is equal to the force acting on it, divided by its mass. For planets and the moons, the force acting on both of them will be the same, but the mass of the planet will always be much larger. This means that the acceleration of the moon is much larger, making the path its’ circular orbit much longer than that of the planet around it.

Fortunately there is one very important celestial body holding this all together (for our Solar System at least) and that is the Sun. The Sun has a by far the biggest gravitational pull which allows it to hold Earth and the other 7 planets (sorry, Pluto) in position. Due to their respective size and distance each of the planets will experience the gravitational pull from the Sun differently.

With so many laws with his name on them, it’s no wonder Isaac Newton was a little uptight. It must have been the apple which probably didn’t actually fall on his head | Image: Eden, Janine and Jim

Newton summed this all up nicely with yet another law: the law of gravitation. The equation calculates the gravitational force between two bodies using their two masses, the distance between them, and a gravitational constant Newton discovered himself. The law is still hugely important to astronomers today.

Hopefully this makes it clear why we shouldn’t say that gravity pulls everything ‘down’! I don’t know exactly what is ‘down’ from our position in the cosmos but I’m not so sure I want to find out. In a way, it would be more correct to say that gravity pulls everything ‘in’.

I’ve mentioned our old friend Sir Isaac Newton a lot now, and we heard about his famous apple at the very start. Legend has it that an apple fell on Newton’s head and just like that, he understood gravity- but did it really happen? Well it certainly seems to be true that a falling apple did inspire Newton’s work on gravity but there was no instant moment of understanding as the story seems to suggest.

The truth is that, whilst sheltering from the wrath of the bubonic plague at his family home in the countryside, a young Newton witnessed an apple fall from a tree. This sight led him to wonder, “Why should that apple always descend perpendicularly to the ground?” However it was not until around 20 years later that Newton first published this principle.

So that’s one myth busted, and another classic example of science, or scientists, being inspired by nature.

See you next time for a futuristic post all about holograms!

 

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Unexplainable Astronomy? Part 1: The Wow! Signal

By Sam Jarman

The scribble that started it all | Image: Big Ear Radio Observatory, NAAPO

Monday was dragging for Jerry R. Ehman, in a way that only a volunteer astronomer at the SETI project could truly understand. The frequency data printed out by the IBM 1130 computer was, as always, infuriatingly ordinary. The stream of paper he needed to analyse by hand was seemingly endless. Coffee in a Styrofoam cup was slowly growing lukewarm. Then… something different.

 

On August 15 1977, Ohio State University’s Big Ear radio telescope picked up an intense and unexpected burst of radio waves, which lasted for a full 72 seconds. Stunned by the break in the monotony of his task, Ehman couldn’t help but briefly forget his deeply engrained skills in data analysis. Taking a bright red marker, he drew a circle around the numbers and letters indicating the burst, and wrote one word next to it: “Wow!”

Ehman wasted no time in letting his fellow members of SETI know about his discovery. The implications of the burst were not lost on any of them. The SETI volunteers knew there and then that the burst could not be explained by any current science. On each of their minds was the possibility that the purpose of their project had at long last been fulfilled: evidence of intelligent life beyond the Solar System.

 It doesn’t sound much like ‘We come in peace’, or ‘As you no doubt will be aware, the plans for the development of the outlying regions of the western spiral arm of the galaxy require the building of a hyperspace express route through your star system and, regrettably, your planet is one of those scheduled for demolition’, but the Wow! Signal could be the closest thing we have to a message from aliens

Hey, I know that frequency!

To understand why Ehman and his colleagues were so excited by the burst, we need to look at the characteristics of the particular frequency their telescope was picking up. The Big Ear radio telescope had been programmed to detect signals with the very specific frequency of 1420.406 Megahertz. That number might not roll off the tongue, but it’s incredibly important in astrophysics, and even has its own name: the Hydrogen Line frequency.

The red colours shows where hydrogen gas has been detected within the Milky Way. As it turns out, there’s a lot of it | Image: NASA

Hydrogen gas is extremely common in the wide expanses of space which lie between the stars. Atoms of the gas, consisting of an electron orbiting a single proton, are normally very stable and pretty uninteresting. But occasionally, the electron will flip over spontaneously due to quantum processes – a phenomenon known as spin flip transition, making the system unstable. To return to normal, the electron needs to flip back around, releasing a flash of light with a specific energy – a radio photon – in the process.

This process is incredibly rare for individual hydrogen atoms, but when hydrogen gas is gathered in clouds which span many light years, enough radio photons are given off by spontaneously flipping electrons that they can be easily picked up by radio telescopes on Earth. These photons make up the radio signal of the Hydrogen Line, which is important both to radio astronomers and to those hopeful that other technologically advanced civilisations could be out there somewhere.

The Hydrogen Line frequency is useful to astrophysicists, as they can use it to detect the exact locations of clouds hydrogen gas within our galaxy, and in those beyond. The clouds will always be densest in galactic arms, allowing radio astronomers to map out the distinctive structures of galaxies. They can also use the Doppler Effect to measure how fast hydrogen gas at various distances from the centre of galaxies is moving. From this, they can then create rotation curves for different galaxies, which currently give the clearest evidence we have for the existence of Dark Matter (but that’s a whole other story!)

So when astronomers point their radio telescopes at hydrogen gas clouds, it’s hardly surprising for them to observe radio waves at the Hydrogen Line frequency. But what if we observe them in places in the sky where we aren’t expecting them, or at higher-than-expected intensities? Any astronomer will agree that if this happens, something unexplained is going on.

“Huh, these aliens know about hydrogen spin-flip transition and have an in-depth understanding of their place in the galaxy… so why haven’t they invented clothes yet?” | Image: NASA

Astronomers at SETI became interested in the Hydrogen Line frequency because it is such a fundamental figure in astronomy. Clouds of hydrogen gas are so abundant in the galaxy that their signal can be picked up no matter where you go in space. SETI figured that if there are any other enlightened civilisations elsewhere in the universe, then they must realise this too. No matter how different their scientific units are to ours, if we asked them to create a radio signal at the Hydrogen Line frequency, it would be exactly the same as the signal we would create. So what better way to announce your presence to the galaxy than to send out a distinct, high-intensity transmission of the frequency?

 

SETI has already sent signals like this out into space, in the hope that others out there may be listening. In fact, they have a strict control over the transmission of the Hydrogen Line signal; it is now illegal to get anyone’s hopes up by transmitting the frequency yourself. But that isn’t the only method we have used to broadcast our knowledge of the Hydrogen Line. In 1972, under the efforts of Carl Sagan, Frank Drake and other journalists and astrophysicists, the famous Pioneer plaque was attached to probes Pioneer 10 and Pioneer 11.

In the top-left of the plaque is etched a diagram representing the distinctive electron flipping process which causes the Hydrogen Line. Between two representations of hydrogen atoms with electrons in the two different states is a horizontal line 21.106 cm long – the exact wavelength of a radio wave at the Hydrogen Line frequency of 1420.406 MHz. If an intelligent civilization ever finds one of the probes then it’s a safe bet that they will understand exactly what the diagram is representing, no matter their language.

 An explanation, or an alien-killing pretender?

Not long after Ehman’s bizarre discovery in 1977, the newly dubbed Wow! Signal, named after Ehman’s hasty scrawl in red pen, had taken the worlds of both science and the media by storm. While astrophysicists rushed to discover the astronomical source of the signal, journalists began to enthusiastically speculate that without any existing scientific explanation, it could have been more purposefully created in origin. For hopefuls of the existence of extra-terrestrial intelligence, the evidence was now more tantalising than ever.

Sorry it was me all along… or was it? | Image: NASA, ESA, J.-Y. Li

Yet for all the attention the Wow! Signal gained, the search for its origin proved fruitless for scientists and alien hunters alike. For over 40 years, the result sat there unexplained; frustrating some, and instilling hope in others. But in April 2017, astronomer Antonio Paris from St Petersburg College, Florida claimed in a paper to have solved the mystery once and for all.

Paris argued that on August 15, 1977, two comets inside the Solar System – 266P/Christensen and 355P/Gibbs – passed directly in front of the Big Ear radio telescope. Surrounding one of the comets was a cloud of hydrogen gas, which was given off by one of the masses of ice and rock. Naturally, the telescope picked up the Hydrogen Line signal of the cloud, but only as it passed through Big Ear’s field of view. For the first time, it looked like the mystery had been solved. But not everyone was satisfied with the new explanation.

Within weeks, Paris was receiving backlash from scientists, who had some strong criticisms of his paper. In June, Robert S. Dixon, director of the SETI project himself, published a rebuttal to Paris’ paper, claiming that the two comets weren’t in fact within Big Ear’s field of view on the day of the Wow! Signal. Other criticisms included claims that the comets were a long way from the Sun and therefore inactive, meaning neither of the comets could possibly maintain a hydrogen cloud around themselves. Some scientists even had many harsh words to say about Paris’ scientific methods in general. Paris stands by his theory, but he’s open to debate.

So for now, many astronomers still regard the Wow! Signal as a mystery, and hope remains that the true explanation of the burst could be another advanced civilization broadcasting its existence. But this isn’t the only case where strange signals in astronomy have gone unanswered for long periods, or where far-fetched and alluring explanation theories have been thought up.

Over the last century, the world of astronomy has been become famous for detecting mysterious signals, making bizarre discoveries, and throwing up seemingly unanswerable questions. Some of these questions have had mundane explanations. Others have led to new research which has come to revolutionize our understanding of the universe. And, like the Wow! Signal, still others remind us just how much we have yet to learn.

In this series, we will find out more about the signals which have both answered and created some of the most enticing questions in modern astronomy. Next time, we will turn back the clock to before 1977, when astrophysics was reeling at the revelation that our place in the universe was far less significant than we realized.

2 comments on “B is for Black Holes”

B is for Black Holes

By Siobhan Fairgreaves

In our last post we looked at atoms and their subatomic particles. That’s the tiny end of physics, this time we look at something at the other end of the scale- black holes.

Cheesy sci-fi films have been trying to warn us for decades… but we never listen! As it turns out, that’s probably for the best | Image: Martin

Ooooo, now this is the good stuff, right? The fuel of sci-fi movies and something that you think you should be mildly concerned about. Remember when scientists were apparently going to make another one in Switzerland? That was a bit of an anti-climax.

I was at school when the Large Hadron Collider in Switzerland was switched on and I remember a lot of panicky talk about black holes and us all being sucked into space. To find out more about what on earth a Large Hadron Collider is you will have to read the next post- C is for Collider, cheeky I know.

For now, though, what is a black hole?

I know you’re hiding in there somewhere – astronomers can only find black holes by mapping out the paths of stars orbiting around them | Image: ESO

Well let’s start off with a quote from the brilliant Stephen Hawking, “It is said that fact is sometimes stranger than fiction, and nowhere is this more true than in the case of black holes.”

He certainly got that right. Black holes are pretty mysterious and teams of scientists are still figuring out what exactly goes on up there. This is made all the more difficult by the fact it’s not even possible to see black holes, only the effect they have on other objects. In a nutshell, though, black holes are an area of space where gravity has become so strong that nothing can get out- not even light.

Born from the death of a star: the Orion Nebula, made up of the explosive remnants of a star which could once be seen just under Orion’s belt, is thought to have a black hole at its centre| Image: Ljubinko Jovanovic

Because this gravity is so strong it’s easy to go along with the assumption that one day we will be sucked into one and disappear. You’ll be pleased to hear that NASA thinks this is very unlikely- there simply isn’t one close enough for us to worry about.

For a long time, I imagined black holes as a sort of Pacman travelling around in space munching on stars, planets and everything else in their way but this is not the case. Black holes are actually caused by a star collapsing and as the star collapses in on itself the gravity gets so strong that a black hole is created.

A horrific yet tasty way to go: the difference in gravity between an astronaut’s head and their feet as they fall into a black hole would lead to the process of ‘spaghettification’ | Image: Cosmocurio

That’s all well and good but there are billions of stars out there, does this mean that every star will one day make a black hole? And, hang on a minute, our Sun is a star- are we orbiting a wannabe black hole? You’ll be pleased to hear that our Sun simply isn’t big enough to become a black hole- it takes a pretty big star to cause such a powerful pull of gravity when it collapses.

Instead of Pacman, you could think of a black hole like water going down a drain. When the bath is full, the water rushes down the drain and sucks everything with it but when there is only a dribble left it isn’t even strong enough to take down any leftover bubbles.

So yes, black holes are crazy giant plugholes travelling through space which, as the European Space Agency says, would see an astronaut “pulled apart by the overpowering gravity” if they were to get too close- but should we be worried about them right now? No.

Until next time!

This probably won’t ever happen to you, but if you do ever find yourself in the devastating clutches of an inescapable gravity source, it might be nice to know what to expect

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Space is Big

By Jonathan Farrow from the Thoughtful Pharaoh

I didn’t grow up by the sea, so every time I’m faced with an ocean, I get a true sense of awe. The sheer magnitude of the thing in front of me leaves me speechless. I look out and it’s just water, as far as the eye can see.

File_000.jpeg
Image my own

On a clear day, the horizon for an average person standing by the sea is about 5 kilometres.

So if looking out 5 kilometres in every direction is enough to impress me (and I’m pretty sure I’m not the only one), you can imagine why I love looking through telescopes so much.

The moon, an easy target for amateur astronomers like myself, is nearly a hundred thousand times further away than that horizon (384000 kilometres on average). When you look at it through a telescope, you can see start to identify craters and “seas”, just like Galileo did 400 years ago.

Full moon.jpg
Image by Gregory Revera via Wikimedia

And that’s the closest non-Earthly object in the Universe. It only gets further from there.

Light, travelling at the speed limit of the universe, takes about one second to reach us from the Moon. The Sun, which by coincidence is the same apparent size as the moon when viewed from Earth, is 400 times further away. Light takes 8 minutes to reach us from its tumultuous, fusion-fuelled surface.

It takes light 4 hours to get from the Sun to Neptune, the edge of the Solar System (sorry Pluto, you don’t count anymore). Light travelling for 4 years will just about get to the nearest star (Proxima Centauri) and to get to the edge of the Milky Way from its centre takes light more than a thousand human generations (50000 years +).

While those distances are starting to get mind-boggling, the Milky Way is only one very tiny part of the Universe. Sure, it contains a billion stars and the only known way that the Universe knows itself, but we’re learning that we’re even smaller than we thought.

The next closest galaxy to the Milky Way is called Andromeda, and together with 52 other mini-galaxies, we live in the Local Group.

Local_Group_and_nearest_galaxies.jpg
Image by Antonio Ciccolella via Wikimedia

The Local Group, in turn, is part of a supercluster of galaxies called Virgo. And that was it – our Universal address was Earth, Solar System, Milky Way, Local Group, Virgo Supercluster.

But in 2014, astronomers redrew the map of the local Universe by looking at where galaxies were moving. It turns out that we’re part of a much larger supercluster called Laniakea. The name is apt, meaning ‘immeasurable heaven’ in Hawaiian.

Another recent discovery has shed new light on the size of the universe. In October 2016, astronomers from the University of Nottingham and the University of Edinburgh used data from a new set of Hubble images called Frontier Fields to recount the number of galaxies in the Universe.

The original Hubble Deep Field images, released in 1996, reached further away (and therefore further back in time) than anything previously available. They glimpsed 12-billion-year-old galaxies from the very early Universe.

These Deep Field images had thousands of galaxies in them, so when astronomers extrapolated that out to the whole sky, 120 billion was the agreed number of galaxies in the Universe.

HubbleDeepField.800px.jpg
The original Hubble Deep Field from 1996, Nasa via Wikimedia

But 120 billion galaxies don’t weigh enough, so astronomers suspected that might be a miscount. This new study uses images that go back 13 billion years and used a mass distribution approach to arrive at a new number that would include galaxies too faint to actually observe.

Their results show that there are 2 trillion galaxies in the Universe, 10 times more than previous thought.

Or, at least, there were 2 trillion galaxies. Many of the small, early galaxies will have merged with others in the intervening 13 billion years, but the light from those mergers hasn’t reached up yet.

With astronomers not only redrawing the map but also doing another census, it turns out space was bigger and fuller than we thought.

What does that mean for the awestruck boy by the sea? I’m not entirely sure, but I think it means that even though he’s smaller than he thought, he should keep wondering and keep seeking to understand his place in the Universe. I take a lot of inspiration from Carl Sagan, so I’ll leave you with this, from Cosmos:

“In a cosmic perspective, most human concerns seem insignificant, even petty. And yet our species is young and curious and brave and shows much promise. In the last few millennia, we have made the most astonishing and unexpected discoveries about the Cosmos and our place within it, explorations that are exhilarating to consider. They remind us that humans have evolved to wonder, that understanding is a joy, that knowledge is a prerequisite to survival. I believe our future depends powerfully on how well we understand this Cosmos in which we float like a mote of dust in the morning sky.”

0 comments on “Vegetarian aliens could save our bacon”

Vegetarian aliens could save our bacon

stephen hawking right about nasty aliens

By James Riley

Bacon is tasty, very tasty. It’s so tasty that my moral objection to the industrial-scale murder of sentient animals dissipates with each and every ketchup-soaked bite. This is a weakness on my part. I’m theoretically ethical but practically perverse. It’s a great way to be. You get to rest your nose on the edge of the moral high ground, whilst your body swings in the succulent depravity below. But in all sincerity, I would argue that an extension of vegetarian philosophy is the only possible way we could survive an encounter with extra-terrestrial life. Let’s just hope astro-porcine is less alluring.

hungry aliens eat space pig rising ape
They came for a piece? (Image: Bell and Jeff/Flickr)

I’m pretty optimistic about alien life, not only about its existence but also about its intelligence and intentions. As unnerving as it is to disagree with such a great man, I must confess I don’t share Stephen Hawking’s view: “If aliens visit us, the outcome would be much as when Columbus landed in America, which didn’t turn out well for the Native Americans.”

stephen hawking right about nasty aliens
(Image: Mike Licht/Flickr)

On earth, species have certain ecological niches, their relational position to other species and their way of life in an ecosystem. Interplanetary, interstellar or even intergalactic life may follow a similar pattern. What niches come down to is competition for resources in a given environment. If one day we do share an interstellar environment with other intelligent species, there will no doubt be different ways of ‘making a living’ between the stars. But as soon as competition for resources enters the equation, we have a problem.

If aliens come here to harvest a resource that we also depend on, then we will undoubtedly lose due to the competitive exclusion principle. According to this principle, also known as Gause’s Law, two species that are competing for the exact same resource cannot stably coexist. Furthermore the species with even the smallest competitive advantage will be successful in the long run. As the aliens will have traversed interstellar space to reach us, our technology and defence capabilities just won’t match up. ET, I’m sad to say, will be holding a horribly beweaponed stick.

cavemen make fire
“Hm, maybe we should start building a bigger stick now…” (Image: Lance Cpl. Nathan McCord/Wiki)

But there’s another scenario. In this case the outcome of an extra-terrestrial meeting isn’t solely left to the will and whim of evolutionary forces. Instead, as has happened in our civilisation, rational choices can overcome biological impulses.

Take eating meat for example. It is generally accepted that our ancestors ate meat in their hunter-gatherer existence. But nowadays some people have come to the conclusion, to the upmost resentment of others, that killing animals and eating meat might be a tad wrong. You know, all the confinement, force-feeding, mechanised slaughter, it is a little unsettling (until you taste the bacon). Others argue the opposite, that eating meat is ‘natural’ therefore it must be the ‘right’ thing to do. This line of reasoning commits my favourite logical fallacy (don’t pretend you haven’t got one), the ad Naturam or appeal to nature logical fallacy. If we solely took our morality from nature we would live in a very cruel world indeed. (Watch a video of Mallards being natural here. Note: Morality not included; viewer discretion is advised.)

So what’s all this got to do with aliens and bacon? Well if aliens take the same stance—the choice not to kill sentient beings based on nothing else but the value that sentience confers—then perhaps we do stand a chance of a peaceful coexistence. But if aliens come with predacious intentions, aiming to harvest, experiment, extract, and/or exploit, there really is little we can do to stop them.

So hope and pray that, when our skies are darkened by the spectre of a flying saucer drifting through trembling clouds, you can smell the pungent aromas of Quorn and lentil burger emanating from the ship’s kitchen. Maybe that’s why they were called little green men all along?

0 comments on “M is for (exo)Moons”

M is for (exo)Moons

By Jonathan Farrow of the Thoughtful Pharaoh

With this post, rising-ape.com is now caught up with my website, thoughfulpharaoh.  From now on, I will be posting articles simultaneously on both sites, on Wednesdays.

Thanks to everyone for following along and as always, if there is a topic you have in mind, don’t hesitate to leave a comment below.

And now for this week’s article: exomoons.

There are 8 planets in our Solar System (sorry Pluto).  Most of these planets have companions that follow them around, like obedient pets and criminal records.  The total count of these moons is 181.  We are all quite familiar with the big shiny one that orbits Earth (that may or may not be made of cheese), but what many people don’t know is the sheer number of other moons that exist in our Solar system.

Just like planets, these moons come in all different shapes and sizes.  S/2009 S1 is only 400m across and orbits in one of Saturn’s rings, making it the very smallest moon.  Ganymede, the solar system’s largest moon, measures in at about 5300km across, almost half the size of earth.

One of the biggest findings to come from the Kepler mission is that most of the stars in the galaxy have planets.  In other words, our solar system isn’t unique.  That means our Solar System probably isn’t the only whose planets have moons.  If our system, with 22 times more moons than planets, is any indication, there are a lot of moons to find.

This presents two immediate problems: firstly, why should we want to find them?  Secondly, how do we go about finding them?

Why find an exomoon?

The same thing that makes seawater rise and fall twice a day, tidal forces, can heat up a moon.  Tides are a result of the fact that the strength of the force of gravity is related to the distance between two objects.  On Earth, the water on the side close to the moon gets pulled out towards the moon stronger than the water on the other side, this creates bulges of water that move around as the earth spins: tides.

Tides stretch.  Image by Krishnavedala
Tides stretch. Image by Krishnavedala

The Earth is too small and our moon is too far away for much more than sea level change to happen, but Io, one of Jupiter’s moons, has over 400 active volcanoes caused by extreme tides from the gravity of its host planet Jupiter. In this case, it’s not just bulges of water that are created, but bulges in the crust of the moon itself.  This creates an immense amount of friction and heat. Europa, another moon of Jupiter, gets enough energy to keep a planet-wide ocean of water liquid under its icy crust.  Some people think Europa might be habitable, even though it is so far away from the Sun.

If there are moons here in our Solar System that can be habitable at Jupiter-like distances, there could be moons in other systems that orbit planets much closer, at Earth- or Mars-like distances.  Some people, like Rene Heller at McMaster University’s Origins Institute (a fine institution, if I do say so mystelf *full disclosure: I did my undergrad there*), think exomoons might be our best shot for finding habitable places in the galaxy simply because of their abundance relative to planets (remember, there are 22 times more moons in our system than planets).

How to find an exomoon

This is the tricky part.  It was hard enough finding exoplanets. Finding a transiting exoplanet is often compared to looking for the effect of a mosquito passing in front of a car’s headlight.  In that analogy, finding an exomoon would be like finding out how many legs it has.  No easy task.

It’s not impossible, though.  Moons do have effects on their planets and if we look carefully enough, we can find them.

One way to find exomoons in transit data takes advantage of the fact that, viewed edge-on, a moon will appear more often at the edges of its orbit.

ExoMoonTransit
Image by Rene Heller

If you capture many transits over time, you can begin to see these wingtips in the transit data.

Image by Rene Heller
Image by Rene Heller

The grayscale bar in the image above represents the average effect of a moon orbiting a planet.  What astronomers can look for in the transit data is a preliminary dip (1) that starts off severe then levels off, followed by the regular planetary transit (2), followed by another characteristic dip (3) as the other wingtip passes in front of the star.

This method only works if you have a lot of data, but luckily Kepler was operational for four years and gathered just the right kind of data.

So now the search will begin.  Who will find the first exomoon?  And what if it turns out to be “no moon” at all?

An artist's impresison of a view from an exomoon with a triple star system.  Far out, dude.  Image by NASA/JPL-Caltech
An artist’s impresison of a view from an exomoon with a triple star system. Far out, dude. Image by NASA/JPL-Caltech
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K is for Kepler

“Truth is the daughter of time, and I feel no shame in being her midwife.” Johannes Kepler

These words, written by Johannes Kepler in 1611, are profound.  At the time, Galileo had just discovered the Galilean moons (including Europa) in Florence but was being persecuted for his belief that the Earth orbits the sun.  Kepler, a staunch supporter of heliocentrism, was working as the Imperial Mathematician in Prague.  When word that Galileo had used a telescope to find the moons reached Kepler, he was so fascinated and impressed that he wrote an enthusiastic letter of support and scrawled that pithy aphorism.

While Kepler enjoyed some social status as Imperial Mathematician and was much more free to contradict Aristotle than his Italian counterparts, his life was by no means a charmed one.  The son of “an immoral, rough and quarrelsome soldier” (his own words), Kepler managed to carve himself a place in history based on his skill as a mathematician and astronomer.  He kept on working through many family disasters, including the deaths of his wife and his seven year old son and a witch trial about his mother.

Kepler was a devout Christian and grew up Lutheran but was excommunicated due to his rejection of the Augsburg Confession.  This left him neither a Lutheran nor a Catholic and between sides when the Thirty Years War broke out in 1618.

You've got to love that frilly collar.  Just like Shakespeare!  Actually, come to think of it, Kepler actually lived at the exact same time as Shakespeare.  I wonder if they ever met and what they might say to each other at a dinner party.  Image is public domain.
You’ve got to love that frilly collar. Just like Shakespeare! Actually, come to think of it, Kepler lived at the same time as Shakespeare. I wonder if they ever met and what they might say to each other at a dinner party. Image is public domain.

Despite all of this, Kepler revolutionized astronomy by formulating mathematical laws that accurately describe the motions of the planets.  These are still taught in astronomy today and are called Kepler’s Laws.

The first law is that planets orbit in ellipses with the sun at one focus.  Before Kepler, most Western astronomers modelled the orbits of planets as circles and had to invoke a strange concepts like epicycles and equant points.

1. Planets orbit in ellipses, not circles.
1. Planets orbit in ellipses, not circles.  Image my own

The second law is that a line between a planet and a star will sweep out equal area in equal time. In other words, planets move faster when they are closer to their star and slower when they are further away.  This law is better understood with a diagram:

asd
2. Planets don’t have constant speed  Image by RJHall

The third law, formulated after the first two, is that the time it takes a planet to make an orbit (orbital period) is directly proportional to its distance from the star.  This law allows astronomers to calculate how far a planet is from its star based only on information about the length of its year and the mass of the star.  Remember this one, because it will become important later.

As you can see, Kepler’s Laws are fundamental to our understanding of how planets move, or orbital dynamics.  It will come as no surprise then that every young astronomer is all too familiar with Kepler’s laws.  This isn’t the only reason he’s familiar though.  He is also shares a name with the most successful exoplanet hunter the world has ever produced.  The Kepler Space Telescope.

Kepler: Planet Hunter is kind of Like Abraham Lincoln: Vampire Hunter.  Except more real.  And frankly, a little more impressive.    Image by Wendy Stenzel at NASA
Kepler: Planet Hunter is kind of like Abraham Lincoln: Vampire Hunter. Except more real. And frankly, a little more impressive. Image by Wendy Stenzel at NASA

Launched in 2009, the Kepler Space Telescope used 42 image sensors to continuously observe over 145,000 stars.  Unlike a lot of other telescopes that try to take magnified images, Kepler wasn’t interested in images.  It wanted accurate data on brightness.  It basically had a staring contest with these 145,000+ stars, waiting for them to blink.  I say blink because Kepler was waiting for the brightness to go down and back up.  The brightness of stars can vary for all sorts of reasons, but planets passing in front of their stars make the brightness dip in a particular way.  This dip is called a transit and finding transits was Kepler’s mission.

When a transit occurs, the size of the brightness dip corresponds to the size of the planet and the length of the dip corresponds to the time it takes a planet to orbit (as well as the size of the star).  Remembering Kepler’s third law,  if we know the time it takes to orbit, we can figure out the distance to the star.  And if we know the brightness of a star and the distance, we can figure out how much energy the planet receives.  Plug all that in to a simple(ish) equation, and out pops temperature.

Stars, just like planets and people, come in all different shapes and sizes.  That means light curves also vary widely.   Image from Planethunters.org
Stars, just like planets and people, come in all different shapes and sizes. That means light curves also vary widely. Image from Planethunters.org, a great citizen science project that combines people’s natural pattern-finding ability with Kepler data to find planets.

So thanks to the Keplers (both Johannes and the Space Telescope) we can start to look for alien worlds that have temperatures similar to the ones we find here.  The hope is that one day we will find evidence of life on another planet.  And then we can begin our transition into any one of several sci-fi galactic civilizations (my personal favourite is Foundation, but some people prefer Star Wars, Star Trek, or Eve Online).

Unfortunately, in May 2013 one of the components that kept Kepler (the telescope) stable failed, meaning the mission was apparently over.  The mission had been hugely successful, discovering over 1000 confirmed planets, with 4000 other planet candidates waiting to be confirmed.  It turns out that most stars probably have planets and that a lot of planets in the galaxy might be the right temperature to be habitable.

Astronomers are nothing if not persistent though, so an ingenious method was devised to make sure Kepler can continue observing even without its stabilizer.  This new mission, dubbed K2, uses the radiation pressure from the sun itself to balance the telescope.  Instead of continuously observing the same 145 000 stars, K2s targets will change periodically as it orbits the sun.  There will be far less data coming down, but as of this writing four new planets have already been found since K2 began in earnest in June 2014.

There's a lot of information there, but I think the most impressive bit is that K2 is metaphorically balancing a pencil on a fingertip, remotely, from 150 million km away.  Image by NASA
There’s a lot of information there, but I think the most impressive bit is that K2 is metaphorically balancing a pencil on a fingertip, remotely, from 150 million km away. Image by NASA

Currently, while there are all sorts of really interesting exoplanets out there (from hot jupiters like 51 peg b to mirror earths like Kepler-438b), we have yet to find signs of life.  But I think that before too long, we will.  Just as the truth of heliocentrism eventually came out thanks to Kepler, a telescope with his name will be instrumental in uncovering the truth of life elsewhere in the universe.  Just like he said,

“Truth is the daughter of time, and I feel no shame in being her midwife” Johannes Kepler

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J is for Jupiter’s Great Red Spot

By Jonathan Farrow from the Thoughtful Pharaoh

If you look up in the night’s sky and point even a simple pair of binoculars at Jupiter, like Galileo did with a rudimentary telescope 405 years ago, you will see what he did: a reddish-pink planet with swirling masses of clouds. These clouds are beautiful in their own right, but there is one particular feature that has drawn the eyes and the fascination of people for over four centuries. The Great Red Spot.

This swirling, gurgling red super-storm could fit three earths inside of it and has been raging on the gas giant ever since we’ve been keeping records. How it has lasted for so long and why it has such a different colour has long been a mystery.

In 2000, on the way to Saturn, an ESA mission called Cassini aimed to give us some clues when it flew within 9.7 million kilometres of Jupiter and looked more closely at the spot than we had ever done before or since. 9.7 million kilometres sounds like a lot, but consider that is only about 1% of the distance between Jupiter and Saturn. (As a side note, did you know that Jupiter and Saturn are further away from each other than Jupiter and Earth? I didn’t!).

It might have looked kind of like this, but with Jupiter instead of Saturn in the background.  Cassini's main mission was to Saturn and its moons.
It might have looked kind of like this, but with Jupiter instead of Saturn in the background. Cassini’s main mission was to study Saturn and its moons.  Image by NASA

With its flyby, Cassini found out that the clouds that form the spot are up to eight kilometres higher than the surrounding clouds and started to understand the chemical composition of the clouds.

14 years later, in November 2014, NASA scientists released results that combine data from the Cassini flyby with lab experiments on Earth. They showed that the colour must come from the interaction of ultraviolet (UV) light from the sun and the ammonia and acetylene in the top layers of the storm. Once the red particles are produced, they are trapped by the circular winds of the storm. This overturns the previous theory that it was the bottom clouds which provided the colour. The NASA scientists compare the colour of the storm to a sunburn rather than a blush.

So, thanks to NASA and the Cassini mission, we have a better idea about how the spot gets its colour, but last spring the astronomy world was in a tizzy because news came that the spot has been shrinking.

That's some pretty serious shrinkage!
That’s some pretty serious shrinkage!  Image by NASA

Since it is so noticeable, the storm has been recorded as far back as the 1800s, when it was believed to be about 41000 km across (roughly equal to the circumference of Earth).  The most recent image, from 2014, puts the size at only 16500 km (less than the length of the great wall of China).  Not only is it much smaller than it used to be, but the rate of shrinkage is increasing.

Totally, 100% peer-reviewed, recollection of secondary school math to figure out when the spot will disappear.
Totally 100% peer-reviewed recollection of secondary school math to figure out when the spot will disappear.  Image my own

If my calculations are correct, and if the storm keeps shrinking the way it has been, it will disappear entirely in about 35 years, in 2059.  That means we may be among the last people to ever see the spot that Galileo spied on that fateful night in 1610.

Instead of relying on me and my calculations, however, NASA sent a spacecraft to go investigate.  Juno left in 2011 and by now is more than halfway to its destination. When it arrives in July 2016, Juno will study the gas giant in a variety of ways and hopefully get the bottom of this whole shrinking storm mystery.

JUNO
Image by NASA
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G is for Gravity Waves

By Jonathan Farrow from the Thoughtful Pharaoh

Deep in Antarctica, right on top of the geographic South Pole, there is a research station that peers back in time to the very beginning of our universe. Named the Amundsen-Scott Station, it is home to instruments such as the creatively named South Pole Telescope (SPT), the Keck Array, and the BICEP experiments.

The temperature is currently sitting at about -30C and it’s the height of summer.  The sun won’t set at the station until March 23rd and once it sets, it won’t rise again until September.  So why the heck (or, one might say…Keck) would we build an observatory there?

Because the temperature is so low and the altitude is so high (2743m) at the South Pole, the air is thin and dry, reducing blurriness normally caused by the atmosphere.  There are no cities nearby to cause light pollution and there are months of nonstop night, allowing for continuous observation.  It’s an astronomer’s dream.  Except the nearly-constant -30C temperatures.  And the remoteness.  But otherwise, dreamlike.

Damn that looks cold! Photo from 2003
The perfect place to set up a top-secret laboratory from which to take over the world!… I mean… uh… from which to observe the beginnings of the universe.  Yeah, that’s what we’re doing.  Definitely that.  Image credit: NASA

So what are astronomers looking for all the way down there at the end of the world?  They are searching for clues as to how the universe started.  Ever heard of the Big Bang Theory?  No, not these clowns, the theory about the beginnings of the universe. Although, come to think of it, the theory is actually pretty well summed up by the first line of the Barenaked Ladies’ theme song to the Big Bang Theory (yes, those clowns):

Our whole universe was in a hot dense state,
Then nearly fourteen billion years ago expansion started. Wait…

That’s really the core of the theory:  everything used to be really hot and dense and now its not.  What happened in between is what the astronomers at the South Pole are trying to figure out.

History of Universe
For a bit of a primer on this diagram, check out A Short History of (The Universe), an essay I wrote which introduces the origins of the universe.  Image by NASA

Astronomy is awesome because when we look up, we are actually looking back in time.  The distances involved are so great that it can take years (or billions of years) for light to reach us.  So, what if we just looked as far as we could, wouldn’t we be able to see the Big Bang happening?  What would that even look like?

Unfortunately, because everything was so hot and dense right at the start of the universe, nothing could stick together so the universe was just a soup of energetic particles.  Any light that was emitted was bounced around like the light from a flashlight in thick fog.  About 380 000 years after the Big Bang , the universe had cooled and expanded enough to let atoms form and collect electrons.  Atoms are mostly empty space, which means that unless they are packed very close together like in a solid or liquid, they are transparent.  What resulted was light spreading pretty evenly throughout the universe, starting 13.7996 billion years ago.  This is what is called the Cosmic Microwave Background Radiation (CMBR).  Cosmic because it comes from space, Microwave because it has lost a lot of energy since the Big Bang and is now only 2.7 degrees above absolute zero, Background because it is there no matter which direction you look, and Radiation because it is light.

WMAP
A map of the Cosmic Microwave Background Radiation. The different colours represent slight anomalies (about 10^-5 degrees C difference). Red is a little bit hotter, dark blue is a little bit colder.  Image by NASA

So, no matter how far you try to look, this map is all that you see.  It is all that can be seen because it is the oldest light that escaped.  Sounds kind of disappointing, but astronomers think that that image (what some refer to as the baby picture of the universe) holds clues to what happened before.

If there was inflation, faster-than-light expansion of space and time (again, check out my essay on the history of the universe if you’re confused), that process should have produced gravitational waves.

“Woah, woah, woah.  Hold up.  I understand gravity, apples falling on heads, etc etc…  How the Keck could there be gravity waves?”

One of Einstein’s key contributions to science was the understanding that space and time are linked and that they are influenced by mass.  He described space-time as a fabric that could be warped by the presence of mass.  All that gravity is, he said, is the curvature of space-time around mass.  A simplified way to understand this is by thinking of space-time as a trampoline.  If you put a mass on the trampoline, it will create a depression.  The heavier the mass, the more extreme the depression.  Now, if you have an extreme depression and move it very quickly back and forth, it will create waves in the same way that a moving hand in a pool will create waves.  Astronomers think that inflation must have created gravity waves with a very specific signature. They also think that very heavy stars moving quickly, like binary neutrino stars, would create these gravitational waves.

Loooook into my gravity waaaaves.  You are not getting sleepy.  You are paying attention, commenting below, and sharing this with your friends.
Loooook into my gravity waaaaves. You are not getting sleepy. You are paying attention, commenting below, and sharing this with your friends.  Image by NASA

If (or, once they are discovered for sure, when) gravity waves pass through you, it is space itself which is expanding and contracting.  You are not moving, but as the wave passes through your arm, your arm will be closer to your body than it was before and time for it will move slower.

The thing about gravity, though, is that it is by far the weakest of the fundamental interactions (Electromagnetic, Weak, Strong being the other, stronger ones).  By a factor of about a nonillion (1 with 30 zeroes after it).  This makes the waves it creates very difficult to detect.  While your arm is probably having a taste of timelordery as you read this, there is no way you could possibly feel it.  Gravity waves are not interesting for how they make us feel, but rather for the challenge they present in detecting, for the possible confirmation of our current physical model, and for what they can tell us about the origin of the universe.

So let’s come back back to the barren, frigid wasteland of Antarctica and the astronomers freezing their buns off for science.  BICEP2, the second iteration of the Background Imaging of Cosmic Extragalactic Polarization experiment, looked at the CMBR and looked for patterns in the light.  These patterns, called b-mode polarization, can be produced by gravity waves, but also by interstellar dust.

In order to cancel out the effect of dust, the BICEP2 team used data from Planck, a European satellite launched in 2009 with a very similar mission: to study the early universe.  Whereas BICEP2 could only look at one particular wavelength with high sensitivity, Planck could look in a few different wavelengths but didn’t have quite as much sensitivity for these b-modes.  Dust doesn’t leave the same polarization patterns in light in different wavelengths, so by comparing the results from different wavelengths from Planck, the BICEP2 team was able to show that the b-modes weren’t from dust and so had to be from gravity waves from the early universe.  Proof of inflation!  Proof of the standard model! A possible Nobel Prize!

./b_over_b_rect.eps
Those swirls are the b-mode polarization that astronomers were looking for.  This diagram, while confusing as Keck (it’s going to catch on!) and quite complicated, was EVERYWHERE when the announcement was made.  Image by BICEP2 team

So, understandably excited and with a positive result in hand, there was a big announcement at the Harvard-Smithsonian in March of last year.  Unfortunately, the data they used was preliminary.  In September, new data was released and the effect of dust seems to have been larger than they thought.  The team reduced the confidence in their findings but still stood by a significant result.  Just last month, in January 2015, another set of data was released that makes the BICEP2 findings inconclusive.

It seems the team jumped the gun a little bit, were blinded by the impact of their apparent discovery, and had too much confidence in preliminary data. The result of all this is that there is still no direct evidence of inflation or of gravitational waves and the teams at Planck and BICEP are going to work together now with the strengths of their instruments.  Within a few years, the effect of dust should be able to be cancelled out and we will be able to see whether we were right about the beginning of the universe.  And all the frostbite will have been worth it.