0 comments on “G is for Gravity”

G is for Gravity

By Siobhan Fairgreaves

‚ÄúGravity pulls everything down‚ÄĚ

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‚Äôm going to clarify- we‚Äôve 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 ‚Äėeureka!‚Äô 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 ‚Äėdown‚Äô. An important law in physics, called Newton‚Äôs Third Law, states that ‚Äúfor every action, there is an equal and opposite reaction‚ÄĚ.

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 Рjust 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‚Äôs laws ‚Äď the second this time ‚Äď 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‚Äô 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‚Äôt say that gravity pulls everything ‚Äėdown‚Äô! I don‚Äôt know exactly what is ‚Äėdown‚Äô from our position in the cosmos but I‚Äôm not so sure I want to find out. In a way, it would be more correct to say that gravity pulls everything ‚Äėin‚Äô.

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, ‚ÄúWhy should that apple always descend perpendicularly to the ground?‚ÄĚ 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!

 

0 comments on “F is for Flying”

F is for Flying

By Siobhan Fairgreaves

Don’t listen to Jon Snow, summer is coming!

Whether you will spend your (hopefully) sunny days looking up at blue skies or jetting off on an adventure, one thing may cross your mind- how do those aeroplanes stay up there!? In this post we will learn a bit more about how aeroplanes get up, stay up and get back down again.

Plane wings: black magic sorcery, or a clever bit of engineering? (This isn’t actually discussed in the article, it’s obviously the second one)

This is one post I’ve been really looking forward to writing- I’ve been well and truly bitten by the travel bug and I can’t think of a better feeling than the rush of the engines as your plane prepares to take off. It’s certainly obvious from the noise of the engines and the speed of the objects flashing past outside that it takes a lot of force to get in the air but what changes between just going forwards really fast and flying?

In order to understand this (and everything else about flying) it’s important to consider another very important F in the physics world- Forces. There are four key forces acting upon an aeroplane.  Horizontally, there is thrust and air resistance. Thrust, generated by those powerful jet engines, propels the plane forwards. Air resistance, or drag, slows the plane down- like when you stick your head out of a car window and the air hits you hard in the face, that force increases the faster you go, and planes go very fast!

Vertically the plane is subject to gravity (more on that next time) and overcoming the weight of the plane which is a downwards force. The final force is lift. This is slightly less obvious but extremely important and keeps the plane in the air.

In order for the plane to change take off it needs to move forwards and upwards (we’re talking passenger planes here- some military aircraft, like the Harrier, are capable of extremely short take offs.

We’ve got moving forwards covered thanks to the powerful jet engines providing enough thrust to overcome the force of drag. Moving upwards requires the cleverly designed wings to come into play. As air rushes over the wings it is thrown down towards the ground creating lift. In order to get off the ground, there must be enough lift created to overcome the weight of the plane due to gravity.

So when thrust is bigger than drag we go forwards and when lift overcomes the weight we go upwards. Very useful for take-off but we don’t want to keep going up forever.

Enough is enough! I’ve had it with these stably-balanced forces on this stably-balanced plane! | Image: Amada44

The wings are shaped and angled to ensure that we stay up, without constantly rising, throughout the flight. The curved and thicker front of the wing is designed to ensure air is at a lower pressure above the wing and a higher pressure underneath. The angle of the wing effectively allows the plane to push down on the air which also helps it stay up- think about pushing down on the water in a swimming pool.

Once the pilot has reached the right altitude they can level out the aircraft and just keep moving forwards. As long as the vertical forces of lift and weight, and horizontal forces of thrust and drag are all balanced, the plane will cruise at a steady altitude at a constant speed.

Getting down again simply (easy for me to say!) requires the forces to be reversed. We now want to go slower so the thrust force can be reduced and drag is allowed to help with the braking. As we also want to get closer to earth we allow the weight of the plane to help. By changing the shape of the wing using flaps, you may have seen these during take-off and landing, the pilot can reduce the strength of the lift force and transfer the weight of the plane onto the wheels which are lowered in time for landing.

Of course, numerous other environmental factors make the business of flying a plane very difficult indeed, but with a little more knowledge of the physics pilots use to help them out you can now sit back, relax and enjoy the journey.

Until next time!

0 comments on “E is for Electricity”

E is for Electricity

By Siobhan Fairgreaves

Last time, in D for Detectors, we looked at some of the applications of physics that you might encounter during your day. In this post, we’re going to find out more about something I can guarantee you use almost every day- electricity!

Far from simply being a piece of tack on your ‘cool’ uncle’s shelf, the plasma lamp is one of the best ways to see¬†electron flow ¬†in action

A reliable source of electricity is something we could easily take for granted, but how does it actually work? Well, surprise surprise, it all comes back to our friend- the humble atom. More specifically, electricity is the flow of electrons – remember them?

Electrons are the tiny negatively charged subatomic particles which whizz around the outside of the nucleus. In some materials, such as copper, the outer electrons break off quite easily and their movement through the material (a copper wire for example) creates an electric current.

Of course, not all materials can conduct electricity. I’m sure you remember the experiment in school where you tried to complete a circuit with different materials- they didn’t all work. Rubber, for example, holds onto its electrons pretty tightly so they can’t easily flow. This means rubber can’t conduct electricity.

Now back to that circuit experiment you may have tried. Your copper wires alone aren‚Äôt enough to light the bulb- you also need a source of power, like a battery.¬† The battery is a source of ‚Äúpushing power‚ÄĚ to move the electrons along. The official name for this is the electromotive force (EMF) but it‚Äôs more commonly known as voltage.

Ah, the good old Mexican current… at least that’s what it’s called among scientists who¬†advocate Mexican wave-particle duality¬†| Image: Martin Thomas

One way of thinking about electricity is a bit like a Mexican wave in a stadium. It usually takes a few people acting together to get it started- that’s the battery, and then the wave (or energy) transfers through each person and onto the next. The moving wave is a bit like the moving electrons.

Time for a fun fact now- did you know that the band AC/DC can actually teach us more about electricity? Their name came from seeing a symbol on their sisters’ electric sewing machine. This symbol stood for Alternating Current/Direct Current and meant that the machine could work with either type or electrical current.

“I’m on the hiiiiiiighwaay to… oh yeah, I’m periodically changing direction, so I guess I’m not really going anywhere” – an electron in an AC power line

Direct Current is best explained by the Mexican wave analogy used above. All the electrons move in the same direction. This type of current is used in toys and small gadgets. Larger machines tend to require Alternating Current.

The electrons forming an Alternating Current reverse direction 50 to 60 times a second. It’s a bit difficult to imagine how that could create a current but remember it’s all about transfer of energy. The battery still provides the initial push but these electrons don’t run in a straight line, they run on the spot instead. It doesn’t work in quite the same way but, just like Direct Current, still requires loose electrons and they still need energy.

See you next time for a convenient start of summer post- F for Flying!

0 comments on “U is for Ununoctium and the Island of Stability”

U is for Ununoctium and the Island of Stability

Quick, without looking it up: how many elements are there on the periodic table?

If I had asked that question before the first hydrogen bomb exploded in 1952, the answer would have been 98. ¬† In that year, humans succeeded in synthesizing the first element that the crucibles of¬†stars¬†and supernovae hadn’t supplied to Earth: Einsteinium.

Boom.  Image public domain
Boom. Image public domain

Since then, we’ve been busy bees, building bigger atoms by smashing protons and neutrons together. ¬†63 years after the first atoms of Einsteinium were made off the coast of an atoll in the Pacific and according to the International Union of Pure and Applied Chemistry (IUPAC), there are 114 official, named elements. ¬†Those 16 additional elements were not easy to make, but we’re far from done.

I want to tell you the story of the outer reaches of the periodic table. The tale involves magic (no, seriously… there’s an important concept called magic numbers)¬†and a legendary island in the midst of a terribly unstable sea (again, not just metaphors here… Chemists have theorized of an island of stability that lies in the midst of a sea of instability), but the edge of the chemical world¬†is dark and full of terrors. ¬†Before making our way to the brink, I need to prepare you with the tools you need to wade out into the sea of instability to find the island of stability.

Always have to be careful in the world of chemistry.  Image by Eliot Phillips
Always have to be careful in the world of chemistry. Image by Eliot Phillips

So what is an “element” anyways?

Atoms, the¬†basic building blocks of matter, are made up of electrons whizzing around in clouds around central nuclei. ¬†A nucleus is made of positively charged protons and neutrons without a charge. An atom is said to be a particular element because of¬†the number of protons it has. ¬†If an atom has one proton, it will be called hydrogen. ¬†A hydrogen with extra neutrons or electrons will still be hydrogen, but as soon as another proton is introduced, you’ve gone and made yourself a helium.

A cartoon of an atom with electrons in black, neutrons in blue, and protons in red.
A cartoon of a Lithium atom with electrons in black, neutrons in blue, and protons in red.

In that sense, atoms are just like me with breakfast: change up the cereal or the fruit but touch the coffee and I turn into a whole different person.

At this point you might be asking yourself what the point of neutrons or electrons is if they have no effect on the name of an atom.  The utility of electrons is pretty obvious: the tiny, whizzing balls of negative charge allow atoms to bind together and, because atoms are mostly empty space, their mutual repulsion is what gives matter the illusion of being solid.

Neutrons and Why We Need Them

The role of neutrons is a little bit less obvious.  They have almost all the same properties as protons (same mass, same size, made up of quarks) but lack a charge.  This similarity but lack of charge keeps them subject to the strong nuclear force, just like protons, but avoids the electromagnetic force.  The strong force acts only at very short distances and, like its name suggests, is very strong.  The electromagnetic force, like Paula Abdul suggested in the 80s, acts to keep like charges apart and opposite charges together.

That means protons have a problem if they want to live together in a nucleus.  Protons are by definition positively charged and would be repelled by each other if it were up to the electromagnetic force alone.  This is where neutrons come in.

Neutrons act like nuclear glue: they exert extra strong nuclear force pressure to keep protons together without any electromagnetic effects. ¬†Small nuclei don’t need much glue: Helium has 2 protons, 2 neutrons; Lithium has 3 protons and 4 neutrons. ¬†Bigger nuclei need a lot more glue (e.g. gold – 79 protons, 118 neutrons, lead – 82 protons, 126 neutrons).

Charting the Nuclear Waters

The question soon became: how big can we go?

It has long been known that any element with more than 82 protons (anything past lead on the periodic table) will be inherently unstable.  It will decay radioactively by shedding protons and neutrons until a stable configuration is reached.

Radioactive elements are still elements, though. ¬†They just don’t stick around for as long. ¬†Typically, heavier atoms are less stable. ¬†Just ask Livermorium, whose atoms have a half-life of only 60 milliseconds.

If you start to graph the stability of atoms according to their number of protons and neutrons, it quickly becomes apparent that larger nuclei need proportionally more neutrons to be stable.

asd
The black line at 45 degrees shows when proton numbers = neutron numbers. The black dots are stable nuclides. Past 82 protons (lead), there are no more permanently stable nuclides.  Image by Sjlegg

Some scientists think there could be as many as 7000 different nuclides (combinations of protons and neutrons) that would be stable enough to observe, if only for a fraction of a second.  We currently know of 3000.

Another trend that scientists noticed is that there appears to be particular numbers of neutrons or protons that make for unusually stable atoms. ¬†Those numbers, as of 2007, are 2, 8, 20, 28, 50, 82, and 126. ¬†They have been dubbed “magic numbers”. ¬†Atoms with a magic number of protons and a magic number of neutrons, like Helium (2 and 2) or Calcium (20 and 20) are said to be “double magic”.

The Island of Stability

In the 60s, it was suggested that beyond the current¬†range of the periodic table lies a set¬†of theoretical atoms that could be very large and very stable. ¬†With a “magic” number of protons and neutrons,¬†the atomic components could be arranged in just such a way as to maximize the glueyness of neutrons and spread out the repulsion of protons.

The fabled island itself.
The fabled island itself.  Image by InvaderXan

The metaphor was so vivid that it soon became adopted and has been used ever since.  Scientists even talk of landing on the shores of the island, but its oases still lie undiscovered and unspoilt.

Ununoctium

Before they were confirmed to be synthesized in the lab, the edges of the periodic table were given temporary names according to a set of naming conventions. ¬†These rules are a¬†strange hybrid¬†of greek and latin roots for the element’s¬†number.

The most recent transition from lati-greek to English and official additions to the periodic table were Flerovium (element 114, previously ununquadium Рquad is latin, tetra would be greek) and Livermorium (element 116, previously ununhexium Рhex is greek, sex would be latin).

The synthesis of element 117, Ununheptium, was announced in 2014, but IUPAC is still reviewing the findings.  The chemistry world continues its search for Ununoctium and speculation about its properties varies from unusually stable to unusually reactive.

One thing is for certain: when it is synthesized, it won’t last long.

0 comments on “K is for Kepler”

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

0 comments on “J is for Jupiter’s Great Red Spot”

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
0 comments on “G is for Gravity Waves”

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.

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F is for Faraday

By Jonathan Farrow from The Thoughtful Pharoah

The year is 1791. ¬†On a crisp autumn morning in South London, Margaret Hastwell, a blackmith’s apprentice, gives birth to her third son. ¬†With her husband, son, and daughter crowded around, she decides to name the newborn¬†Michael. ¬†Michael Faraday.

Margaret had a lot on her plate, what with two young children, a husband who was often sick, and quite a few bills to pay. ¬†She probably didn’t have much time or energy for idle thought or daydreaming. ¬†I doubt if she much considered what Michael might do with his life other than get by. ¬†There is no way it occurred to her that Michael would grow up to revolutionize the world of physics, make electricity a viable source of mechanical energy, and inspire countless scientists, engineers, and young people (including but not limited to Einstein, Rutherford, and this young science communicator, 223 years later). But that is exactly what he would do.

Faraday went to elementary school and learned to read and write, but by the time he turned 13, he had to start work in order to help his parents make ends meet. ¬†He was apprenticed to a local bookbinder and spent the next 7 years diligently mending books. ¬†But that wasn’t all he was doing. ¬†He was also reading. ¬†Over those 7 years, Faraday read voraciously and became interested in science, particularly the topics of Chemistry and Electricity. Luckily for him, George Riebau, the bookbinder to whom he was apprenticed, took an interest in young Faraday’s education and bought him tickets to lectures by¬†Humphry Davy¬†at the Royal Institution in 1812. ¬†This was only¬†shortly after Davy had¬†discovered calcium and chlorine through electrolysis. ¬†Davy was a big name in science¬†at the time, comparable to today’s Stephen Hawking, Neil Degrasse-Tyson, or Jane Gooddall, so it was with wide eyes that young Faraday attended. ¬†He was so blown away by what he saw and heard that he faithfully wrote notes and drew diagrams. ¬†These meticulous notes would prove to be his ticket into Davy’s lab.

Davy Notes
“I got a golden ticket!” Image from the Royal Society of Chemistry

Later that year, Faraday sent a letter to¬†Davy asking for a job¬†and attached a few of his notes. ¬†Davy was impressed and so interviewed young Faraday, but ultimately rejected the eager young fellow, saying “Science [is] a harsh mistress, and in a pecuniary point of view but poorly rewarding those who devote themselves to her service.” ¬†Translation: ¬†“Sorry, I don’t have space for you in my lab, but just to let you know… Science really isn’t very profitable.” ¬†A few months later, one of Davy’s assistants got in a fight and was fired, so guess who got a call? ¬†That’s right, Mikey F.

Not only did Faraday get a spot in Davy’s lab, but he also got to go on a European¬†tour with Mr. and Mrs. Davy. ¬†Pretty sweet deal, right? ¬†On the eighteen month journey, Faraday got to meet the likes of Amp√®re and Volta. ¬†If those names are ringing distant bells, it should be no surprise. ¬†Those eminent continental scientists give their names to standard units of electrical current¬†(Ampere)¬†and potential difference¬†(Volt). ¬†Re-invigorated, 22-year-old Faraday returned to London and took up a¬†post at the Royal Institution as Davy’s assistant.

The next two decades saw Faraday make great advances in chemistry, including discovering benzene, liquefying gases, and exploring the properties of chlorine. ¬†He didn’t get much chance to focus on electricity, however, until 1821. ¬†In that year, Faraday started experimenting with chemical batteries, copper wire, and magnets. ¬†Building on the work of¬†Hans Christian √ėrsted, Faraday’s¬†work was some of the first to show that light, electricity, and magnetism are all inextricably linked (we now know that they are all manifestations of the electromagnetic force). He was a dedicated experimentalist and between 1821 and 1831, he effectively invented the first electric motor and, later, the first electric generator. ¬†These two inventions form the basis for much of today’s modern power system. ¬†The electric motor that opens your garage door as well as wind and hydro-electric generators work on the exact same principle that was discovered by Faraday back in 1831: electromagnetic induction.

Faraday’s insight was that when connected¬†by conductive material, an electric¬†current could make¬†a magnet move. ¬†He also found that the reverse was true: a moving magnet can¬†create a flow of electrons: an electric current.¬†The experiment is actually quite simple and you can even¬†try it at home. Induction enables the transformation of energy between¬†mechanical, electrical, and magnetic states. ¬†Before Faraday, electricity was seen simply as a novelty. ¬†Since Faraday, we’ve been able to use it for all sorts of things. ¬†Like writing science blogs!

The famous iron ring experiment.  Two insulated coils of wire are wrapped around an iron ring but kept separate.  Attaching one to a battery will create a momentary current in the other.  Induction!
The famous iron ring experiment. Two insulated coils of wire are wrapped around an iron ring but kept separate. Attaching one to a battery will create a momentary current in the other. Induction!   Image by Eviatar Bach

[While he was definitely a gifted scientist, Faraday knew next to nothing about mathematics. ¬†He observed, took careful notes, and had an intuition for how to design experiments, but could not formalize his theories in mathematical language. ¬†He would have to wait for James Clerk Maxwell, a young Scottish¬†prodigy, to do the math and formalize¬†Faraday’s Law¬†in the 1860s.]

Faraday continued his work on electricity and gained all sorts of recognition, including medals, honorary degrees, and prestigious positions.  This increased pressure may have been to blame for a nervous breakdown in 1839.  He took a few years off, but by 1845 he was back at it, trying to bend light with strong magnets.  He discovered little else after the 1850s, but continued to lecture and participate in the scientific community.

Older Faraday with glass bar
While that does look remarkably like a cigar, Faraday is actually holding a glass tube in his hand. A glass tube… of Science! ¬† ¬†Public Domain image from Wikimedia

So not only can Faraday be considered to be one of the fathers of the modern world because of his breakthroughs in electricity, but he can¬†also be considered to be one of the fathers of modern popular science communication. ¬†In 1825, he decided to give a series of Christmas lectures at the Royal Institution, specifically aimed at children and non-specialists. ¬†He gave these lectures every year until his death in 1867 and was renowned as a charismatic, engaging speaker. ¬†He tried to explain the science behind everyday phenomena and in 1860 gave a famous lecture on the candle, something which everyone had used but which few actually understood. ¬†The¬†Christmas lectures continue to this day and, continuing with Faraday’s legacy, the Royal Institution is one of the UK’s leading science communication organizations.

Doesn't that look fun!?
Doesn’t that look fun!? ¬† ¬†Public Domain image from Wikimedia

It is not simply that Faraday was a great scientist and lecturer, nor that he managed to escape poverty in 19th century England to become world-renowned. ¬†Michael Faraday’s story is so¬†great¬†because by all accounts, he deserved every bit of success he gained. ¬†One biographer, Thomas Martin, wrote in 1934:

He was by any sense and by any standard a good man; and yet his goodness was not of the kind that make others uncomfortable in his presence. His strong personal sense of duty did not take the gaiety out of his life. … his virtues were those of action, not of mere abstention

It’s no wonder that Einstein had a picture of him up in his office. ¬†I think I might just print one off myself.

Faraday painting 1842
Still pretty handsome considering this painting is from 1842, making Faraday 51 years old.   Public Domain image from Wikimedia