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Jon Hiller
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Jon Hiller

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The Dark Matter Series

Thanks to everyone who plussed, shared, commented etc.  Here's the complete series in one place: - Introduction - The old model doesn't work - Alternative gravity models don't work - The dark matter model does work - Known dark matter isn't enough - We already know quite a bit

On a related note, several people have pointed out that G+ doesn't make it easy to catch every post, which is a particular problem when I do a connected series of posts.  I have several ideas on how to make following posts easier:

1. Tweet when I have a new post.  I do this already, but not everyone on G+ has or wants a Twitter account.  If you want to follow me, I'm @briankoberlein.

2. Edit posts so that there is a previously/next on every post.  That way if you find one, you can click through to others.

3. Make an RSS feed of my G+ posts.  There is apparently a way to do this, and people could have added it to their google reader accounts.

4. I could make a blog and post things on G+ and the blog.  The downside is you guys would have to help me find a name for it.

5. I could group posts into ebooks or something similar. 

Just to be clear, don't plan on shifting away from Google+.  There's a strong community here, and I plan on posting on G+ just as I have been for the foreseeable future.  But I also realize my posts have become very blog-like, and I'd like to make posts easier to follow if I can.

I'd love to hear your ideas/preferences/opposition.  

Image by +Keith Lohse  (
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Jon, so sad to see you no longer post. You were one of the best.
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Study reveals potential vaccination against HIV!
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only 1 problem. the treatment kills you faster.? just kidding.
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Some great science stuff to do with your leftover Easter candy!

#scienceeveryday when it's not #sciencesunday
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When it comes to Cadbury creme eggs, I think I'd rather just eat them. =P
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It's outreach but also training our replacements.
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I think it should be an obsession everywhere. #STEM in general is becoming less of a career choice for young adults in this country. It seems boring to them with just books but by exposing them to real R&D labs sparks an interest.
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Part 3:  Time After Time

Imagine you are travelling in a train.  If you were to walk down the aisle of the train, you would be moving at a walking pace relative to the other passengers, but someone watching the train go by would see you and all the other passengers race by at great speed.  In other words, your speed is relative.  It depends on what you are measuring it against.  Relative to another passenger your speed is slow, but relative to the ground your speed is fast.  That, in a nutshell, is relativity.

This concept of relativity dates back at least as far as Galileo (which is why it is sometimes called Galilean relativity).  Before Galileo’s time it may have been known, but it wasn’t a big deal because motion could always be measured relative to the fixed Earth.  But as we learned the Earth moves around the Sun, this raised an interesting philosophical puzzle.  Is there some great cosmic vantage point against which all speeds can be measured, or is it really the case that speed is always relative?  Is there such a thing as absolute speed?  

In the mid-1800s, physicists came to understand that light was a wave.  At the time it was thought that all waves travel through a medium.  Sound waves travel through air, water waves travel through water, and so on.  That means there must be a medium through which light travels.  Physicists couldn’t observe this medium, but they called it the luminiferous (light-bearing) ether.  There soon began a hunt to observe the ether, because the ether was a way to measure absolute speed.

If you drop a pebble in a calm lake, you can see the ripples flow outward at a particular speed.  The ripples flow with the same speed in every direction.  But if you were moving in a boat and dropped a pebble into the water, the ripples would seem to move slower in the direction of the boat’s motion, and faster in the opposite direction.  Because of the boat’s motion the speed of the ripples would be different in different directions.  The same would be true with the ether.  Since the Earth must be moving through the ether, the speed of light must be different in different directions.  

In 1887, Albert Michelson and Edward Morley performed an experiment to measure this difference in the speed of light.  But what they found was the speed of light was always the same.  No matter what direction light travelled, no matter how they oriented their experiment, the speed of light never changed.  This was not only surprising, it violated the principle of relativity.  After all, if you stand on a moving train and toss a ball, the speed of the ball relative to the ground is the speed of the ball plus the speed of the train, not just the speed of the ball.  Basically what Michelson and Morley found was that if your “ball” was light, the speed of your ball relative to the  train and the speed of the ball relative to the ground is the same.  It seemed the speed of light (and only the speed of light) is absolute, and this made no sense at all.

Then in 1905 Albert Einstein published a solution to the problem, known as special relativity.  He demonstrated that if the speed of light is absolute, then time must be relative, as given in the equation below.  It relates the different times of two observers, say you and me.  In this case, T is your time as you measure it, T’ is your time as I measure it, V is your speed relative to me, and C is the speed of light.  What it says is that your time appears slower to me than it does to you.  The faster you move relative to me, the slower your time appears to me.  This sounds insane.  How can time be relative?  It is, however, very real.    

We can see how this works if we imagine a clock made with light.  Take two mirrors and place one above the other and facing each other, then bounce a pulse of light between them.  We can measure time by counting the number of times the light bounces off a mirror.  Each bounce is like the tick or tock of a mechanical clock.  If you could watch the pulse of light, you would see it move up and down between the mirrors at the speed of light.  Up and down at a constant rate.  Now suppose you took your clock on a fast moving train.  Standing in the aisle of the train, you would see the light pulse move up and down at the same rate as before.  Up and down at the speed of light.  

But as I watch you speed past, I see something slightly different.  I would also see the pulse move at the speed of light, but from my view the light can’t move straight up and down because it must also be moving along with you.  I would see the pulse move diagonally up then diagonally down, which is a slightly longer distance between each bounce.  That means it would take the light longer to travel from bounce to bounce.  So from my point of view the ticks and tocks of your clock are slower than the ticks and tocks as you see them.  Your clock appears to be running slow because of your motion relative to me.  The faster you move relative to me, the more your clock will slow down from my point of view.

You might think this effect only occurs because the clock relied on light to tell time, but this effect is real for everything.  If you have a GPS in your phone or car, you rely on relative time being true every time you use it.  A GPS determines your location by receiving signals from satellites orbiting the Earth.  Those satellites broadcast their time and location, which your GPS uses to determine your position, so it is vitally important that the satellites broadcast the proper time.  But the satellites are moving at high speed relative to you, which means their clocks run slightly slow.  To give you the accurate time the satellites have to account for that slowdown effect.  When your phone tells you where the nearest coffee shop is, it’s using special relativity to do it.

So how does all this relate to astrophysics?  It’s one of the ways we know the universe is expanding.  When we observe the light from distant galaxies, the light appears more red than we would expect.    The more distant the galaxies, the more their light is redshifted.  This effect is known as the Doppler effect, and it is due to the fact that the galaxy is moving away from us.  The galaxies are moving away from us because the universe is expanding.  But suppose over long periods of time light just naturally reddens?  How do we know astronomers are not being fooled?

Special relativity tells us we’re not.  We can observe supernovae in nearby and distant galaxies, and what we find is that when a supernova goes off in a distant galaxy it happens more slowly than a supernova in a closer galaxy.  The time of a distant supernova appears slower to us because the distant galaxy is moving away from us at a faster rate than the closer galaxy.

Strange as it is, special relativity works.  Time after time.

Tomorrow:  Flying kites in a thunderstorm leads us to a single elegant theory describing lightning, magnets and light.  Don’t try this at home, just stay tuned for Part 4.
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Makes perfect sense so leave trains out of it. Trains are the reason millions of Americans will never understand math.
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Part 2:  Mutual Attraction

Medieval astronomy was dominated by the writings of Aristotle.  Aristotle divided motion into earthly lines and heavenly circles, so the planets must surely move about us in perfect circles.  Astronomers soon learned this wasn’t true, but the physics of Aristotle was so deeply rooted in the minds of scholars that astronomers imposed circular motion upon the heavens for a thousand years.  When a single circle could not describe the motion of a planet, they placed circles upon circles (known as epicycles), each rotating just so, to match a planet’s motion.  As more precise measurements of the planets were made, more epicycles were needed.  

Then in the early seventeenth century Johannes Kepler published three simple rules that described the motion of the planets.  They are now known as Kepler’s laws of planetary motion.  Kepler did not use circles to move the planets.  He allowed them to move in a more general shape, known as an ellipse.  What made Kepler’s approach so radical is that an ellipse is neither a circle nor a line.  It is a geometric form that connects the two, unifying earthly and heavenly motion.  Kepler’s theory was the first step toward modern astrophysics, giving us an accurate description of planetary motion.  But Kepler’s laws were still merely a description of motion.  Kepler gave us form, but not function.

It was Isaac Newton who gave us the mechanism.  In the late seventeenth century Newton published his Principia, which described a world governed by a simple set of rules for forces and motion.  The equation below is one of these rules, and is known as Newton’s law of gravity.  In it F represents the force between two bodies (the subscript G just denotes it is a gravitational force), the M’s are the masses of the two bodies, R is the distance between them, and G is a number known as the gravitational constant.  What the equation says is that bodies are drawn to each other through gravitational attraction.  The strength of their attraction is greater if they are close together, and lesser if they are more distant.  This force of attraction exists between any two bodies.  Between Sun and planet, between Earth and moon, and between me and you.

Newton’s triumph was that he could use his rules to explain why the planets moved in ellipses.  They didn’t move in ellipses just because, they were driven to move by forces that followed simple rules.  Rules you could test here on Earth.  It is hard to overstate the effect Newton’s work had on our view of the universe.  At the beginning of the 1600s the universe was one of epicycles and celestial spheres.  By the end that century the universe was driven by fundamental physical laws we could prove and understand.

One thing Newton couldn’t do was determine the value of his gravitational constant.  The only gravitational forces he could observe were between the planets Moon and Sun, and no one had any idea what their masses were.  Without them, the value of G couldn’t be determined.  A solution wasn’t found until 1797 when Henry Cavendish devised a clever experiment.  He placed lead balls in wooden frame suspended by a thin wire that was free to twist.  He then placed larger lead balls near the frame.  By measuring just how much the frame twisted, Cavendish could measure the gravitational attraction between masses, and thereby determine the value of G.  This experiment is now known as the Cavendish experiment, but it could also be called "weighing the heavens."  With the gravitational constant known, astronomers could observe the motions of the Sun and planets to determine their mass.  It is a technique we still use today to measure the mass of stars, planets, and even galaxies.

There is, however, a mysterious consequence of Newton’s equation.  The force of gravity is always attractive, and the closer two bodies are the stronger their attraction.  It would seem then that if large enough masses got close enough together the gravitational attraction would be so strong that the objects would be crushed under their own weight.  Gravity would pull ever stronger, squeezing the objects more and more, making them smaller and smaller until they finally collapsed into a single, infinitely dense point.  A gravitational singularity.

This was such a bizarre idea that astronomers long thought it was impossible.  Surely there must be some unknown physical mechanism that would prevent singularities.  But in the early 1900s, Einstein’s theory of general relativity was confirmed, and the singularity problem became more severe.  In essence Einstein combined Newton’s gravity with relativity.  If you remember from yesterday ( mass and energy are connected.  This means the energy of gravitational attraction is itself gravitationally attractive.  Put simply, not just mass, but gravity itself is heavy.  Put enough mass in a small enough volume, and it will collapse under its own gravitational weight.  Einstein’s theory made gravitational singularities inevitable.  Near such a singularity the gravitational attraction is so strong that nothing can escape its pull, not even light, which is why they are now known as black holes.

In 1974, radio astronomers discovered an intense energy source at the center of our galaxy.  Named Sagittarius A*, it appeared to be a large black hole.  By the dawn of the twenty-first century, astronomers were able to observe stars orbiting this galactic black hole.  The motions of these stars follow the ellipses of Kepler, driven by Newton’s gravity.  By observing their motions, and with the equation below, we can determine the black hole’s mass (  In the center of our galaxy, just 27,000 light years away, is a black hole with a mass of more than four million Suns.

Newton’s equation gave us the mechanism behind the motion of the planets.  It tells how we are connected to everything in the universe through mutual attraction.  

It has also revealed the gravitational dragon that rests at the heart of our galaxy.
Next time:   How a beam of light overturned 300 years of physics, and changed our view of the universe.  Part 3, coming tomorrow.
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Part 1:  A Muse of Fire

In the mid-1800s, astronomy faced a serious problem.  No one knew how the stars shone.  Now a little mystery never hurt anyone, but in this case it was deeply perplexing.  By this time we had a solid understanding of energy, and that energy is conserved.  That is, energy must come from somewhere, and it must go to somewhere.  We also had a general understanding of thermodynamics, specifically that you could squeeze something to heat it up.  This gave us a mechanism which could cause the stars to shine, known as the Kelvin-Helmholtz mechanism.

The basic idea of this mechanism is that for a large body like a planet or star, gravity tries to compress the star or planet smaller and smaller.  This compression heats the core of the body, which is radiated as light.  In this way a star could be heated by its own weight.  This is a very real effect for gas planets and brown dwarfs.  Jupiter, for example, radiates more heat than it receives from the Sun because of this mechanism.  

But for a star such as the Sun there is a problem.  Gravity can only squeeze a body so far, so there’s a limit to how much heat can be generated by the Kelvin-Helmholtz mechanism.  And by conservation of energy, once the Sun has radiated all its heat energy as light, it is done shining.  It’s fairly easy to estimate the rate at which the Sun loses energy given its brightness and size.  Its also fairly straightforward to calculate just how much energy the Sun could gain by gravitational compression.  If you apply conservation of energy, then you can determine how long the sun could shine before it runs out of energy, and you get a clear answer:  about twenty million years.  

That’s quite a long time, but it disagreed horribly with geology, where fossil evidence demonstrated that life existed on Earth for several hundred million years, likely much longer.  How is that possible if the Sun could only be tens of millions of years old?  Kelvin actually argued that the geologists must be wrong, and the Earth was only millions of years old.  But by the early 1900s, we understood that life on Earth was around not only millions, but billions of years.  So the Sun must have shone for billions of years, but astronomers and physicists had no explanation for how that was possible.  Gravitational compression couldn’t provide enough energy, nor could chemical reactions, and what else was there?

Then in 1905 Albert Einstein published his paper on special relativity. Usually when people talk about relativity they mention that time slows down at high speeds, or as the figure below claims the faster you move the more mass you have (which isn’t technically true, but I’ll explain that in a couple days).  But central to all this wibbly-wobbly timey-wimey stuff is that energy and mass are two sides of the same coin.  They are connected.  Not only that, mass can become energy and energy can become mass.  This connection is summarized in equation  below.  In the equation E stands for energy, m for mass, and c for the speed of light.  What the equation says is that given a certain amount of mass, it is possible in principle to convert it into a certain amount of energy.  Just how much energy you can get is surprisingly huge.  The speed of light is about 3 million meters per second, and it is squared in the equation.  To give you an idea of just how big this is, if we could convert one paper clip entirely to energy, it would produce enough electrical energy to power the entire world for about 800 billion years. 

Einstein gave us the key to understanding the stars.  Somehow the Sun was converting a bit of its mass into energy, and with it’s great mass the Sun could shine for billions upon billions of years.  But while special relativity showed it was possible, it gave no clue as to how it actually occurred.  There were, however, tantalizing clues.  By the late 1800s Marie Curie and others had begun to study radioactive decay.  By the early 1900s it was demonstrated that radioactive elements could transmute into other elements, which gave us another key to the puzzle.  For example, through radioactive decay, a thorium atom can break apart into a radium atom and a helium atom (also known as an alpha particle).  The mass of the radium and helium atoms is less than the mass of the original thorium, and the “missing mass” is converted to energy, as per Einstein’s equation below.

But this fission process only works for heavy elements.  The sun and stars are mostly made of the light elements hydrogen and helium, and those can’t be split into lighter elements.  But perhaps the tremendous heat and pressure of a sun’s core could be fuse lighter elements into heavier ones.  In 1939, Hans Bethe demonstrated how four hydrogen atoms could be fused into a single helium atom.  A helium atom has less mass than four hydrogen, so the result was helium plus energy.  We then learned how helium could become carbon, nitrogen and oxygen, and on to heavier and heavier elements.

This gave us far more answers than we expected.  It not only gave us fusion as the source of a star’s power, but explained from whence the diversity of elements came.  Hydrogen and helium fusing into heavier elements.  Exploding stars scattering those elements across the cosmos.  New stars forming, with planets, one of which is home to us.  From a single, simple equation we came to know that we are the dust of stars. 

Of course this equation is also a stark reminder that knowledge can be double-edged sword.  In understanding the source of the Sun’s power, we longed to wield that power ourselves.  By the mid-twentieth century we succeeded.  We can now drop the heart of a star over the cities of our enemies, or power the probes that travel to the furthest reaches of our solar system and beyond. 

Which muse we follow is up to us.

Coming tomorrow:  how Newton united physics and astronomy, and brought us face to face with one of the most mysterious and terrifying objects in the universe.  All in part two of this six part series.
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Jon Hiller

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The Science on Google+ Community is getting ready to cross the 100K followers mark!!! Thanks for your support. To celebrate, we’re getting ready to make some structural changes to the community to increase engagement and to make it easier to find high quality posts. We will also be launching a new Science Hangout On Air series. Stay tuned!!
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Sorry Science Peeps, I've been off the radar for a bit.  Let's revisit this lesson :)
#scienceeveryday  when it's not #sciencesunday  
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I think children should teach us 
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Thanks to everyone who gave a +1 and/or a share to the series on six equations to live by.  I'm glad you liked them.  If you missed any of them here's the entire list:

Proven World: (Introduction)
A Muse of Fire: (How mass and energy are connected)
Mutual Attraction: (Newton's gravity)
Time After Time: (Special relativity and relative time)
Unity: (Electricity, magnetism and light)
Memory Hole: (Black hole information paradox)
Dying of the Light: (Entropy and the end of time)

I'll likely do another series at some point, but starting tomorrow I'll go back to regular posts on astrophysics, physics and astronomy.  I have a few ideas for posts, but I'd also like to hear what you'd be interested in.  

If there's a topic you'd like me to write about, just add it in the comments.  
If you see a suggestion you like, give the comment a +1.  

And if you're willing, give this post a share and encourage your friends to add me to their circles.  There seems to be a lot of interest in my recent posts, and the more attention they get, the more motivation I have to keep writing them.
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Cavitation Bubble Collapse:

To get a molecular-level understanding of nanobubble collapse near a solid surface, Priya Vashishta and his colleagues at the University of Southern California used supercomputers to simulate and unravel the complex mechanochemistry problem. The goal of this nanobubble collapse simulation, which was run on 163,840 cores, was to improve both the safety and longevity of nuclear reactors.

Science contributors:
Priya Vashishta, University of Southern California
Ken-ichi Nomura, University of Southern California
Adarsh Shekhar, University of Southern California

Visualization contributor:
Joseph A. Insley, Argonne

#scienceeveryday  when it's not #sciencesunday  
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1; my hypotheses   till me the hypo-these is flat. 2; the it decathletes waves and in controlling seconds in to a conman light wave .
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+Chad Haney nailed this one.
Equal Trilobite
h/t to +Glendon Mellow

Edit I dig this because if you aren't for equality, you are a fossil.

Image source:
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Electron Microscopist, Materials Scientist, Father, Son and Brother.
My research focus revolves around nano-fabrication and nano-manipulation using focused ion beams and the characterization of materials using various electron microscopy techniques.  For a complete listing of publications please visit:

My work interests are in:

Electron and Ion Optic Engineering
Materials Characterization
Ion Beam Lithography
Google+ Curator of:
Applied Sciences, Physics and Materials Science for Science on Google+: A Public Database

I rarely post updates about my personal life.  Most updates and posts revolve around the hard sciences and scientific articles.  I will not bombard you with reposts.  With that said, the circles I fit into the best are:

Computer Science
Science Photography

If you need some guidance in understanding circles I advise giving this a look.
On a more personal note, I'm an avid fan of the Green Bay Packers and the Chicago Cubs.  I like all things Apple but also own a few PC's running some version of Windows.  For fun I like to take my children geocaching, hiking, canoeing and fishing in Northern Wisconsin. 

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Electron Microscopist, Science, Physics, Nanotechnology
Focused Ion Beam, Nano-fabrication, Exceptional TEM sample preparation methods geared to very high end aberration corrected TEM's.
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