Tag Archives: Michael J. I. Brown

Looking at the universe through very different ‘eyes’

The Conversation

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The Small Magellanic Cloud galaxy here seen in infrared light, but it looks different when viewed at other wavelengths. ESA/NASA/JPL-Caltech/STScI

Michael J. I. Brown, Monash University

We are bathed in starlight. During the day we see the Sun, light reflected off the surface of the Earth and blue sunlight scattered by the air. At night we see the stars, as well as sunlight reflected off the Moon and the planets.

But there are more ways of seeing the universe. Beyond visible light there are gamma rays, X-rays, ultraviolet light, infrared light, and radio waves. They provide us with new ways of appreciating the universe.

Read more:
What to look for when buying a telescope

X-ray Moon

Have you looked at the Moon during the daytime? You will see part of the Moon bathed in sunlight and the Earth’s blue sky in front of the Moon.

The Moon behind a blue sky. Flickr/Ed Dunens, CC BY

Now put on your X-ray specs, courtesy of the ROSAT satellite, and you will see something intriguing.

The Sun emits X-rays, so you can see the daytime side of the Moon easily enough. But the night time side of the Moon is silhouetted against the X-ray sky. The X-ray sky is behind the Moon!

The Moon seen in X-rays by ROSAT. The night side of the Moon is silhouetted against the X-ray background. DARA, ESA, MPE, NASA, J.H.M.M. Schmitt

Just what is the X-ray sky? Well, X-rays are more energetic than visible light photons, so X-rays often come from the hottest and most violent celestial objects. Much of the X-ray sky is produced by active galactic nuclei, which are powered by matter falling towards black holes.

In X-rays, the Moon is silhouetted against many millions of celestial sources, powered by black holes, scattered across billions of light years of space.

Radio skies

If you’re in the southern sky and away from light pollution (including the Moon), then you can see the Small Magellanic Cloud. This is a companion galaxy to our own Milky Way. With the unaided eye it looks like a diffuse cloud, but what we are actually seeing is the combined light of millions of distant stars.

Visible light images of the Small Magellanic Cloud are dominated by starlight. ESA/Hubble and Digitized Sky Survey/Davide De Martin

Radio waves provide a very different view of the Small Magellanic Cloud. Using the Australian Square Kilometre Array Pathfinder, tuned to 1,420.4MHz, we no longer see stars but instead see atomic hydrogen gas.

Radio waves can trace the hydrogen gas in the Small Magellanic Cloud. ANU and CSIRO

The hydrogen gas is cold enough that the atoms hang onto their electrons (unlike ionised hydrogen). It can also cool further and collapse (under the force of gravity) to produce clouds of molecular hydrogen gas and eventually new stars.

Radio waves thus allow us to see the fuel for star formation, and the Small Magellanic Cloud is indeed producing new stars right now.

Feeling the heat in the microwave

If the universe were infinitely large and infinitely old, then presumably every direction would eventually lead the surface of a star. This would lead to a rather bright night sky. The German astronomer Heinrich Olbers, among others, recognised this “paradox” centuries ago.

A visible light image of the entire night sky is dominated by starlight from the Milky Way. ESO/S. Brunier, CC BY

When we look up at the night sky, we can see the stars, planets and Milky Way. But most of the night sky is black, and this tells us something important.

But lets take a look at the universe in microwave light. The Planck satellite reveals glowing gas and dust in the Milky Way. Beyond that, in every direction, there is light! Where does it come from?

The microwave sky is glowing in every direction. ESA, HFI & LFI consortia

At microwave wavelengths we can observe the afterglow of the Big Bang. This afterglow was produced 380,000 years after the Big Bang, when the universe had a temperature of roughly 2,700℃.

But the afterglow we see now doesn’t look like a 2,700℃ ball of gas. Instead, we see a glow equivalent to -270℃. Why? Because we live in an expanding universe. The light we observe now from the Big Bang’s afterglow has been stretched from visible light into lower-energy microwave light, resulting in the colder observed temperature.

Planetary radio

Jupiter is one of the most rewarding planets to observe with a small telescope – you can see the cloud bands stretching across the giant planet. Even binoculars can reveal the four moons discovered by Galileo centuries ago.

A visible light image of Jupiter, taken by the Cassini spacecraft. NASA/JPL/Space Science Institute

But you get a less familiar view of Jupiter when you switch to radio waves. A radio telescope reveals the dull warm glow of the planet itself. But what really stands out are radio waves coming from above the planet.

Jupiter is a copious emitter of radio waves. CSIRO

Much of the radio emission from Jupiter is produced by synchrotron and cyclotron radiation, which results from speeding electrons spiralling in a magnetic field.

Read more:
Fifty years ago Jocelyn Bell discovered pulsars and changed our view of the universe

On Earth we use particle accelerators to produce such radiation. But in Jupiter’s powerful magnetic field it occurs naturally (and copiously).

The ConversationThe synchrotron produced by Jupiter is so powerful that you can detect it on Earth – not just with multimillion-dollar radio telescopes, but with equipment that can be bought for several hundred dollars. You don’t need to be a professional astronomer to expand your view of the universe beyond visible light.

Michael J. I. Brown, Associate professor, Monash University

This article was originally published on The Conversation. (Reblogged by permission). Read the original article.

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You too can be an astrophysicist with your new telescope

The Conversation

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Look up … some things to do with your new telescope. Flickr/Grand Canyon National Park, CC BY

Michael J. I. Brown, Monash University

A telescope can reveal the beauty of the universe, such as the Moon’s craters, Saturn’s rings, and the glowing gas of the Orion nebula. But a telescope isn’t just for sightseeing – it is also a scientific instrument.

If you’ve just received a telescope as a present then it’s probably better than any used by the Italian scientist Galileo Galilei (1564-1642). A small telescope with a modern camera can be more capable than professional telescopes from just a century ago.

An illustration of Galileo Galilei with a telescope. Iryna/Shutterstock

You can use your telescope to see astrophysics in action, such as the planets travelling around the Sun, see how stars have different colours and even detect worlds orbiting distant stars.

Read more: What to look for when buying a telescope

At the eyepiece

Look through the eyepiece of your telescope and you can retrace the beginnings of astrophysics.

Galileo only had a tiny telescope with a lens just a few centimetres across. Yet he mapped the Moon, saw Saturn’s rings, and discovered Jupiter’s four largest moons – Io, Europa, Ganymede and Callisto – now known as the Galilean moons.

Galileo was also persecuted for advocating the theory that the planets (including Earth) orbit around the Sun, at a time when the popular belief was that Earth was the centre of the universe.

His observation of the phases of Venus are among his most compelling pieces of evidence that Earth and the other planets of our Solar System orbit the Sun.

Galileo charted the apparent size and phases of Venus with his small telescope. NASA

If the planets travel around the Sun, as Galileo believed, then sometimes the Sun will be (almost) between us and Venus, so we can view most of the daytime side of Venus. At other times, Venus will be between us and the Sun, and will appear as larger (since it’s closer) crescent.

Venus is never too far from the Sun in the sky (indeed it’s lost in the Sun’s glare during January 2018), and is only visible near sunrise or sunset. The phases of Venus, which resemble those of the Moon, can be seen with even a small telescope.

There are plenty of guides on how to find Venus (and other planets, stars, constellations, galaxies and so on) including Sky and Telescope, apps for Android and Apple devices and the free Stellarium computer software.

Use any of these to find Venus, and then use your telescope to see the phases of the planet as Galileo did four centuries ago.

The lives of stars

Understanding the lives of stars was the biggest puzzle for astrophysicists during the early 20th century. One of the first clues is the fact that different stars have different colours, which tells us they have different temperatures.

Even without a telescope, you can see the red star Betelgeuse and the blue star Rigel in the constellation of Orion. Betelgeuse has a surface temperature of 3,000℃, while Rigel’s surface is at 12,000℃.

Why do different stars have different temperatures? Measuring the luminosities of stars with different colours provides a critical clue. Look at open star clusters such as Pleiades and you will see that (with some exceptions) the brightest stars are blue.

The most luminous stars in the Pleiades star cluster are blue. Flickr/Joel Tonyan, CC BY-NC-ND

Blue stars are often the most luminous (and most massive), and their high temperatures result from the rapid fusion of hydrogen into helium. Some blue stars are 100 times as bright as the Sun.

These stars live for just millions of years, as they are using their hydrogen fuel so rapidly. In contrast, some dull red stars may live for tens of billions of years.

What about the exceptions – the very luminous stars that are red, such as Betelgeuse? Some stars have run out of hydrogen in their cores, and instead fuse hydrogen in shells and/or fuse helium in their cores.

These stars can become enormous in size but have (relatively) cool surface temperatures. These red giants are also approaching the end of their lives.

Strange new worlds

So far your telescope has been used for simple observations of stars and planets. With the addition of some more equipment you can use your telescope to detect planets around distant stars.

To do this you need a good digital camera, the ability to track a star for a few hours, and some free software for your computer.

The first planets orbiting other stars were detected in the 1990s and now thousands of such worlds are known. Some of these planets orbit stars that are 100 times fainter than the unaided eye can see, and such stars are easily seen with small telescopes.

Read more: Google’s artificial intelligence finds two new exoplanets missed by human eyes

But what about the planets? Well, at predictable times planets pass between us and their stars, making the stars dim by about 1%. You can’t see that tiny change in brightness with your eye, but you can record it digitally.

The ConversationIf you can take digital images of a star with a planet and several neighbouring stars, then you can use computer programs (such as OSCAAR) to measure how the star dims relative to its neighbours. You can thus see the passage of a distant world around its star.

You don’t need a big telescope to detect a planet orbiting a distant star, and a bit of DIY can help.

Michael J. I. Brown, Associate professor, Monash University

This article was originally published on The Conversation. (Reblogged by permission). Read the original article.

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Why is Einstein’s general relativity such a popular target for cranks?

The Conversation

Michael J. I. Brown, Monash University

Scientists maybe celebrating the 100th anniversary of Albert Einstein’s general theory of relativity, but there was also a death in 1915. It was one of the many deaths of simple and intuitive physics that has happened over the past four centuries.

Today the concepts and mathematics of physics are often removed from everyday experience. Consequently, cutting edge physics is largely the domain of professional physicists, with years of university education.

But there are people who hanker for a simpler physics, toiling away on their own cosmologies. Rightly or wrongly, these people are often labelled cranks, but their endeavours tell us much misconceptions about science, its history and what it should be.

I regularly browse open access website arxiv.org to look for the latest astrophysics research. Real astrophysics, that is. But if I want to take a look at what pseudoscientists are up to, I can browse vixra.org. That’s right, “arxiv” backwards. The vixra.org website was founded by “scientists who find they are unable to submit their articles to arXiv.org” because that website’s owners filter material they “consider inappropriate”.

There are more than 1,800 articles on vixra.org discussing relativity and cosmology, and many don’t like relativity at all. Perhaps one reason why cranks particularly dislike relativity is because it is so unlike our everyday experiences.

Einstein predicted that the passage of time is not absolute, and can slow for speeding objects and near very massive bodies such as planets, stars and black holes. Over the past century, this bizarre predication has been measured with planes, satellites, and speeding muons.

But the varying passage of time is nothing like our everyday experience, which isn’t surprising as we don’t swing by black holes on our way to the shops. Everyday experience is often central to cranky ideas, with the most extreme example being flat earthers.

Thus many crank theories postulate that time is absolute, because that matches everyday experience. Of course, these crank theories are overlooking experimental data, or at least most of it.

History and linearity

One of the most curious aspects of pseudoscience is an oddly linear approach to science. To be fair, this can result from an overly literal approach to popular histories of science, which emphasise pioneering work over replication.

A pivotal moment in relativity’s history is Albert Michelson and Edward Morley’s demonstration that the speed of light didn’t depend on its direction of travel nor the motion of the Earth.

Of course, since 1887 the Michelson-Morley experiment has been confirmed many times. Modern measurements have a precision orders of magnitude better than the original 1887 Michelson-Morley experiment, but these don’t feature prominently in popular histories of science.

Interestingly many pseudoscientists are fixated on the original Michelson-Morley experiment, and how it could be in error. This fixation assumes science is so linear that the downfall a 19th century experiment will rewrite 21st century physics. This overlooks how key theories are tested (and retested) with a myriad of experiments with greater precision and different methodologies.

Another consequence of the pseudoscientific approach to history is that debunked results from decades past are often used by buttress pseudoscientific ideas. For example, many pseudoscientists claim Dayton Miller detected “aether drift” in the 1930s. But Miller probably underestimated his errors, as far more precise studies in subsequent decades did not confirm his findings.

Unfortunately this linear and selective approach to science isn’t limited to relativity. It turns up in cranky theories ranging from evolution to climate.

Climate scientist Michael E Mann is still dealing with cranky accusations about his seminal 1998 paper on the Earth’s temperature history, despite the fact it has been superseded by more recent studies that achieve comparable results. Indeed, it devoured so much of Mann’s time he has literally written a book about his experience.

What about the maths?

During the birth of physics, one could gain insights with relatively simple (and beautiful) mathematics. My favourite example is Johannes Kepler’s charting of the orbit of Mars via triangulation.

In the 17th century, Johannes Kepler used elegantly simple mathematics to chart the motion of Mars. Johannes Kepler / University of Sydney

Over subsequent centuries, the mathematics required for new physical insights has become more complex, as illustrated by Newton’s use of calculus and Einstein’s use of tensors. This level of mathematics is rarely in the domain of the enthusiastic but untrained amateur? So what do they do?

One option is to hark back to an earlier era. For example, trying to disprove general relativity by using the assumptions of special relativity or even Newtonian physics (again, despite the experiments to the contrary). Occasionally even numerology makes an appearance.

Another option is arguments by analogy. Analogies are useful when explaining science to a broad audience, but they aren’t the be-all and end-all of science.

In pseudoscience, the analogy is taken to the point of absurdity, with sprawling articles (or blog posts) weighed down with laboured analogies rather than meaningful analyses.

Desiring simplicity but getting complexity

Perhaps the most fascinating aspect of pseudoscientific theories is they hark for simplicity, but really just displace complexity.

A desire for naively simple science can produce bizarrely complex conclusions, like the moon landing hoax conspiracy theories. NASA/flickr

Ardents of the most simplistic pseudoscientific theories often project complexity onto the motives of professional scientists. How else can one explain scientists ignoring their brilliant theories? Claims of hoaxes and scams are commonplace. Although, to be honest, even I laughed out loud the first time I saw someone describe dark matter was a “modelling scam”.

Again, this isn’t limited to those who don’t believe in relativity. Simple misunderstandings about photography, lighting and perspective are the launch pad for moon landing conspiracy theories. Naively simple approaches to science can lead to complex conspiracy theories.

Changing intuition

Some have suggested that pseudoscience is becoming more popular and the internet certainly aids the transmission of nonsense. But when I look at history I wonder if pseudoscience will decay.

In the 19th century, Samuel Rowbotham promoted Flat Earthism to large audiences via lectures that combined wit and fierce debating skills. Perhaps in the 19th century a spherical world orbiting a sun millions of kilometres away didn’t seem intuitive.

But today we can fly around the globe, navigate with GPS and Skype friends in different timezones. Today, a spherical Earth is far more intuitive than it once was, and Flat Earthism is the exemplar of absurd beliefs.

Could history repeat with relativity? Already GPS utilises general relativity to achieve its amazing precision. A key plot device in the movie Interstellar was relativistic time dilation.

Perhaps with time, a greater exposure to general relativity will make it more intuitive. And if this happens, a key motivation of crank theories will be diminished.

Will general relativity become more widely understood via popular media, such as the movie Interstellar?

Michael will be on hand for an Author Q&A between 4 and 5pm AEDT on Tuesday, November 24, 2015. Post your questions in the comments section below.

The ConversationMichael J. I. Brown, Associate professor, Monash University

This article was originally published on The Conversation. (Reblogged by permission). Read the original article.


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