Guardians of the Galaxy…er, black holes vol. 3

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Part 3 of my 4-part series on black holes for Medium members is up; part 1 is here and part 2 is here. If enough of you read, they may keep me around to write more, so please read and share!

Seeing the Invisible

Black holes are invisible, but astronomers have developed a lot of ways to see them through the matter that surrounds them

No Rocket Raccoon, but my latest does have a guy named Grote. [Credit: National Radio Astronomy Observatory/moi]

For Medium:

In 1937, a deeply weird engineer named Grote Reber built a telescope in the lot next to his mother’s house in Wheaton, Illinois. Home observatories aren’t unusual, but Reber’s project was the first telescope designed to look for radio waves from space, and he was only the second person in history to find them. Karl Jansky, the first radio astronomer, had accidentally discovered astronomical radio waves while working on shortwave radio communications.

But Reber set out deliberately to study the cosmos in radio light. He found that the center of the Milky Way emitted a lot of radio waves and discovered an intense radio source in the constellation Cygnus. By the 1950s, astronomers found many other radio galaxies (as they were creatively named) that emitted very powerful radio waves from small regions at the centers of those galaxies.

As we learned in Part 2 of this series, the sources of the radio waves in the Milky Way and beyond turned out to be supermassive black holes: powerful gravitational dynamos millions or billions of times the mass of our sun. As with Reber’s discoveries, the study of black holes has been driven by invention and creativity. In fact, every new advance in astronomy has led to new discoveries about black holes, and new technologies are being invented for the purpose of studying these weird objects.

Read the rest at Medium…

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How physics and biology work together to understand cell organization

[ This blog is dedicated to tracking my most recent publications. Subscribe to the feed to keep up with all the science stories I write! ]

Cells get organized

How researchers probe the physics of motion, communication and organization in cell networks, and how understanding these systems could help us tackle serious issues in medicine and biology

self-organized bacterial community

A colony of bacteria organize with each other under certain conditions to maximize nutrient intake. [Credit: Eshel Ben-Jacob]

From Physics World:

Consider this scenario: in your haste to grab the latest issue of Physics World, you scrape your hand on your postbox. It’s nothing severe, just a little scratch, but if your immune system is functioning as it should, your body will perform an amazing feat of microscopic organization. Your body assesses the level of damage and threat from infection, sending security cells to the site to hoover up intrusive bacteria and seal the wound. Within a few days you’d hardly know the scrape was ever there: your skin and blood vessels repair themselves.

Except of course there’s no mind behind this repair. Your brain isn’t required to heal a wound: there’s no local oversight from any intelligent agent, and the cells involved don’t think. Instead, cells interact with their neighbours, and a larger pattern emerges from those small-scale interactions. That’s the key to “self-organization”, whether it occurs in the human immune system, swarms of locusts, water molecules in a snowflake or electrons in a magnetic material.

For that reason, researchers studying biological self-organization draw heavily on physics. Some directly investigate the physical interactions between cells and their environments; others use theoretical models drawn or adapted from physics to understand emergent behaviours in biological systems. It’s an interdisciplinary field, involving physicists, computer scientists, biologists, mathematicians and medical doctors.

The rest of this story is in the print edition of Physics World, which you can subscribe to through membership in the Institute of Physics, which costs £15, €20, or $25 per year. You can join by clicking here. You can also get a nice mobile- and tablet-formatted version of the story using the Physics World app, available in the Google Play and iTunes stores. However, if you just want to read the rest of this article, Physics World has kindly allowed me to offer it to you as a PDF download, which looks exactly like the printed version!

The Care and Feeding of Black Holes

[ This blog is dedicated to tracking my most recent publications. Subscribe to the feed to keep up with all the science stories I write! ]

Part 2 of my 4-part series on black holes for Medium members is up; you can read part 1 here. If enough of you read, they may keep me around to write more, so please read and share!

The Care and Feeding of Black Holes

How intrinsically invisible objects become the brightest things in the universe

For Medium:

In the late 1950s, astronomers began spotting a number of bright sources of radio waves and visible light. These sources were pinpoints resembling blue stars, but further investigation showed they had to be something very different. For one thing, these quasi-stellar objects, as they were known then, were extraordinarily distant, much farther than any single star would be visible.

The spectra of these new quasi-stellar objects, or quasars, as physicist Hong-Yee Chiu abbreviated their name in 1964, showed they were emitting light through a completely different mechanism than starlight. The quantity of light quasars emitted to be visible across the universe meant they had to be driven by gravity.

Based on the data, astronomers concluded that each quasar was powered by a black hole millions or billions of times the mass of our sun. These supermassive black holes pull huge amounts of matter onto themselves, accelerating it until it glows very brightly. Additionally, the black hole jets a lot of matter away from itself rather than eating it, and those jets also glow intensely. These processes turn the ordinarily invisible black hole into something bright enough to see from billions of light-years away, outshining whole galaxies.

[read the read at Medium…]