Book: The Four Percent Universe

Chad Orzel at Uncertain Principles reviews Richard Panek’s The Four Percent Universe. The subtitle is Dark Matter, Dark Energy, and the Race to Discover the Rest of Reality.

It’s not a book about the known facts regarding the nature of the universe so much as a book about the process by which those facts were determined and became accepted.

Here’s a snippet from an interview with Panek on Amazon:

Q: Well, then, what do astronomers mean by “dark matter”?

Panek: A mysterious substance that comprises about 23 percent of the universe.

Q: And dark energy?

Panek: Something even more mysterious that comprises about 73 percent of the universe.

Q: Okay, 73 and 23 add up to 96 percent, which does leave a four percent universe. But if we don’t know what dark matter and dark energy are, how do we even know they’re there?

Panek: In the 1970s, astronomers observed that the motions of galaxies, including our own Milky Way, seem to be violating the universal law of gravitation. They’re spinning way too fast to survive more than a single rotation, yet we know that our galaxy has gone through dozens of rotations in its billions of years of life. Galaxies are living fast but not dying young—a fact that makes sense only if we say that there’s more matter out there, gravitationally holding galaxies and even clusters of galaxies together, than we can see. Astronomers call this substance dark matter.

Q: And the mysterious dark energy?

Panek: In the 1990s, two independent teams of astronomers set out to discover the fate of the universe. They knew the universe was born in a big bang and has been expanding ever since. Now they wanted to know how much the mutual gravitation among all this matter—dark or otherwise—was affecting the expansion of the universe. Enough to slow it down so that the universe would eventually grind to a halt, then collapse on itself? Or just enough that the expansion would grind to a halt and stay there? In 1998 the two teams came to the same conclusion: the expansion of the universe isn’t slowing down at all. In fact, it’s speeding up. And whatever force is counteracting gravity is what they call dark energy.


Aphids can make carotenoids to capture solar energy



Aphids can make their own carotenoids and may be able to capture chemical energy directly from the sun. Green or orange individuals contain more carotenoids and more ATP than white ones. The secret of plant growth is that they capture photons and use them to create high-energy atomic bonds that can be used elsewhere to run chemical reactions that build plant material.

Unlike other organisms, they are not ingesting or otherwise harbouring photosynthetic symbionts such as bacteria or algae. They are making their own photosynthetic chemicals. They may not be able to do full photosynthesis as plants do, but among animals they are unique.

It will be interesting to find out how they evolved this unique (for animals) biochemical machinery.

Babies speak “dog”!

That was too cute a title to give up. At a surprisingly young age, human babies are aware of their surroundings and the emotions around them. They can even tell when a dog is being friendly or aggressive. That’s a good trait considering that we’ve lived with dogs for at least ten thousand years.

Taxon of the week: Aeromonas

Aeromonas colonies on blood agar (image from Janda & Abbott)

I’ve found a new website: Catalogue of Organisms. Their post, “Taxon of the week: Aeromonas” describes a genus of aquatic bacteria that are responsible for some ugly infections in fish, humans, and other animals: The Genus Aeromonas: Taxonomy, Pathogenicity, and Infection by J. Michael Janda and Sharon L. Abbott.

The bacterial colonies to the left are illuminated by transmitted light.

Evolution 2012 in Ottawa, Ontario

Check out the reaction and link fest at Jeremy Voder’s Denim and Tweed: Evol2012.

All in all, I had a great time, and saw a lot of really cool science. This was the first Evolution meeting I’ve been to where I was never at a loose end—every moment I was in the Convention Centre, I had someone to go see, or a talk to go hear. And, honestly, I finished the meeting without having checked in with everyone I’d have liked to.

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