Category: Natural World

What Happens When Two Black Holes Collide?

A student asked this question about black holes during a discussion, and I didn’t have a good answer. Now there’s this:

A study last year found unusually high levels of the isotope carbon-14 in ancient rings of Japanese cedar trees and a corresponding spike in beryllium-10 in Antarctic ice.

The readings were traced back to a point in AD 774 or 775, suggesting that during that period the Earth was hit by an intense burst of radiation, but researchers were initially unable to determine its cause.

Now a separate team of astronomers have suggested it could have been due to the collision of two compact stellar remnants such as black holes, neutron stars or white dwarfs.

— via The Weather Channel (2013): Black Hole Collision May Have Irradiated Earth in 8th Century.

From the original article:

While long [Gamma Ray Bursts (GRBs)] are caused by the core collapse of a very massive star, short GRBs are explained by the merger of two compact objects … [such as] a neutron star with either a black hole becoming a more massive black hole, or with another neutron star becoming either a relatively massive stable neutron star or otherwise a black hole.

— Hambaryan and Neuhäuser (2013): A Galactic short gamma-ray burst as cause for the 14C peak in AD 774/5 in

More info via The Telegraph, and the original article discussing the spike in carbon-14 in tree rings is here.

Choosing Extinction

We talked about the Voluntary Human Extinction Project (VHMET) in Environmental Science, when we were covering issues related to overpopulation and the need for genetic diversity. While I’ve never been quite sure just how serious VHMET is, I just came across this 2007 article by Robert Krulwich on NPR about a tribe of pygmies in the mountains bordering China and Burma that chose extinction because of all the genetic problems that were being caused by inbreeding.

Improvisational War

Rebel catapult. Image by Tauseef Mustafa.

Fighting against a well armed military, the rebels in Syria have had to do a lot of improvisation. A basic knowledge of physics and chemistry has proven somewhat useful.

The Atlantic has a collection of photos of DIY (do it yourself) weapons, that includes catapults and sling-shots.

A rebel carries his home-made grenade. Youssef, 28 year old FSA fighter says: “my home made grenades, I am the only one in our Katiba able to build them, the guys like me for that, thats why I always carry them, for me and my comrades, its my mark and I want to leave one.”. Image by Sabastiano Piccolomini.

Sebastiano Tomada Piccolomini has a fascinating photo-essay in the New Republic showing the one item that members of one group of rebels considered as their most crucial weapon. These range from a radio, to a packet of cigarettes, to improvised grenades.

Finally, one of my students discovered that a cell phone and power-source from a computer can be made to look an awful lot like and improvised explosive device.

We are living in the future, but sometimes I wonder if it’s where we want to be.

Simulated IED.

Albedo and Absorption

Ice melts around an embedded leaf, taking the pattern of the leaf.

Darker colored objects absorb more light than lighter colored objects. Darker objects reflect less light; they have a lower albedo. So a deep brown leaf embedded in the ice will absorb more heat than the clear ice around it, warming up the leaf and melting the ice in contact with it. The result, is melting ice with shape and pattern of the leaf. It’s rather neat.

The History of Pharmaceutical Penicillin

For ten years after discovering penicillin, Fleming and his contemporaries could not get the penicillium mold to grow fast enough for mass production. Finally, in 1942, scientists isolated a strain of the mold from a piece of moldy cantaloupe in a garbage can.

Penicillium mold on mandarin oranges. Image by Wikimedia User:Bios.

Gravel Bar in the Creek

A wavelike bar of loose gravel in the creek.

In addition to clearing out the leaves, the fast flow in the creek created some interesting fluvial features. Example number one is this curious gravel bar that was not there a week ago. The gravel is quite coarse — 2-4 cm in diameter — but it’s extremely loose, which is typically of recently deposited sediment.

It seems likely that the sediment comes from beneath the fallen tree that cuts across the creek just upstream of the gravel bar. The tree restricts the stream flow, forcing the water to speed up, and when the water found it’s way through by cutting under the tree, it had enough energy to excavate a hole under the tree and deposit the resulting sediment just a meter or so away.

Constriction of the stream by the fallen tree focused flow beneath it, digging out sediment and depositing just downstream on the gravel bar.

It’s a neat piece of fluvial geomorphology.