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Dying bugs flip, Black holes collide, Dimmers chop electricity

Q: Why do bugs turn over onto their backs when they are ready to die? Lisa T., Fredricksburg, Virginia

Colorado potato beetle. Photo courtesy of Scott Bauer, US Department of Agriculture.

A: They don't turn over onto their backs as an intended act. Instead, their nervous system isn't working well by this time. So, if they land on their back (perhaps from a fall, a cat bumps them, or a breeze blows them), they can't do much about righting themselves.

"[then] coordination declines and the ability to do complex tasks like turning over (in this case, with six legs to coordinate) ceases," explains Robert Suter, biology professor at Vassar College.

"Also, many of the synthetic organic insecticides we use these days target the insect's nervous system," says John Meyer, entomology professor at North Carolina State University.

The poison causes tremors and convulsions. The insect often flips on her back as she kicks her legs in an uncoordinated way. The poison continues the death process by undermining the insect's nervous system and her ability to right herself.

Death may come quickly since she can't get food, water, or out of a predator's way, says Suter.

Further Surfing:

John Meyer, Insect nervous system

Robert Suter, Locomotion on the water's surface

Q: What will happen if two black holes are close to each other? Do they collide? --Bambing, Quebec, Canada

[NASA] Smoking gun (inset) of colliding black holes, NGC 326

A: Yes, they collide and become one bigger black hole. (A black hole is an object so collapsed and, consequently, with such a large gravity field that its escape velocity exceeds the speed of light.) Black holes lurk in the hearts of many galaxies. When two such galaxies merge, current theory predicts that the two black holes will sink toward the center like stones in swirling water and form a binary pair (circling each other like double stars). However, we don't see this. Instead, recently we found direct evidence the black holes actually coalesce, says astronomer David Merritt of Rutgers University in New Brunswick, New Jersey.

In August 2002, Merritt and Ronald D. Ekers used existing pictures of colliding black holes taken with the Very Large Array of the National Radio Astronomy Observatory at Socorro, New Mexico. The jets seen in the inset of the figure are the smoking gun. Jets orient parallel to the spin axis of the black hole. Sometimes the jets flip.

"The jets initially pointed to the 10 o'clock and 4 o'clock directions. They now point to 8 o'clock and 2 o'clock," say Merritt and Ekers. That happens when the black hole suddenly realigns itself. The only thing big and massive enough to realign a black hole is another black hole. The two merged.

Even a small black hole can significantly influence how another black hole orients. The little guy can realign one up to five times more massive.

How such a cosmic crash happens isn't well understood. Merritt believes that, as the distance between two black holes shrinks to solar-system size, the holes radiate gravity waves and this causes their mechanical energy to decrease. This brings them still closer and they rotate around each other faster and faster as they close. Eventually they collide, sending an incredible burst of gravity waves radiating into space. Astronomers estimate such a demolition derby happens about once a year someplace in the Universe.

Gravity waves are extremely weak wavelike disturbances that Einstein predicted. Massive bodies produce them whenever the mass accelerates or is disturbed. Gravity waves are ripples in space-time and travel at near light speed.

Further Surfing:

National Radio Astronomy Observatory: Scientists detect 'smoking gun' of colliding black holes

Q: Does lowering the brightness of lights via a dimmer cause less electricity to be consumed? If so, is it proportional to the degree of dimness (i.e., does lowering the brightness by 50% lower the consumption by 50%)? --RT Lennox, Strongsville, Ohio

A: Yes, dimming lights--with a modern dimmer switch-- consumes less electricity. Years ago, dimmer switches used a variable-resister (called a rheostat) to dim lights and these switches did not reduce electricity consumption. They also generated much heat.

Yes, if you lower the brightness by 50%, you sure do lower the power consumed by 50% for fluorescent lights and almost as much-- 40%-- for incandescent lights. It's neat how this modern efficient switch works because the brightness is directly related to the power consumed.

Click for tables showing how much electricity you can save for different light levels.

Modern dimmer switches chop up the electrical power by switching the power on and off 120 times a second. They use a transistor-like device called a triac (triode alternating current switch) to do the job.

The figure depicts one cycle of 60 hertz alternating electrical voltage--an undulating sine wave that varies from positive to negative. For one half the cycle, the voltage is positive and the other half, negative. The electrons surging through a household line change direction as the voltage changes polarity.

The red line in the figure shows when the dimmer switch turns the light's voltage on and off. The switch turns the voltage on (red line) depending on where we set the knob on the switch. The switch turns off each time the voltage reverses polarity (or crosses the black zero-line in the figure).

When we turn the switch knob to make the light brighter, that moves the red line to the left so the total voltage and power going to the light increases. Likewise, turning the knob the other way, decreases the light's power and dims the light.

Dimming lights makes incandescent light bulbs last much longer (greater than 20 times longer at a 25 % light level) because the bulbs generate less heat.

Further Surfing:

Lutron Electronics Company: Why dim?

Home Repairs Stuff: How a dimmer switch works

How stuff works: How dimmer switches work

(Answered Jan. 2, 2003)