WonderQuest:  On the web since 1997...      

Life lasts about a billion heartbeats, Flash in a pan

Q: Why do larger animals live longer than smaller ones? (Bobbie, Sesser, Illinois)

A: It depends on what clock you use. You’re right — by Sun time. But wrong by biological clocks. An elephant lives about 69 years and a mouse 4 years. Yet the elephant lives a slightly shorter life when measured by a metabolic clock. Indeed, the elephant gets somewhat less than a billion heartbeats and the mouse slightly more.

Over their lives, an elephant’s heart beats a few strokes less than a mouse’s. [Courtesy of U.S. Fish and Wildlife Service]

Metabolism is the key. Apparently, a body has only so many heartbeats (about a billion) and so many breaths. A large animal, with a lower metabolism rate, breathes slower and his heart beats slower. He reaches sexual maturity later and lasts longer than a smaller creature — by Sun time.

Why is this so? We know that byproducts of normal metabolism cause oxidative damage to DNA. Such damage can cause cancer. So, a slower metabolism might diminish DNA damage in tissue and thereby inhibit cancerous growth. Thus, a larger animal could live longer — by the Sun.

"The situation appears to be a bit more complex," emails John Speakman, of the University of Aberdeen in Scotland, when we examine one gram of body tissue and the amount of energy it uses over an animal’s life.

Speakman measured the total energy that animals of different sizes require. He then calculated the amount of energy each gram of tissue those animals burn in their life spans and found a startling result. "Tissue in smaller animals use more energy than tissue in larger animals." So, equating ‘living’ with total energy used, a gram of mouse tissue lives more (during its short life) than a gram of elephant tissue.

Further Reading:

Journal of Experimental Biology: 2005 May; 208(Pt 9):1717-30. "Body size, energy metabolism, and lifespan" by John Speakman

University of California at Santa Barbara: Of mice and elephants: a matter of scale by George Johnson.

Tufts University: Allometric scaling by Mark Pokras

Q: I got an ice cube tray out of the freezer one night without turning on the kitchen light. Much to my surprise, when I twisted the tray to get the cubes out, a streak of light went through the ice. I've had this happen several times since. My question: what causes the quick spark of light in the ice? (Tori, Somewhere in Washington State)

A: I stressed ice cubes different ways but saw no light. A friend even put an ice cube in a vice and pulverized the cube in the dark. Still nothing (probably too slow a stress). If anybody succeeds with this experiment, please tell me how you did it. By the way, let your eyes adapt to the dark, beforehand, a good 10 minutes.

A stressed ice cube gives off light much like an aurora. [Courtesy of Corel Corporation and the NOAA.]

I’ve read it’s true. The ice, however, must experience an extremely abrupt stress to spark flashes intense enough to see, says Chemist Colin Freeman of the University of Canterbury in New Zealand. A few years back, he and colleagues (Terry Quickenden and Brendan Selby) used "extremely sensitive light-detection equipment" and a "light tight" enclosure. So, they didn’t actually see the light with their "naked eyes," he emails. Also, instead of twisting the tray (which Freeman terms "too gentle"), they plunged the ice cubes into liquid nitrogen (-320 degrees Fahrenheit, i.e., -196̊ C). The cubes shattered and emitted light.

Their equipment recorded tiny bluish-green electrical sparks scintillating in the ice. This phenomenon (called electroluminescence) is light generated in a substance by applying an electric field. The electric discharge excites the molecules and they give off light — much like an aurora.

Triboluminence (a special case of electroluminescence) takes the phenomenon one step further by stipulating how we generate the electric field. We stress the substance (ice, in our case). Stressing ice creates spatially separated electric charges. When the charges neutralize by jumping back together, the electric discharge ionizes the surrounding space, and we see a flash of light.

At least, we’re supposed to. Reader Tori did. Anybody else?

Diamond cutters see blue or red sparks when sawing a diamond — another instance of triboluminescence. I haven’t tried that...

Further Reading:

Quickenden, T.I., Selby, B.J. & Freeman, C.G. Ice triboluminescence. J. Phys. Chem. A , 1998,102, 6713-5.

Princeton Instruments: Luminescence and fluorescence spectroscopy

NRC Research Press/Canadian J. Phys.Rev. Can. Phys. 81(1-2): 71-80 (2003) Photon emission during deformation and fracture of ice by Y. Mizuno and T. Mizuno

(Answered Sep. 16, 2005)

Comments

It seems to me you may want to try over-filling your cube trays.  If you fill them only to where you should be, you will not see this effect.  Also, you need to have hard plastic cube trays from my experience.  I have trays from a fridge bought in the 80's that does it while all new trays (cheap wamart trays) I have do not.  (The two that came with the newer Amana fridge do it RARELY.  I think the old ones that do it so often were in a GE fridge.  The Amana ones have a mid-range hardness to the plastic, closer to the GE in strength, while the el-cheepos are flimsy)  I should add also that it is much harder to twist the ice free in those trays that do cause the effect.  I would estimate at LEAST twice the pressure (although, I have not tested this)

Ok, so conclusion; if you want to see the electroluminescence from ice, try hard trays (high tensile strength) and proceed to overfill them.  The temperature that you put the water in the trays at also seems to be of some effect, where sometimes the ice is harder than others.  I do not know what temp to say you should put in that creates the strongest ice, but I am sure if you look that up, that is the the temp you want to go for.  It seems to be the stronger the ice, the more likely it is to be noticeable.  (The hard ice I am referring to is almost perfectly clear, and has almost no air in it.) 
 

When you see it you with know it is the same thing as an aurora (if you have seen that) it at least for me has been that exact blue with maybe the slightest hint of green, but well more blue-- this is to abstract to finish this thought.  If you have seen the auroras, you will know what I mean.  There are essentially 3 basic colors (blue, green, red), and they never really shift.
 

I know I didn't type this in a easy to read thought process, but all the important information should be there :)

Ryan, Someplace, World

New Comment --- add your comments to the discussion: