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Reptiles see color, no 24-hour flu, gravitons carry gravity

Q: Do reptiles see in color like birds and humans? Do they see things in their visual spectrum that we don't (like birds seeing into the ultraviolet)? John, Albuquerque, New Mexico

Two rainbow views. The left is how we perceive it and the right is how many reptiles (including dinosaurs) might see it. [M.P. Rowe, Palaeontologia Electronica]

A: Yes, many reptiles appear to see in color much as birds do but unlike humans. What a perceptive question! As you imply, seeing in color depends on the animal. Different species can look at the same object but see different colors and patterns.

Human eyes have three types of color cones that absorb red, blue, and green light best. These colors are primary for us. Many reptiles (11 species) have four color cone types and, consequently, have four primary colors. They see a different world.

We see a blue sky. A reptile may see a green one or some other color we can’t even dream of. Turtles, lizards, and birds can see in ultraviolet and probably dinosaurs could too. Imagine a reddish-ultraviolet rose. I can’t. A turtle might see such a combination, though.

A rainbow illustrates some of the differences among birds, reptiles, and humans. Probably all birds perceive rainbows but the colors are too close together for many reptiles to resolve, says Mickey Rowe, neuroscientist at University of California, Santa Barbara.

Their eye optics is too poor and they have too sparse a density of color-sensing cones. Also, humans may see more bow hues, not because we have more cone types (we generally have fewer) but because we have vastly more neurons than reptiles to process visual information.

Further Surfing:

WonderQuest: Color — all in the eye of the beholder

Palaeontologia Electronica: Vertebrate visual capacities by M.P. Rowe

Melissa Kaplan’s Herp Care Collection: Reptile vision

Talk Origins: Evolution of color vision

No 24-hour flu

Q: I am the principal at a school in Missouri and I get parents calling all the time saying "Johnny won't be at school today, he has the 24-hour flu". Having taught science for 17 years I tell them there is no such thing. Where can I find proof to back my claim? Brad, Chamois, Missouri

Influenza viruses [CDC]

A: The 24-hour flu does not exist, say the Centers for Disease Control and Prevention (CDC). The flu is a respiratory disease and not a stomach or intestinal disease. The fever and body aches associated with the flu lasts three to four days — not 24 hours.

"There is no such thing as the 24-hour flu," says Alaska’s Environmental and Food Safety expert Nancy Napolilli. "It’s food poisoning."

If Johnny has the "24-hour flu" or food poisoning, he might feel queasy all day. On the other hand, he could suffer intense abdominal pain and diarrhea if he ate food contaminated, for example, by the bacteria called Clostridium perfringes. These bacteria infest soils, intestines, and sewage.

So, you’re absolutely right. There’s no such thing as the 24-hour flu but the kid is really sick anyway.

By the way, to avoid these miseries: cook food long enough and at a high enough temperature (above 140 degrees F, 60 degrees C) to kill bacteria.

Further Surfing:

CDC: Influenza

Ohio State University: Clostridium perfringesns, not the 24-hour flu

Gravitons carry gravity

Q: If gravity is nothing but the bumps, depressions and warpings of geometrical space-time, why is anybody talking about ‘gravitons’ to explain gravity? Doesn’t Einstein's General Theory of Relativity do the job? — Peter

A model of Earth’s gravitational field based on satellite data [University of Texas and NASA]

A: Trying to explain all the forces and elementary particles in the Universe with a single theory — is the culprit.

Sure, we think Newton explained gravity wonderfully well. Einstein extended Newton’s notions, giving us, as you say, insights into the geometry of space and time. All that’s well established.

Then, why do we need gravitons? To pull all of physics under a one-theory umbrella and to understand physics on a deeper level.

"If we hope to understand the unification of forces, the big bang, cosmic inflation, or even certain details of black holes, we will surely need a quantum theory of gravity at some point," says Steven Pollock, physics professor at the University of Colorado, Boulder. (Related information: Steven Pollock http://www.teach12.com/store/professor.asp?ID=251&d=Steven+Pollock)

Our present theory (the Standard Model of fundamental particles and interactions) does explain the other two fundamental forces (the strong and electroweak). We still, however, haven’t included gravity, although Einstein tried.

First, a word about the forces the Standard Model covers. The "strong interaction" is the force that binds protons and neutrons together to form atomic nuclei. The "electroweak interaction" is actually two forces — electromagnetism (electro) and radioactive decay (weak). We recently found out that these two forces are different manifestations of the same force (electroweak).

We hope to use quantum mechanics and gravitons to bring gravity into the Standard Model. A graviton is a hypothetical (we still haven’t found any) elementary particle having no mass and no charge. We can think of the gravitational attraction between two objects as the exchange of gravitons. Gravitons are analogous to photons. Gravitons and photons — both massless — travel at the speed of light.

Quantum mechanics says that light travels in particle packets called photons. Photons carry the electromagnetic force. We know this to be true experimentally. The quantum theory of electrodynamics works superbly — to incredible accuracy. For example, the theory predicts the magnetic strength of an electron to 11 decimal places: 2.00231930435. The unitless number (which compares the electron intrinsic magnetic moment with a Bohr magneton) checks with experiments.

That’s why we’re using quantum mechanics, with gravitons instead of photons, to explain gravity. If we succeed, then we will be able to explain every force (including gravity) and every elementary particle with a single theory.

Further Surfing:

Lawrence Berkeley National Laboratory: The particle adventure

HyperPhysics by Rod Nave: How the fundamental forces work by exchanging particles, like photons and gravitons

University of Texas and NASA: Animated model of Earth’s gravity field

(Answered Jan. 2, 2004)