Animal Lifespans

How do some animals, like turtles and parrots, live for over
a hundred years but others, like dogs and cats, live for
only a short time?

Hmm, interesting question. I had to hit the internet for answers to this one.

This is a question that many scientists study. Understanding life spans can help us to better understand the human aging process. There are several theories, but we really don't know for sure why some animals live longer than others.

One theory is related to metabolism rates. Animals with faster metabolisms tend to have shorter lifespans than animals with slower metabolisms. However, there are many exceptions to this rule, like birds and bats having high metabolize rates but relatively long lives.

Other theories suggest that evolution factors into lifespan. Some species follow the evolutionary strategy of early and rapid reproduction, at a sacrifice to longevity. Other species, that are more likely to survive early death from predators, etc, can have a more leisurely reproductive cycle and subsequently a slower aging process.

Reference:
http://www.bbc.co.uk/radio4/science/lifespans.shtml

In photos, why do some people get red eye more than others?

Red eye occurs when the bright flash from the camera enters the eye and reflects off the retina back into the camera. I suppose one reason that some people are more susceptible is that they probably stare directly into the camera more. Staring straight back increases the chance of red eye. The other reason would be related to the size and color of a person's iris, which controls how much light can get into the eye. (I wonder if blondes have more red eye?) Cameras with red eye reduction turn the flash on early in order to cause the subjects iris to contract to reduce the amount of light getting in (and out) of the eye.

Edit: After reading the comments, I looked further into the effect of eye color on causing red eye. It's not the color of the iris that has an effect, it's the amount of melanin in the eye. Melanin absorbs the red light, reducing the amount of red light reflected back to the camera.

How does the sun create dust?

I believe that the young man who asked this questions was noticing that you can see a lot of dust when the sun shines through the window. The reason for this has to do with contrast. When you typically observe an object, your observation is based on a change in contrast/color from the surrounding view.

Try this experiment...

• Find a room with a white wall (or any kind of white background)
• Tape a small piece of white paper on the wall (say about the size of a quater)
• Take another small piece of paper, make it black by writing on it with a pen, and also stick it on the wall
• Go as far away from the wall as possible and look at the pieces of paper.
• Which piece of paper is easier to see?

Pieces of dust are so small, that they are generally difficult for our eyes to see. However, when exposed to bright sunlight, the bright light is reflected off the dust particals making them appear very bright against a dark background.

On a side note, all of the matter on the planet was originally created in the stars many billions of years ago. So, I guess you can say the sun (or rather, some other star) creates dust.

Why does only one side of the car have a mirror that says "objects may be closer than they appear"

Many cars have a mirror on the passenger side that is curved to provide a wide angle view. This is so that the driver can see a car in the blind spot (which is worse on the passenger side of the car). The downside of this mirror is that it gives the impression that objects are farther away than they really are. It is decided that the danger of not seeing a car in the blind spot outweighs the danger of mistaking the distance of the car. Most people can learn to adjust to the distorted distance perception anyway. However, on the driver's side, it is more important to provide an undistorted view, so a standard flat mirror is used.

Why are Power Lines High Voltage?

This is a good question because we know high voltage lines can be dangerous to people. Why not use low voltage power lines?

The amount of power that is delivered through an electric power line is the product of the voltage and current going through it (Power = Current x Voltage). Thus, high power transmission can be achieved by having either high current or high voltage.

However, a small amount of this power is lost through heating of the power line due to its resistance. The amount of power dissipated by the transmission line is proportional to the current going through it and the square of the resistance (Power Loss = Current x Resistance x Resistance). In order to minimize the heating of the power line, the current must be kept to a minimum.

Therefore, the best way to deliver the most power, and keep loss to a minimum, is to have a high voltage and a low current.

Why is staring at the sun bad?

Why do people tell kids not to look at the sun, when the body's natural reaction is to look away anyhow?

It is true that the human body naturally reacts to bright light. However, when staring at the sun, this is not always the case. It is especially dangerous during an eclipse because the illumination is less, reducing your tendancy to look away.

The most common injury to the eye from looking at the sun is a retinal burn. The retina has no pain recepters, so you will not realize that you are damaging your eye until it is too late. As a person stares at the sun, the sun's image on the retina is heating up and the retina may become severly burned.

Apparently kids are at the greatest risk for retinal damage(http://www.drgreene.com/21_169.html). Tell your kids to imagine what happens when they hold a magnifying glass up to a piece of paper. If it is held there too long, the paper gets burned. The lens of your eye is like a magnifying glass, and you don't want to burn your retina!

Warning, techno-babble: Unlike a light bulb, which is an extended source, the sun is acts like a point source, which means that the light will be more focused on your retina causing greater risk of damage. However, because the sun is a point source, you can easily "view" the sun, or a solar eclipse by using a pin-hole camera. One simple trick I used during a solar eclipse was to criss-cross my fingers between my hands and look at the shadow on the ground. I could see an image of the sun on the ground through every space between the shadows of my fingers.

Remember, the only safe time to stare at the sun is at night!

What is a laser?

I'll start things off by asking the first question myself... what is a laser?

A laser is a light source that exhibits several properties that make it unique compared to other types of light sources (incandescent and fluorescent light bulbs, the sun, etc).

1. Laser light is monochromatic - this means that the light that comes from a laser is a single wavelength (one color). This is why you usually see red or green lasers, for example, and not white lasers. The color white is a combination of many colors.
2. Laser light is coherent - this means that all the light "waves" are organized with respect to each other. Think of this like synchronized swimming, whereas most other light sources are more like the random collection of people swimming down at the local pool.
3. Laser light is directional - ...hence, the laser beam. Whereas, your typical light bulb emits light in all directions.

These properties of lasers make them extremely valuable tools for many applications including metrology (precise measurements), remote sensing, industrial processing, medical procedures, and, of course, the all-important laser light show.