Ask Brian

Laser Toys for Cats

2011-07-15T07:14:00.003-04:00

In response to this post, I have a question. My cats love playing with the red dot of a laser pointer but I am concerned about the safety and health of their eyes. I don't point it at their eyes...but they do stare at it for over 10 seconds and sometimes run into the path of it. I am wondering if a LED pinpoint flashlight (one that focuses as small as a laser beam would)....would be safer? If so where could I purchase one?

There is no risk to your cats' eyes from staring at the spot a laser pointer makes on the ground, even if they stare at it for a long time. The only concern would be if you aimed the laser pointer directly into their eyes and held it there a while. And it is likely your cat would find this unpleasant and turn its eyes away.

If you are still concerned, a LED or incandescent flashlight would be even safer since the beam will not focus as tightly even if the beam gets directly in your cats eyes.

Unfortunately, I am not sure where you would find a LED "pinpoint" flashlight. Typically you want a flashlight to have a wide beam and a laser pointer to have a small beam, so that is the way they are manufactured. Also, lasers are inherently narrow beamed while it would require additional components to make an LED have a small beam.

You could try one of the cat toys that keep the beam moving, like this one at Think Geek.

Who will I marry?

2011-05-09T10:09:00.002-04:00

Who will I marry? -Leanne

Great question Leanne! From a social pyschology point of view, you are most likely to form a relationship with somebody you are frequently exposed to. Take a look around, maybe you already met your future spouse!

Nuclear Plants

2010-12-25T14:16:00.002-05:00

Does some nuclear waste have to be stored for 100's of years?
Have some states banned nuclear plants?
Which are more expensive to build, nuclear or coal plants?

Spent nuclear fuel rods from nuclear plants remain highly radioactive and need to be stored until they are safe. Some elements can remain radioactive for thousands of years. Currently, used nuclear fuel is stored at the nuclear plant facilities as an interim solution to disposal.

Several U.S. states have a ban on (new) nuclear plants, including California, Connecticut, Hawaii, Kentucky, Maine, Massachusetts, Minnesota, Oregon, Wisconsin and West Virginia.

It typically costs more to build a nuclear plant than a coal plant.

What are photons and how do they differ from electrons?

2010-09-21T12:43:00.002-04:00

The photon is an elementary massless particle representing a quantum of electromagnetic radiation, or light. Albert Einstein was instrumental in developing the concept of the particle nature of light and, in fact, received his Nobel Prize for using the quantum nature of light to explain the photoelectric effect.

Electrons are also elementary particles. Unlike photons, they have mass and charge. Electrons are also sub-atomic particles (along with protons and neutrons).

Why does my son always stare off at lights?

2010-09-15T15:46:00.002-04:00

Why does my son always stare off at the light, Lamps, ceiling fixtures, any kind of light fixtures?

I am assuming that your son is an infant. This is more of a question about child psychology than optical phenomena and I am afraid I don't know much about child behavior. Scanning a few websites, though, I see many parents commenting on how their babies love to stare at lights (see this link). I would guess that your son stares at lights because they are fascinating. Bright shiny sources of light are a new experience for him.

Light Bulbs in your Field of View

2009-09-12T09:50:00.002-04:00

I've read your response about incandescent lights being generally eye safe to look at but I still have some questions. Is a clear bulb safe even if its within your field of view? If you were watching TV would it be damaging to the eyes to have the image of the filament sit on your periphery? I understand the eye moves while watching TV so it wouldn't stay on the same location on the retina. Also what if it was right next to your central vision, say a clear bulb next to your television, would it cause damage then? if you were watching the TV for hours upon hours?. I've tried to find the answer to these questions about how dangerous the clear incandescent light bulbs are but there doesn't seem to be much information regarding it, especially light damage on the peripheral of your eye.

An incandescent lightbulb in your field of view over an extended period of time is generally safe to view, whether it is in the center of your view or in the peripheral. Your eyes will provide you with some feedback if it is not good. If your eyes squint, or you feel discomfort, then that is your body telling you that maybe it isn't a good idea.

Can staring at an L.E.D. flashight be dangerous?

2009-04-23T17:08:00.003-04:00

If you have time will you please settle a family dispute. will staring at an l.e.d. flashlight or shining it directly into someone's eyes be damaging?

My first thought is that it's always the best policy simply to not stare into any light sources.

It is unlikely that you are going to cause damage to someone's eyes by accidentally, or momentarily, shining it into their eyes. L.E.D. flashlights are more powerful than incadescent ones, but they are still generally safer than laser pointers. The reason for this is that the beam from a laser pointer will focus to a smaller spot on your retina than the beam from a flashlight. (Technically speaking, the laser pointer is a point source, the flashlight is an extended source.)

I hope that answer restores peace to your family.

Is Wireless Radiation Dangerous?

2008-12-28T12:19:00.000-05:00

I wonder about the electro-radiation in my home from our wireless transmitter for our computer-internet connection. I increasingly get the feeling that I can "feel" it at the computer, sometimes get headaches or my hands get "hot" (resting near the keyboard). I've been strongly considering going back to CAT-5e hardline connections and getting rid of the wireless. Are there risks? I have young children as well. This is an issue that has been lingering for years

One thing you have to be careful of, when dealing with issues like this, is pseudoscience. You often find conflicting information regarding the harmful effects of wireless radiation, especially from cell phones. You should seek advice from a TRUSTED source in such matters. Thus, I won't be giving you an answer.

Pay attention to the results of the Interphone study on cell phone usage. If they don't find a risk, then it is doubtful that your wireless connection poses a risk.

Also, I seriously doubt your hands are getting "hot" from your router. Router's typically put out 10's of mW of power, which is a really small amount.

Interphone Study Links
International Agency for Research on Cancer (IARC)
International Herald Tribune

Candle Meditation

2008-12-11T09:11:00.002-05:00

I would like to practice a kind of meditation where you stare at a candle light as the meditation object (Trataka). Although this practice involves alternating between looking at the flame with open eyes and than looking at the after image with your eyes closed, I find it much comfortable for me to simply stare at the candle flame for an hour a day (which pretty much provides the same desired effects for me). I am only concerned about the health of my eyes which I read somewhere that performing this kind of meditation can damage my retinas if performed for more than 2 months at a stretch. I plan to meditate for life as it is a great pursuit, however I would like to know if this meditation object is safe for a lifelong meditation pursuer as myself.

I'm afraid that I can't give you much help with this question. All I can say is that candles give off visible and infrared light. The eye is especially sensitive to visible and near-infrared light, which falls into what is called the Retinal Hazard Region of the optical spectrum. Given the low brightness of a candle, I would guess that there isn't a high risk of retinal damage, though there could be other physiological issues. You'd need to seek advice from an eye doctor to know for sure. However, there are several things you can do to reduce the potential risks of injury,

Don't stare at a candle. Can you stare at something else and get the same effect?
Use a dim candle and sit as far away as you can.
Keep the lights on in the room

Where Can I Find Candle that Changes Color as it Burns?

2008-09-15T09:05:00.003-04:00

Some where in the past I saw a very pretty candle that changes colors as it supposedly burns and I believe it was powered by a battery or something.

I think you are referring to the fake candles that use LED's to mimic a real candle. Here are some links for you to try:

http://www.bluegoosecandlesandmolds.com/index.cfm/fa/items.main/parentcat/12150/subcatid/0/id/325044

http://www.lighting-china-supplier.com/d-p13153498-Candle_with_Multi_Color_Changing_Light/

http://www.epromos.com/product/8825707.html

I couldn't find any references to a multi-color wax candle. It would be a challenge to make because you would have to put additional chemicals in the wax to make the flame different colors. This would be a neat thing for somebody to try and make.

Can staring at a light bulb for periods of one to two minutes at a time cause permanent eye damage?

2008-02-05T15:12:00.001-05:00

Incandescent light bulbs are generally safe to look at. I am wondering why would you stare at an incandescent light bulb for such a long time?

One might think that a 50W incandescent light bulb is more dangerous than a 50 mW laser pen (1000 times less power) but power is only one factor to consider. (Also 50W represents the power consumed by the incandescent light bulb, the emitted power is significantly less than that).

The main factor that makes the laser pen MUCH more dangerous is that the light pen emits a collimated beam, all of which could potentially enter the eye, whereas the light bulb emits in all directions. The amount of power that gets into your eye from the light bulb drops off significantly with the square of the distance from the bulb (if you move twice as far away, the power drops by a factor of 4).

Another factor to consider is the size the the image on your retina. A lightbulb is an "extended source" whereas the laser pen is a "point source". This means that the size of the image spot on the retina will be larger for a lightbulb, and the energy density will be less, reducing the risk of injury.

Also, don't stare at the sun! Staring at the sun is dangerous.

Is this caterpillar poisonous to pets?

2007-09-27T17:09:00.000-04:00

Hello Science Brian, I just wanted to know if this is a caterpillar, because I find these in my backyard and my dogs might want to eat them. Are they poisonous if eaten by a pet?

What a nice picture!

I am not an expert in caterpillars, so I had to ask for help with this one. (Thanks Dave!) This is a Tobacco Hornworm (manduca sexta). I thought it was a tomato hornworm, but what do I know? They are often confused. Like most caterpillars, it's main job is to eat! Tobacco hornworms feed on tomato, tobacco and Jimson weed leaves.

My expert friend says that your dogs probably won't have much interest in eating these because they can taste bad. I didn't ask him how he knew that. The hornworm can get your pets sick, if it has been eating a toxic plant like Jimson weed (also known as stink weed). However, most likely your dog would spit it out before swallowing it because of the bad tasted.

What Causes Hemophilia?

2007-05-15T11:41:00.000-04:00

Hemophilia is a rare inherited blood disorder. This genetic disease is caused by a defect in the genes that determine how the body makes blood clotting factors. Because these genes are on the X chromosome (men have XY women have XX), women can be carriers of the disease (if they have one defective X chromosome) whereas men with the defective gene will have hemophilia.

Why Isn't Black a Color?

2007-04-26T09:38:00.000-04:00

Color is based on human perception of the visual spectrum of light. Our ability to see different colors is due having a variety of cone cells on the retina that are sensitive to different wavelengths of light.

Black is the label we give to the perception of the absence of light reaching the eye. Objects that absorb all wavelengths of light, rather than reflect them, appear black. We also see black (or darkness) at night or when we shut off the lights.

When somebody says "black is not a color" they are referring to the fact that black is not a scientific observation of light. However, since color science is based on human perception, and our eyes perceive the absence of light, it is OK to call black a color.

Why Are Candles Made of Wax?

2007-04-20T11:44:00.000-04:00

Well, one might argue that by definition we call a light source made of wax a "candle" (as opposed to an oil lamp or match which has a similar purpose but uses different materials).

But what is special about the wax in a candle?

To understand the mechanisms of how a wax candle burns, read Why doesn't candle wax burn without a wick? first.

Wax has several unique properties that make it an ideal material to be used as the "fuel" of a candle. It is solid at room temperature, which makes it easier to handle than liquid lamp oil which must be kept in a container. It is also malleable and melts at a low temperature, making it easy to shape into whatever form you want it to be. The low melting point is very important because the energy required to melt the wax must be less than what is generated burning it, or the flame would not be self-sustaining. Natural sources of waxes (such as beeswax and paraffin) are commonly available for use in candles.

Why doesn't candle wax burn without a wick?

2006-04-24T12:50:00.000-04:00

The wick is the most important part of a candle! The mechanics of a burning candle are actually quite interesting. The wax, in it's solid form, does not burn. When you bring the flame of a match near the wick, the wax directly below starts to melt due to the heat (or in some cases, the actual wick material will start to burn and then heat up the wax below). The melted liquid wax is then drawn up to the flame on the wick through capilary action. As the liquid wax is drawn up into the flame, it is heated until it vaporizes. Once it is in gaseous form, it is ignited by the flame. The combustion of the gaseous wax keeps the flame going and generates enough heat to warm up some more wax. The cycle continues as the candle wax is burned away. Nifty!

Why do our eyes tear when we cry?

2006-03-06T20:45:00.000-05:00

Scientists distinguish three kinds of tears, basal, reflex and emotional.

Emotional tears are the ones that occur when we cry. These tears contain high concentrations of hormones that build up when the body withstands emotional stress. The reason people will frequently report feeling better after a well-placed cry is doubtlessly connected to the discharge of these stress-related hormones.

In case you are curious about the other types of tears, basal tears are the secretions responsible for keeping the eye lubricated and flow continously as we blink, and reflext tears are the secretions that occur to flush out irritants (dust, hair, etc.) from our eyes.

Resources:
Tearful Serenity
Cool Quiz

Why Do Smoke Detectors Contain Radioactive Materials?

2006-01-19T19:58:00.000-05:00

One of the most common types of smoke detectors is called an ionization detector. This type of smoke detector contains a small quantity of Americium-241, a radioactive element that emits alpha particles. The alpha particles emitted by the americium ionizes the air molecules (oxygen and nitrogen) allowing electric current to flow between a set of metal plates hooked up to a battery. When smoke is present, the ions attach to the smoke particles and are neutralized. This reduces the electric current between the plates which triggers the detector to sound the alarm.

Before you worry, the alpha particles emitted by the americium do not travel very far in air and are not any danger to you. This is as long as you don't DISTURB the americium. Americium can be very dangerous if inhaled. So do not tinker with the smoke detector or try to examine/play with the americium.

Animal Lifespans

2005-12-05T19:34:00.000-05:00

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?

2005-11-10T19:02:00.001-05:00

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?

2005-11-09T19:30:00.000-05:00

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"

2005-10-26T19:58:00.000-04:00

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?

2005-10-25T18:20:00.000-04:00

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?

2005-10-18T17:57:00.000-04:00

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?

2005-10-14T21:39:00.000-04:00

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).

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.
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.
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.