Why does this happen?
(a) When a straw is put into a glass of water the water level in the straw will rise a little higher than the level of water in the glass.
(b) When a straw with a narrower tube is used, the water level in it will be even higher than the water level in straw(a).
Thanks
D.C.H.
The fact that the water level in a straw will rise a little higher than the water level in the glass is the result of a property of liquids called "surface tension". The surface tension of a liquid can be viewed as a property which draws a liquid together. The surface tension of water helps hold raindrops together and gives them a spherical shape as they fall.
Let's consider the straw in a glass. When a straw is placed in water, the water "wets" the surface of the straw. In other words, the water adheres to the sides of the straw and hence creates a thin film of water on the surface of the straw. The water molecules in this thin film of water (on the sides of the straw) then pulls the water up the straw as a result of the surface tension that I discussed above.
In response to your second question, the water level will indeed rise further in a smaller diameter straw. The water will rise in a straw until the force due to surface tension pulling the liquid up the tube is counterbalanced by the force of gravity pulling it downward. In a small diameter straw the lifting force caused by surface tension will lift the smaller diameter column of water higher.
This question was so funny that I couldn't resist posting it. I hope that you enjoy.
Okay Dr. Bob,
Answer this one for me... If when you drop a buttered piece of toast it always lands with the butter down and when you drop a cat, they always land with their feet on the ground, what would happen if you taped a buttered piece of toast to a cat with the butter facing upwards, and then dropped the cat?
Spankk
This is without a doubt the most complex question that I have received. I have exhausted all of my reference resources and have been unable to find a definitive answer to your question. However, as any good scientist would do, I decided that I should actually conduct the experiment.
At this point in time I have loaf of bread, a toaster, a tub of butter, and a roll of duct tape for attaching the toast to the cat. Unfortunately I don't have a cat. I plan to conduct the experiment out of my third story attic window directly over my concrete driveway. If any of my readers would like to loan me their cat (for the sake of science) please let me know.
Who Invented the computer?
Thanks
Carlo
A number of mechanical calculating machines (computer ancestors) were invented during the 1800s. However, the first electronic computer was developed by Howard Aiken of Harvard University in association with IBM Corporation in 1944. This machine was a huge electromechanical calculator that incorporated approximately 3000 telephone relays and was controlled by a paper punch. The machine was over 50 feet (15 meters) long and 8 feet (2.4 meters) high. (Imagine that in your living room as a PC!). It took .3 seconds to add and subtract, 4.0 seconds to multiply, and 12.0 seconds to divide!
Will the bite of a Black Widow spider kill the average person? Also could you show a picture of a Black Widow spider?
Thanks
Phillip
The bite of a Black Widow spider is generally not fatal unless the person receiving the bite is small (e.g. young children). For the 10 year period from 1960 to 1969, only 4 deaths were attributed to the Black Widow spider in the USA. Even though the venom of the Black Widow is considerably more toxic than that of a rattlesnake, the spider injects a much smaller amount of venom therefore there is a lower mortality rate. Since the Black Widow's venom is a neurotoxin, symptoms may include tremors, nausea, labored breathing / speech, profuse perspiration and vomiting.
A good picture of a Black Widow spider can be found at http://mwanal.lanl.gov/Bench/bh4.html .
Great Web page Dr. Bob!!!!!
I hope you don't mind if I have my students check this out when I am stumped. Anyway I was wondering if you knew anything about a controversial subject I had heard of. Is the speed of light constant or is it slowing down? If so what does this mean for some of the other constants related to C such as permeativity and permeability as well as for radiometric dating processes.
Any help or resources would be greatly appreciated.
Dan
What a great question! This is one that I had to do some research on. One thing that is for sure is that this is a highly controversial subject. Fortunately, I met a Physicist named Lambert Dolphin, who is an expert in this area and has conducted studies indicating that the speed of light is slowing. Lambert was kind enough to provide the following response to your question:
Until the time of Galileo the velocity of light was assumed to be infinite.
A few individuals dissented, but the scientific community in general did
not question the instantaneous transmission of light.
Galileo attempted the first measurements over a path of about a mile in
1638, using lamps with shutters. This was of course unsuccessful, however
others rushed in to attempt measurements.
Danish astronomer Olaf Roemer in 1676 announced a successful measurement of
c (the speed of light) by noting the eclipse times of Jupiter's moon Io were delayed by many
minutes when Jupiter was far from the earth.
Bradley's work in 1729 clinched the case for a finite value of c.
Since then we have a data base of about 160 or so highly reliable
measurements of c by 16 different measurement methods.
When very careful statistical analysis is done of the available data,
confidence levels of 95% or greater that c has decreased are the result.
Although this conclusion is hotly disputed, the statistics speak for
themselves. Of course we could wish there were more data points available
to improve the analysis.
c cannot change if other time-related "constants" are not also changing.
This is consistent with the data on these other constants.
At least two new cosmological models have been proposed that allow c to
change over the history of the universe. These models are alternative
models for Big Bang Cosmology and also explain the Red Shift in other ways
than Hubble's model.
The principal consequence of a non-constant c is that the run rate of
atomic clocks has slowed with respect to dynamical time clocks.
The velocity of light appears to have decreased rapidly after the creation
of the universe and tailed off exponentially in the past 3000 years.
The velocity of light is a metric property of space itself, which simply
measures how space is stretched out, and/or the energy density of the
vacuum per unit volume.
The velocity of light was defined to be constant in 1967. The velocity of
light is decreasing slowly at this time. This shows up only as a slight
drift between atomic and dynamical clocks.
Complete information is available at
http://www.best.com/~dolphin/constc.shtml
Since this is such a controversial subject, Dr. Bob would also welcome and post input from physicists from the "constant speed" school of thought.
Hi Dr. Bob,
What causes ice to be less dense and take up more space? In other words why does ice expand rather than contract?
Thanks,
Mark
Ice is less dense than water because of its crystal structure. Chemists have determined, by X-Ray studies, that the water molecules in ice crystals are arranged in such a way that they contain a considerable amount of empty space between them. Water also has empty space between the molecules, but the spaces are much smaller. The larger amount of empty space between water molecules in ice crystals causes ice to occupy more space than an equivalent amount of water and to be less dense.
Hey Dr. Bob,
What causes areas of low pressure and areas of high pressure in the atmosphere? Also why is low pressure associated with storms and high pressure with blue skies?
Thanks,
Niko
Low and high pressure areas form as a result of temperature differences on the Earth's surface. Following is an explanation of how a low pressure area would form.
When heat energy is absorbed by the atmosphere, the molecules move faster, the volume that these molecules occupy increases, and the air becomes less dense. Since the air is less dense than other surrounding air, it is buoyant and pushes upward. A low pressure area forms because the resulting area has a lower density of air molecules.
On the other hand, a high pressure area results from the convergence of cooler, denser air. A high pressure area has a higher density of air molecules relative to a low pressure area.
Low pressure areas are frequently associated with storms. In the northern hemisphere, air moves inward in a counterclockwise direction around regions of low pressure. This type of wind flow is known as cyclonic flow. Cyclonic wind patterns can build in intensity until they produce very severe storms (e.g. hurricanes). Cyclonic winds cause differing air masses to interact. The interacting air masses have different pressures, temperatures, and humidity levels. When this happens the atmosphere becomes very unstable and a storm occurs.
Hello Dr. Bob,
Why do the skies turn green sometimes during severe thunderstorms?
Thanks,
Katie
To answer your question, let's first discuss why a clear sky appears blue. Sunlight consists of many different wavelengths (i.e. colors) of light. This is observable if you separate the colors with a prism. Sunlight that interacts with the atmosphere is SCATTERED by small atmospheric air molecules. Blue light is scattered much more than other colors contained in sunlight. Therefore the sky appears blue.
Next let's consider what happens with clouds. Water droplets that make up clouds cause light to be REFLECTED because of their large size. Clouds are strong reflectors of sunlight. A thin cloud appears white because it allows reflected light to pass through. A very thick cloud, however, will appear black because no reflected light will pass through.
With that background, I can now answer your question. The combination of the blue sky and the darkness of thick clouds in a thunderstorm can sometime produce a green - gray color.
If space was full of air would the sun be loud? Also, if space was full of air (actually just oxygen for this question) would there be a big explosion and everything would turn to water because the Oxygen would combine with Hydrogen (the most common element in the universe) to form water; would that happen? Please respond, I really am curious.
Myles
Hypothetically speaking, if outer space were filled with air, the sun would indeed be very loud. Of course, the loudness would depend upon how far away you were. The reason that you would not hear the sun in outer space is because there are very few air or other molecules to propagate the sound. Sound moves through the air as a result of molecules transferring their energy by bumping into neighboring molecules. This is called a sound wave. The surface of the sun is very violent. Massive explosions, such as solar flares, occur in the chromosphere. These enormous spurts of energy would indeed be very, very loud.
Regarding your second question, water would not form on the surface of the sun. A water molecule is made up of two hydrogen atoms and an oxygen atom that are held together by chemical bonds. The extreme temperatures on the sun's surface would cause these chemical bonds to break and, as a result, a water molecule would not form or could not exist on the sun.
Could a tornado, as the movie Twister would have us believe, lift and throw large construction machinery?
Thanks,
Ronald
Yes. If you would like to read more about tornadoes please check out the Meteorology portion of the
Science Circle on my web site. Here is an excerpt from that article:
" Tornadoes have been known to pick up automobiles,
horses, and whole trees. In one very strange incident, a
tornado in Minnesota (year 1931) lifted an 83-ton
railroad car containing 117 passengers and moved it 80
feet. The car was dropped into a ditch and all the
passengers survived. "
Can you please tell me what the temperature is on the sun?
Thanks,
Eric
The sun is incredibly hot. The sun's surface (which is called the photosphere) is approximately 10,000 degrees F (5538 degrees C). The sun's core is much hotter - an amazing 27,000,000 degrees F (14,999,982 degrees C). At this temperature, thermonuclear fusion of hydrogen takes place which produces the sun's enormous energy.
Another interesting tidbit is that the sun's corona (its faintly luminous outer atmosphere) is much hotter than the sun's surface. The corona is approximately 3,600,000 degrees F (1,999,982 degrees C). The corona consists of plasma which is essentially a gaseous mixture of charged particles.
The coolest spot on the sun is the dark, circular center of a sunspot, which is called the umbra. This area is typically 3,100 degrees F (1,704 degrees C) cooler than the surrounding areas.
I saw your web page and I have a question that has been driving a bunch of us crazy. Here's the question: If two people are directly across from each other on a merry-go-round or the roto ride at a carnival and one person throws a ball directly across to the other person, what happens?
Does the ball travel in a straight line, or will it curve? If the ball is thrown directly across towards the other person, will it pass through the center of the circle? If you throw the ball with very little force, will it come back to you? (If it comes back to you, then from an outside observer's point of view, it must curve).
What other strange things come into play when you do this? (We have been assuming no wind resistance, like it was in a vacuum.) Any response would be great.
Thanks,
David
You asked a great question here!
The ball would NOT pass through the center point. The ball would go off on an angle. The reason that that this would occur is because there is a vector component for sideways movement (perpendicular to the direction that you throw the ball). You can see this if you swing a rope with a weight on the end in a circle. If you suddenly let go, the rope and weight will take a straight path. Likewise if you spin very fast on a merry-go-round and let an object go, it will take a straight path and not a curved path like the rider. These are examples of the sideways vector component.
If a person is rapidly spinning on a merry-go-round and he throws a ball toward the center, it would have 2 directional forces acting on it: 1) the straight out force (throwing it to the center) and 2) the sideways force caused by the spinning (discussed above). Therefore the ball would not pass through the center but would pass somewhere between the center point and the side of the merry-go-round.
A movie called "Coreolis effect in daily life" shows an example of this situation. The URL is: http://covis.atmos.uiuc.edu/guide/forces/html/coriolis1.html . Please note that this movie example introduces another complicating factor; the element of friction when the ball rolls. If you throw the ball very gently, it would land on the floor of the merry-go-round and not come back to you. In the movie the ball returns to you due to the centrifugal force on the ball by the spinning carousel.
Real neat home page, Dr. Bob. However, I doubt that the beetle can shoot a "boiling hot" spray.
regards, Tony
I really appreciate your comments regarding my home page. I know that it sounds "far out," but bombardier beetles do indeed shoot out a "boiling hot" spray. Let me explain. They store two separate chemicals (hydroquinone and hydrogen peroxide) that are NOT mixed until threatened. When this occurs, the 2 chemicals are squirted through 2 tubes where they are mixed (along with a small amount of another chemical called an anti-inhibitor). When these chemicals mix, they undergo a violent "exothermic" (as we chemists call it) chemical reaction. The temperature of the resultant gaseous mixture exceeds 210 degrees F.
I know it sounds hard to believe, but it is true and Interesting Science Stuff at its best. I will add this additional information to the article.