Archive for August, 2010

What do snakes eat?

This is a very generic question, but one that actually gets asked quite frequently.  Of course, the short answer is that snakes have a varied diet, depending on factors such as their species, size, age, geographic locale, etc. A fairly accurate answer for what most snakes eat might be: insects, worms, lizards, birds, small amphibians such as frogs and salamanders, and small mammals such as rats, mice and voles. But even this answer could vary depending on a location. A common garter snake that lives in a wooded area near a pond will likely eat more frogs than the garter snake found in your backyard which might live entirely on insects and the occasional mouse.

The more interesting answer is to the question: what do some of the larger more exotic snakes eat? Some snakes primarily eat other snakes (the bandy-bandy of Australia). Some snakes eat mostly the eggs of other animals (see image above). And some of the larger snakes such as pythons and other constrictors will eat small mammals when young and begin to eat larger animals such as pigs, monkeys and deer as they mature.

What was the largest dinosaur?

It is believed that the Brachiosaurus is the largest dinosaur that ever lived. It is also the largest species in which a whole skeleton has been discovered. This skeleton is in the Humboldt Museum in Berlin and measures 73 feet long and 46 feet tall. Its estimated weight is 35 tons, or about 70,000 pounds. Read more…

How dense is matter inside a black hole?

First, the simplest definition of density: it is how heavy something is relative to its size. A pound of rocks weighs the same as a pound of ping pong balls. But the ping pong balls take up a lot more space. Hence, the rocks are much more dense. Another way to look at density is to think of it as a measure of the “compactness” of matter.

More background… at the center of an atom is a very dense core called the nucleus. It’s composed of protons and neutrons (held very tightly together). Surrounding this nucleus in somewhat of a cloud are the electrons. Atomically speaking, the electrons are very far apart and far from the nucleus. Consider this: the entire atom composed of an electron cloud surrounding the nucleus is about 99.9% empty space.

The electrons are negatively charged and repel anything else negatively charged with a very strong electromagnetic force, or EMF. Now imagine a force strong enough to overcome this EMF and compress atoms to a much greater density. This is what happens in old and dying stars– the compressing force of gravity starts to overcome this electromagnetic force. The atoms start squeezing together resulting in what’s called degenerate matter. Stars involved in this process are called white dwarfs and the matter in them can reach a density of one million times that of water.

While this is very dense, it is not the densest state that matter can reach. If the dying star is massive enough, its gravitational force can be powerful enough to overcome the repelling force in the degenerate matter. The center of this body is now called neutronic fluid and these stars are now called neutron stars or pulsars. Now we’re getting pretty dense. A 1cm cube of neutron star material would weigh 100 million tons and if dropped would fall straight through to the center of the earth.

Now for even bigger stars (more than three times the mass of our sun), it can have a gravitational force strong enough to break down even this neutronic matter. After this, there will be no barrier left. The matter can not compress any further and it is basically a single point called a singularity. A star that has collapsed into itself to this point is called a black hole.

Since there is no way to measure anything of this magnitude, estimates are made by estimating the matter outside and near this singularity. If we use matter on Earth as a first order of magnitude, degenerate matter (inside white dwarfs) is about one million times as dense. Neutronium (inside neutron stars) is about one trillion times as dense. And finally, black holes, which are about ten trillion times as dense.

Source: Why Nothing Can Travel Faster than Light. Contemporary Books, 1993.

How does the Tickle Me Plant work?

Mimosa pudica (also known as the “sensitive plant” or “Tickle Me plant”) is well known for its rapid leaf movement. In the evening the leaflets will fold together and the whole leaf droops downward. It then re-opens at sunrise. This type of movement is called nyctinastic movement. The leaves also close up under various other stimuli, such as touching, warming, or shaking (hence the name, Tickle Me plant).

The stimulus can also be transmitted to neighboring leaves. The scientific term for these are seismonastic movements. The movement is caused by “a rapid loss of pressure in strategically situated cells that cause the leaves to droop right before one’s eyes”. [Wikipedia] This characteristic is quite common within the Mimosaceae family. Gradual loss of pressure can also cause the plant to close its fronds as is sometimes the case when it is exposed to a strong wind, rain or sunlight.

Why the plant’s leaves close up when exposed to these external stimuli is most likely an evolutionary response. As the leaves fold down, sharp thorns are exposed and would make the plant less tasty for herbivore animals that might want to eat them.

Why do stars twinkle?

Actually, the intensity of the stars themselves doesn’t fluctuate, rather it is the light they emit that appears to brighten and dim as it passes through the air in our earthly environment. Were you to look at the stars from an airless environment, say the moon, you would see them as solid luminous points of light.

So why does the air make them appear to twinkle? Basically, our atmospheric air is constantly moving, with warm air masses constantly rising and cool ones sinking. The densities of these masses is different and thus the refractive (light bending) characteristics are also different. So when starlight passes through thinner air, then thicker, then thinner again, it bends accordingly and appears to shimmer.

Now you may wonder, if light passing through our atmosphere refracts like this, why don’t planets seem to twinkle? It’s because the planets are much much closer to Earth than are the stars. We actually see planets as tiny disks rather than single points of light. The light from planets will still be bent, but since we see it as a “disk,” it is made up of many points of light. Each of them may brighten and dim as they pass through our atmosphere, but the average intensity of these points of light is fairly constant.

Source: How Come? by Kathy Wollard.

How fast do fingernails grow?

In adults, they grow about 0.02 inches a week, or about 0.9 inches per year. For some it may seem like they grow much faster than that, and for some they probably do. Fingernails and toenails grow faster in younger people than in older. Read more…

What is radioactive half-life?

The half-life of a substance is the time it takes for the number of radioactive nuclei to decrease to one half of the original number. The halflife of a given isotope is always the same, meaning it doesn’t matter how many you have at any given time. Read more…