SCIENCE QUESTIONS AND ANSWERS

What are stem cells?

Stem cells, the basic building blocks of human development, are sometimes called “magic seeds.” That’s because they can regenerate human tissue of various kinds. The use of stem cells is controversial because the best source for the cells is human embryos. Stem cells form four to five days after an egg is fertilized. These embryos must be destroyed to harvest the cells, and those opposing the research consider this the same as taking human life. Those who support stem cell research say that an embryo that is just a few days old is simply a miniscule cluster of cells and not the same as a human life. They maintain that stem cells have the potential to save human lives. Stem cells show promise in being able to one day be able to treat and cure many illnesses and diseases, such as Alzheimer's, diabetes, Parkinson's, spinal cord injuries and other medical conditions.

Why do stars twinkle?

We see the stars through the atmosphere. Their light passes through millions of miles of constantly moving pockets and streams of air, which distort the image of the stars. Even though many stars are much larger than planets, they're so far away from us that they seem smaller, like tiny dots. The distortions make it seem as if the shining lights are moving or blinking. In outer space, where there is no atmosphere, stars don't twinkle.

What causes thunder?

When a bolt of lightning shoots through the atmosphere, it heats the air to an amazing 50,000 degrees Fahrenheit in a fraction of a second. The superheated air rapidly expands, cools and then contracts, causing shock waves. These shock waves create sound waves, which we hear as thunder.

Why don't the oceans freeze?

In the Arctic and Antarctic, the oceans do freeze. The ice cap at the North Pole is entirely over ocean; the ice, however, is only a few feet deep. Oceans don't freeze solid for because they contain a lot of water, which is constantly circulating around the world. In addition, water flowing from warmer oceans (and from areas near underground volcanoes) takes off some of the chill. Another important factor is that oceans contain salt water, which has a higher freezing point than fresh water.

Why do boats float?

A steel bar dropped into water sinks, but a huge boat made of steel floats. Why? Most of the space in the boat is taken up by air. The air makes the boat less dense than water. Objects of lesser density float on liquids of greater density. This is also why holes in the bottom of a boat cause it to sink: as air floods out of the boat and water rushes in, the overall density of the boat increases to become more dense than the surrounding water.

What's the difference between bacteria and virus?

Bacteria are tiny, one-celled living organisms that can only be seen with a microscope. They live and breed in warm, moist environments in the body and elsewhere, growing quickly and causing infection. Bacterial infections can usually be treated with an antibiotic. Viruses are smaller than bacteria and cannot be seen with a microscope. They grow inside the body and produce toxins (poisons) that can cause rashes, aches and fevers. Viruses cannot be killed with antibiotics.

Why do I have brown eyes?

The genes we inherit from our parents determine things like our height, looks, hair color and eye color. This passing of characteristics from parent to child is called heredity. If your mother has brown eyes, and your father has blue eyes, there’s a good chance you’ll have brown eyes. That’s because the brown-eye gene is dominant, and the blue-eye gene is recessive. The dominant gene usually prevails over the recessive one. It’s possible, however, for you to have blue eyes if both your parents have brown eyes. They probably inherited recessive blue-eye genes from their parents and passed them on to you.