BIO 600 Class 1

Science Misconceptions QUESTION 1: FALSE A widely held misconception in life science is that deoxygenated human blood, the blood returning to the heart and lungs in veins, is blue. After all, when we look at the blood vessels in our arms, legs, and hands, they look blue. Shouldn't it be because the blood inside them is blue? It's not quite that simple. First, are we sure that the vessels we're seeing through the skin are veins? Could they be arteries carrying oxygen-rich blood? If that's the case, shouldn't they look bright red? Some very small ones do look bright red--they're the tiny blood vessels near the skin's surface. And there's our clue. When we look at larger blood vessels not so near the skin surface, such as the ones we can see on our arms and hands, the light allowing us to see is refracted by the skin and vessel walls, causing the vessels to take on a bluish color. So we think of the blood inside the vessels as being blue.

Science Misconceptions QUESTION 2: FALSE A common misconception is that the Earth's proximity to the sun gives us the seasons. Because it is warmer in the summer than in the winter, it is easy to see how one would think that the Earth must be closer to the sun during the summer. In fact, the distance between the Earth and the sun doesn't really change all that much throughout the year. The orbit of the Earth around the sun is a slight ellipse. Textbook diagrams, however, typically show an exaggerated ellipse as in Figure 1. So what is the cause of the Earth's seasons? It's the tilt of the Earth on its axis. The tilt of the Earth is constant throughout the year at 23.5° from perpendicular. During summer in the United States, the northern hemisphere is tilted toward the sun and receives more direct rays from the sun. During winter in the United States, the southern hemisphere is tilted toward the sun receiving the more direct rays. That is why seasons in the northern and southern hemisphere are always the opposite of one another.

Science Misconceptions QUESTION 3: True This statement is true, but be careful. It's easy to state this fact without a clear picture of how atoms and molecules are arranged in matter. A common misconception surrounding this concept is that matter is continuous, that there are no spaces between atoms and molecules. According to this faulty theory, when air in a balloon heats up, for example, the balloon expands because the molecules of gas get bigger filling up the space. In actuality, as molecules of gas are heated, they gain energy. With increased energy comes increased activity, and the molecules are able to move farther apart. Gas molecules will continue to move in one direction until they encounter a barrier such as another molecule or the wall of the balloon. Energized gas molecules move at a faster rate and strike barriers with more force. The energized gas molecules in the balloon strike the walls of the balloon with more force, causing the balloon to expand. One of the best ways to debunk the idea of continuous matter is to revisit one of the most fundamental characteristics of gases--that they expand to fill their container (without any change in temperature). If it is thought that there are no spaces between atoms, then how are they able to expand? Expansion would require additional space between molecules, so we know the theory is a misconception.

Science Misconceptions QUESTION 4: FALSE This statement is a misconception. The term "weightlessness" is more accurately described as microgravity, where objects are in a continuous freefall pattern. Astronauts are constantly in two-dimensional motion (that which occurs along the x-axis while also occurring along the y-axis). We know that for every movement in the x-direction there is a corresponding movement in the y-direction. To understand how this affects astronauts in space, let's first consider motion on the Earth, in which the y-direction is dictated largely by the pull of gravity. When you throw a ball, it doesn't reach its peak and drop straight down; it curves back toward the Earth because motion is still occurring in the x-direction. Eventually the ball does hit the ground. However, in space, the object (in this case the astronaut) continues to fall in the y-direction because the surface of the Earth is constantly curving away from him or her, allowing additional motion. The velocity of the space shuttle in the x-direction perpetuates this motion so a continual "free fall" is experienced and the astronaut seems to be weightless although gravity continues to act on him or her. To understand this concept, we need to remember there is gravity in space. In fact, according to Newton's Law of Universal Gravitation any two masses exert force on one another. It is this attraction, or "pull," between the spacecraft and the Earth that keeps the spacecraft traveling in an orbit.