Have you ever wondered why temperatures are cooler in the winter and warmer in the summer? This happens because the Earth’s axis is tilted. The Earth remains tilted as it revolves around the sun. Because of this tilt, different locations on the Earth receive different amounts of solar radiation at different times of the year. The amount of solar radiation received by the Earth or another planet is called insolation. The angle of insolation is the angle at which the sun’s rays strike a particular location on Earth. When the north end of the Earth’s axis points toward the sun, the Northern Hemisphere experiences summer. At the same time, the south end of the axis points away from the sun and the Southern Hemisphere experiences winter.

In this experiment you will investigate the relationship between angle of insolation and temperature change due to energy absorption from a simulated sun—a light bulb.

When you think of pH, you probably think of liquid acids and bases. But soil can be acidic or basic, too. Soil pH, sometimes referred to as soil acidity, can be expressed using the pH scale. The pH scale ranges from 0 to 14. Soils with pH above 7 are basic or sweet. Soils with pH below 7 are acidic or sour. A soil with a pH of 7 is neither acidic nor basic, but is neutral.

The pH of soil is an important factor in determining which plants will grow because it controls which nutrients are available for the plants to use. Three primary plant nutrients – nitrogen, phosphorus, and potassium – are required for healthy plant growth. Because plants need them in large quantities, they are called macronutrients. They are the main ingredients of most fertilizers that farmers and gardeners add to their soil. Other nutrients such as iron and manganese are also needed by plants, but only in very small amounts. These nutrients are called micronutrients.

The availability of these nutrients depends not only on the amount but also on the form that is present, on the rate they are released from the soil, and on the pH of the soil. In general, macronutrients are more available in soil with high pH and micronutrients are more available in soil with low pH. Figure 1 shows the effect of pH on the availability of nutrients in the soil.

It depends. Do you mean geographic north or magnetic north? The geographic (true) north pole is the point at 90° N latitude. It is aligned with the rotational axis of the Earth. The Earth is surrounded by a magnetic field with a north and south magnetic pole. The magnetic north pole is the point to which a compass needle points. It is currently in northern Canada, but moves at an average rate of 15 km per year due to complex fluid motion in the outer core of Earth. Depending on your location, the difference between magnetic north and geographic north, called magnetic declination, can range from 0° to 30°.

In Part I of this experiment, you will measure the magnetic field of the Earth. You will use this data to determine magnetic north. Knowing the direction of true north, you will calculate the magnetic declination at your location. In Part II you will measure the magnetic inclination of your location.