mercury (inHg) or in millibars (mb). On average, the air pressure at

ay have experienced the impacts of less dense air at higher elevations. If you usually live, work, and recreate at lower elevations, you might find yourself getting short of breath while doing some of those same things at higher elevations. You may even get a headache or feel sluggish. This is because the molecules are further apart, resulting in air that is less dense, or “rarified”. Although you are filling your lungs, you still are not getting as many oxygen molecules in.

August 16:

Earth revolves around the Sun every 365.25 days, which we consider to be one year. This orbit is not a perfect circle as we might imagine; it is actually an elliptical orbit (Figure 3.2). In one revolution, Earth travels approximately 940 million kilometers (584 million miles)! Because Earth is traveling in an elliptical orbit, it is closer to the Sun on or around January 3 (known as perihelion) than it is on or around July 4 (known as aphelion). At perihelion, Earth is 147.5 million kilometers (approximately 91 million miles) from the Sun and at aphelion Earth is 152.6 million kilometers