• Earth is usually depicted as round in shape, but it is actually an oblate spheroid—meaning it’s roundish, but bulges in the center, at the equator. This is due to the centrifugal force of Earth’s rotation.
• One hundred tons of space dust falls to Earth every day.
• With a radius of 763 miles (1,228 km), the innermost core of Earth is about the size of our moon and is comprised mostly of a solid iron-nickel alloy. The outer core, with a radius of 1,408 miles (2,226 km), is liquid. The outer core is crucial to the processes that produce Earth’s magnetic field.
• For a sense of proportion, Earth’s total radius is 3,959 miles (6,371 km).
• Earth’s mass is known to be approximately 13,173,000,000,000,000,000,000,000, which is about 13 septillion pounds! That’s approximately 6,000,000,000,000,000,000,000,000 (6E+24) kg. Or, more specifically: 5.98x10^24 kg. [Source: NASA].
• Earth’s atmosphere, which is rather thin, is a mixture of 78% nitrogen, 21% oxygen, 0.9% argon, 0.03% carbon dioxide, and trace amounts of other gases. That said, it’s thick enough to insulate us from extreme temperature fluctuations and to block much of the Sun’s damaging—and potentially lethal—ultraviolet radiations (better known as UV rays).
• Approximately 70% of Earth’s surface is ocean, and the remaining 30% of Earth’s surface is land, which is why Earth is often called the “Blue Planet.”
• Earth’s only known natural satellite is the Moon.
• What’s in a name? In Greek mythology, Earth—whose Greek name was Gaea—was the mother of the mountains, valleys, streams, and all other terrestrial formations and she was the wife of Uranus. The word “earth” comes from the Old English word eorthe, which means “ground.” Remember, to ancient peoples, Earth wasn’t a planet, she was the very ground we walked upon.
Earthquakes
• The largest recorded earthquake in the world to date had a magnitude 9.5 (Mw) and occurred in Chile on May 22, 1960.
• The largest recorded earthquake in the United States to date had a magnitude 9.2 and struck Prince William Sound, Alaska, on March 28, 1964, which was Good Friday. Not such a good Friday.
• Before electronics, scientists built large spring-pendulum seismometers (like, 15 tons large!) in an attempt to record the long-period motion produced by such quakes. There’s one three stories high in Mexico City that’s still in operation!
• There is no such thing as “earthquake weather.” Statistically, there’s an equal distribution of earthquakes in all types of weather, including cold weather, hot weather, and rainy weather.
• The San Andreas Fault is NOT a single continuous fault, but rather is actually a fault zone made up of many segments.
• Aristotle (circa 350 BC) wrote about earthquakes! He recognized that “soft ground shakes more than hard rock.”
• In 1760, a British engineer named John Michell—one of the first fathers of seismology—accurately wrote in his memoirs that “shifting masses of rock miles below the surface” and the waves of energy they make cause earthquakes.
• Each year, the southern California area has about 10,000 earthquakes. Most of them are so small they’re not felt.
• About 90% of the world’s earthquakes occur in the Pacific Ocean’s Ring of Fire. [See Tsunamis.]
• From 1975 to 1995 there were only four states in the U.S. that didn’t have any earthquakes! They were Florida, Iowa, North Dakota, and Wisconsin.
• The hypocenter of an earthquake is the location beneath Earth’s surface where the rupture of the fault begins.
• The epicenter of an earthquake is the location directly above the hypocenter on the surface of Earth.
Echinoderms
• Echinoderms are a phylum of marine animals that include sea stars (starfish), brittle stars, sand dollars, sea urchins, sea cucumbers, and crinoids.
• When a sea cucumber is attacked, it may expel some of its internal organs! This may satisfy the predator or scare it off. The sea cucumber then grows another set of organs. (How awesome and really disgusting!)
• Sea stars have the amazing ability to regenerate limbs that have been severed or damaged.
• Echinodermata are the largest phylum without any freshwater or terrestrial forms. There are upward of 7,000 living species of Echinodermata and approximately 13,000 species of echinoderms that are known to be extinct, based upon fossil records.
• The word “echinoderm” derives from the Greek word echino—meaning “spiny”—and derm, meaning “skin.”
• All echinoderms have radial symmetry. This means their appendages point outward from the center, like the spokes on a bike’s wheels.
• For achieving locomotion, food and waste transportation, and respiration, echinoderms have hydraulic-pressured water vascular systems!
• The common sea urchin, or European edible sea urchin (Echinus esculentus), has been designated “near threatened” on the IUCN Red List of Threatened Species.
Electricity
• While electric current is measured in amperes (amps), electrical potential energy is measured in volts.
• AC/DC: The electrons of AC power—which stands for “alternating current”—have electrons that move back and forth. The electrons of DC power—which stands for “direct current”—move in a single direction.
• Nikola Tesla helped invent AC power, and Thomas Edison helped invent DC power. AC power is safer and can be used over longer distances. The electricity use in homes is AC; batteries use DC.
• The world’s biggest source of energy comes from coal. In the United States, coal accounts for about 42% of the four trillion kilowatt hours of electricity generated. After coal, the world’s biggest sources of energy come from natural gas (25%), nuclear power (19%), hydropower (8%), wind power (3%), and biomass (1%). Propane, geothermal, and solar power each provide less than 1% of the world’s energy.
• In the United States, most of the energy used in homes is for space heating (41%), followed by electronics, lighting, and other appliances (26%), water heating (20%), air-conditioning (8%), and refrigeration (5%).
• Due to the longer heating seasons, the Northeast and Midwest regions of the United States consume the most energy per household, at 123 and 110 million Btu (British thermal units) per household, respectively. The world per capita consumption of energy averages about 81 million Btu.
Energy
• Named after James Prescott Joule, the Standard International (SI) unit of measure for energy and work is called the “joule” (J).
• There are two types of energy:
• Stored (potential) energy
• Working (kinetic) energy
• Energy comes in many forms, including heat (thermal), light (radiant), motion (kinetic), electrical, chemical, nuclear, dark, and gravitational.
• The United States Energy Information Administration (EIA) estimates that of the annual world energy consumption of 500+ quadrillion Btus, only about 10% is gleaned