We have just as much hair all over our bodies as chimpanzees or monkeys or any other furry primate. Most of it is just very short and light. It's called "vellus hair" or "peach fuzz". I think it's bizarre that most of our thick hair is on the tops of our heads. Imagine if dogs looked like that! On second thought, maybe it's better if you don't imagine that.
Research shows that we humans lost all our body hair through evolution about a million years before somebody finally figured out how to purchase clothes at one of the first primitive Walmarts.
One theory says that we lost our all body hair in an attempt to avoid parasites like ticks, fleas, and lice, and that we've only kept the hair on our heads because other people think it's pretty. As proof, consider that you haven't seen many bald pregnant women.
There is a very special kind of louse that only lives in human clothing. DNA tests indicate that it evolved from a louse that only lives in human hair, and that this happened about 42,000 to 72,000 years ago. So, that's probably roughly when clothes first went on sale. There are no special lice that live in any form of footwear, so DNA testing cannot solve the troubling mystery of exactly at what point in the past Hello Kitty themed socks were invented.
Space Shuttle
OK here is the deal with the space shuttle. It has three rocket engines in the
back, but there's absolutely no room inside for all the fuel it needs to launch itself up into space. All of that fuel is stored outside the shuttle, in the big brown cylinder, called the external tank.
The tank containing all the rocket fuel weighs seven times more than the space shuttle itself! That's a lot of really heavy fuel, and the space shuttle engines aren't quite strong enough to push the combined weight of the shuttle and the big bloated external tank up off the ground.
That's what the two long white solid rocket boosters strapped onto the sides of the external tank are for. They lift the tank! Fortunately, it was not necessary to strap an infinite series of smaller and smaller rockets to the sides of the solid rocket boosters.
It is not widely known that just behind the main flight deck of the space shuttle is a small Starbucks adapted for use in zero gravity.
Gravity
The force of gravity seems like a big deal when you have to get out of bed in the morning, or you're helping a friend move furniture around, or when somebody drops a bucket of rocks and gravy out of a window onto your head. However, compared to the other forces, gravity is pretty weak.
There are four known forces in the Universe. Two of them, the strong and weak nuclear forces, keep atoms from flying apart and stuff like that. You shouldn't be concerned about them unless you are a nuclear physicist. If anybody asks, you didn't hear about them from me.
The other two forces are electromagnetism and gravity. If you slam your hand on a table, electromagnetism is what keeps your hand from flying through the table into your lap. This force is widely credited with the success of the restaurant industry.
Gravity pulls you toward the center of the Earth, and keeps you from drifting up toward the ceiling and getting it dirty.
Incidentally, Deimos, one of the two moons of Mars, is so small ("only" two million billion kilograms), and consequently has such weak gravity, that if you were standing on it, and you jumped hard, you could easily achieve escape velocity and never land back down on the ground.
Electromagnetism is also generated by magnets, and causes metal objects to be attracted to each other. A hand-held magnet is strong enough to lift a small screwdriver off a table.
Think about what's happening with gravity in this situation. The electromagnetic force generated by the magnet is strong enough to lift the screwdriver up off the table, overcoming the force of gravity. But what's generating the gravitational force?
The whole Earth!
The Earth has a mass of six million billion billion kilograms, and yet its gravity isn't enough to overcome the magnetic force generated by a magnet whose mass is a small fraction of one kilogram.
I'm out of shape and I have a desk job, and I can overcome the gravitational force created by the mass of the entire Earth with my little finger. Gravity isn't all that impressive.
Mechanics
Weight (force of gravity) decreases as you move away from the earth by distance squared.
Mass and inertia are the same thing.
Constant velocity and zero velocity means the net force is zero and acceleration is zero.
Weight (in newtons) is mass x acceleration (w = mg). Mass is not weight!
Velocity, displacement [s], momentum, force and acceleration are vectors.
Speed, distance [d], time, and energy (joules) are scalar quantities.
The slope of the velocity-time graph is acceleration.
At zero (0) degrees two vectors have a resultant equal to their sum. At 180 degrees two vectors have a resultant equal to their difference. From the difference to the sum is the total range of possible resultants.
Centripetal force and centripetal acceleration vectors are toward the center of the circle- while the velocity vector is tangent to the circle.
An unbalanced force (object not in equilibrium) must produce acceleration.
The slope of the distance-tine graph is velocity.
The equilibrant force is equal in magnitude but opposite in direction to the resultant vector.
Momentum is conserved in all collision systems.
Magnitude is a term use to state how large a vector quantity is.
Energy
Mechanical energy is the sum of the potential and kinetic energy.
Units: a = [m/sec2], F = [kg•m/sec2] (newton), work = pe= ke = [kg•m2/sec2] (joule)
An ev is an energy unit equal to 1.6 x 10-19 joules
Gravitational potential energy increases as height increases.
Kinetic energy changes only if velocity changes.
Mechanical energy (pe + ke) does not change for a free falling mass or a swinging pendulum. (when ignoring air friction)
The units for power are [joules/sec] or the rate of change of energy.
Electricity
A coulomb is charge, an amp is current [coulomb/sec] and a volt is potential difference [joule/coulomb].
Short fat cold wires make the best conductors.
Electrons and protons have equal amounts of charge (1.6 x 10-19 coulombs each).
Adding a resistor in parallel decreases the total resistance of a circuit.
Adding a resistor in series increases the total resistance of a circuit.
All resistors in series have equal current (I).
All resistors in parallel have equal voltage (V).
If two charged spheres touch each other add the charges and divide by two to find the final charge on each sphere.
Insulators contain no free electrons.
Ionized gases conduct electric current using positive ions, negative ions and electrons.
Electric fields all point in the direction of the force on a positive test charge.
Electric fields between two parallel plates are uniform in strength except at the edges.
Millikan determined the charge on a single electron using his famous oil-drop experiment.
All charge changes result from the movement of electrons not protons (an object becomes positive by losing electrons)
Magnetism
The direction of a magnetic field is defined by the direction a compass needle points.
Magnetic fields point from the north to the south outside the magnet and south to north inside the magnet.
Magnetic flux is measured in webers.
Left hands are for negative charges and right hands are for positive charges.
The first hand rule deals with the B-field around a current bearing wire, the third hand rule looks at the force on charges moving in a B-field, and the second hand rule is redundant.
Solenoids are stronger with more current or more wire turns or adding a soft iron core.
Wave Phenomena
Sound waves are longitudinal and mechanical.
Light slows down, bends toward the normal and has a shorter wavelength when it enters a higher (n) value medium.
All angles in wave theory problems are measured to the normal.
Blue light has more energy. A shorter wavelength and a higher frequency than red light (remember- ROYGBIV).
The electromagnetic spectrum (radio, infrared, visible. Ultraviolet x-ray and gamma) are listed lowest energy to highest.
A prism produces a rainbow from white light by dispersion (red bends the least because it slows the least).
Light wave are transverse (they can be polarized).
The speed of all types of electromagnetic waves is 3.0 x 108 m/sec in a vacuum.
The amplitude of a sound wave determines its energy.
Constructive interference occurs when two waves are zero (0) degrees out of phase or a whole number of wavelengths (360 degrees.) out of phase.
At the critical angle a wave will be refracted to 90 degrees.
According to the Doppler effect a wave source moving toward you will generate waves with a shorter wavelength and higher frequency.
Double slit diffraction works because of diffraction and interference.
Single slit diffraction produces a much wider central maximum than double slit.
Diffuse reflection occurs from dull surfaces while regular reflection occurs from mirror type surfaces.
As the frequency of a wave increases its energy increases and its wavelength decreases.
Transverse wave particles vibrate back and forth perpendicular to the wave direction.
Wave behavior is proven by diffraction, interference and the polarization of light.
Shorter waves with higher frequencies have shorter periods.
Radiowaves are electromagnetic and travel at the speed of light (c).
Monochromatic light has one frequency.
Coherent light waves are all in phase.
Geometric Optics
Real images are always inverted.
Virtual images are always upright.
Diverging lens (concave) produce only small virtual images.
Light rays bend away from the normal as they gain speed and a longer wavelength by entering a slower (n) medium {frequency remains constant}.
The focal length of a converging lens (convex) is shorter with a higher (n) value lens or if blue light replaces red.
Modern Physics
The particle behavior of light is proven by the photoelectric effect.
A photon is a particle of light {wave packet}.
Large objects have very short wavelengths when moving and thus can not be observed behaving as a wave. (DeBroglie Waves)
All electromagnetic waves originate from accelerating charged particles.
The frequency of a light wave determines its energy (E = hf).
The lowest energy state of a atom is called the ground state.
Increasing light frequency increases the kinetic energy of the emitted photo-electrons.
As the threshold frequency increase for a photo-cell (photo emissive material) the work function also increases.
Increasing light intensity increases the number of emitted photo-electrons but not their KE.
Internal Energy
Internal energy is the sum of temperature (ke) and phase (pe) conditions.
Steam and liquid water molecules at 100 degrees have equal kinetic energies.
Degrees Kelvin (absolute temp.) Is equal to zero (0) degrees Celsius.
Temperature measures the average kinetic energy of the molecules.
Phase changes are due to potential energy changes.
Internal energy always flows from an object at higher temperature to one of lower temperature.
Nuclear Physics
Alpha particles are the same as helium nuclei and have the symbol .
The atomic number is equal to the number of protons (2 for alpha)
Deuterium () is an isotope of hydrogen ()
The number of nucleons is equal to protons + neutrons (4 for alpha)
Only charged particles can be accelerated in a particle accelerator such as a cyclotron or Van Der Graaf generator.
Natural radiation is alpha (), beta () and gamma (high energy x-rays)
A loss of a beta particle results in an increase in atomic number.
All nuclei weigh less than their parts. This mass defect is converted into binding energy. (E=mc2)
Isotopes have different neutron numbers and atomic masses but the same number of protons (atomic numbers).
Geiger counters, photographic plates, cloud and bubble chambers are all used to detect or observe radiation.
Rutherford discovered the positive nucleus using his famous gold-foil experiment.
Fusion requires that hydrogen be combined to make helium.
Fission requires that a neutron causes uranium to be split into middle size atoms and produce extra neutrons.
Radioactive half-lives can not be changed by heat or pressure.
One AMU of mass is equal to 931 meV of energy (E = mc2).
Nuclear forces are strong and short ranged.
SOME SCIENCE QUICK FACTS
Human Facts
1. If stomachs did not have a lining of mucus, your stomach would digest itself.
2. There are 60,000 miles of blood vessels in the human body.
3. It takes about 60 seconds for a human blood cell to make a complete circuit of the body.
4. The average person will shed 40 pounds of skin in his/her lifetime.
5. 1/15th of a pint of blood is pumped with every heartbeat.
6. Humans share 98.4% of our DNA with chimps. In comparison, we share 70% of our DNA with a slug.
7. The lightest baby to survive weighed a mere 283 grams.
8. On average, women say 7,000 words per day while men manage just over 2,000 words.
9. The human brain uses 20% of the body’s energy but is only 2% of the body’s weight.
10. On average, humans lose 40-100 strands of hair per day.
11. A sneeze can exceed the speed of 100mph.
12. A cough can reach the speed of 60mph.
13. The average person will drink about 16,000 gallons of water in his/her lifetime.
14. It takes 17 muscles to smile while taking 43 muscles to frown.
15. The human brain is composed of 75% water.
16. Human thigh bones are stronger than concrete.
17. More germs are transferred while shaking hands compared to kissing.
18. There are approximately 550 hairs in a person’s eyebrow.
19. The strongest muscle in the human body is the tongue.
20. A person produces 10,000 gallons of saliva in an average lifetime.
21. The hardest bone in the human body is the jawbone.
22. The number of eye blinks varies greatly from about 29 blinks each minute if you are talking to someone to only 4 blinks each minute if you are reading.
23. The average human blinks 25 times per minute.
24. A nail takes around 6 months to grow from base to the tip.
25. Each second 10,000,000 cells die and are replaced in your body.
26. Your liver performs over 500 functions in your body.
27. The average person spends 1/3 of their lifetime sleeping.
28. More germs are transferred when shaking hands than kissing.
29. The average person (from western culture) consumes 10 liters of alcohol per year.
30. Roughly 75% of people who play the radio in their car sing along to it.
31. Human thigh bones are stronger than concrete.
32. Your right lung takes in more air than your left one does.
33. The human brain is composed of 75% water.
34. 70% of the composition of dust in your home is made up of shed human skin and hair.
35. The tooth is the only part of the human body that can’t repair itself.
36. One human hair can support 3kg.
37. Humans are the only animals that cry tears and blush.
38. It takes the interaction of 72 different muscles to produce human speech.
39. If the normal one hundred thousand hairs on a head were woven into a rope, it could support a weight of more than twelve tons.
40. The fingernail grows about 1.5 inches per year.
41. The total amount of skin covering an adult human weighs 6 lbs.
42. The average person flexes the joints in their fingers 24 million times during a lifetime.
43. Each person inhales about seven quarts of air every minute.
44. On average, we breathe between 12 and 18 times a minute.
45. The average guy will grow about 27 feet of hair out of his face during his lifetime.
46. Approximately 1 out of 25 people suffers from asthma.
47. The average man sweats 2 1/2 quarts every day.
48. One out of every hundred American citizens is color blind.
49. An average person laughs about 15 times a day.
50. A human heart beats 100,000 times a day.
Animal Facts
1. Humpback whales create the loudest sound of any living creature.
2. A giant squid’s eyes have a diameter of 15 inches which are the largest of any animal.
3. 3 out of 10 Dalmation dogs suffer from hearing loss due to inbreeding.
4. The African Elephant has a gestation period of 22 months while a short-nosed bandicoot gestates for 12 days.
5. The mortality rate if bitten by a Black Mambo snake is over 95%.
6. A dog’s sense of smell is 1,000 times stronger than humans.
7. Hummingbird’s consume half of their weight in food daily.
8. A cockroach can survive for about a week without its head before dying of starvation.
9. The whale shark has over 4,000 teeth. Each tooth is only 3mm long.
10. Polar Bears are capable of jumping as high as 6 feet and can run as fast as 25mph.
11. The ‘crosshairs’ of gun sights were made of spider web filaments until the 1960′s.
12. Mosquitos are attracted most to the color blue.
13. The heart of a shrimp is located in its head.
14. Some frogs are able to be frozen and then thawed, and continue living.
15. A goldfish is the only animal that can see infrared and ultraviolet light.
16. A snail can sleep for 3 years.
17. There are 701 types of pure breed dogs.
18. The fastest bird, the spine-tailed swift, can fly as fast as 106mph.
19. A cow gives nearly 200,000 glasses of milk in her lifetime.
20. A newborn kangaroo is about 1 inch in length.
21. In 1872, a virus epidemic killed a quarter of all the horses in the United States.
22. A woodpecker can peck 20 times per second.
23. An electric eel can produce a shock of up to 650 volts.
24. Camels have three eyelids to protect themselves from blowing sand.
25. Cojo, the 1st gorilla born in captivity, was born at the Columbus, Oho Zoo in 1956 and weighed 3 1/4 pounds.
26. Dragonflies are one of the fastest insects, flying 50 to 60 mph.
27. Every year, $1.5 billion is spent on pet food. This is four times the amount spent on baby food.
28. It takes a lobster about seven years to grow to be one pound.
29. Large kangaroos can cover over 30 feet with each jump.
30. Of all known forms of animals life ever to inhabit the Earth, only about 10 percent still exist today.
31. On average, pigs live for about 15 years.
32. Sharks apparently are the only animals that never get sick. They are immune to every type of disease including cancer.
33. A chameleon’s tongue is twice the length of its body.
34. Male seahorses produce offspring.
35. Giraffes have no vocal cords.
36. Elephants have been known to remain standing after they die.
37. An albatross can sleep while flying.
38. A mosquito has 47 teeth.
39. Research indicates that mosquitoes are attracted to people who have recently eaten bananas.
40. The sex organ on a male spider is located at the end of one of its legs.
41. Armadillos, opossums, and sloth’s spend about 80% of their lives sleeping.
42. The ears of a cricket are located on the front legs, just below the knee.
Space Facts
1. Saturn’s rings are made up of particles of ice, dust and rock. Some particles are as small as grains of sand while others are much larger than skyscrapers.
2. Jupiter is larger than 1,000 Earths.
3. The Great Red Spot on Jupiter is a hurricane-like storm system that was first detected in the early 1600′s.
4. Comet Hale-Bopp is putting out approximately 250 tons of gas and dust per second. This is about 50 times more than most comets produce.
5. The Sun looks 1600 times fainter from Pluto than it does from the Earth.
6. There is a supermassive black hole right in the middle of the Milky Way galaxy that is 4 million times the mass of the Sun.
7. Halley’s Comet appears about every 76 years.
8. The orbits of most asteroids lie partially between the orbits of Mars and Jupiter.
9. Asteroids and comets are believed to be ancient remnants of the formation of our Solar System (More than 4 billion years ago!).
10. Comets are bodies of ice, rock and organic compounds that can be several miles in diameter.
11. The most dangerous asteroids, those capable of causing major regional or global disasters, usually impact the Earth only once every 100,000 years on average.
12. Some large asteroids even have their own moon.
13. Near-Earth asteriods have orbits that cross the Earth’s orbit. These could potentially impact the Earth.
14. There are over 20 million observable meteors per day.
15. Only one or two meteorites per day reach the surface of Earth.
16. The largest found meteorite was found in Hoba, Namibia. It weighed 60 tons.
17. The typical size of a meteor is about one cubic centimeter, which is equivalent to the size of a sugar cube.
18. Each day, Earth accumulate 10 to 100 tons of material.
19. There are over 100 billion galaxies in the universe.
20. The largest galaxies contain nearly 400 billion stars.
21. The risk of a falling meteorite striking a human occurs once every 9,300 years.
22. A piece of a neutron star the size of a pin point would way 1 million tons.
23. Europa, Jupiter’s moon, is completely covered in ice.
24. Light reflecting off the moon takes 1.2822 seconds to reach Earth.
25. There has only been one satellite destroyed by a meteor, it was the European Space Agency’s Olympus in 1993.
26. The International Space Station orbits at 248 miles above the Earth.
27. The Earth orbits the Sun at 66,700mph.
28. Venus spins in the opposite direction compared to the Earth and most other planets. This means that the Sun rises in the West and sets in the East.
29. The Moon is moving away from the Earth at about 34cm per year.
30. The Sun, composed mostly of helium and hydrogen, has a surface temperature of 6000 degrees Celsius.
31. A manned rocket reaches the moon in less time than it took a stagecoach to travel the length of England.
32. The nearest known black hole is 1,600 light years (10 quadrillion miles/16 quadrillion kilometers) away.
Weather Facts
1. The fastest speed a falling raindrop can hit you is 18mph.
2. During a hurricane, 90% of the people who die end up dying from drowning.
3. The coldest temperature ever recorded was a negative 126.9 degrees fahrenheit in Vostok Station, Antarctica.
4. Between evaporation and falling as precipitation, a droplet of water may travel thousands of miles.
5. The typical lifetime of a small cumulus cloud is between 10 to 15 minutes.
6. A corn field of one acre gives of 4,000 gallons off water per day in evaporation.
7. A molecule of water will stay in Earth’s atmosphere for an average duration of 10-12 days.
8. Snowflakes falling at 2-4 mph can take about 1 hr to reach the ground.
9. For each minute of the day, 1 billion tons of rain falls on the Earth.
10. At any given time, on average there are about 1800 thunderstorms occurring on earth with 100 lightning strikes per second.
11. Lightning bolts can travel 60 miles.
12. A lightning bolt travels at about 14,000mph and brings 300,000 volts of electricity to the ground.
13. The air located around a lightning bolt is heated to around 30,000 degrees Celsius. This is 5 times hotter than the surface of the sun.
14. The chances of being struck by lightning is about one in three million.
15. The largest hailstone ever recorded in the United States was nearly the size of a soccer ball. It was a 7-inch wide chunk of ice.
16. Lightning sets about 10,000 forest fires every year in the United States.
17. In one day a hurricane can release enough energy to supply all of the nation’s electrical needs for about six months.
18. The highest temperature ever recorded in the United States was 134 degrees F at Greenland Ranch in Death Valley, California.
19. In 1899, it was so cold that the Mississippi River froze over its entire length.
20. The United States uses an estimated 10 million tons of salt each year to melt ice on the roads.
21. A cubic mile of ordinary fog contains less than a gallon of water.
22. An inch of rain water is equivalent to 15 inches of dry, powdery snow.
23. Every year in the US, 625 people are struck by lightning.
24. The average width of a tornado’s funnel averages about 100 to 200 yards but may be as wide as a mile.
Thank You
