Owls have tubular eyes that are fixed in the sockets. This gives them excellent night vision, but means they must turn the whole head to look around.
Barn owls have one of the largest ranges of any land bird.
The human skull attaches to the spine at the bottom instead of the back. This allows the brain case to grow very large.
The human body is among the most energy efficient designs for long distance walking in the animal kingdom.
The human hand is the perfect design for making a rigid, solid fist. Our hands have evolved to be both weapons and tools.
Human bone is very lightweight to save energy. Apes have much stronger bones, but they have much heavier skeletons.
The femur is the longest bone in the human body, but the skull bones are the strongest.
In some media, such as acrylic, a particle beam will briefly travel faster than light, since the light is slowed down by the air/acrylic interface. This produces a soft blue light, and a shower of sparks that crack the material.
Air is an excellent insulator, but a sufficient voltage potential can ionize it into plasma. This plasma is a great conductor of electricity.
If you had a sufficiently powerful laser, you could create a channel of ionized air that would conduct electricity. You could use this to transmit power without wires, but the efficiency would be low.
There is some evidence to suggest that the Ancient Babylonians created primitive voltaic cells millennia ago. However, at the time of this writing this is still conjecture.
There are fundamental limits to the storage capacity of a useful battery. As you pack more and more energy into a smaller space, the risk of a catastrophic discharge become higher. While super high density batteries can be built, there are numerous safety concerns.
Resistance in most metals drops to nothing around absolute zero. Some ceramics can maintain zero resistance up to the temperature of liquid nitrogen. This property is called superconductivity.
A high resistance is sometimes valuable, as in the case of electric heaters.
Plastics and ceramics have the highest resistances of materials, and are often used as electrical insulators.
Diamonds make excellent electrical insulators and excellent conductors of heat.
Neodymium is a rare earth metal. When alloyed with other metals, usually nickel or cobalt, it forms extremely strong permanent magnets. These are currently the strongest magnets yet invented.
Electromagnets depend on a current to maintain the magnetic field. The advantage is they can be turned on and off as needed, unlike permanent magnets. The disadvantage is they require a constant supply of electricity.
The right hand rule can be used to electromagnetically accelerate a projectile placed between two conductive rails. Attempts have been made to weaponize this effect, but the amount of electricity required to accomplish the task ends up destroying the gun through heat.
Nikola Tesla invented a high frequency coil that could transmit electricity without wires. While this is obviously very convenient, the efficiency is very low. Tesla ran out of funding before he could improve his design.
Tesla coils have found use in generating high frequency current to check metal pipes for cracks. Beyond that, they remain mostly scientific curiosities.
Convection is one of the three methods of heat transport, the other two being conduction and radiation. It occurs only in fluids. As a part of a fluid is heated, it becomes less dense, and thus floats upwards, carrying heat with it.
Convection currents are highly desirable in cooking, since they stir the food all by themselves.
All mechanical devices are amalgamations of simple machines arranged in a certain way. For example, a car is a system of pulleys, wheels, and levers, admittedly in a very complex arrangement.
The wheel and lever are arguably the most important machines ever invented, even to this day.
Gyroscopes attain their stability by generating large amounts of angular momentum, which is the momentum of a mass moving around a central point. It takes a lot of energy to change the orientation of the spinning mass, hence the stability.
A pendulum's period, or the time it takes to swing, is dependent on the length of the string, not the mass of the bob.
A pendulum can never rise higher than the initial starting point. If you hold a lead brick against your chin and let it swing, you are perfectly safe.
Gasses cannot be compressed indefinitely, because eventually the atoms themselves will press into each other.
As you compress a gas, it gets hotter. Compress enough hydrogen together, and it will get hot enough to fuse.
The pressures inside gun barrels routinely exceed 40,000 psi. The barrel does not shatter because the expanding gas escapes through the muzzle, taking the bullet with it.
Some materials, like water and bismuth, have a curious property: the solid form will float in the liquid form.
Granular solids can behave somewhat like fluids, but they are not. For example, sand can be poured, but is still a solid.
Water attains its greatest density while still in liquid form. Thus, the water at the bottom of the sea is unable to freeze or boil, due to the enormous pressures on it. It can still be carried upwards by convection though.
The size of a mole of a certain substance depends greatly on how closely the atoms are packed together. Thus, a mole of iron will be many times smaller than a mole of hydrogen at STP.
A diffraction grating is a clear film with opaque lines placed on it very close together, like a picket fence. If the spacing is similar to the wavelength of light, the light can't get through uniformly and will be split.
If you take a clear substance and laminate many layers together, with each layer being one wavelength of light thick, it will produce an iridescent pattern. This is why mother of pearl and oil slicks have a rainbow sheen.