Excerpted from Wikipedia
Source: http://en.wikipedia.org/wiki/Physics
Date: 08-Dec-2014
Physics (from Ancient Greek: φυσική (ἐπιστήμη) phusikḗ (epistḗmē) “knowledge of nature”, from φύσις phúsis “nature”) is the natural science that involves the study of matter and its motion through space and time, along with related concepts such as energy and force. More broadly, it is the general analysis of nature, conducted in order to understand how the universe behaves.
Physics is one of the oldest academic disciplines, perhaps the oldest through its inclusion of astronomy. Over the last two millennia, physics was a part of natural philosophy along with chemistry, certain branches of mathematics, and biology, but during the Scientific Revolution in the 17th century, the natural sciences emerged as unique research programs in their own right. Physics intersects with many interdisciplinary areas of research, such as biophysics and quantum chemistry, and the boundaries of physics are not rigidly defined. New ideas in physics often explain the fundamental mechanisms of other sciences while opening new avenues of research in areas such as mathematics and philosophy.
Physics also makes significant contributions through advances in new technologies that arise from theoretical breakthroughs. For example, advances in the understanding of electromagnetism or nuclear physics led directly to the development of new products that have dramatically transformed modern-day society, such as television, computers, domestic appliances, and nuclear weapons; advances in thermodynamics led to the development of industrialization, and advances in mechanics inspired the development of calculus.
My Own Writing
Basic Principles of Physics
Matter is anything that has mass.
Mass is anything that can be influenced by a gravitational field.
Energy is the capacity to do work.
There are four known forces in nature: gravity, electromagnetism, the strong force (which binds protons and neutrons in atomic nuclei) and the weak force (which causes radioactive decay).
The speed of light is 186,000 miles (or 300,000 kilometers) per second.
Nothing can be accelerated past the speed of light. Thus, if an object is moving slower than light, it can never be made to go faster than light. Conversely, if an object is travelling faster than light, it can never be made to go slower than light.
Splitting the constituent protons and neutrons of an atomic nucleus is called atomic fission. Driving two atomic nuclei together is called atomic fiusion. Both reactions result in an enormous amount of energy as a byproduct.
Matter and energy can be interconverted. One unit of matter can be converted into one unit of energy, times the speed of light squared.
As an object approaches the speed of light, the passage of time slows down for the traveler. This effect is called time dilation.
As an object approaches the spped of light, it increases in mass.
Force is mass times acceleration.
Acceleration is any change in velocity.
Velocity is distance travelled per unit time.
Work is weight moved times distance over which it was moved.
Time Travel
Time travel into the past is unlikely because it violates the principle of causality. But (faster than normal) time travel into the future is possible because of the relativistic effect of time dilation, whereby time slows down for you as you move more quickly. So given a fast enough spaceship, you could go on a journey and return to Earth hundreds or even thousands of years in the future.
Gravity Waves
Even if direct detection of gravitons turns out to be impossible (as it very well might) that doesn’t necessarily mean it will be impossible to detect a passing gravity wave as it distorts space-time. For that, space-based laser interferometry is probably the best bet, as it would allow for relatively larger (i.e. several million km) and thus more sensitive arms in the detection array, avoid seismic noise, and operate in a near vacuum.
Space-Time
Einstein’s theory of general relativity predicts that extremely massive objects can bend the space–time around them and thus indirectly appear to bend the light traveling through them. This theory was confirmed in 1919 during a solar eclipse, when the light from stars passing close to the Sun was slightly bent, so that stars appeared slightly out of position.