# Physics

Physics is the natural science that studies matter, its motion and behavior through space and time, and the related entities of energy and force. Physics is one of the most fundamental scientific disciplines, and its main goal is to understand how the universe behaves. https://en.wikipedia.org/wiki/Physics

## Signals

A signal is usually defined as:

In electronics, a signal is an electric current or electromagnetic field used to convey data from one place to another. The simplest form of signal is a direct current (DC) that is switched on and off; this is the principle by which the early telegraph worked. More complex signals consist of an alternating-current (AC) or electromagnetic carrier that contains one or more data streams. https://searchnetworking.techtarget.com/definition/signal

Sound, images and videos are also considered to be signals. https://en.wikipedia.org/wiki/Signal#Classification

It is not clear if a signal must be a function of time/space; or if it can be of any other parameter.

It is neither clear if the signal is the physical phenomenon (for example, the seismic wave) or the functional representation of the physical phenomenon (the seismogram).

### Signal analysis - Signal processing

One of the applications of Mathematical analysis (Calculus in particular) is for Signal processing. When processing signals, such as audio, radio waves, light waves, seismic waves, and even images, Fourier analysis can isolate individual components of a compound waveform, concentrating them for easier detection or removal. A large family of signal processing techniques consists of Fourier-transforming a signal, manipulating the Fourier-transformed data in a simple way, and reversing the transformation. https://en.wikipedia.org/wiki/Mathematical_analysis#Signal_processing

• Seismic processing
• Time-frequency analysis in Seismic processing:
A set of mathematical formulas used to convert a time function, such as a seismic trace, to a function in the frequency domain (Fourier analysis) and back (Fourier synthesis). The Fourier transform is used extensively in signal processing to design filters and remove coherent noise. Many filtering operations are performed in the frequency domain. The Fourier transform has applications in image analysis and in pattern recognition in geological systems. https://www.glossary.oilfield.slb.com/en/Terms/f/fourier_transform.aspx#:~:text=A%20set%20of%20mathematical%20formulas,and%20back%20(Fourier%20synthesis).&text=The%20Fourier%20transform%20is%20used,filters%20and%20remove%20coherent%20noise.

## Relativity and the nature of time

 Theory of relativity 1879 14 March Albert Einstein's birth 14 March 1879, Ulm, Kingdom of Württemberg, German Empire - 18 April 1955 (aged 76), Princeton, New Jersey, United States

## The history of understanding the Atom

 The history of understanding the Atom Fifth Solvay Conference