Prior the recombination into atoms, the now visible matter of the universe consisted of electron-nucleus plasma. The nuclei in there were basically hydrogen (three fourth) and helium (one fourth). Their abundances were defined by the available number of protons … Continue reading
There are four parameters that govern the universe expansion. First, the energy density of relativistic particles mostly is that of Cosmic Microwave Background photons. This quickly falls as the space scale-factor grows so contributes to the expansion very little. … Continue reading
Supernova explosions are rather rare events so the last one seen by the naked eye in our galaxy was described by Johannes Kepler in 1604. For several months, that was the brightest star in the sky so one can … Continue reading
The simplest and the oldest way to measure distances to stars is the parallax method. This utilizes variation of the angle between a star and a benchmark direction as an observer changes its position in space, basically moving with … Continue reading
The zero-zero component of the Einstein’s equations for gravity with the metric of the expending universe is called the Friedman equation. We use this differential equation to calculate the behavior of the expending space. The equation includes two unknown functions … Continue reading
Nuclear fusion power should be much chipper an safer than that from uranium-plutonium fission. The fuel for the fission not only needs expensive mining but also enrichment by a fissile uranium isotope. Conversely, the fusion fuel, deuterium is readily … Continue reading
The speed of sound waves as well as the speed of light is not changed by the motion of a source of waves. For example, when a sound source moves towards a listener, each next vibration reaches the listener’s … Continue reading
The electric field strength of light waves coming from the Sun is of course oriented randomly. There were found some transparent compounds which allow a light wave to pass through only having definite direction of the wave field strength. … Continue reading
The first thing which the Newton second law failed to foretell were distances between electron possible orbitals in an atom. The electron’s energy spectrum appeared to be discontinuous so a novel equation had to give a set of discrete … Continue reading
Look, to know the exact value of some physical quantity you have to measure it using some instruments — devices made of artificial and natural materials. In the process of measurement, the material of instruments interacts with with the … Continue reading
Indeed, we can see stars and planets while particles of cosmic dust are only detectable since they change spectra of stars’ radiation reddening them. As light passes through interstellar cosmic dust, its particles absorb blue photons more than the … Continue reading
First of all, it was recently discovered that despite the temperature and matter density being cosmically low, chemical reactions at the surface of a dust particle can create organics that could be a cradle of life. Being glued up … Continue reading
Thanks Faraday we learned the change of magnetic flux through a conductor results in a circular current appearing in this conductor. The Lenz’s law defines such a direction of this current that magnetic field induced by the current compensates … Continue reading
Indeed, electrons undergo diffraction at a crystalline target. Therefore an electron beam hits a suitable crystal lattice, one can see on a screen an interference pattern typical for waves. The beam here is comprised of a lot of electrons … Continue reading
Electrons are tiny, so a nickel surface should reflect them at various angles since a sample of nickel consists of many randomly oriented small crystals. This is called the diffuse reflection. This is what Davisson and Germer thought in … Continue reading
What is light had always been mysterious for thinking people. Newton believed there are particles carrying light, explaining thereby why an obstacle in the light way creates a shadow on a screen. A century later, they discovered light is … Continue reading
It appears that periodical phenomena, e.g. waves are of utmost importance in nature. In practice, waves of different frequencies are superimposed so that the resulting periodical phenomenon is not of sinusoidal shape. Then, how can we deal with them … Continue reading
Perception by ear (listening) is easy for someone while for others it is difficult to understand what is said in a foreign language, even though all the words are known to the listener. He/she just does not recognize them. … Continue reading
You know, electromagnetic waves bring information from the early Universe as well as provide the information exchange between our smartphones. In physics, to mathematically describe waves, we use so called complex exponential function. Its exponent includes an imaginary unit. … Continue reading
Precision here implies repetition of measurement to minimize deviation of the average result of the measurements from the expected value of physics quantity. Such deviation is normally caused by random (stochastic) errors. Nonetheless, this average value may still appreciably … Continue reading
By the end of the 19th century, it became clear from the development of chemistry that substances are composed of atoms. Guesses about their existence arose earlier, in ancient Greek science, from the desire to give nature a coherent … Continue reading