a greeting to all stemians, According to the most accepted theory, the universe originated about 15,000 million years ago, from a great explosion (the Big Bang), in which matter, energy, space and time was created (and, therefore, it makes no sense to speak before that instant). At that time, at one time, the universe was compressed into a minuscule volume, in a state of practically infinite density and temperature. Since then it has not ceased to expand. A few minutes after the initial explosion, atomic particles came together to form helium and hydrogen, which after millions of years gave rise to galaxies, stars and the universe as we know it today.
the surface of an inflating balloon is a good two-dimensional analogy of the expanding universe. an observer located at one point (Galaxy) on the surface sees that all other points (galaxies) are moving away: there is no privileged point on the surface of the balloon.
the light waves have a certain length (figure above), if the radiation source moves towards the receiver (figure on the right), a shorter wave is received, with a higher frequency. If, on the other hand, the source moves away (figure below), it increases the wavelength and decreases the frequency that the receiver picks up. the high frequency light is blue; when it decreases, it tends to red. this property has allowed astronomers to know at what speed a galaxy moves away from us.
in the following image positioned below, the red light from a galaxy indicates that it is moving away from us; the blue light indicates that the galaxy is moving away faster and further from the earth than the previous galaxy. Therefore, the shift of light towards blue allows us to deduce the distance a given galaxy is from us.
galaxies, formed by tens of billions of stars and with diameters of tens of thousands of light years, are the basic constituent elements of the universe. They are classified according to their shape (above) into four main types: epirals, barred spirals, elliptical and irregular.
Stars are the most important constituent elements of galaxies. Varian in size, brightness and surface temperature. When you look at them, you can see differences in the color of the light they emit. The hot sun blues; the cold reds. Stars are born, evolve and die.
