Albert Einstein’s Theory of General Relativity, which completely changed the understanding of the Universe and its most exotic phenomena, celebrates this year a hundred years, without losing its freshness and despite numerous expert attempts to find flaws.
„Einstein changed the way we think about the most basic things, which are space and time. And that opened our eyes to the universe / cosmos, and how the most interesting things in it work, like black holes”, said David Kaiser, professor of the history of science, technology and society at the Massachusetts Institute of Technology (MIT).
The famous physicist, who spent the final years of his life at Princeton University in the northeastern United States, presented his theory on November 25, 1915 before the Prussian Academy of Science, and the document was published in March 1916 in a journal called „Annalen der Physik”.
The general relativity, one of the most revolutionary scientific theories in history, was a huge leap from the law of universal gravitation put forth by Sir Isaac Newton in 1687, showing that „space and time are not immutable, but dynamic phenomena, subject to evolution, like other processes of the universe”, said Michael Turner, professor of physics and cosmology at the University of Chicago.
Einstein had put forth a more restrained version of the Theory of General Relativity since 1905, describing the distortion of time and space when passing an object moving forward at a speed close to the speed of light, which is constant. He also came up with his famous equation, E=mc2, questioning the assumptions of that time, according to which energy and mass were distinct. Einstein has shown that mass and energy are the same, but in different forms.
Ten years later, the general theory of relativity offered a larger vision, showing that gravity is a curvature of space and time in the presence of masses. Therefore, time is running slower in proximity to a powerful gravitational field, such as that of a planet in the void of space.
The theory was verified by comparing two atomic clocks, one on Earth and the other in an airplane flying at high altitude; in the second situation (the high-altitude airplane), a slight delay was observed.
The GPS (Global positioning systems) are an application of this phenomenon. The satellites have extremely accurate clocks, suitable to take into account the implications of general relativity; otherwise GPS would not be able to function.
According to the theory of general relativity, light is also warped by powerful gravitational fields, which British astronomer Arthur Eddington confirmed with his observations, in 1919.
Einstein also predicted that stars at the end of their lives, who have exhausted their nuclear fuel, would collapse under their own gravity. Their external layer would explode in a supernova, while their core / heart would form a very dense object, known as a „neutron star” or „pulsar”. They can also transform into black holes, whose gravity field bends space so much, that even light could not escape from a black hole.
According to Einstein, these celestial bodies, given their masses, should provoke waves in space time, much like a thrown stone causes ripples in the water. The astronomers hope to observe these gravitational waves directly.
This would „confirm one of the last great but as yet untested predictions from Einstein”, he added. Instruments have been designed to capture this phenomenon, including the LIGO (Laser Interferometer Gravitational-Wave Observatory) in the US and VIRGO in Europe could detect these ripples in the coming years.
But the major challenge is to reconcile the general theory of relativity with quantum physics, the two big pillars of modern physics. Quantum physics, contrary to relativity, perfectly describes phenomena on an atomic level has numerous applications, from transistors to computers, but not the whole universe.
Professor Turner believes the most popular theory for reconciling the two is string theory, according to which elementary particles are made of strings under excitation. Elastic strings vibrate at different frequencies and are not attached to a support, but float in space-time continuum. „This theory might answer that deep question on the nature of time and space and also suggests the possible existence of other dimensions”, Turner told AFP.
According to the quoted professor, „string theory is like an empty vessel, to put our hopes and dreams in it”, while „we are now ready for the next step, for the next Einstein”, he concludes.
