Arquivo da Categoria: Física

Prémio Nobel da Física - 2017

Gravitational waves are produced in acceleration of masses with spherical asymmetry. They propagate at the speed of light, stressing and compressing spacetime; distances in space increase and decrease with a steady cadence in two directions at 90 degrees to each other, orthogonal to the direction of motion of the wave. The effect is very small: for a released energy corresponding to about 3 solar masses like in the first event detected by LIGO in 2015, the relative strain at Earth is about 10^-22 – i.e., the distance between the Earth and the Sun changes by about the size of an atom.

International Energy Agency

Data, data, data...

Energy efficiency stands at a crossroads today. Strong efficiency gains continued to be made in 2016, even as energy prices fell. But at the same time, governments are not coming up with new policies fast enough, relying on existing regulations instead, precisely at the time when a pipeline of new efficiency policies should be coming into force. There is a risk that efficiency gains could take a step back. - Energy Efficiency 2017

International Energy Agency

Paul Dirac

The strange world of Paul DiracDirac was a peculiar man. Stories of his eccentricities abound.When Dirac first visited Niels Bohr’s institute in Copenhagen, his utterances consisted almost entirely of three phrases: “Yes”, “No” and “I don’t mind”.Later, he became more flexible. When astrophysicist Subrahmanyan Chandrasekhar expounded his views, Dirac repeatedly interjected with “Yes” but explained, “When I say ‘yes’, it does not mean that I agree; it means only that you should go on.”In 1929, Dirac sailed from America to Japan with Werner Heisenberg. During the trip, Heisenberg spent the evenings dancing while Dirac looked on, puzzled. Eventually Dirac asked his friend why he danced.Heisenberg replied: “Well, when there are nice girls it is a pleasure to dance.”After thinking for five minutes, Dirac said: “But how do you know beforehand that the girls are nice?”

Fonte: How Dirac predicted antimatter