While the debate continues over whether travelling into the past is possible, physicists have determined that travelling to the future most certainly is. And you don’t need a wormhole or a DeLorean to do it. Real-life time travel occurs through time dilation, a property of Einstein’s special relativity.

They do not circle the nucleus like the earth orbits the sun, but are rather found in electron orbitals. These relatively complex shapes result from the fact that electrons behave not just like particles, but also like waves.

Electrons in atoms orbit the nucleus. The electrons can only orbit stably, without radiating, in certain orbits (called by Bohr the “stationary orbits”) at a certain discrete set of distances from the nucleus. These orbits are associated with definite energies and are also called energy shells or energy levels.

The answer is: although it is convenient to think of the electron moving around the nucleus along circular paths, the correct description is a quantum mechanical one. In the more accurate quantum picture, the motion of the electron is described by probability functions and there is no fixed orbit.

Electrons are moving randomly, but it’s important to keep in mind that electrons aren’t really particles, and so they’re not circling around the nucleus like planets. Instead, they have probability distributions around the nucleus that take the form of the spherical harmonics.

When the problem or paradox is solved, then the person loses the attribute, or maintains the attribute in a more dated sense. The person may now have the attribute of the group of problems generalized to mean similar things.

Russell’s paradox

noun. a phenomenon predicted by relativity. One of a pair of identical twins is supposed to live normally in an inertial system whilst the other is accelerated to a high speed in a spaceship, travels for a long time, and finally returns to rest beside his twin.

The logical paradox has given researchers a headache, in part because according to Einstein’s theory of general relativity, “closed timelike curves” are possible, theoretically allowing an observer to travel back in time and interact with their past self — potentially endangering their own existence.