BLACK HOLES AND TYPE OF BLACK HOLES AND FACTS

 4 improbable things that the laws of physics can enable

Einstein's general theory of relativity is known for predicting wormholes, which are time-traveling shortcuts that link various regions of space and time. Nobody has ever seen one, and whether you could fly down one even if they did exist is a point of contention. As we wait for a visitor from the future to inform us, consider the following physical impossibilities.

MATTER MARRIED WITH ANTI-MATTER

Normally, when matter collides with its antimatter counterpart, both “annihilate” in a burst of energy. It's just as well that we exist in a world of so much matter and so little antimatter.

Strangely enough, certain matter can even be antimatter. Majorana fermions will be their own antiparticles, capable of annihilating themselves in the right circumstances. Physicists have long speculated that neutrinos fit into this category, but demonstrating it would require observing some of the universe's rarest processes in motion, which would only happen once every 100 trillion trillion years.

Meanwhile, rumors abound that we've done something similar in the lab. When an electron is ripped from a superconductor, a void is left behind that behaves just like a positively charged particle with the same mass. They can be made to behave like Majorana particles if the two are combined in the right way.

NEGATIVE TEMPRATURES 

If you want to be a part of this world, you must follow its laws. There is no travelling faster than the speed of light, dividing by infinity, or cooling below absolute zero.

Absolute zero, or -273°C, is the temperature at which atoms cease to move. As a result, it is logical that you cannot go below it. In reality, as physicists finally demonstrated earlier this year, you can't even hit the end of the universe.

You can, however, jump under it. Temperature, by strict thermodynamic definition, is a measure of order: the lower something's temperature, the quieter and more organised it is. So, in 2013, physicists at Germany's Ludwig Maximilian University of Munich took the next logical step: they cleaned up a sample of atoms that had been cooled to almost absolute zero and created a temperature well below absolute zero

Such states aren't very effective in practise. They may, however, aid research into dark energy, the enigmatic substance tearing the universe apart, as some have suggested it has a negative temperature.

PERPETUAL MOTION MACHINES

Over the ages, the concept of machines that can travel and perform other useful tasks without the use of external power has enticed some well-known figures. Several designs involving spinning weights were created by Leonardo da Vinci. Robert Boyle pictured a self-feeding funnel. Blaise Pascal made the wise decision to forego the hunt and instead invent the roulette wheel.

Large-scale perpetual motion devices defy all kinds of physical laws, including the hard-and-fast laws of thermodynamics. However, Nobel Laureate Frank Wilczek's "time crystals" – materials that eternally repeat in time without the need for external power – seem to be similar. However, the most recent examples created in the lab are useless, so the quest continues.

INVISIBILITY CLOKS

The invisibility cloak worn by Harry Potter is only one fictional example of magical clothing that makes you vanish. However, so-called metamaterials say that a similar possibility exists in the physical world as well.

Metamaterial cloaks work on a basic principle: waves of light bend around an object in your field of vision, similar to how water bends around a boulder in a sea. In practice, however, entirely new nanostructured materials that can bend light in unexpected ways must be created.

In the year 2000, the first metamaterials and simple cloaking devices were created in the lab. Cloaking for human-sized objects has recently been ruled impractical, but that's no big deal: even if it were, you'd only be able to reroute unique wavelengths of light, making the cloaked object strangely colored and more noticeable. Instead, similar cloaking concepts might be used to divert seismic waves and shield entire cities from earthquakes.