What follows is in answer to a question about whether we could make metal object fly without any help from engine-like things.
If you live on Earth or anywhere that gravity exists, and you have mass (that is, you are made up of atoms and have weight), then gravity will always want to pull you toward the Earth. Actually, anything with a mass with have a gravitational force. The bigger the mass, the greater the gravitational force, and the Earth is really big. To overcome gravity, you need some sort of opposing force. The greater your mass, however, the greater the opposing force that is needed to overcome gravity and make you (or the metal object) levitate or fly. But you need a force or some sort to do it. In space it is easy because there is no gravity, which is why anything will levitate in space.
But I will give you two examples of how we can levitate things, though not necessarily make them fly. A force or energy is still required to make this happen.
Superconductors
Superconductors are good at levitating an object, but…there is always a but.
Superconductors are materials that are able to conduct electricity without resistance. This means they conduct electricity without transforming any of that electrical energy to heat. This heat energy is energy lost to the system. Normally we use metals to conduct electricity. All the electrical cords, power lines, and circuits in your electric toys or computers are made of metal because they are good conductors of electricity – but not perfect conductors. They are not perfect because even the best conductor has resistance and loses some of its electrical energy as heat. That means we have to burn more coal (or generate more electricity) than we need to make up for what is lost as heat.
Superconductors can conduct electricity without wasting any energy. But superconductors have the problem that they only act as superconductors when they are about -170 degrees Celsius – and that is colder than outer space. Not practical really to power your mobile phone or fridge.
The superconductors we have today are not metal, but ceramic materials – but we have to work with what we have got. Superconductors only gain their superconducting powers at these really cold temperatures. In their super conducting state, they will levitate on a magnetic track because at this super cold temperature the electrons in the atoms of the ceramic material interact with the magnetic fields from the magnets on the track. This interaction is sort of like the repulsion you witness when you try to join two magnets together that have the same poles ie North to North, or South to South. Try this at home with two magnets. This behaviour is what makes the Maglev train work – see below.
Check the Royal Institute’s video below on levitating superconductors below. You might also want to check out SciShow’s The real science of hoverboards.
Are hoverboards real?
Assume we have found a superconductor that can operate at normal room temperature. Could we make metal objects levitate or fly. Yes, hoverboards and hover cars could become a reality. We could also generate and conduct electricity really cheaply and efficiently – much better for the environment.
We could technically make a hoverboard now using the same ceramic superconductors as in the videos and lots of really strong magnets, but the hoverboard would crash to the ground as soon as the superconductor heated up even a tiny bit above -170 degrees. And it would cost more pocket money than you could ever earn. And you could only ride it in a skate park with a track of the really strong magnets. This BBC program below takes us into the possibility of levitation with some cool inventors and even makes one of those hoverboards.
Maglev trains
The repulsion of magnetic poles is what enables the Maglev train to levitate above its track. Opposite magnetic poles will attract each other. These opposing and attractive magnetic forces and a new-ish type of electric motor are what makes the maglev train move – really fast. The latest Maglev train has been reported to reach speed of 600 kilometres per hour, though it is still a prototype and not used for passengers yet.
The ‘but’ moment here is that it still requires lots of electrical energy to propel these trains (make them move along the tracks). The latest Maglev train apparently uses cooled superconducting magnets that are cooled by liquid helium. The machinery required to make the liquid helium uses a lot of energy.
In short, there is no levitation without a massive input of energy.
The person who can develop a superconductor that will operate at room temperature will change the world as we know it.
Acoustic levitation
One other thing to check out is levitation using sound. We can only levitate really small, lightweight things, but it is still cool.
Check out Physics Girl showing you how it is done