Astral travel is real. I don't know about Remote Viewing. There is some confusion in usage of the term Astral Projection. Yogi's claim to be able to project an image of themselves somewhere else without actually going there in spirit. But, most people use Astral Projection to refer to OBE, or Out-of-Body experience. The OBE form is the only one I know about personally. It's the same process that you go through when you die, with the exception that the link with the physical body is not permanently broken, so you can return to the body and reactivate it.
Basically, the process is EARTH ==> WATER ==> FIRE ==> AIR
For the first 15 to 20 years of a person's life, it's usually relatively easy to astral project. Thereafter, as time passes it gets more and more difficult if you haven't been practising this stuff, until it becomes nearly impossible for older adults to experience (until they die, or have some physical accident that gives them a jolt, or use special drugs, etc..). It seems the spirit unites more strongly with the body with age, or gets more comfortable with it, or more compatable, or whatever, and forgets the time when it was free before birth into this world.
You can see the process in symbols in the East where the Square or Cube is used to represent Earth; Sphere is water; Cone or Pyramid is Fire; and Half moon is Air; such as with the "Stupa" structures in buddhist lands of the east.
The Stupa is a reminder of the process of leaving the body, or astral projection as we call it here in the west.
There are two swords that guard the gates to astral projection, which make it very difficult for the average person to project. They occur in right at the Water to Fire transition, and again at the Fire to Air transition.
What does all this mean?
Well, Earth, Water, Fire, and Air, represent psychological states the mind experiences when undergoing the transition. Earth is touchy feely; water is heavy feeling; fire is light and rising; air or wind is movement.
Let's see how it works, and what the obstacles are;
Scenario:
You sit in a quiet room, by yourself, and contemplate the calm serenity of your being. After awhile your body begins to feel heavy, and you loose pinpoint sensitivity, you are simply aware of your whole being at the same time, and the body begins to feel heavier and heavier, as you sink down further into the depths of consciousness. It's quite pleasant at this point, and most people get here easily. This is the EARTH to WATER transition.
Continuing the quiet contemplation, the feeling begins to change, you begin to feel somewhat lighter again. At this point in time we meet the first sword, or first obstacle. The mind encounters sexual arousal, and gets distracted into thoughts of lust and the concentration is broken by those useless ideas that prevent one from continuing the process. It's hard to get over this hurdle, and most people never make it past this point. Everytime they get here, they get distracted, quit the contemplation, and lose sight of the goal. This is the WATER to FIRE transition. The fire mixing with the water gives rise to the sexual distractions. A few people make it past here, however, and are able to carry on.
Those that make it past here then come to the next obstacle or sword. There is a sharp snapping sensation and the body feels suddenly lighter. (first time there is a distinct snap, subsequent times the snap is less distinct) In fact, you feel two bodies at the same time, one floating lightly inside the other, and it is usually a little displaced from it, or out of sync. Your open eyes may see the physical body in one spot, but you distinctly feel your body to be in a slightly different location. Soon as this snap is experienced, and you realise your astral body is coming out, you feel tremendous fear, and your heart begins to pound in your chest. This again causes you to lose concentration, and the two bodies re-sync with each other, and you fall back down into your normal conscious state. Extremely few people ever make it past this point. It is almost impossible to overcome the fear. However, those that make it to this point, often astral project thereafter during sleep, and have lucid dreams. They are able to overcome the fear once they are not paying attention to the details of the process. It happens unconsciously in sleep transitions for many, whereafter the fear simply wakes them up inside the dream, but they are already out and about by that time, so they stay outside the body half-believing its just a dream, and half-believing they are traveling. This is the FIRE to AIR transition, from lightness to movement.
Anyway, that's the basics of astral travel. Lust and Fear are the barriers. First you meet lust, then you meet fear. If you overcome these two, you can travel around at will. Don't worry about other people hopping out of their bodies to visit you, however, because the vast majority of people cannot overcome these two swords. And those that can, probably have better things to do, and other places to visit.
These two flaming swords guards the gates and prevent those carnal minded individuals from entering the astral realm. (They can get around this with drugs, however, but that's another story).