Dyson Sphere: A hypothetical megasphere.

 Dyson Sphere

The Dyson sphere is a hypothetical megastructure that completely encompasses a star and captures a large percentage of its power output. This is basically a huge structure that could cover the entire sun and harness its power. As only a small portion of the star's energy reaches the planet, the Dyson sphere would significantly increase the amount of energy that could be obtained from the star. 

Obviously, it's not an easy job to do. If we think of making one for the sun, the Dyson sphere would have to be very big as it has to cover an area that is more than the circumference of the sun. For this, we require massive amounts of material that the earth itself cannot provide. But in the coming future, if we colonize other planets, we would be able to extract the materials required. Also, the time required to build this enormous structure would definitely be a lot. Let's say a few hundred years or so.  This asks for massive levels of manpower or robotic power. Plus we need to pass down the knowledge of building this to the next generations and hope they don't make a mistake. Moreover, if we send humans to build this in space, they would die due to high amounts of UV radiation and the heat from the sun.  This makes it clear that robots should be built to do this job. But for that, we need to have a material that doesn't melt easily, like tungsten. 

It could be used to harness the energy of other planets as well. Building a Dyson sphere around Jupiter would be exponentially easier than building one around the sun. The size of Jupiter is much smaller. If this is the case, we would be able to access the energy that is there in the storms of Jupiter. Which, again, would be enormous.

Being a huge and time-consuming project, it still remains hypothetical. But in a few thousand years, if humanity has developed the technology to explore other planets and extract various materials from there, this doesn't seem like a hypothetical one. Who knows, the technology then would be so advanced that it would not even take 100+ years to build it. Maybe it could be done in a span of 5-10 years. Once, this is built, humanity will get access to the billions of tons of energy the sun has and life would be different.