Some people believe it's all a grand conspiracy by the evil government to prevent people from knowing the truth. They maintain there was never a moon landing; it was all simulated; the NASA did an excellent job of faking it. Most important of these beliefs is that the earth is flat. These set of people are known as the flat-earthers. They even have a "helpful" website where issues relating to flat earth are promoted and shared for "discovery of truth through free discussion and argument."
The first "proof" a genuine flat earther has to the earth being flat is simply an everyday phenomenon; if you take a walk on any earth surface, it mostly feels and looks flat.
But if the earth is flat what keeps people from walking off the edge of the Earth? A flat Earth should have an edge, doesn't it? Or aeroplanes like the experimental aircraft, Voyager which circumnavigate the world nonstop, in 1986 accomplished that without falling off earth's edge.
As they say, if there is a question, there is someone out there who has the answers. The flat-earthers believe the Earth is flat and surrounded by an ice wall. Heck, the 
The wall must have been the giant 150-foot ice wall that somehow prevents people from falling off the edge of the earth. Which, true to a lot of things believed by the flat-Earthers, has some element of government in the mix. Some armed government agents guard the wall to prevent voyeurists from climbing the wall or worst falling off the edge of the earth unwittingly.
Ancient Greeks as far back as around 500 B.C when Pythagoras came up with the idea of a spherical earth. Though the possibility that it was Aristotle who around 384-322 B.C proposed sperical Earth due to some particular observations he had as evidence.
First of which is the "disappearing" departing ships. The ships first have its hull disappear which is followed by the sails. If approaching the seaport, the sail appears and the hull emerges as it gets nearer. He noticed this was a result of the curvature of the earth, the missing section of the ship was a result of the curve.
That was not all; the Earth causes a circular shadow to be visible at the time of a lunar eclipse which shows the different constellations to be visible when looked at from different latitudes.
The Greek mathematician and poet, Eratosthenes, was able to calculate the circumference of the earth to within 10% error around 250BC using only the position of the shadow casts by two sticks.
The Ancient Greeks placed two sticks around 500 miles apart. Recall if the sun is directly above a stick, there will be no shadow. But, if we check a city some 500 miles away, another stick on the ground will have a shadow. This shadow is proof that if the Earth is flat as some people will have us believe, the two sticks should either have a shadow or not have one as the angle will be same towards the sun. But the shadow did not behave the same way on the two locations which goes to show the Earth's curvature is why both sticks were at a different angle hence cast a different shadow on the ground.
That was thousands of years ago, but what happened to today? How do I see the Earth's curvature to see for myself that it is real?
It is hard to see the Earth's curvature without moving up high. But not to worry, you do not have to be an astronaut to enjoy the beautiful curve.
To see the curve while on the ground is similar to trying to observe the curve of a huge ball while standing 1/10th of an inch from it. If you can pull off that, then you will have no problem just looking over the horizon and seeing the curve.
But too long ago, passengers in the commercial jet of Concord travelling can see it. You can take at this video made by a passenger onboard the Concorde Flight in 1998 at over 50,000 feet while travelling at twice the speed of light (Mach 2).
But even though the Concorde is no longer flying, not to worry, you can put a camera on a balloon. This was exactly what the physics students from the University of Leicester did when using a high altitude weather balloon.
They were able to fly up to heights of 23.6km (86286 ft) which beats the maximum height a Boeing 737 can climb by almost twice.
You can watch the breathtaking HD video of the Earth's curvature as captured by the high altitude balloon camera here.
Let us imagine you do not have the time to go flying upwards; we can just look at the simple phenomenon of the day and night.
In a dark room, take up a torchlight with streamline beam and shine a light on a ball. You will notice some part of the ball will be illuminated. If the ball is spinning, the illuminated portion will change. The ball is the earth spinning, and the torch in this little experiment is the Sun. The Earth gets its day when the torchlight, the Sun, is shinning on that part of the world, another part of the world may be in darkness.
Flat earth will not have a different time zone. Everyone will have daylight at the same time as well as the night on the same period. No time zone.
Although the earth is not a perfectly spherical, saying that it is flat is just something someone will say if they refuse to see the many obvious reasons which point to it being false.
But there is no way of really convincing a man that is hell bent with all the evidence that the earth is not flat. We can only hope they do not fall off the surface of the earth or like a friend once mentioned we should send them to the moon to see the roundness of the Earth.
