How difficult is it to go deep into the universe?

People on earth had the idea of exploring the depths of the universe at a very early age, and it was also a long-time idea to move to other planets, and Mars has always been regarded as the first choice for people to move. Specifically, from Earth to Mars, there are three routes to choose from: the first route is called Homan transfer orbit, called Walter? Herman's mathematicians discovered it. People on earth had the idea of exploring the depths of the universe at a very early age, and it was also a long-time idea to move to other planets, and Mars has always been regarded as the first choice for people to move. Many people imagine that Mars is close to the earth, but it is not. So, how difficult is it to reach the depths of the universe? We might as well take Mars as an example to explore. Both the Earth and Mars revolve around the sun, but their speeds are different, and their paths (ellipses) and lengths around the sun are different, so their relative positions are always changing. When Mars and the Earth are on the same side of the sun and basically in a straight line, and Mars is at perihelion and the Earth is at apohelion, the distance between Mars and the Earth is the closest (called "Chong" by ancient astrologers), about 56 million kilometers; When Mars and the Earth are on both sides of the sun and basically in a straight line, and both Mars and the Earth are at apohelion, Mars is the farthest from the Earth (called "conjunction" by ancient astrologers), about 400 million kilometers. But the distances mentioned here are all linear distances, and the route from the earth to Mars can't be a straight line, only an arc or an elliptical route. Obviously, when the fire hits the ground, the route to Mars is also different. Specifically, from Earth to Mars, there are three routes to choose from: the first route is called Homan transfer orbit, called Walter? Herman's mathematicians discovered it. This route is a huge ellipse, with one end tangent to the earth at the starting point and one end tangent to Mars at the ending point. When the fire meets the earth, the spacecraft sets out, because the direction of the spacecraft is consistent with the direction of the earth at this time, and the speed of the earth can be about 30 km/s, so it is the most fuel-efficient and least difficult route. The only problem is that it takes a long time.