How did the strange slope of Fenghuangling in Beijing come into being?

In order to make it easier for the audience to grasp the main points, we draw a simple schematic diagram here according to the introduction of People's Daily: OA means the uphill road from the foot of the mountain to the mountainside, AB turns downhill, and BC continues uphill. The so-called strange slope refers to this downhill AB between the previous two uphill roads.

We stood at the beginning of that strange slope and looked ahead. We really think this is a downhill road. Driving forward, after more than 20 meters, there is indeed a feeling of so-called downhill force. Turning around and walking back, the car really started to slide, and the first few tens of meters felt quite automatic uphill. Maybe that's why many people believe what they see.

So we took out the simple test tools prepared in advance and began to do some basic investigations quietly. We hung a plastic ball and an iron ball side by side and saw that the two attractive ones were completely parallel. This comparative experiment shows that the iron ball is not attracted by magnetic force on the inclined plane. Our compass also repeatedly shows that there is no abnormality in the local magnetic field.

The next experiment is equally simple. In the process of the so-called car sliding on the slope, we pour the mineral water with us on the ground, and an important fact appears: the water also flows upward along the so-called slope, exactly in the same direction as the car sliding freely, and there is no newspaper saying that the water flow is in the opposite direction to the car sliding. At this point, the strange slope has come to the following conclusion: here, the car slides to the "high place" and the water also flows to the "high place".

Then, what is the basis for proving that the slope has a high starting point and a low ending point? What makes you think that there is a downhill road between these two uphill roads? Just feel it. So, is our relationship reliable?

The film crew set up the theodolite they brought with them and began the most basic field measurement. This is a simple operation within the scope of common sense. From one end to the other, after repeated surveying and mapping with horizontal method and trigonometric height method, the truth is finally clear: this feeling is a strange slope downhill, and its main part is actually uphill. However, the slope is much gentler than the first two sections.

Please look at the field survey map of strange slope: the first section of AD is indeed a downhill slope of about 20 meters. Then it gradually turned uphill, and people regarded AB as a downhill road from beginning to end. This is the answer to the mystery of strange slope.

We put the camera in the middle of the strange slope, adjust the level of the tripod head and the support plate, and rotate the strange slope from beginning to end 180 degrees. At this time, it can be clearly seen that the starting point A of the slope is below the horizontal line of the lens and the ending point B is above the horizontal line, which is completely consistent with the measured results.

Driving the car and verifying it again, the measured results are not bad at all. No matter which end of the strange slope the car starts to slide, it will finally stop at the lowest point D. There is nothing strange here because the strange slope strictly abides by the known scientific laws everywhere.

So, why do so many people have the illusion? The film crew then explored the reasons.

As we all know, all our orienteering activities are always inseparable from the frame of reference. This strange slope lies between two steep slopes. Looking forward from one end, there is a mountain in front of you. Looking back from the other end, it is the dividing line between the road surface and the sky. In addition, there are sloping slopes all around, and no horizontal plane can be used as a benchmark. This kind of terrain is easy to cause visual errors.

If people are unconsciously looking for a frame of reference, then the only thing that can be used as a ruler here is about these guardrails and stone pillars.

We began to investigate these stone pillars that have no practical significance to the road. Hanging a plumb line from the top of the pillar, you can immediately find that each pillar is not vertical, but inclined about 5 degrees in parallel. This illusion was thus reinforced. In our living habits, we always regard the column as vertical. A horizontal road, if all the pillars are inclined to the left, we will think it is a downhill road with high left and low right; On the contrary, if the column leans to the right, we will think it is an uphill road with high right and low left. Now in the case of a small slope, no one thought of suspecting that the column was tilted, so naturally the road was tilted.

Besides the angle of the stone pillars, what is even more misleading is the way they are placed. The strange slope did have a short downhill at first, and then it gradually turned into an uphill slope. Imagine that if all the pillars on the roadside have the same height, then the connecting line at the top of each pillar can naturally describe the ups and downs of the road. The mystery of the strange slope can be seen through at a glance. Here, the height of each column is different, and the only criterion for designers to determine the length of each column is that their respective endpoints must be in a straight line. In this way, the fact that the road goes downhill first and then uphill is concealed by the vertices of evenly brushed columns. People mistakenly think that the trend of the top of the column is the trend of the road. In this way, the latter part of the uphill is mistaken for the continuation of the first downhill.

In addition, many places can find the painstaking efforts of the makers of Qipo. At the top of the strange slope, the starting point on the right is several tens of centimeters higher than the returning point on the left. What is the reason? The right side is convex for people to come to strange slopes. Looking around, the first impression will be the obvious downhill feeling. The left shovel is low, in order to ensure that you can slide further by inertia when you come back.

For another example, if the strange slope is built into asphalt or cement pavement as in the previous paragraph, it is said that the friction is smaller and the sliding effect will be better. The smooth road surface is easy to reveal the true direction, so the dirt road with high sides and concave middle is reserved. The roots of the columns are all surrounded and buried by broken clods, and there is no boundary line showing the angular relationship. It also hides the true height of the column on the ground. Even the base of the statue was deliberately crooked. This is not a natural mystery, but a man-made mystery.

Behavior is an illusion that people produce visually. The real situation is a downhill slope.