## 10 great undiscovered secrets of physics. Part 2

Toward bright spark; In the continuation of the previous article, we will examine the undiscovered secrets in the world of physics.

### 6- How does measurement cause the wave function to collapse?

In the strange world of electrons, photons and other elementary particles; The laws of quantum physics determine behaviors. At this size, the particles behave not like small balls but like waves left in a large space. Each particle is explained by a wave function or probability distribution. This probability distribution tells us what the location, velocity, and other properties of each variable can be, but we cannot get the exact values from it. The wave function gives us a range of probabilities until we can experimentally obtain the exact amount and location of each particle. But there is an obstacle to getting the exact amount. When measuring the properties of particles, we can not get a result. But how and why does measuring a particle cause its wave function to collapse? This problem, known as measurement error, is a major obstacle to our understanding of the world. Understanding what reality is and whether there is a reality at all depends on the answer to this question.

### 7- Is string theory correct?

Physicists once decided to think of all elementary particles as one-dimensional strings. Strings that are wrapped around themselves and differ in the different frequencies of their vibrations. With the advent of this theory, the science of physics became much simpler; With string theory, physicists were able to reconcile the laws of quantum physics with the laws of space-time, that is, general relativity, and to place the four forces of nature in a single framework and theory. But the problem starts with the fact that string theory can only work in 10 or 11 dimensional space. 3 dimensions of large space that we can see in addition to 6 or 7 dimensions of compact and very small space and time dimension. Compact spaces, like these vibrating strings themselves, are about one billionth the size of an atomic nucleus. There is no known or even conceivable way to test such a small size, and therefore there is no way to experimentally prove string theory.

### 8- Why the arrow of time is one-way direction?

The forward motion of time is explained by a feature of the universe called entropy. Almost entropy can be explained by the degree of disorder in the universe. As irregularities increase, so does time. The fact that entropy is increasing can be explained by the logic that there are more irregular order than regular order in the universe, and that this is why particles tend to move irregularly rather than orderly. But the question is, why has entropy been so low in the past? In other words, was it because of this very low entropy that the universe was originally made up of infinite matter and energy at very small points and spread rapidly around it after birth? To better understand this, we recommend reading our previous article on moving forward the arrow of time.

### 9- Is there order in disorder?

Physicists cannot predict certain fluid behaviors, from liquids such as water to gases and other fluids, and arrive at answers consistent with experimental experiments. In fact, it is not even clear whether there is a general solution to what is called the Navier-Stokes equations, and if so, whether it can correctly describe the behavior of liquids everywhere and explain the unknown points of the singularity. Because of these problems, the nature of the chaos seems to be still not well understood. Physicists and mathematicians are surprised when they can not accurately predict the weather. Are these disturbances inherently unpredictable? Does turbulence go beyond mathematical equations? Or will we finally come to a general conclusion with the correct mathematical equation?

### 10- How does gravity work?

We all know that the gravity of the moon creates tides on the earth and the gravity of the sun causes the earth to revolve around it and keep our planet in orbit around the sun. But what is our understanding of this fact? Gravity is a powerful force created by materials, and heavier objects with higher gravity attract lighter objects. While scientists have done a lot of research on the effects of this force, they are still not sure why this force exists. Why is the force that holds atoms together different from gravity? Is gravity a particle? These are questions that our current knowledge of physics is not yet able to answer.