little joke

This book mentions some of the theoretical models that attempt to explain the universe.

Science Trial guides everyone to become a scientist and philosopher, allowing everyone to participate in the discussion of why our universe exists.

String theory combines relativity and quantum mechanics.

unified theory

Hawking believes that excellent physics theories should be understood by everyone.

time travel

The paradox of time travel, quantum mechanics believes that there are multiple possible histories in the universe.

Time has three arrows →

Entropy The degree of disorder in the universe never decreases automatically; entropy always increases. Even as the universe expands and contracts, the degree of disorder continues to increase.

The principle of survival for the strong and the survival of the weak. Scientists try to explain why humans exist, and explore and unify the theory of the beginning of the Big Bang to create a new theory - quantum gravity theory (not yet complete).

The gravitational force between the two stars causes them to orbit each other. Scientists have discovered that a planet is orbiting another invisible object. There are two possibilities for this invisible object: 1. It is a planet that does not emit light, 2. .is a black hole.

Detect whether it "emits" radiation into the universe. There are particles and antiparticles surrounding a black hole. The particles are attracted to the black hole, and the escape of antiparticles looks like the black hole emitting matter.

The presence of black hole radiation seems to mean that gravitational collapse is not as final and irreversible as we once thought.

General relativity determines that the universe began with the Big Bang at a point with infinite density and infinite compression of space and time; it also predicts that there is also a point with infinite density and infinite compression of space and time inside a black hole. The difference between them is that one is the starting point of expansion and the other is the end point of contraction. In these two singularities, general relativity fails.

Newton's laws of motion

Hubble - discovered that the universe is expanding.

Einstein's Theory of Relativity.

Quantum theory (quantum theory believes that the universe is full of randomness and uncertainty).

Kepler discovered that planets move in ellipses.

Newton's laws of motion reveal the fact that the motion states of objects are all relative. There are no absolutely stationary objects and there is no absolutely stationary space.

However, not only was there no way to assign an absolute spatial position to this object, scientists 200 years later even believed that there was no absolute time. In 1887, two scientists (Michelson-Morley experiment) measured the speed of light with season as the only variable, and surprisingly came to the conclusion that the speed of light is constant.

Time Scientists assume that light travels in the ether. The medium of ether is not to prove the propagation path of light, but to explain the movement of light relative to the reference object, thereby calculating the speed of light and stipulating time.

Einstein's theory of relativity

four dimensional space

A prism separates sunlight to obtain the visible spectrum ↓. When Hubble observed the galaxies in the universe, he found that all stars showed a red shift. The red light waves were longer than the blue light waves, which led to the inference that the universe was expanding.

If the universe is constantly expanding, the universe should be very small and hot at the beginning, emitting huge light, which has been transformed into a kind of microwave (which has been detected). If you turn on the TV📺 and adjust it to no video signal, white snowflakes will appear. There are probably 1/20 is the microwave left behind by the early universe.

The uncertainty principle is a principle stated by Heisenberg "We can never know the position and velocity of a particle exactly at the same time."

Atoms are composed of nuclei and electrons. When using photons to measure the speed and position of electrons, it will cause interference to the electrons and increase the measurement error. Because it cannot be measured, the "uncertainty principle" is also called the "uncertainty principle."

quantum mechanics

gravitational.

Electromagnetic force is much stronger than gravity. Electrons rotate around the nucleus and are bound by the electromagnetic force.

Strong nuclear force, the nucleus of an atom is composed of protons and neutrons, and the strong nuclear force binds protons and neutrons (and the smaller particles within them) together.

The weak nuclear force causes large atomic nuclei to decay into small atomic nuclei.

Scientists are trying to find a single theory that unifies these four forces. However, the theories describing electromagnetic force, strong nuclear force, and weak nuclear force all rely on quantum mechanics and belong to the research direction of the microscopic world. However, quantum mechanics and relativity still cannot be reconciled.

Chandrasekhar limit: the maximum mass possible for a stable cold star. A star with a mass exceeding this must collapse into a black hole due to the gravitational attraction and the repulsive force generated by the burning of gas (fuel) (Pauli exclusion principle).

Nuclear fusion occurs in the sun (hydrogen atoms turn into helium atoms). When the nuclear fusion stops and the temperature decreases, the star loses the power to expand, and the gravitational force between the gases causes the star to collapse.

The gravitational pull of a black hole is so strong that even light cannot escape, making the black hole unobservable.