On what basis did scientists discover that the universe is expanding at an accelerated rate?

The expansion of the universe was originally caused by Hubble in the 20s of the 20th century through the redshift of galaxies.

But Hubble's discovery did not give evidence that the universe was expanding at an accelerated pace, so the subject should not be led astray by some respondents.

Since discovering that the universe is expanding, astronomers have suggested that the rate of expansion of the universe should be slower and slower, because the gravitational pull between all things slows things down. However, in 1998, astronomers were analyzing distant Type IA supernovae.

The universe is not slowing down, but accelerating, breaking the decades-old assumption. So, how do type Ia supernovae prove the accelerated expansion of the universe?

Type IA supernovae are a special type of supernovae that are produced by the same process, white dwarfs.

Occurs by accretion exceeding the critical mass**, so they have the same absolute brightness. Based on observations of type Ia supernovae, astronomers have calculated the second derivative of time from the cosmic scale factor in Friedman's equation.

greater than zero because of the first derivative.

Represents the rate of change of the cosmic scale factor, which indicates that the cosmic scale accelerates over time.

In layman's terms, astronomers use the brightness of Type Ia supernovae to determine their luminosity distance, and then use their spectral lines to determine the redshift value caused by spatial expansion. In the range of about 1.4 billion light-years, the distance and redshift value show a linear relationship, which is typical of Hubble's law.

However, when the distance is farther away, the distance and redshift values are no longer linear, indicating that the expansion rate of the universe changes significantly over time. Calculations show that the high-redshift Type IA supernovae are at least 10% farther away than expected. This shows that in the distant past, the universe did not expand as fast as it does now, which also means that the expansion rate of the universe has accelerated.

For this major discovery, three leading physicists were awarded the Nobel Prize in Physics in 2011.

Type IA supernovae are only the first evidence of the accelerating expansion of the universe, and there are other pieces of evidence that support this conclusion. The best explanation for this phenomenon at the moment is that there is a driving force in the universe – dark energy.

It is estimated that dark energy caused the expansion rate of the universe to shift from deceleration to acceleration about 5 billion years ago.

The law of galaxy redshift. In the 20s of the 20th century, scientists Hubble discovered, but at that time did not find evidence that the universe was expanding at an accelerated pace.

The big ** theory is now the most mainstream astronomical theory, describing the circumstances of the birth of the universe. This theory also has some speculation about how the universe will develop and how it will end, but it is much rougher than the part where the universe was born.

This theory says that after the big **, under the action of dark energy, the universe has been in a state of accelerated expansion. For the future, there are roughly three models.

One model suggests that the universe will expand at an accelerated rate all the time; The second model suggests that the rate of inflation will begin to slow down at some uncertain point in the future, most likely much later. The study delves into a third model, which argues that the acceleration of the expansion of the universe is already decreasing.

The study likened the expansion of the universe to a car that starts at a traffic light, with the driver stepping on the gas pedal deeply, but then relaxing a little at some point. As a result, the universe expands at the fastest rate at the beginning, but the acceleration gradually decreases later on.

In this case, eventually the acceleration of the expansion of the universe will disappear, and at some point the expansion of the universe will stabilize, and then it will begin to slow down, and eventually it will stop expanding and begin to contract.

This theory has been proposed before. Paul Steinhardt, the lead author of the study, is one of the active scholars who support this theory. His new study calculates on this basis, proposing two points in time when the expansion acceleration stops and when it begins to contract, and it turns out that the universe will stop expanding "soon".

So far, there are 3 pieces of evidence we know about the universe, which is why the big ** is called the mainstream theory

The first evidence was discovered in 1929: the discovery of galaxies by Edwin Hubble.

The distance between galaxies is widening, and the phenomenon of galaxies moving away from each other is a sign of the expansion of the universe in the grand ** theory;

The second piece of evidence is called "primordial nuclear fusion."

In the 60s of the last century, it was observed that the proportion of various atoms in the universe (75% of hydrogen atoms, 24% of helium atoms, and only 1% of heavier elements) was basically consistent with the predicted value of the big ** theory. Because according to this theory, at the beginning of the formation of the universe, only those lightest atoms (hydrogen and helium) existed, and the heavier atoms were formed later, in the stars, and in much smaller quantities;

The third piece of evidence is the discovery of cosmic background radiation in 1965.

This indicates that the entire universe is immersed at -270 (that is, more than absolute zero.)

Where does the weak radiation come from at a temperature of about 3 years high? The only plausible explanation seems to be that it is the embers of the huge light radiation emitted when the universe was still a hot gas, after it has cooled after the expansion of the universe.

The universe is currently in a stage of expansion, and the reason for the expansion is that the space in the universe, that is, the empty field, is expanding. The reason for the expansion of the empty field is that the energy gathered by the matter in the universe is in the release stage, and most of the energy released is transformed into the existence form of the empty field, and the volume of the empty field is expanding, and the internal space of the universe is expanding as a result, and the distance between the matter in the universe is increasing. This increase in distance is related to the expansion of the empty field volume, and the average increase in distance is 1/3 of the power of the increase in the empty field volume.

When the energy released by the cosmic matter is close to exhaustion, the gravitational effect between the cosmic matter dominates, and the expansion process of the universe ends. The universe begins to enter a contraction phase, and this contraction is bound to be an accelerated process, because the gravitational force will increase as the internal space of the universe, that is, the empty field, shrinks. As the universe shrinks, planets will one day fall into the stars around them, and the stars will merge with each other, and the density of matter, energy, and empty fields in the universe will increase.

The process will be that the universe is shrinking at the same time, the stars merge with each other, the temperature of the cosmic matter will rise, the matter will disintegrate, and finally the stars will expand and spread and merge with each other to form a pot of cosmic soup, and the matter, energy and empty field will return to the original state, and the sharp collapse of the moment will occur, and at the same time, the new universe will begin to enter a new round of creation process.

This is part of the Tuobian view of the universe – the evolution of the universe. The process of empty field expansion increases the volume of the empty field and attenuates the intensity of gravity. In the process of shrinking the empty field, the gravitational force causes the universe to shrink and the gravitational strength increases. The expansion process of the empty field is the release and transformation of the energy accumulated by matter into the increase of the energy stored in the empty field. The process of gravitational contraction is the release of energy in the empty field, and the increase in the temperature of the matter, that is, the increase in the conversion into heat energy.

Einstein made the biggest mistake he ever made, the universe has been expanding, and there is no explanation for it.

In some senses, the universe cannot expand forever, and for us, the universe may expand for a period of time, and it will continue to shrink.

The universe doesn't expand forever. Scientists believe that when the expansion of the universe reaches its limit, the universe will begin to shrink backwards, and galaxies will get closer and closer together, and will eventually be squeezed into a singularity.

1.The universe doesn't expand forever.

2.The universe we live in is composed of repulsion, gravity and tangent force, and the gravitational force and tangent force come from the rotational force and centrifugal force of the mother body before the birth of the universe