The simple Hubble constant is very small. Why can it cause cosmic crisis?

Hubble constant, seemingly normal, but in fact, the crisis is in full swing

Since 2014, the measurement value of Hubble's constant -the rate of swelling in the universe is now controversial. The measurement data obtained from the stars in the distance is about 10%smaller than that of the nearby star measurement data. Although they sound small (in fact, this is not the case, huge scientific achievements always require the most accurate measurement value), but their uncertainty should be only 2%. Statistically speaking, in 2%uncertainty, 10%of errors need to be paid attention to and investigate. Since 2014, people have proposed more than 300 solutions to this "cosmic crisis". However, no solution has been generally approved by cosmologists, and as scientists continue to measure, the crisis is still increasing.

LCDM model

Our modern understanding of cosmic science is on the verge of danger. We summarize it as the λ-CDM model and abbreviate it as the LCDM model. Like other scientific models, this model has made several basic assumptions. It assumes that the general theory of relativity is applied under the size of the cosmic science, and the universe has the same sex. The universe is flat. Some of them are empty and are called dark substances. They do not respond to ordinary substances. To. There are also some other substances called dark energy (that is, λ), which maintains cosmic density in the expansion of the universe.

Once these assumptions are established (in fact, they are indeed established in a large number of observations), LCDM has only six free parameters. You need to do various cosmic measurements to get these data. Once you get these parameters, you can predict all things about the universe, including and not only limited to the current universe expansion rate.

The best way to fix these parameters is the cosmic microwave background radiation (CMB), which is the light left by 380,000 years in the universe. CMB is used in a lot of use, it is very grand, easy to measure, and easy to understand.

When you have the CMB measurement value, you can fill the unknown part of LCDM like the Planck satellite mission of the European Space Agency and master the entire history of the universe.

Ladder leading to the stars

This brings a tension atmosphere. Early cosmic measurement brought us a lot of LCDM parameters. This information not only came from CMB, but also from the acoustic oscillation of Chongzi -the huge sound waves in the early universe in the universe, the galaxy left in the universe, and the elements of a large amount of light.

No matter how you combine the early cosmic measurement data to complete the LCDM model, you will eventually get the Hubble constant about 68km/s/mpc.

Then, the problem is solved. Yeah? No, not that fast.

You can also directly measure the Hubble constant. You need to measure the distance and speed of a large amount of objects. You can choose the IA supernova, galaxy nature, Mira star and some types of red superstars.

Except for Red superstars, the Hubble constant measured by other methods is a higher number -more than 74km/s/mpc.

What is fun but frustrated is that the results of the red superstar measured between these two extreme numbers -therefore, we ushered in a crisis.

No solution

We already have two very different methods to measure Hubble constant, each of which has been tested and studied and understood. The LCDM model has achieved great success in forecasting many cosmic observations, and no one is willing to abandon this model. The measurement value of CMB is accurate -almost the most accurate measurement in the history of astronomy.

On the other hand, the measurement of supernova is also reasonable. Some other detectors give similar Hubble constant values. The early universe and the later universe, the overall measurement of the overall measurement, the large -scale and small scale, have formed a comparison -no matter how you distinguish them, we always have two different views that should match. We should have a universal and consistent measurement result, but we did not.

Cosmic scholars are very interested in this "crisis", because since more than 20 years ago, we found that there was no such interesting thing after dark energy. When the measurement results have different differences, this is the nature of nature telling us that there is a new space here, a new opportunity for us to unveil the truth of the universe.

So far, there are more than 300 solutions to the cosmic crisis. Some people have called for more physical research on the CMB. Some people think that dark energy has been making strange research in recent years. Some people have changed the physical theory from more basic aspects and make the observation results more complicated.

However, there is no solution that can explain a large number of cosmic facts, and we have a long way to reach an agreement.

I personally believe that "an interesting thing is likely to be a wrong thing." The most boring explanation in this crisis is: in the process of measured the Hubble constant in our local scale, errors occurred.

But only time tells us the truth.

By: Paul M. Sutter

Fy: Jing Crac

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