[Extended information, select reading, free.]

Regarding how to measure the mass of the universe, the following excerpts are two methods, which are not accurate and are for reference only—

Calculation 1:

If the total mass of our universe remains unchanged and the law of conservation of mass is followed, photons with relativistic mass are not allowed to escape our universe. The more the universe expands, the density of matter gradually becomes thinner and the temperature gradually decreases, and it reaches the critical point of photon escape.

Suppose the mass of the universe and the photon are m and m respectively, the distance between the photon and the center of the universe is r (also the maximum radius allowed by the universe), and the velocity of the photon is c. Since the centripetal force required for the motion of the photon is provided by the gravity between the two, we can obtain: f=gmm/, f=m2/r, m=pv=4pπ/3, and g=6.67x10-11n·m2/kg2, c=2.99792458x108 meters/second, the critical density calculated by the theoretical is p=5x10-27kg/m3, π=3.141592653,

The total mass of the universe m=3 (3/4pπg3)0.5=3.415788x1053kg,

The maximum allowable radius r = 264.5 billion light years,

There are about 200 billion galaxies in the universe in which we live, small galaxies have billions of stars, large galaxies have about 400 billion stars, and each galaxy has an average of about 200 billion stars, and there are about 3-4 trillion stars in total. That is (3-4)x1022. The value is 3x1022

The sun in our solar system is a medium-sized star, and the mass of the sun is 1.98892 times 10 to the power of 33. According to the above, we can get the

The mass of visible matter in the universe: m1 = 5.96676 times 10 to the power of 55 = 0.596676x1053kg.

Other matter mass (maybe dark matter mass): m2=m-m1=3.415788x1053kg-0.596676x1053kg=2.819112x1053kg. The matter we can see only accounts for about 17.46% of the total mass of the universe.

Other matter mass (maybe dark matter mass) accounts for 82.54% of the total mass of the universe:—

Calculation 2:

Measuring quality requires considerable prior knowledge, and it is really a bit of time to put it in detail

First, you need to obtain the mass of the sun:

By computed by relatively simple Newton's law, the approximate mass of the sun can be obtained

But other stars are different from the sun

According to the observation of some binary star systems, the mass of the star can be calculated in the orbits, rates, periods, etc. of the planets, and the orbits, the rate, periods of the celestial bodies, etc.

But not every star can calculate this way

After observing the mass of a certain number of stars, you can obtain a rule, which describes the relationship between mass and luminosity. The one that links them together is the spectrum of the star. For example, the larger the mass of the star in the main star sequence, the higher the temperature. The spectrum type also has corresponding characteristics. In this way, analyze the spectrum of a star, use the measured brightness to deduce the absolute brightness, and then invert it according to the above rules to calculate the mass of a star.

So do you get the mass of all stars?

No, because almost all the stars we can see are in the Milky Way, and we cannot see most of the stars in the Milky Way (the part blocked by the Milky Way itself is on the other side), so we need to determine the structure of the Milky Way. First, draw the distribution of the stars in the visible part based on observations, and second, observe the shape of the extra-river galaxy to reverse the Milky Way. So we get the rough shape of the Milky Way, which is a spiral galaxy.

This gives the quality of the visible part

The part we can see accounts for about 40% of the Milky Way. This proportion is large enough, so we can use its characteristics to imply the characteristics of the entire Milky Way. So we know that 70% of the Milky Way are stars like the Sun (or even weaker) and the remaining 30% are large-mass stars, neutron stars, black holes, and a considerable number of brown dwarfs (and countless planets, gravels, nebula, etc., but their mass is negligible), so we get the mass of visible matter

So did you get the mass of the Milky Way?

No. By observing the rotation rate of stars at different distances orbiting the galaxy center, it can be seen that visible matter alone is not enough to maintain the revolving of most stars around the galaxy center. Calculations can show that dark matter accounts for a considerable proportion; by observing the speed at which some dwarf galaxies fall to the galaxy in the galaxy cluster, it can be seen that visible matter alone cannot allow them to achieve such acceleration; some stars thrown out of the galaxy can also provide data. Based on many observations and calculations, dark matter accounts for more than 70% of the mass of the galaxy. Only by counting their mass can the total mass of the galaxy be obtained.

Then you can use the characteristics of the Milky Way to calculate the mass of extraterrestrial galaxies

Just like judging the mass of a star according to the law, after obtaining the data of the Milky Way, you can observe the total luminosity, spectral composition, size, orbiting speed of nearby dwarf galaxies, etc., and calculate the approximate mass of an extra-river galaxy.

Do you have to calculate every galaxy?

Of course not. There are hundreds of billions of galaxies in the universe. However, after considerable observations, it can be considered that the distribution of galaxies is basically isotropic. If you can see 100 galaxies when you look east, you can see 100 galaxies when you look west, and the proportions of different types are similar. Therefore, the mass of the uncounted region can be calculated based on the conditions of the known regions. This can obtain the total mass of all visible matter

So what about dark matter?

This requires the problem of accelerated expansion of the universe. Assuming that the energy that expands space is called dark energy, and the mass of visible matter is known, then calculating the speed of expansion, etc. (I don’t know which ones to calculate) can obtain the approximate mass of dark matter. The results measured now are that dark energy accounts for 73%, dark matter accounts for 23%, and ordinary matter is less than 4%.

What is the final result?
Chapter completed!