Our goal is: a sea of stars!
This classic line comes from "The Legend of the Galactic Heroes", but it tells the dreams of many people. But how vast is this "sea of stars"? In fact, it has far exceeded the human imagination, and in comparison, human beings are really a little too small.
Some people may not agree with this view, but we can look back at Earth from some probes: How small are humans?
Dull blue dots
On December 7, 1972, Apollo 17 took a very shocking photo of the earth at a distance of 29,000 kilometers from the earth, and named the photo: blue marble.
Due to the proximity, the land and sea on this photo are clearly visible.
On December 24, 1968, as Helios 8 was orbiting the moon, astronaut William Anders took out his camera and took an equally shocking picture of the Earth, which was named: Earth Out.
Although the distance between the spacecraft and the Earth at the time of shooting is no longer verifiable, the average distance of the moon from the earth is 380,000 kilometers, and it is not difficult to conclude that this distance is an order of magnitude larger than the distance when shooting the "blue marble". From this photo, as the distance increases, the outline of the Earth's surface is already a little blurred.
In 2017, the probe OSIRIS-Rex took a family portrait of Earth and the moon at a distance of 5 million kilometers from Earth.
This distance is an order of magnitude larger than the distance at which the "ground out" was taken, but by this time the surface outline of the Earth was already very blurry, and the moon was only the size of a "point". So what if you expand the distance a little bit?
Let's take a look directly at the farthest probes taking pictures of the Earth. Of the many probes, the furthest away from Earth now is Voyager One.
Launched on September 5, 1977, Voyager I flew away from the solar system after completing its main mission, and it has been nearly 45 years since it reached 23.28 billion kilometers from Earth.
On February 14, 1990, Voyager 1, at a distance of 6.4 billion kilometers from Earth, once took the last set of photos of the planets in the solar system toward the inner side of the solar system, and scientists used computers to make a family photo of the solar system.
Among the family portraits, one photo is particularly eye-catching. In this photo, there is only one "bright spot" the size of 0.12 pixels, which is our home Earth, and the famous astronomer Carl Sagan called this photo: Dim Blue Dot.
This photo is very shocking, even thought-provoking. You know, after Voyager One took this photo, it has continued to fly for 32 years, but it still hasn't flown out of the solar system. After this photo was released, it was also frightening for a while, after all, human beings have always thought that they are the masters of the universe, but they did not expect it to be so small
How big is the universe?
What's even more frightening is that scientists estimate that it will take at least 30,000 years for Voyager 1 to fly out of the solar system, which means that the "big" of the solar system is already an astronomical number. In the solar system alone, the Earth is already so small that it is almost negligible.
So the question is, is the solar system really big enough?
Of course not, in fact, the solar system is also a small point. The Solar System is located in the Orion Spiral Arm of the Milky Way, where stars like the Sun are about 100 billion to 400 billion, the total mass of the Milky Way is 1.5 trillion times the mass of the Sun, and it takes about 250 million years for the Sun to orbit the center of the Milky Way. The solar system is as negligible to the Milky Way as the Earth is relative to the solar system.
Is the Milky Way big enough?
The answer is clearly not like that either. Larger than the Milky Way are groups of galaxies (or clusters of galaxies), which are, to put it bluntly, a combination of galaxies. The group of galaxies in which the Milky Way is located is called: the Local Galaxy Group. The local galaxy group is 10 million light-years in diameter, with a total mass of about 65 trillion times the mass of the Sun, and there are probably dozens of galaxies like the Milky Way, such as the Andromeda Galaxy and the Magellan Nebula.
Is that galaxy big enough?
Nor is it! Larger than the Local Group are the Superclusters (or Superclusters), which are located in the Virgo Supercluster. The Virgo Supercluster is 110 million light-years in diameter and has a total mass of about 100 million billion times the mass of the Sun, containing about 100 clusters (or clusters) of galaxies similar to the Local Group, and about 47,000 galaxies of the same magnitude as the Milky Way.
The Virgo Supercluster sounds exaggerated, so it's big enough, right?
The answer is still no! The Virgo Supercluster is part of the Raniakea Supercluster. There are 3 superclusters in the Raniakea Supercluster, which are about 520 million light-years in diameter and have a total mass of about 1 billion billion times the mass of the Sun, which contains about 100,000 galaxies of the same magnitude as the Milky Way.
The Raniakea Supercluster is large enough, right?
In fact, the largest known structure of the universe is called: a large-scale fibrous structure, which can be said to be a supercluster complex. The Raniakea Supercluster is part of the Pisces-Cetus supercluster complex. The Pisces-Cetus supercluster complex is about 1 billion light-years long, about 150 million light-years wide, and has a total mass of about 10 billion billion times the mass of the Sun.
Although the Pisces-Cetus supercluster complex belongs to the large-scale fibrous structure, it is a relatively small presence in the large-scale fibrous structure, and there are many large-scale fibrous structures that are much larger than it, the largest of which is known: the Wuxian-Northern Corona Great Wall, with the longest end spanning about 10 billion light-years, and the length of the other end is 7.2 billion light-years.
And these large-scale fibrous structures are actually located in the observable universe, so what is the observable universe?
According to the results derived from the theory of relativity, the limit of the speed of matter, information, and energy is the speed of light, and the speed of gravitational waves is also the speed of light, and the universe was born 13.8 billion years ago.
Since then, the universe has been expanding, taking into account the expansion effect, and the largest range that humans can theoretically observe is a spherical space with the earth as the center of the sphere and a diameter of 93 billion light years, beyond this range, the light it emits cannot reach the earth for the time being.
In the observable universe, there are about 2.2 trillion galaxies of the same magnitude as the Milky Way. From the perspective of the observable universe, not to mention the Milky Way, that is, the local galaxy group, the Virgo supercluster are small and completely negligible.
The observable universe should be large enough, right?
Actually, it's not! The observable universe is not actually the whole universe, it is only a small part of the universe. Not only is the universe much larger than the observable universe, but it is also constantly expanding outwards.
So how big is the universe?
The answer is: we don't know yet, but many scientists believe that the probability of the universe is infinite. How can this be understood?
Hubble Deep Space
In 1995, Hubble was called upon to conduct 10 consecutive days of exposure toward one of the darkest areas of the night sky. Astronomers at the time were furious because they thought Hubble was a precious observational resource that was used to do things of no scientific value. So, they were all waiting to see the joke.
As a result, the scientific research institute finally superimposed these photos and published them, shocking the entire astronomical community at that time. So the area is very dark and small, about the size of a tennis ball 100 meters away, and the result is that there are more than 3,000 galaxies similar to the Milky Way on this picture.
Not only did the discovery have deep scientific implications, but the photograph was later cited thousands of times.
This photograph later became known as: Hubble Deep Space.
Not only that, but later, the Hubble telescope also made several similar attempts, shooting Hubble extreme deep space and Hubble ultra deep space. Among them, the Hubble Ultra Deep Space Project launched in 2003, in this photo, there are about 10,000 galaxies similar to the Milky Way.
Whether it is Hubble deep space, Hubble extreme deep space, or Hubble ultra deep space, in fact, they are telling us one thing, that is, no matter from the earth to any direction of the universe, you can not look at the edge, but also find that it seems that each direction is similar, which actually indicates a possibility, that is, the universe may be infinitely large, the universe is everywhere is the center, no matter which direction it looks in.
How small are human beings?
It is likely to be believed that human beings are only small on a spatial scale. But is the situation really that optimistic? Apparently not!
Let's look at this problem from two levels, one is the material dimension, and the other is the temporal dimension.
Let's look at this problem from the material dimension, and scientists have found that there are actually some matter in the universe that we can't observe. Why can't it be observed?
According to this universe, there are four basic functions: strong interaction, weak interaction, electromagnetic interaction, and gravitational interaction.
Among them, the strong interaction and the weak interaction are mainly concentrated in the atom and below scale in play, we can usually contact the interaction, either gravitational interaction, or electromagnetic interaction.
Those "forces" we often say, in addition to gravity, are actually electromagnetic interactions, such as: elasticity, friction and so on. Human observations, observations of astronomical equipment, also rely on electromagnetic interactions.
In other words, if matter is not involved in electromagnetic interactions, then we cannot observe. In fact, there is really matter (or energy) in the universe that does not participate in electromagnetic interactions, which is dark matter and dark energy.
Not only that, with the study of dark matter and dark energy, scientists have found that the proportion of known matter in the universe is less than 5%, and dark matter and dark energy are the majority in the universe, and their proportion has reached more than 95%.
That is to say, human beings can see, and if they observe, including human beings, they are only a minority in the universe, and the majority of the universe, we can't see, and we don't even know what the other side looks like.
Looking at the temporal dimension, according to cosmological theory, the universe was born in a big bang 13.8 billion years ago, and then the universe began to expand violently.
In other words, the universe has a total history of 13.8 billion years from birth to the present, and if the 13.8 billion years of the universe are condensed into a year, the appearance of the sun is about September 1 of this year, and the appearance of the earth is about September 2 of this year.
At 23:59:52 on the evening of the last day of the year, human civilization was born.
In the last second of this year, the modern civilization of mankind appeared, science was born, and it was in this last second that mankind finally touched some essential problems of the universe through unremitting exploration of the unknown territory, clarified the various knowledge and theories mentioned in this article, and invented cutting-edge technologies such as aircraft, rockets, atomic bombs, and chips. From this point of view, although this second is broken, it is wonderful because of human beings, who are small but have the universe in their hearts.