There is such a video that if the sun is a ball with a diameter of 1.5 meters, then Mercury is 68 meters away. The earth is at 176 meters, the size of a glass ball. Neptune is at 5.6 kilometers. If the boundary of the solar system is calculated according to the Oort cloud, even if the sun is only 1.5 meters, the solar system is 5000 kilometers away!
The solar system is empty. In fact, the whole universe is empty, and so are the atoms. In the Big Bang, all matter exploded from one point.
Suppose again: the sun shrinks to the size of a standard basketball. So:
Earth: a grain of rice, 26 meters away from basketball;
Moon: half a sesame seed, 6 cm away from this grain of rice on the earth;
Jupiter: the size of a common Chinese medicine pill, which is 0/35 meters away from the sun/kloc-;
Apohelion of Pluto: 2000 meters from the sun, yes, that's right, 2 kilometers.
The periphery of the Kuiper Belt: from the sun 13km.
So how far is it for 13 km to enter the real universe? It is about 500 astronomical units, which is 75 billion kilometers. Very big!
But in the basketball solar system, the nearest star is also 8000 kilometers away.
So how big is the Milky Way in the basketball solar system? Its diameter is 200 million kilometers, which is 500 times the distance between the earth and the moon in reality.
In a big disc with a diameter of 200 million kilometers, there is a basketball. There is a grain of rice 26 meters away from it, and 7 billion people live there.
The following leads to self-knowledge:
In fact, our solar system is not as big as what we learned in physics and geography books. For example, if the diameter of the sun is 65,438+0,392,000 km, and we reduce it to 65,438+0.5 m, then the first planet Mercury is 68 meters away from the sun, Venus is 65,438+0.20 m, and the earth is 65,438+0.76.
(The first white orbit is Mercury)
These are only near-earth planets, and Neptune, the farthest from us, is 5600 meters.
(The blue orbit in the picture is Neptune, and Mercury is almost invisible. )
This is only 40AU away from Pluto's orbit (astronomical unit, the distance from the sun to the earth is 1AU, that is, 65438+496 million kilometers). If the solar system in question is the gravity of the sun, then the range is about 15-230000 AU, and the sun is the largest celestial body in the solar system with a diameter of 1. At this scale, the diameter of Mercury is only 0.005m, that is, only 0.5cm, but the distance between them is 68m, the farthest Neptune is 5600m, only 40AU away from Pluto (astronomical unit, the distance from the sun to the earth is 1AU, that is, 65438+496 million kilometers), and the gravitational range to the sun is about 65438. The sun is the largest celestial body in the solar system. At this scale, the diameter of the sun is 1.5 meters. Mercury is only 0.005 meters on this scale, that is, only 0.5 cm, but the distance between them is 68 meters.
After understanding the size of the solar system, let's talk about our human aircraft, the fastest aircraft Voyager-1.
(Voyager One)
There are many definitions of the boundary of the solar system. In this answer, I take the Oort Cloud, about 50,000 to 65,438+000,000 astronomical units as the boundary of the sun, and one astronomical unit is 65,438+0496,000 kilometers, while travelers can fly 3.5 astronomical units a year. Only if we fly 63,240 astronomical units, it is 65,438+.
As for why? The argument that the universe broke out from one point is mainly the other way around. 1929, Edwin Hubble summed up a landmark discovery, that is, no matter which direction you look, distant galaxies are rapidly leaving us, while nearby galaxies are approaching us. In other words, the universe is expanding. This means that the distance between early stars is closer. In fact, it seems that they happened to be in the same place at some time from about 65.438 billion to 20 billion years ago, so Hubble's discovery suggested that there was a moment called the Big Bang, when the universe was at a singularity with infinite density. At present, there are still many imperfections in the big bang theory, and many problems have not been solved, but it is indeed the most successful deduction of all theories. The following leads to self-knowledge:
See why we choose the Big Bang Theory.
This starts with the standard cosmological model. Most of the current observation data include cosmological redshift, cosmic microwave background radiation, supernovae and so on. It shows that on a large scale, the visible substances around us are far away from us. And the principle of matter in all directions around us is similar to our speed. In other words, every direction is the same.
Then the problem is coming. What do these things mean when they are far away from us? Then we must first think about a question: what kind of position are we in as observers of the universe? Objectively speaking, there is no reason to say that we are the center of the universe. Of course, there is no reason to say that we are not in the center. The rest is a question of faith. However, from our scanning all day, the distribution of matter in the universe is very uniform on a large scale. Since it is unified, we think there is probably no center. If we are not in the center, then galaxies in all directions around us are moving away from us at the same speed, indicating that the whole universe is expanding.
Now we have proved that the universe is expanding. Then using the hypothesis of isotropy and uniformity (called cosmology principle), and then we know the existing equation of state of matter, we can find that the universe expanded in the past. Then let's go back. If the universe has been expanding, then the past should be a very small universe. This is the general logic of the Big Bang Theory.
In addition, if the universe is infinite and exists forever, and the stars are evenly distributed in it, then you should be able to see a star from any direction. In this way, the night sky should not be black, but should be full of uniform starlight, because there are countless stars emitting light coming towards us. But the night is really dark. This contradiction is called Olbers Paradox.
Now the explanation of this paradox is that the speed of light is limited and the age of the universe is limited. Even though the universe itself is infinite, as long as there is a creative moment like the Big Bang, the universe will have a "boundary" and the light outside will not reach our eyes. Therefore, from the universal fact that night is dark, astronomers can draw the inference that the age of the universe is limited and space-time has a beginning.