Modern Physics

# Interesting facts about the Universe

Our Universe is fascinating and holds a great amount of curiosities and knowledge to be discovered.

The Universe is vast and must have existed for at least 13 billion years. Despite containing a gigantic number of galaxies , stars and planets , the Universe is emptier than we imagine: the distance separating celestial bodies is usually very large. Check out, in the course of this text, some curiosities about our cosmos.

## 1. The Sun we see is from the past

The light that reaches our eyes when we look at the Sun is from 499 seconds ago.

Sunlight takes just over eight minutes to reach us . This is because the speed of light is finite (approximately 300,000 kilometers per second) and the distance between the Earth and the Sun is about 150 million kilometers. So when we look at this star, the image we see is from the past! If she disappeared for some unexpected reason, we wouldn’t know until eight minutes and 18 seconds later.

For comparison, the Moon is, on average, 1,282 light-seconds away from Earth. This indicates that the light it reflects takes that long to reach here, while sunlight takes more than five and a half hours to reach Pluto.

## 2. We are traveling over 100,000 km/h

Did you know that the Earth orbits the Sun moving at speeds close to 107,000 km/h? This speed is variable, since the Earth’s orbit is not perfectly spherical but elliptical .

This is why the Earth’s speed changes: when we are closer to the Sun, its gravity becomes more intense, pulling the Earth with a greater force. The position where the Earth is closest to the Sun is called perihelion, while the farthest position is called aphelion.

As if that wasn’t enough, in addition to rotating around the Sun with such speed, the Earth still rotates around its own axis, with a speed that can reach more than 1500 km / h. This depends on its position in relation to the equator : the closer it is to it, the greater the rotation speed.

The reason we don’t feel any of these rotational motions is related to centripetal acceleration . Centripetal acceleration allows us to feel that we are rotating, however, in the case of the Earth, as the radii of the rotation and translation movements are very large, the centripetal acceleration produced by them is very small compared to the acceleration of gravity .

## 3. Big Balls of Gas

Only four planets in the Solar System are telluric, that is, they have rocky soil. The rocky planets in the Solar System are Mercury , Venus , Earth and Mars . The other planets in the system are formed exclusively by a large heap of gases trapped by a large gravitational interaction.

Jupiter , Saturn , Uranus and Neptune are the largest planets in the Solar System and also the ones with the greatest masses, even though they are formed exclusively by gases . Despite being giant and heavy, these planets are much less dense than the terrestrial planets.

Jupiter, for example, is the most massive planet in the entire Solar System. Its mass is less than one-thousandth of the Sun. However, it is also 2.5 times the mass of all the planets in the Solar System combined, equivalent to 317 times the mass of Earth.

## 4. The Galactic Year

The galactic year is the time required for the Sun to complete one revolution around the center of our galaxy , a time of approximately 250 million years. The Milky Way is a spiral galaxy, and the Solar System is in one of its arms.

The Solar System orbits the center of our galaxy, as it is bound by the gravitational pull exerted by the Sun. It is estimated that the entire Solar System performs this orbital movement at a speed of approximately 828 thousand kilometers per hour. However, this speed is very small compared to our galaxy, which is more than 100,000 light years in diameter.

## 5. Black holes

Contrary to what many think, black holes were not discovered by Albert Einstein , but were proposed by Karl Schwarzschild. The existence of these structures was predicted by Schwarzschild as possible solutions to Einstein’s equations of general relativity.

Until recently, it was believed that it would not be possible to obtain a direct image of a black hole, however the Event Horizon Telescope project has shown us otherwise by publishing the first real photograph of a black hole.

Black holes are formed in the final stages of the life of very massive stars , that is, those with at least 6 times the mass of the Sun. When these stars run out of fuel, their gravity wins out and they undergo an intense gravitational collapse, drastically reducing their size.

Check Also
Close