🌍 the Universe is infinite? The answer may surprise you! The fact is, we'll probably never know...
Theoretically, it's impossible to answer this question. Even though the theory of general relativity allows us to describe the evolution of the entire Universe since its birth, it tells us nothing about its geometric properties.
All that Einstein's relativistic theory of gravitation tells us is that the curvature of the Universe is zero. What does this mean in concrete terms? Let's take three points in space-time. Now, let's link these three points together. Without curvature, we get not a pyramid, but a triangle, i.e. a flat object.
A flat Universe, without curvature, and therefore infinite... This doesn't convince all cosmologists!
🔥 As a reminder, videos are published on SUNDAYS at 6pm.
-------------------------
💥The Observable Universe:
- The Observable Universe is the name given to the visible part of our Universe in cosmology. As we have seen, the observable Universe is finite.
Its boundary is called the cosmological horizon. This horizon is the limit of the Universe observable from a given point, usually the Earth. It may correspond to the limit from which electromagnetic radiation can be emitted, or the limit from which a signal of any type, such as gravitational waves or neutrinos, can be received.
The cosmological horizon can also be defined as the boundary between the visible part of the Universe, made up of objects whose light will have traveled for less than 13.7 billion years, and the invisible part of the Universe, whose galaxies are too far away for their light to have had time to reach us. However, to say that the cosmological horizon is 13.7 billion light-years away is a simplification, as it does not take into account the expansion of the Universe. If we add the expansion of the Universe into the equation, we can say that the photons emitted by the cosmological horizon are located more than 13.7 billion light-years from us today, because the speed of the expansion of the Universe is faster than the speed of light.
In reality, the most distant signals that reach an observer on Earth come from the cosmic microwave background, a radiation that fills the entire Universe but whose region of emission is located at the edge of the observable Universe. This region is known as the last scattering surface. Cosmological models estimate that the last scattering surface is now 46.5 billion light-years away, due to the expansion of the Universe.
The observable Universe can be described as a sphere with the Earth at its center. It's not a question of geocentrism, the ancient physical model according to which the Earth was immobile at the center of the Universe. Our planet is at the center of the observable Universe, simply because observers are located on Earth! This is a relative notion. Observers located elsewhere in the Universe would not have the same observable Universe, but the radius of this sphere would be the same.
The observable Universe is defined by what is observable and measurable. The further we advance in time, the more distant objects we can observe, as their light finally reaches us. The observable Universe thus expands over time. The visible ray is one light-second larger with each passing second, or one light-year larger with each passing year. We can also put it this way: light travels at a speed of 300,000 km/s. With each passing second, we discover a new depth of space of 300,000 km. In a single year, we can discover several new galaxies.
Objects at the very edge of the observable Universe are observed in their primitive state, because they are the ones whose light has taken the longest to reach us - billions of light-years! And the further away the objects are, the higher their redshift, due to the expansion of the Universe.
-------------------------
🎬 Today's program:
- 00:00 - Introduction
- 00:58 - What is the observable Universe?
- 15:17 - Observing the Universe: challenges ahead
- 22:04 - What are the dimensions of the observable Universe?
- 29:50 - What's in the observable Universe?
This channel is an official affiliate of the ORBINEA STUDIO network.
22 май 2024
