Cosmos against autumn depression

Our planet is rolling in a circle, so after summer comes autumn again. The Internet begins its mournful hurdy-gurdy about how to deal with depression, thereby evoking even more depression. Every year the same thing: warm cocoa, a soft blanket, elegiac moods and a divine runny nose!

Stop moping, explore space! He doesn’t care about the seasons at all. Here are some delicacies for the intellect from my favorite book, Now. The Physics of Time. By the way, I started with the planet in a circle – and it turns out that it moves in a straight line. Read on.

Faster than the speed of light!

Although no ordinary object can move faster than the speed of light, the distance between us and a distant object can be reduced at an arbitrarily high superluminal speed without violating the laws of relativity.

Lawrence Laboratory at the University of California, Berkeley. The rig, only 9 cm long, provides incredible particle acceleration in a very compact space. Let’s direct our BELLA installation to Sirius, which is 8.6 light years away.

In the own frame of reference of an electron that has just entered the setup, this is the distance to the star. A few billionths of a second later, the electron is moving at 0.9999999927 the speed of light. In the electron’s own frame of reference, Sirius is 8317 times closer, that is, only 0.001 light years away. The distance between Sirius and the electron, measured in the electron’s own frame of reference, has decreased by almost 8.6 light-years in about one billionth of a second. Thus, the rate of change of distance is more than 8.6 billion times faster than the speed of light.

Such a rapid change in distance turns out to be very important for general relativity, since it treats gravity as an acceleration. The possibility of achieving superluminal speed will have a great impact on cosmology.

For example, in the Big Bang theory, one can postulate that galaxies are stationary, just the distance between them increases.

The rate of change of this distance is not limited by the speed of light.

Time slows down

Clocks on Earth run slower than those in space, by 0.7 parts per billion. Compared to clocks in space, time on the surface of the Sun slows down by 6 billionths, and on the surface of a white dwarf, by one thousandth. Time stops completely at the surface of a black hole (Schwarzschild radius).

Why Pluto is not a planet

Everyone has heard that Pluto is no longer a planet, but who knows why?

By the decision of the 26th Assembly of the IAU (2006), Pluto was excluded from the category of planets. It was decided to consider a planet as a body that, along with other criteria, “cleans” the space in its orbit. That is, apart from the planet itself and its satellites, no other bodies can be in the heliocentric orbit. For Pluto, this condition is not met, so it was officially excluded from the number of “real” planets and classified as a dwarf planet.

The planets move in a straight line

Einstein allowed space-time to have arbitrary geometry, including warps and stretches. Just as there are mountains and valleys on the surface of the Earth, the four dimensions of space-time can twist and turn, contract and expand, while remaining extended and whole.

The planets and their satellites, according to these views, simply moved in orbit around massive bodies, obeying the forces acting on them and following the course that seemed to them a “straight line” (they are also called geodesics).

The planets in their orbits around the stars do not follow a straight line through outer space, but through space-time.

The old Newtonian gravitational field was gone, replaced by non-Euclidean geometry that depended on the density of nearby energy (including mass energy).

Black hole

Physicists are often dumbfounded by their own equations. It is often difficult to immediately draw any conclusions from them, even if they are epochal in nature. To help themselves understand their own mathematical constructions, they look at exceptional examples and see what happens in the end.

And in our universe there are no more exceptional and extreme examples than black holes.

If you are orbiting a small black hole (say, the mass of our Sun) at a decent distance – say 1500 kilometers – you will not feel anything special. You are in a circular orbit over a massive object that you cannot see. In orbit, you experience weightlessness, like all astronauts. You are not sucked into the hole. Black holes, unlike those depicted in science fiction, do not suck in. In such a close orbit from the Sun, in a millionth of a second you would already be inside the star, but before that you would have burned out instantly. However, a black hole is dark. Microscopically small black holes emit radiation, but large black holes emit nothing.

Weightlessness at the center of the sun

On the Sun, the maximum force of gravity acts on its surface, as is the case with the Earth. It is necessary to take root under its surface, as the mass that attracts objects begins to act less in the depths of the star than on the surface. At the very center of the Sun, gravity is zero.

Mole Hole

A wormhole is a hypothetical object similar to a black hole. But instead of a curved space that rushes towards a hole with a colossal mass, in the end the space opens into another neck. The simplest example of such a tunnel is two “not quite black holes” connected at a narrow point. (“Not quite” means that you can fall into a hole from one entrance and exit another in a finite amount of time.)

The problem with simple wormholes is that the calculations indicate they are unstable. Since there is no mass at the bottom of the hole to concentrate the curved space, it is believed that the wormhole will cease to exist faster than a person can “slip” through it. We could stabilize it (as they do in mines by placing props), but, according to modern views on the problem, this requires something that humanity has not yet discovered – some kind of particle with negative energy in its field. Such a field is possible (in any case, it cannot be excluded).

CMB radiation

You are referring to the past all the time. When you look at a person standing one and a half meters away from you, you see him not momentary: you see how he was 5 billionths of a second ago (so much light is needed to fly this distance). Looking up at the Moon, you also see it not as it is now, but as it was 1.3 seconds ago. When you squint at the Sun, you see what state it was in 8.3 minutes ago. If the Sun suddenly exploded 7 minutes ago, then so far we have not the slightest idea about it.

The most distant and ancient signals from space that have been captured are cosmic microwave (relict) radiation. These are the so-called primary signals. We believe they started their journey 14 billion years ago. And when we look at them (using a microwave camera), we see the Universe of that time. Light (microwaves are low-frequency light) shows what existed in the universe a long time ago and at a great distance from us. This light traveled through space for 14 billion years to reach us.

Childhood photo of the universe

The discovery of cosmic microwave radiation, which confirmed the theory of the Big Bang, became the deepest source of information about the nature of the universe in the first half a million years after the explosion. But scientists have not yet come to the beginning of time, but only to the mark of half a million years after it.

To humans, “half a million years” sounds like an incredibly huge number, but when compared to the 14 billion years that have passed since then, it turns out that we managed to photograph the Universe as a child of a few hours old would be. And what is important, this is not a theory, but the data of real observations.

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