Everything and Nothing
The Void in our Universe - Everything Came From Nothing

Everything and Nothing
The Void in our Universe - Everything Came From Nothing

What is nothing? Nothing is defined as the absence of something, the property of having nothing. Our universe is defined as the totality of everything that exists.

In everyday usage, vacuum is a volume of space that is essentially empty of matter, such that its gaseous pressure is much less than atmospheric pressure.

But is the vacuum of space really full of nothing?

What is everything, and what is nothing? Professor Jim Al-Khalili searches for an answer to these questions as he explores the true size and shape of the universe and delves into the amazing science behind apparent nothingness.

Nothing, explores science at the very limits of human perception, where we now understand the deepest mysteries of the universe lie. Jim sets out to answer one very simple question - what is nothing?

His journey ends with perhaps the most profound insight about reality that humanity has ever made. Everything came from nothing.

The quantum world of the super-small shaped the vast universe we inhabit today, and Jim can prove it.

Nothing is no thing, denoting the absence of something. In nontechnical uses, nothing denotes things lacking importance, interest, value, relevance, or significance.

Nothingness is the state of being nothing, the state of nonexistence of anything, or the property of having nothing.

In physics, the word nothing is not used in any technical sense. A region of space is called a vacuum if it does not contain any matter, though it can contain physical fields.

In fact, it is practically impossible to construct a region of space that contains no matter or fields, since gravity cannot be blocked and all objects at a non-zero temperature radiate electromagnetically.

However, even if such a region existed, it could still not be referred to as "nothing", since it has properties and a measurable existence as part of the quantum-mechanical vacuum.

Outer space has very low density and pressure, and is the closest physical approximation of a perfect vacuum.

It has effectively no friction, allowing stars, planets and moons to move freely along ideal gravitational trajectories. But no vacuum is truly perfect, not even in interstellar space, where there are still a few hydrogen atoms per cubic centimeter.

Stars, planets and moons keep their atmospheres by gravitational attraction, and as such, atmospheres have no clearly delineated boundary: the density of atmospheric gas simply decreases with distance from the object.

The Earth's atmospheric pressure drops to about 1 Pa (10−3 Torr) at 100 km of altitude, the Kármán line which is a common definition of the boundary with outer space.

Beyond this line, isotropic gas pressure rapidly becomes insignificant when compared to radiation pressure from the sun and the dynamic pressure of the solar wind, so the definition of pressure becomes difficult to interpret.

The thermosphere in this range has large gradients of pressure, temperature and composition, and varies greatly due to space weather. Astrophysicists prefer to use number density to describe these environments, in units of particles per cubic centimetre.

But although it meets the definition of outer space, the atmospheric density within the first few hundred kilometers above the Kármán line is still sufficient to produce significant drag on satellites. Most artificial satellites operate in this region called low earth orbit and must fire their engines every few days to maintain orbit.

The drag here is low enough that it could theoretically be overcome by radiation pressure on solar sails, a proposed propulsion system for interplanetary travel. Planets are too massive for their trajectories to be significantly affected by these forces, although their atmospheres are eroded by the solar winds.

All of the observable universe is filled with large numbers of photons, the so-called cosmic background radiation, and quite likely a correspondingly large number of neutrinos. The current temperature of this radiation is about 3 K, or -270 degrees Celsius or -454 degrees Fahrenheit.

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