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The received view in physics is that the direction of time is provided by the second law of thermodynamics, according to which the passage of time is measured by ever-increasing disorder in the universe. This view, Julian Barbour argues, is wrong. If we reject Newton’s faulty assumptions about the existence of absolute space and time, Newtonian dynamics can be shown to provide a very different arrow of time. Its direction, according to this theory, is given by the increase in the complexity and order of a system of particles, exactly the opposite of what the received view about time suggests.

Two of the most established beliefs of contemporary cosmology are that the universe is expanding and that the direction of the arrow of time in the universe is defined by ever-increasing disorder (entropy), as described by the second law of thermodynamics. But both of these beliefs rest on shaky ground. In saying that the universe is expanding, physicists implicitly assume its size is measured by a rod that exists outside the universe, providing an absolute scale. It’s the last vestige of Newton’s absolute space and should have no place in modern cosmology. And in claiming that entropy is what gives time its arrow, physicists uncritically apply the laws of thermodynamics, originally discovered through the study of steam engines, to the universe as a whole. That too needs to be questioned.

Time min

Einstein and why the block universe is a mistake Read more In the absence of an absolute space and external measuring rods, size is always relative — relative to a measure of distance internal to the system. Starting from the simplest case, a triangle, what we find is that the internal measure of size produces a ratio which also happens to be related to a mathematical measure of complexity that intriguingly plays the central role in Newtonian universal gravitation. Applying these findings to the universe as a whole, we find that Newton’s theory of gravity, contrary to what physicists believe, contains within it an intrinsic arrow of time. This provides a strong hint that the direction of time is not defined by an increase in entropy, but by an increase in structure and complexity.

Scientists at Nagoya University in Japan claim to have discovered dark matter that dates back 12 billion years ago, which would make it the earliest observation of the hypothetical substance to date.

Their findings — as detailed in a new paper published in the journal Physical Review Letters — could potentially offer some tantalizing answers about the nature of the universe.

Until now, observations of dark matter only went as far back as ten billion years. Any further than that, and the light was too faint to observe.

Outer space is already an essential part of America’s ability to fight wars. Our military depends on satellites for many things, such as communications, reconnaissance and targeting information. See more in Season 4, Episode 8, “Space Wars.”

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What remains are mostly neutron stars or black holes. And now, Hubble seems to have documented the instant when a supernova blinked out — implying that it captured the moment a black hole took control.

While some supernova explosions, such as SN 1,054, are violent and leave clouds of debris for thousands of years (a.k.a. nebula), the star in question seems to have exploded and then had all its gas pulled back into the black hole at the core. This may occur if the star’s core collapse is very big. Rather than exploding, the gas falls into the star’s core.

Gravitational lensing of the cosmic microwave background has been used to probe the distribution of dark matter around some of the earliest galaxies in the Universe.

Investigating the properties of galaxies is fundamental to uncovering the still-unknown nature of the dominant forms of mass and energy in the Universe: dark matter and dark energy. Dark matter resides in “halos” surrounding galaxies, and information on the evolution of this invisible substance can be obtained by examining galaxies over a wide range of cosmic time. But observing distant galaxies—those at high redshifts—poses a challenge for astronomers because these objects look very dim. Fortunately, there is another way to probe the dark matter around such galaxies: via the imprint it leaves on the pattern of cosmic microwave background (CMB) temperature fluctuations through gravitational lensing (Fig. 1).