We know today that this explanation was completely wrong. In the 1500s, Copernicus explained retrograde motion with a far more simple, heliocentric theory that was largely correct.

Copernican heliocentrism is the name given to the astronomical model developed by Nicolaus Copernicus and published in 1543. This model positioned the Sun at the center of the Universe, motionless, with Earth and the other planets orbiting around it in circular paths, modified by epicycles, and at uniform speeds.

5. One of the advantages of the heliocentric theory which could have been understood and known by Copernicus’ contemporaries was its ability to explain the variations in brightness of planets (such as Mars), and the phases of the inner planets (Mercury and especially Venus).

Galileo discovered evidence to support Copernicus’ heliocentric theory when he observed four moons in orbit around Jupiter. Still in use today, the mathematical equations provided accurate predictions of the planets’ movement under Copernican theory.

The heliocentric model was generally rejected by the ancient philosophers for three main reasons: If the Earth is rotating about its axis, and orbiting around the Sun, then the Earth must be in motion. Nor does this motion give rise to any obvious observational consequences. Hence, the Earth must be stationary.

The geocentric model states that the Sun and the planets move around the Earth instead of the heliocentric model with the Sun in the center. That’s just silly, right? Obviously the Earth orbits the Sun. Sure, the textbooks all say that the solar system is heliocentric.

Nicolaus Copernicus

The Ptolemaic system was a geocentric system that postulated that the apparently irregular paths of the Sun, Moon, and planets were actually a combination of several regular circular motions seen in perspective from a stationary Earth.

The intersection of the two axii is where Earth is located. We are at the center of the universe. In 2005, data from the Sloan Digital Sky Survey showed us that galaxies are arranged in concentric spheres with Earth and the Milky Way galaxy at the center. Centrifugal force keeps the sun from crashing into the Earth.

On November 4, 2013, astronomers reported, based on Kepler space mission data, that there could be as many as 40 billion Earth-sized planets orbiting in the habitable zones of Sun-like stars and red dwarf stars within the Milky Way Galaxy. The nearest such planet may be 12 light-years away.

There is no centre of the universe! According to the standard theories of cosmology, the universe started with a “Big Bang” about 14 thousand million years ago and has been expanding ever since. Yet there is no centre to the expansion; it is the same everywhere.

First, it’s still possible the universe is finite. The observable universe is still huge, but it has limits. That’s because we know the universe isn’t infinitely old — we know the Big Bang occurred some 13.8 billion years ago. That means that light has had “only” 13.8 billion years to travel.

No, they don’t believe there’s an end to space. However, we can only see a certain volume of all that’s out there. Since the universe is 13.8 billion years old, light from a galaxy more than 13.8 billion light-years away hasn’t had time to reach us yet, so we have no way of knowing such a galaxy exists.

It is expected that between 1011 (100 billion) and 1012 (1 trillion) years from now, their orbits will decay and the entire Local Group will merge into one large galaxy.

It’s matter that has negative energy density and/or negative pressure. Holman explains that it’s possible inserting anything that isn’t exotic matter would destabilize the wormhole completely. In other words: Entering a wormhole could immediately kill you.

Einstein denied several times that black holes could form. In 1939 he published a paper that argues that a star collapsing would spin faster and faster, spinning at the speed of light with infinite energy well before the point where it is about to collapse into a Schwarzchild singularity, or black hole.

Stars rarely collide, but when they do, the result depends on factors like mass and speed. When two stars merge slowly, they can create a new, brighter star called a blue straggler. Stars that collide with a black hole are ultimately consumed. …

The merging of galaxies will radically affect their shape. For example, two spiral galaxies can merge and form an elliptical galaxy. Sometimes even more than two galaxies can collide with each other. Merging galaxies can also trigger the creation of new stars.