The materialistic mindset looks at everything that can be seen and touched as reality and anything we cannot see or touch as non-existent. What we see and touch is a consequence of motion of invisible particles and an illusion generated by our senses.
In the world of the small or quantum mechanics, events occur and have effects which are not understood completely. The quest continues to find the smallest component of matter using particle accelerators like the Large Hadron Collider (LHC). Today, we know even the once thought smallest of particles (protons, electrons and neutrons) are made of sub-particles, i.e. quarks, leptons, and many other smaller particles and these smaller particles could be a product of yet smaller particles.
A neutron star is a star that has collapsed because it has run out of nuclear fuel and is extremely dense. A teaspoon of a neutron star would weigh about 8 billion tons. Or the equivalent of 2 cubic miles of concrete compressed to the size of a teaspoon. This shows how much empty space there is between some of the visible objects we see vs compressed known matter.
If one theory, (String Theory) is correct then it states that even the particles are made of strings which vibrate, and the manner in which they vibrate determines the type particle. A string is extremely small, they would be a millionth of a billionth of a billionth of a billionth of a centimeter. If you inflated the size of an atom to the size of our universe, a string would be the size of an average size tree. Consider there are approximately 20 trillion (20.000,000,000,000) atoms in an average grain of sand.
If you were to ask a string theorist what a string is made of, they would tell you it is a mathematical construct (code for they do not know). It could be that if mankind were given enough time we could learn that all matter (objects around us) are no more than motion.
In recent years scientists have proposed that the universe is actually expanding at an accelerated rate. Physicists were perplexed when they found that the stars at the outer perimeter of spiral-type galaxies rotate around the center close to the same speed of the inner stars. This caused physicists to look for some other unknown force that could possibly explain these observations.
From this, it was surmised there must be much, much more invisible and undetectable dark matter which would cause this effect. It is currently estimated we can only detect 5% of the matter in the universe, the remaining 95% would be mostly dark matter and dark energy. Both can not be detected with any methods we currently use.
The Universe is full of matter and the attractive force of gravity pulls all matter together. In 1998 the Hubble Space Telescope (HST) made an observation of very distant supernova which showed us the Universe was actually expanding more slowly than it is today. This led to the conclusion that the Universe has not been slowing due to gravity, as everyone thought, it has been accelerating. No one expected this, no one knew how to explain it.
Eventually, theorists came up with several explanations. Maybe it was a result of a version of Einstein's theory of gravity that had a problem, another suggested that it was due to something they named the "cosmological constant", which was an unknown incredibly small and precise force. It could also be some strange kind of energy-fluid that filled space.
What Is Dark Energy?
More is unknown than is known. We know how much dark energy there is because we know how it affects the Universe's expansion. Other than that, it is a complete mystery. But it is an important mystery. It turns out that roughly 68% of the Universe is dark energy. Dark matter makes up about 27%.
The balance of normal matter, everything on Earth, everything ever observed with all of our instruments, all normal matter - adds up to less than 5% of the Universe. Come to think of it, maybe it shouldn't be called "normal" matter since it is such a small fraction of the Universe.
One explanation for dark energy is that it is a property of space. Albert Einstein was the first person to realize that empty space is not truly empty. Space has amazing and mystifying properties, many of which are just beginning to be understood. The first property that Einstein discovered is that it is possible for more space or the vacuum of space to come into existence.
One version of Einstein's gravity theory, the version that contains a cosmological constant, makes a second prediction: "empty space" can possess its own energy. Because this energy is a property of space itself, it would not be diluted as space expands.
As more space comes into existence, more of this energy-of-space would appear. As a result, this form of energy would cause the Universe to expand faster and faster. Unfortunately, no one understands why the cosmological constant should even be there, much less why it would have exactly the right value to cause the observed acceleration of the Universe.
If you could jump a spaceship that could take you to other star systems, you would find worlds beyond your dreams. For example, there is a planet about 40 light years (235,144,513,728,000 miles) away from Earth that is made of 1/3 diamond and its value would be $30 nonillion dollars, that is 30 with 29 zeros after it.
A few thousand light years away from Earth, you can find a planet which completes it's orbit around its star in only 6 hours time unlike the earth's 365 days.
Another planet about 30 light years away has an exotic form of ice which scientists call "hot ice" because it exists at a temperature of 570 degrees F and high pressure. Of course, a little further out at 480 light years is a planet that has a surface temperature of 4000 degrees F and rains molten rock.
Of course, if we were able to visit other parts of the universe we would continue to find exotic stars and planets where pressure, temperature and various sizes would serve to provide a vast array of weird and very strange worlds.