What is Space?
🛰️ Space, the final frontier, what is it?
Where does space begin and, more importantly, what is it?
📕 Definition
Space is an almost perfect vacuum, nearly void of matter and with extremely low pressure. In space, sound doesn't carry because there aren't molecules close enough together to transmit sound between them. Not quite empty, bits of gas, dust and other matter floats around "emptier" areas of the universe, while more crowded regions can host planets, stars and galaxies.
From our Earth-bound perspective, outer space is most often thought to begin about 62 miles (100 kilometers) above sea level at what is known as the Kármán line. This is an imaginary boundary at an altitude where there is no appreciable air to breathe or scatter light. Passing this altitude, blue starts to give way to black because oxygen molecules are not in enough abundance to make the sky blue.
No one knows exactly how big space is. It's difficult to determine because of what we can see in our detectors. We measure long distances in space in "light-years," representing the distance it takes for light to travel in a year (roughly 5.8 trillion miles (9.3 trillion kilometers)).
👩🏽🚀 Space Radiation to Human Eyes
The majority of space is relatively empty, with just stray bits of dust and gas floating around. This means that when humans send a probe to a distant planet or asteroid, the craft will not encounter "drag" in the same way that an airplane does as it sails through space.
In fact, the universe as a whole is inundated with what is known as the cosmic microwave background (CMB), which is essentially the leftover radiation from the explosion mostly commonly known as the Big Bang. The CMB is the oldest radiation that our instruments can detect.
🌑 Dark Matter and Energy
While scientists have provided extensive evidence for the existence of dark matter and dark energy, they are each still poorly understood as, so far, scientists cannot directly observe them and can only observe their effects.
Thought to make up nearly 75% of the universe, dark energy is a mysterious and unknown force or entity that scientists think is responsible for the universe's ongoing expansion.
Dark energy might have a similar name to dark matter, but it's a whole different component entirely.
🕳️ Black Holes
Origin
Smaller black holes can form from the gravitational collapse of a gigantic star, which forms a singularity from which nothing can escape — not even light, hence the name of the object. No one is quite sure what lies within a black hole, or what would happen to a person or object who fell into it - but research is ongoing.
Milestones
An example is gravitational waves, or ripples in space-time that come from interactions between black holes. This was first predicted by Albert Einstein at the turn of the last century, when he showed that time and space are linked; time speeds up or slows down when space is distorted.
As of mid-2017, the Laser Interferometer Gravitational-Wave Observatory (LIGO) Scientific Collaboration has announced three black-hole interactions and mergers detected through gravitational waves, in just two years.
Conclusion
The team found these three events in about two years, indicating that when LIGO is implemented at full sensitivity, the observatory may be able to find these sorts of events frequently, scientists said in May 2017. Should a bunch of these black hole events be detected, it could help scientists learn how black holes of a certain size (several tens of sun masses) are born, and later merge into new black holes.
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