What are the big unanswered questions about space?

Main topic: Science

Other topics: Space

Short answer: There are several unanswered questions about space/universe, including its shape, boundary, mass, energy, gravitational fields, what existed before, stars, black holes, planets, etc.

The recent strides in astronomy, the discovery of the universe, and its best-kept secrets have been astounding. Barely a century ago, we had no idea about the universe's age. Now, we have created complex maps of what astronomers refer to as cosmic microwave backgrounds to precisely calculate that the universe is 13.8 billion years old. The margin of error in this calculation is a lowly 10 million years.

Despite all the achievements from the Hadron particle accelerator to Hubble and James Webb deep space telescope continuously operating, we have barely started understanding the universe around us.

Several big questions still puzzle scientists and astronomers.

We do not yet understand the dark matter and dark energy that space is made of

Astronomical observations have revealed a massive disparity in the visible matter in galaxies (gas clouds, planetary objects, stars, etc.) and the actual mass they have been holding. The visible matter in the universe only accounts for slightly less than 5% of the total mass. The invisible mass is attributed to dark matter and dark energy.

Dark matter is matter which is not visible, and it constitutes about 26.8% of the universe.

The remaining 68.3% is attributed to dark energy pushing the expansion of our universe. The discovery was made by observing data sets received from Hubble, which revealed that all galaxies are accelerating away from each other due to unexplained force or energy, now called dark energy.

Is space infinite in nature? Does our universe has a boundary?

The problem in theorizing the finiteness or infinity of the universe lies in various contradictory studies about the universe's shape. Some studies show that the universe's geometry may be 'flat' and infinite. Some studies show that the universe could be in a 'closed' geometrical shape and hence finite.

Our observable universe is 92 billion lightyears wide and is 410 nonillion (a unit of thousand billion billion billion) cubic lightyears volumetrically. There are unanswered questions about the edge of the universe and, if it exists, then what lies beyond.

Do multiverse/parallel universes exist?

According to physicists, several scenarios might produce "alternate" or "parallel" universes. Some of these include the division of space due to uneven inflation of matter preceding the Big Bang.

Others are based on the simultaneous existence of multiple space-time interpretations of quantum physics, the string theory of fundamental particles, the fact that the constants of nature are so delicately balanced, or the simple premise that the universe may be endless.

A couple of investigations have hinted at the possibility of parallel world detection:

• One from the discovery of neutrinos in Antarctica
• Another from the fluctuations in the 'cosmic microwave background'.

Both of these were eventually revealed to be false. Some scientists reject the concept of parallel worlds for logical reasons or because it cannot be proved or disproved (unfalsifiability).

What existed before our universe and the event of Big Bang?

A prevalent myth is that the Big Bang created both space and time. There is no tangible evidence to suggest that such was the case.

Due to the complicated mathematical "singularities", current physics breaks down totally at the instant of "creation" and fails to explain what existed before. Therefore, it is impossible to state with certainty what may have occurred or existed before the creation of the current universe.

Scientists have been theorizing several scenarios:

• Before the Big Bang, there may have been no space, no time, and not even an endless vacuum.
• There may have been earlier worlds, an energy field, other copies of our universe, or many universes with distinct physical principles.

Similar to parallel universe/multiverse, such hypotheses are an integral element of contemporary astronomy. However, obtaining observable proof for them is exceedingly difficult, if not impossible.

Consequently, astronomers and scientists cannot answer this mystery due to our current limitations of technology and understanding.

What is gravity?

Einstein's general theory of relativity has toppled over Newton's epiphany based on the falling apple and his simple explanation. General relativity observes gravity as geometry and a universal force.

There is a need for new explanations to describe how specific strong and weak gravity fields function. There is no consensus in the scientific community about what gravity is.

What are black holes?

While we have some answers, we mostly do not understand black holes and what constitutes them. They are notoriously tricky to spot because they absorb light and are usually highly compact due to forces that we do not entirely understand either.

Unanswered questions about our immediate universe, our solar system

We don't have to look so far for mysteries of space. There are several unresolved questions about our solar system:

• How did the moon come into existence?
• Why does Venus rotate in the opposite direction of all other planets?
• Why do all planets have a vastly different constitutions?
• Do gas giants in our solar system have a core?
• Why the Kuiper asteroid belt ends abruptly around Neptune?
• Is Oort cloud there, or is it just a theory?