We’ve learned so much over the centuries, but science still can’t definitively answer these surprisingly fundamental questions.

What came before the Big Bang?

What came before the Big Bang? Courtesy NASA/ESA

If the universe began billions of years ago with the Big Bang, what preceded it? According to renowned physicist Stephen William Hawking, PhD: Nothing. However, no one can know for sure; any events that happened before the universe came into existence are without “observational consequence,” as Hawking put it, and therefore, we “may as well cut them out of the theory, and say that time began at the Big Bang.” 

What is dark matter?

What is dark matter? Courtesy NASA/JPL-Caltech/ESA/Institute of Astrophysics of Andalusia, University of Basque Country/JHU

Everything and everyone is made up of “baryonic matter:” protons, neutrons, and electrons. Until about 30 years ago, astronomers thought that the universe followed the same rules—it was entirely baryonic matter. Over the last few decades, however, scientists have found that only 5 percent of the universe is composed of baryonic matter—and they can’t even detect the other 95 percent. Scientists believe that some 25 percent consists of dark matter—but nobody can say definitively what dark matter actually is or what it’s made of yet. 

What is dark energy?

What is dark energy? Courtesy NASA Goddard

The other 70 percent of the universe is thought to be comprised of dark energy. What scientists do know about dark energy is that it has a gravitationally repulsive effect (which is to say, the opposite of gravitational pull) and that it’s responsible for the expansion of the universe. But what exactly is dark energy continues to elude scientists, leaving NASA scratching their heads and wondering if Einstein got his theory of gravity wrong. One thing Albert Einstein definitely got right was the secret to happiness—and it’s genius.

How can gravity be so strong and yet so weak?

How can gravity be so strong and yet so weak? Courtesy NASA

Gravity poses a vexing paradox that can be summed up with this question: Why can a mere refrigerator magnet defy an entire planet’s gravitational pull? Some scientists believe that gravity may well be as strong as the other fundamental forces (such as electromagnetism and the force that holds the nucleus together), but its influence is dissipated because it leaks into extra dimensions. That explanation will have to do until they come up something better.

How big is the universe?

How big is the universe? Courtesy NASA, ESA, and the Hubble Heritage (STScI/AURA)-ESA/Hubble Collaboration Acknowledgment: R. O'Connell (University of Virginia) and the WFC3 Scientific Oversight Committee

If scientists know that the universe is expanding, then they must be able to hazard a guess at how big it is, right? Unfortunately, scientists can’t pin a number on it. They would have to know the universe’s shape and rate of expansion, among other things—and those are mysteries as well. 

What is the shape of the universe?

What is the shape of the universe? Courtesy NASA Goddard

Scientists have a number of theories about the shape of the universe. But according to NASA, the leading theory is that the universe is flat, which leads them to believe that it’s infinite in size. However, since the universe has a known beginning, and perhaps an expected endpoint, we can only observe a finite volume of it. As NASA says, “All we can truly conclude is that the universe is much larger than the volume we can directly observe.”

How fast is the universe expanding?

How fast is the universe expanding? Courtesy NASA/JPL/California Institute of Technology

For the past six years, the Hubble Space Telescope has been calculating the speed at which the universe is expanding and recently came up with what is accepted as the most precise measurement to date—except that the rate stands in direct conflict with independent (and supposedly precise) measurements of the early universe’s expansion. That’s unsettling for astrophysicists because it means we know even less about our universe and its ways than we thought. “The community is really grappling with understanding the meaning of this discrepancy,” said the lead researcher, Adam Riess, a Nobel Laureate and Bloomberg Distinguished Professor at Johns Hopkins University. 

Is the universe actually a multiverse?

 Is the universe actually a multiverse? manjik/Shutterstock

“Our universe could be just one of an infinite number of universes making up a ‘multiverse,’” according to astronomy news site space.com, and as bizarre as that may seem, there’s actual science behind it. Because there are only a finite number of ways particles can be arranged in space and time (and remember the universe is flat and infinite), then the universe would have to start repeating at some point. Which leads to the question…

Could there be another you?

Could there be another you? Courtesy NASA/Ames/SETI Institute/JPL-Caltech

If the universe is compelled to repeat itself—to be part of a multiverse—could there be another version (or multiple versions) of you? “If you look far enough, you would encounter another version of you—in fact, infinite versions of you,” according to space.com. “Some of these twins will be doing exactly what you’re doing right now, while others will have worn a different sweater this morning, and still others will have made vastly different career and life choices.” This counts as one of the mysteries we’re unlikely to ever get an answer for, but it’s intriguing nonetheless. (Maybe the other version of you isn’t hopelessly addicted to Girl Scout cookies.) The experts say that this theory would require additional dimensions, and if so…

How many dimensions are there really?

How many dimensions are there really? Fred Mantel/Shutterstock

The three dimensions of which we can be certain pertain to what we can perceive: length, width, and depth. Scientists also point to the fourth dimension of time. But according to Phys.org, while still a mystery, some potential dimensions include:

  • Fifth: In which we can see a world slightly different from our own (which would give us the means of gauging similarities and differences between it and ours).
  • Sixth: We can see all possible universes that have begun the same as our own
  • Seventh: We can perceive all possible universes that began differently than our own.
  • Eighth: We see all possible universes. Period.
  • Ninth: We are aware of all possible laws of physics and universe beginnings.
  • Tenth: We can see all things possible and imaginable.

How did the moon form?

How did the moon form? Courtesy NASA/JPL

The moon’s gravitational pull is responsible for the rise and fall of the ocean tides, but how did the moon come to be? After all, it took a hundred million years after the solar system and its planets began to form before the moon actually sprang into existence. Several theories exist, none of which is close to being proven. Meanwhile, one potential key to figuring out how we got a moon is to understand why Venus doesn’t have one, according to Dave Stevenson, a professor of planetary science at the California Institute of Technology. We still haven’t figured that one out, either.

Did life originate on Earth?

Did life originate on Earth? Courtesy Ocean Biology Processing Group

We take it for granted that life on Earth actually began here—but that’s not actually accurate. Scientists are finding evidence that life on Earth may have come from Mars and was brought to this planet by a meteorite. The trouble is that scientists can’t even agree on which area of science will provide the answer, let alone whether science is even where we should look.

Is there alien life?

Is there alien life? Ursatii/Shutterstock

Since the early 1960s, scientists have theorized that it’s extremely likely that intelligent life exists outside of Earth. The trouble is that we have zero scientific evidence. In fact, we have no hard scientific evidence that any life exists outside of earth, at least so far. But the time may be drawing closer when science confirms that there is life elsewhere in our solar system, or the galaxy, or at least somewhere in the universe.

Who’s in charge here?

Who’s in charge here? Thoom/Shutterstock

Does someone or something start the whole process that led to you reading these words on an electronic screen? Or is everything that’s happened in the history of ever simply the result of a process guided by laws of science? While many notable scientific thinkers say God is a myth, not all scientists are atheists. This is one we’re unlikely to solve—at least during our lifetime.

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