What Are The Biggest Mysteries in Astronomy?

Article written: 22 Jun , 2015
Updated: 27 Feb , 2017

Black Holes? Dark Energy? Dark Matter? Alien Life? What are the biggest mysteries that still exist out there for us to figure out?

“The more I learn, the more I realize how much I don’t know.” These are the words of Albert Einstein. I assume he was talking about Minecraft, but I guess it applies to the Universe too.

There are many examples: astronomers try to discover the rate of the expansion of the Universe, and learn a dark energy is accelerating its expansion. NASA’s Cassini spacecraft finally images Saturn’s moon Iapetus, and finds a strange equatorial ridge – how the heck did that get there? Did the Celestials forget to trim it when it came out of the packaging?

There have always been, and, let’s go as far as to say that there always will be, mysteries in astronomy. Although the nature of the mysteries may change, the total number is always going up.

Hundreds of years ago, people wanted to know how the planets moved through sky (conservation of angular momentum), how old the Earth was (4.54 billion years), or what kept the Moon from flying off into space (gravity). Just a century ago, astronomers weren’t sure what galaxies were (islands of stars), or how the Sun generated energy (nuclear fusion). And just a few decades ago, we didn’t know what caused quasars (feeding supermassive black holes), or how old the Universe was (13.8 billion years). Each of these mysteries has been solved, or at least, we’ve a got a pretty good understanding of what’s going on.

Science continues to explore and seek answers to the mysteries we have, and as it does it opens up new brand doors. Fortunately for anyone who’s thinking of going into astronomy as a career, there are a handful of really compelling mysteries to explore right now:

Is the Universe finite or infinite? We can see light that left shortly after the Big Bang, 13.8 billion years in all directions. And the expansion of the Universe has carried these regions more than 45 billion light-years away from us. But the Universe is probably much larger than that, and may be even infinite.

Images from the Hubble Space Telescope showing a gravitational lensing effect. Credit: NASA/ESA.

Images from the Hubble Space Telescope showing a gravitational lensing effect. Credit: NASA/ESA.

What is dark matter? Thanks to gravitational lensing, astronomers can perceive vast halos of invisible material around all galaxies. But what is this stuff, and why doesn’t it interact with any other matter?

What is dark energy? When trying to discover the expansion rate of the Universe, astronomers discovered that the expansion is actually accelerating? Why is this happening? Is something causing this force, or do we just not understand gravity at the largest scales?

There are supermassive black holes at the heart of pretty much every galaxy. Did these supermassive black holes form first, and then the galaxies around them? Or was it the other way around?

The Big Bang occurred 13.8 billion years ago, and the expansion of the Universe has continued ever since. But what came before the Big Bang? In fact, what even caused the Big Bang? Has it been Big Bangs over and over again?

The Universe 590 million years after the Big Bang. Credit: Alvaro Orsi, Institute for Computational Cosmology, Durham University.

The Universe 590 million years after the Big Bang. Credit: Alvaro Orsi, Institute for Computational Cosmology, Durham University.

Are we alone in the Universe? Is there life on any other world or star system? And is anyone out there we could talk to?

Shortly after the Big Bang, incomprehensible amounts of matter and antimatter annihilated each other. But for some reason, there was a slightly higher ratio of matter – and so we have a matter dominated Universe. Why?

Is this the only Universe? Is there a multiverse of universes out there? How do I get to the Whedonverse?

In the distant future, after all the stars are dead and gone, maybe protons themselves will decay and there will be nothing left but energy. Physicists haven’t been able to catch a proton decaying yet. Will the ever?

And these are just some of the big ones. There are hundreds, thousands, millions of unanswered questions. The more we learn, the more we discover how little we actually understand.

Whenever we do a video about concepts in astronomy where we have a basic understanding, like gravity, evolution, or the Big Bang, trolls show up and say that scientists are so arrogant. That they think they know everything. But scientists don’t know everything, and they’re willing to admit when something is a mystery. When the answer to the question is: I don’t know.

What’s your favorite unanswered question in space and astronomy? Give us your best mystery in the comments below.

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19 Responses

  1. Please try to tell, what is the meaning of life in the universe, is it all coincidence? pure philosofical that is……

    • Wayne Roberts says

      42, of course.

    • FarAwayLongAgo says

      Sounds like you should have a look at ibiology dot org, a site dedicated to outreach about biology from chemistry to ecology. Have a look at some lectures about microbiology or cellular biology. They describe what you yourself actually are. You can ask your own “microtubulae” what meaning they have. Please let the rest of us know once you find it out!

  2. elvigy says

    Dark energy. Not having any clue about it, it’s easy to project all my hopes for future space travel on it. If we can figure out what it is and manipulate it somehow, can it solve some of the basic obstacles we face in space travel? Is it something that can be used to bypass the limits to how fast we can travel in/through/around space? Who knows.

    • FarAwayLongAgo says

      Its just vacuum energy, the cosmological constant in Einstein’s relativity theory. Nothing strange at all. And it is useless since it is so extremely evenly distributed. It cannot be concentrated or discharged. It is as powerful as vacuum. But dark matter might have some potential. Neutrino astronomy is already beginning, and neutrinos are almost dark matter. Maybe a product of dark matter decay?

  3. metalman_5150 says

    The prominence of Saturn in the Tool song, “The Grudge,” has always peeked my interest. ..,

    “Saturn ascends, choose one or ten. Hang on or be humbled again.”

    “Saturn comes back around to show you everything.
    Let’s you choose what you will not see and then,
    Drags you down like a stone or lifts you up again;
    Spits you out like a child, light and innocent.”

    Something to do with the orbit of Saturn lasting roughly 30 years or so?

    • FarAwayLongAgo says

      Saturn in latin is Chronos in greek. The god of time. The lyrics probably refers to the mythology and not to the planets named after it.

      Maybe the ancients gave that name to the Saturn planet because it was the slowest one visible? The outer planets happen to be well named: Wisdom (Jupiter) son of, Age (Saturn) son of, Space (Uranus/Celestus), Sea (Neptune), Pluto (a cartoon dog, ehm, no the god of death, brother of Neptune).

    • weeasle says

      In Astrology there is something called “Saturn Returns” In mythology of astrology which relates to Saturn ascending in a persona natal star chart every 30 yrs (its orbit). it is believed the greco-roman god of Saturn represents transformation and change in a persons life (often causing discomfort as change can). That is what the song refers to. Although I do not accept such superstition, I do appreciate the ancient mythos of various cultures and how they relate to the stars – And thats my hook to this artice – A great question science could answer is were there cultures with advanced technology before ours – 100,000 seems a long time to go from hunter gathering to space travel.. Then again maybe it isnt??

      • FarAwayLongAgo says

        weeasle, Even 3000 years ago, the pyramids were mysteriously old. Imagine a history a thousand times older than the pyramids. 3+ million years ago apes manufactured stone tools already.

        The human mind flies to the sky while the body crawls slowly slowly on the ground. We might dream about interstellar spaceflight, like our ancestors dreamt about having machines, dead matter, doing the hard work for them.

  4. Rhodam says

    Are we alone in the Universe? Is there life on any other world or star system? And is anyone out there we could talk to?
    There is such a simple answer to ALL these questions and it’s been in right in front of us, over us and around us since the beginning of time. The answers are found in the Bible and it begins with “In the beginning, God created the heaven and the earth.” Genesis 1:1 And yes, we can talk to God and we can accept his personal gift of salvation through the blood of Jesus Christ that was shed for the sins of all mankind.

  5. rajen0201 says

    Cause of Gravity is the biggest mystery of Astronomy. Yes, Einstein GR is only a geometrical representation of how gravity works but does not give fundamental physics answer why it attracts. Author of this blog is requeste to refer below fundamental cause of gravity.

    I have prepared a paper on cause of gravity-Disruption of intermolecular bonds(that causes vacuum drag towards planet) which can alter the belief that gravity depends on mass and Einstein GR. Rather it depends on surface topography/Volcano Eruption which will show why ancient dinosaurs are very big in size. My manuscript is in [Promotion of personal website and URL removed by moderator.] for publish (Any one can see).

    You can see my abstract here and comment for the same.

    Abstract: Gravity is considered as one of the four fundamental forces, but is not been unified with the other fundamental forces. Scientists are clueless about the weakness of gravity and hence, it remained an unsolved mystery. There are number of scientists who feel that there must be a physical mechanism for gravity which causes only attraction. Below hypothesis uses surface energy that is known as work has been done to create a surface. Surface energy quantifies the disruption of intermolecular bonds that occurs when a surface is created. Most of this work is utilized to create elastic membrane in liquid and for solid (consider Earth without atmosphere) it is to be utilized to conserve the law of energy, some of it converted in heat energy and the energy remaining creates absolute internal pressure. Here, this thermodynamic phenomenon leads to Young-Laplace theory that is “if pressure on one side of the surface differs from the pressure on the other side, the pressure difference times projected area results in a normal force [1]. If no force acts normal to a tensioned surface, the surface must remain flat”. Einstein predicted the same logic for space time geometry in general relativity that is why his predictions are confirming, except related to graviton. Here, Absolute Internal pressure must be balanced by same magnitude inward pressure to conserve the law of energy. Earth atmospheric pressure (created due to air mass) tends to balance it. Here, the remained pressure difference is absolute which answers why gravity is so weak. Multiplication of this remained absolute pressure and Earth cross section area causes normal force that is to be balanced by same magnitude inward force that is known as gravity. Objects over the surface experiences vacuum drag towards the Earth cross section. That is why all physical objects experience same inward acceleration and seems attractive in nature. This hypothesis will give all known-unknown answers like why gravity seems it cannot be shielded, why universal gravitational constant value varies, Why Einstein’s gravity theory significantly changes at distances smaller than an atom. That is because the surface energy concept in the limit of a single molecule not works, etc.
    Waiting for your positive reply.

  6. SlappyBags says

    To me, the greatest mystery in astronomy is The Great Attractor.

    • FarAwayLongAgo says

      What about the Backward galaxy?
      The rotational direction of thousands of spiral galaxies have been determined. All but one, NGC4622 rotate in the obvious direction. One wants to be different. How do we tame a galaxy? Can a galaxy be wrong? Like one car driving on the wrong side of the road in England or Japan.

  7. Member
    Pete says

    Whether the universe is closed (finite), flat (infinite) or hyperbolic (open and infinite) or something else entirely is as much a mystery today as it was when I started college 65 years ago – all despite the incredible advances in observational tools and formal theory that have happened in the interim.
    But it IS fun to watch the spurts of insight and the setbacks as mankind continues to try to understand it.

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