What Shape is the Universe?

Article written: 11 May , 2015
Updated: 23 Dec , 2015
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It’s a reasonable question to wonder what the shape of the Universe is. Is it a sphere? A torus? Is it open or closed, or flat? And what does that all mean anyway?

The Universe. It’s the only home we’ve ever known. Thanks to its intrinsic physical laws, the known constants of nature, and the heavy-metal-spewing fireballs known as supernovae we are little tiny beings held fast to a spinning ball of rock in a distant corner of space and time.

Doesn’t it seem a little rude not to know much about the Universe itself? For instance, if we could look at it from outside, what would we see? A vast blackness? A sea of bubbles? Snow globe? Rat maze? A marble in the hands of a larger-dimensional aliens or some other prog rock album cover?

As it turns out, the answer is both simpler and weirder than all those options. What does the Universe look like is a question we love to guess at as a species and make up all kinds of nonsense.

Hindu texts describe the Universe as a cosmic egg, the Jains believed it was human-shaped. The Greek Stoics saw the Universe as a single island floating in an otherwise infinite void, while Aristotle believed it was made up of a finite series of concentric spheres, or perhaps it’s simply “turtles all the way down”.

Thanks to the mathematical genius of Einstein, cosmologists can actually test out the validity of various models that describe the Universe’s shape, turtles, mazes, and otherwise.

There are three main flavors that scientists consider: positively-curved, negatively-curved, and flat. We know it exists in at least four dimensions, so any of the shapes we are about to describe are bordering on Lovecraftian madness geometry, so fire up your madness abacus. Ya! Ya! Cthulhu ftagen.

A positively-curved Universe would look somewhat like a four-dimensional sphere. This type of Universe would be finite in space, but with no discernible edge. In fact, two distant particles travelling in two straight lines would actually intersect before ending up back where they started.

You can try this at home. Grab a balloon and draw a straight line with a sharpie. Your line eventually meets its starting point. A second line starting on the opposite side of the balloon will do the same thing, and it will cross your first line before meeting itself again.

This type of Universe, conveniently easy to imagine in three dimensions – would only arise if the cosmos contained a certain, large amount of energy.

To be positively-curved, or closed, the Universe would first have to stop expanding – something that would only happen if the cosmos housed enough energy to give gravity the leading edge. Present cosmological observations suggest that the Universe should expand forever. So, for now, we’re tossing out the easy to imagine scenario.

A negatively-curved Universe would look like a four-dimensional saddle. Open, without boundaries in space or time. It would contain too little energy to ever stop expanding.

Here two particles traveling on straight paths would never meet. In fact, they would continuously diverge, getting farther and farther away from each other as infinite time spiraled on.

If the Universe is found to contain a Goldilocks-specific, critical amount of energy, teetering perilously between the extremes, its expansion will halt after an infinite amount of time,

This type of Universe is called a flat Universe. Particles in a flat cosmos continue on their merry way in parallel straight paths, never to meet, but never to diverge either.

Sphere, saddle, flat plane. Those are pretty easily to picture. There are other options too – like a soccer ball, a doughnut, or a trumpet.

A soccer ball would look much like a spherical Universe, but one with a very particular signature – a sort of hall of mirrors imprinted on the cosmic microwave background.

The doughnut is technically a flat Universe, but one that is connected in multiple places. Some scientists believe that large warm and cool spots in the CMB could actually be evidence for this kind of tasty topology.

Lastly, we come to the trumpet. This is another way to visualize a negatively-curved cosmos: like a saddle curled into a long tube, with one very flared end and one very narrow end. Someone in the narrow end would find their cosmos to be so cramped, it only had two dimensions. Meanwhile, someone else in the flared end could only travel so far before they found themselves inexplicably turned around and flying the other way.

So which is it? Is our Universe an orange or a bagel? Is it Pringles? A cheese slice? Brass or woodwind? Scientists have not yet ruled out the more wacky, negatively-curved suggestions, such as the saddle or the trumpet.

WMAP data of the Cosmic Microwave Background. Credit: NASA

WMAP data of the Cosmic Microwave Background. Credit: NASA

Haters are going to argue that we will never know what the true shape of our Universe is. Those people are no fun, and are just obstructionists. Seriously, let us help you get better friends.

Based on the most recent Planck data, released in February 2015, our Universe is most likely… Flat. Infinitely finite, not curved even a little bit, with an exact, critical amount of energy supplied by dark matter and dark energy.

I know this gets a little confusing, and meanders right up to the border of nap time, but here’s what I’m hoping you’ll take away from all this.

It’s amazing that not only can we make guesses at what our incredible universe looks like, but that there’s clever people working tirelessly to help us figure that out. It’s one of the things that makes me happiest about talking every week about space and astronomy. I just can’t wait to see what’s next.

So what do you think? Is a flat Universe too boring for your taste? What shape would you like the Universe to be, given the wide array of options?

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10 Responses

  1. kwestdjonmaarc says

    That moon article is creeping back in! haha

  2. Steven says

    So what about the dark energy making things seem like the universe should be negatively curved where things are to spread out forever. How are these reconciled? I’m very confused about dark energy (not dark matter) because it is – as best I can determine – on the basis of the observation that the universe is flat and thus there must be unaccounted for matter/energy to close the universe more than the visible and dark matter allows for but ALSO has the property of accelerating things apart just like if space were actually negatively bent.

    It bends me too.

    or put another way “Based on the most recent Planck data, released in February 2015, our Universe is most likely… Flat. ” almost contradicts “Present cosmological observations suggest that the Universe should expand forever.” (ie not positively curved)

  3. My guess, based upon the “Big Bang” theory, would have to say the Universe is somewhat spherical in shape. Everything within the Universe is nearly spherical, giving rise to the fact that enough gravity in a mass causes this shape, while the rotation tends to slightly flatten out the perfect sphere, like our Earth.

    While I don’t think the Universe is perfectly spherical, I think it is much like the planets, stars and galaxies within it – a slightly flattened out sphere as a result of the combined forces of gravity and rotation. The reason I discount the flat Universe is simple. You can look to the stars and see they exist in all directions from Earth, making the cosmos at the very least, three dimensional.

    • BlackWolfStanding says

      I don’t think they mean flat like the Flat Earthers called the Earth flat back in the day. You only need to look at a picture of the Cosmic Web to know that. They are not even arguing against Einstein’s curved space which has been proven to be true. You need to read the article again.

  4. Member
    Pete says

    This was being argued sixty-plus years ago when I was entering college.
    Some arguments then were relating the shape of the universe to conic sections. Closed (circular or eliptical), flat (parabolic, infinite yet finite) or open (hyperbolic).
    I’m sort of surprised, yet not so, to see it back in discussion – and we seem to be no closer now than we were then to a sensible answer. I guess that’s the surprise, given the incredible, some even bordering on unbelievable, advances in most of science.

  5. Paul Gracey says

    It should be remembered that all our observations are made from just a single point in space/time, ‘relatively’ speaking. It’s a bit like trying to describe the entirety of a landscape painting from the point of view of the artist’s “vanishing point”. When we look at a painting done with proper perspective, we do not see the world that surrounds that vanishing point on the horizon and someone painting from there cannot accurately describe where we are located either.
    Should we find a means of communication( time travel, in essence) with some distant parts of the Universe, most of these questions will be rendered moot.

    • BlackWolfStanding says

      I agree with you that our perspective is very limited. We are trying to make a movie out of one frame. And we don’t know how accurately that frame was made.

    • TedH says

      Or… as I like to see it: you are in the position of a fly / beetle / moth on a window…. 37th floor… on a high rise in… NYC / Singapore / Tokio… and you should draw a map of the city without leaving the window! Good luck 😉

  6. Ian Elliott says

    I’ll go with the Jains, and the human body I’d prefer for the Universe would be Christina Hendricks’.

  7. fowlowl1955 says

    We’ve been told a la the big bang that the whole thing started from a single point flying outward in all directions. This suggests a round shape. But we know galaxies collide so some force (Gravity?Dark Energy?Dark Matter?) must have pulled things back in some areas. But nature seems to like spheres. Perhaps the universe started out to be positively curved but ended up like a basketball without enough air with dents in it, clusters and seemingly empty areas. Nebulous in a way.

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