How big is the universe

Just How Big Is The Universe?

The observable universe appears to be finitely large and has been measured, but no one can say for sure whether our universe (in totality) is infinite, or even if ours is the only one to exist.

“Two things are infinite: the universe and human stupidity; and I’m not sure about the universe.” – Albert Einstein

Lying outside on a moonlit night, relaxing in peace, have you ever considered that the light falling on your eyes might have started its journey billions of years ago from a galaxy so far away that it might not even exist anymore?

For centuries, humans have been trying to assess the scale of the universe in which we live, but to our great disappointment, these efforts have thus far been in vain. However, as with every domain, technology has evolved tremendously in this sector of science, and researchers now claim that we’ve never been closer to assessing the exact size of the universe. Let’s take a closer look…

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What is the shape of the Universe?

Einstein’s theory of relativity taught us one very important and fundamental concept—mass causes space to curve, so it is the mass (density) of the universe that governs its size. Scientists often describe the shape of the universe in terms of the density parameter (Ω), defined as the ratio between the actual density of the universe and its critical density, which is required to stop its current expansion rate (more on universe expansion shortly).

There are basically three shapes to be considered here: flat (Ω=1), closed or positive curve (Ω>1), and open or negative curve (Ω

How Big is the Entire Universe?

To the limits of our observable Universe and well beyond, here’s what we know the minimum size of the Universe must be, along with how we know it.

The Universe is a vast, seemingly unending marvel of existence. Over the past century, we’ve learned that the Universe stretches out beyond the billions of stars in our Milky Way, out across tens of billions of light years, containing close to a trillion galaxies all told.

And yet, that’s just the observable Universe! There are good reasons to believe that the Universe continues on and on beyond the limits of what we can see; the question is, how far does it go on? Forever? Or does it close back upon itself at some point?

To help us better understand this question, let’s turn to something more familiar (and smaller) that we know how to measure the size of: the Earth.

From the top of a tall mountain, like Mauna Kea, shown here, you might hope to measure the Earth’s curvature, but your efforts would be in vain. From even 14,000 feet up, the curvature of the Earth is totally indistinguishable from flat.

There are images out there where the Earth appears curved when you look out at the water, and indeed, they’re not hard to find. But is that because of the Earth’s curvature?

Not at all; it’s because of atmospheric distortion. If you were to try and calculate the circumference of the Earth from a photo like this, you’d get a world that was smaller than even the Moon is; you cannot measure the curvature of the Earth from any known location on the surface of the planet.

Moreover, when we’re talking about the land surface, the Earth itself isn’t perfectly smooth. Some places are curved upwards, others downwards, and any small region visible to you is unlikely to be a fair representation of the entire planet.

There is a way that you’d be able to tell, though, what the shape and size of the planet actually is. All you’d have to do is take the appropriate measurements and use geometry.

It’s as simple as going to three separate locations on Earth and drawing a triangle to connect those three points.

On a flat sheet of paper, the three angles of any triangle will always add up to 180°, as you well know. But if you’re on the surface of a sphere (or, mathematically, any surface of positive curvature), those angles will add up to more than 180°. Knowing the distance between each of those three points and the measure of all three angles allows you to calculate what the circumference of the Earth is.

And, of course, the farther away your three points are from one another, the less important the mountains, valleys and oceans are, and the more important the overall shape of the Earth is to your measurement. The converse would have been true if the Earth were shaped with negative curvature, like a saddle, as shown below.

A surface of negative curvature has any three points form a triangle whose three angles sum to less than 180°, and again, knowing the distances and measurements of all three angles allows you to calculate the radius of curvature.

In practice, the very first calculation of the circumference of the Earth — dating to the 3rd Century B.C. — used a very similar method, again reliant on simple geometry.

It would not be until the 20th Century that we were actually able to achieve altitudes capable of measuring the curvature of the Earth from space, something we are only able to do because we can step off of the two-dimensional surface of the Earth and look at it from afar.

By 1948, we were creating mosaics of the Earth by stitching together multiple images of the Earth from space, and there could no longer be any doubt as to its circumference.

But space itself is a little trickier. Yes, it is just a geometric construct (albeit a slightly more complicated one), but it comes along with an inherent curvature to it. According to the rules of Einstein’s General Relativity, the amount that the space of our Universe is curved is directly related to the amount of matter and energy that we have in it, as well as its global expansion.

Dense, heavy masses like the Sun cause very large amounts of curvature in very small spaces, significant enough to bend starlight by amounts significant enough that you could notice it with 1919′s technology. But that’s local curvature, the same way mountains, valleys and ocean waves are local curvature here on Earth. What we’re interested in is whether the entire Universe ever closes back in on itself, and if so, how big it is. In other words, these local sources of curvature are things we need to not be fooled by.

The Earth, too, curves the spacetime around it. Remember that we use two dimensions as an illustration, but unlike measuring the curvature of the two-dimensional surface of the Earth, where we can fly “up” and observe the planet below, there is no extra spatial dimension to move through to step back from the curvature of our three-dimensional space.

And all of the spatial dimensions are curved. Since stepping back from the Universe and observing it from afar isn’t an option, the only way to get a good handle on its curvature is to examine it on its largest scales — the same way we did it before spaceflight on Earth — and try to infer its geometry.

In principle, this is pretty straightforward. Just as any three points on a surface can help you calculate that surface’s curvature, you can do the exact same thing with the Universe! Take any three points that are far enough apart, measure the distances between those points and the relative angles between them as well, and you’ll be able to figure out not only how your space is curved, but also what the radius of curvature is!

You can imagine three possible cases, of course. One is where the Universe is positively curved, like a higher-dimensional sphere, one is where the Universe is totally flat, like a higher-dimensional grid, and one where the Universe is negatively curved, like a higher-dimensional saddle. In the context of general relativity, it’s the energy density — the amount of matter and all other forms of energy — that determine this curvature.

In real life, we don’t have man-made objects far enough away to communicate with us across the necessary distances to measure curvature. Even if we did, it would take billions of years to do it, which is a disheartening way to attempt to do science. But we have light signals from when the Universe was just 380,000 years old, that tell us what the Universe is like 46 billion light years away.

The fluctuations in the cosmic microwave background — the leftover glow from the big bang — provide a window allowing us to see how our Universe is curved.

The first robust measurements of this came from the BOOMERanG experiment in the late 1990s (hearing Paolo de Bernardis talk about this in 2004 was a highlight for me during the early stages of my scientific career), where they first determined that rather than having significant positive or negative curvature, the Universe was indistinguishable from flat.

That doesn’t mean that it is flat, of course. If you walked outside and tried to measure the curvature of the Earth right now, but only within 5 km (or 3 miles) of your current location, you would find that the Earth is consistent with being flat, but it could also be positively or negatively curved on a larger scale than you’re currently measuring.

So it goes with the Universe as well. We were able to measure that the Universe, if it is curved, has a much larger radius of curvature than that of our observable Universe, which is about 46 billion light years. But if we could make that measurement more precise, we could conceivably measure a much smaller curvature than even that. Thanks to the Planck satellite, we now have the temperature fluctuations over the entire sky measured at a very narrow, tenth-of-a-degree resolution.

And what they teach us is that not only is the Universe consistent with being flat, it’s really, really, REALLY flat! If the Universe does curve back and close on itself, its radius of curvature is at least 150 times as large as the part that’s observable to us! Meaning that — even without speculative physics like cosmic inflation and multiverses — we know that the entire Universe extends for at least 14 trillion light years in diameter, including the part that’s unobservable to us today.

Just because the part of it we can see is indistinguishable from flat doesn’t mean it’s intrinsically flat in its entirety. But it does mean that the Universe is far larger than we’ll ever see. Even taking this minimum allowable estimate for the size of the Universe means that, at most, less than 0.0001% of the volume of the Universe is presently or will ever be observable to us. Once you put our knowledge about dark matter and dark energy in there, and consider how the Universe will expand into the future, you’ll realize that we’ll never see more of the Universe than we can right now.

So all that we see — from the billions of stars in our galaxy to the hundreds of billions of galaxies lighting up the observable Universe — is just a teeny-tiny fraction of what’s actually out there, beyond what the speed of light allows us to see.

And yet, we can know that it’s there. Isn’t science wonderful?

An earlier version of this post originally appeared on the old Starts With A Bang blog at Scienceblogs.

Features

The universe is a big, big place. But how big? And how do we know?

Throughout history, humans have used a variety of techniques and methods to help them answer the questions ‘How far?’ and ‘How big?’ Generations of explorers have looked deeper and deeper into the vast expanse of the universe. And the journey continues today, as new methods are used, and new discoveries are made. (To learn more about distance, visit How Big is Our Universe.)

In the third century B.C., Aristarchus of Samos asked the question ‘How far away is the Moon?’ He was able to measure the distance by looking at the shadow of the Earth on the Moon during a lunar eclipse.

It was Edmund Halley, famous for predicting the return of the comet that bears his name, who three centuries ago found a way to measure the distance to the Sun and to the planet Venus. He knew that the planet Venus would very rarely, every 121 years, pass directly between the Earth and the Sun. The apparent position of the planet, relative to the disk of the Sun behind it, is shifted depending on where you are on Earth. And how different that shift is depends on the distance from both Venus and the Sun to the Earth. This rare event, the transit of Venus, occurred again quite recently, June 8, 2004.

It was knowing this fundamental distance from the Earth to the Sun that helped us find the true scale of the entire Solar system for the first time.

When we leave the solar system, we find our star and its planets are just one small part of the Milky Way galaxy. The Milky Way is a huge city of stars, so big that even at the speed of light, it would take 100,000 years to travel across it. All the stars in the night sky, including our Sun, are just some of the residents of this galaxy, along with millions of other stars too faint to be seen.

The further away a star is, the fainter it looks. Astronomers use this as a clue to figure out the distance to stars that are very far away. But how do you know if the star really is far away, or just not very bright to begin with? This problem was solved in 1908 when Henrietta Leavitt discovered a way to tell the ‘wattage’ of certain stars that changed their pulse rate linked to their wattage. This allowed their distances to be measured all the way across the Milky Way.

Beyond our own galaxy lies a vast expanse of galaxies. The deeper we see into space, the more galaxies we discover. There are billions of galaxies, the most distant of which are so far away that the light arriving from them on Earth today set out from the galaxies billions of years ago. So we see them not as they are today, but as they looked long before there was any life on Earth.

The image below is both the oldest and youngest picture ever taken. It is the oldest because it has taken the light nearly 14 billion years to reach us. And it is the youngest because it is a snapshot of our newborn universe, long before the first stars and galaxies formed. The bright patterns show clumps of simple matter that will eventually form stars and galaxies. This is as far as we can see into the universe. It is time, not space, which limits our view. Beyond a certain distance, light hasn’t had time to reach us yet.

So how big is the universe? No one knows if the universe is infinitely large, or even if ours is the only universe that exists. And other parts of the universe, very far away, might be quite different from the universe closer to home. Future NASA missions will continue to search for clues to the ultimate size and scale of our cosmic home.

Go on the full exploration of the size of our universe at: How big is our universe? Beautiful images and straight-forward methods and ideas take you from our solar system, into the realm of the stars, the galaxies and finally into the vast panorama of the observable universe. You can also download and print a pdf version of these explorations.
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The Universe Forum talks more about size and distance in the universe.
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Learn more about the recent transit of Venus.
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Learn more about the WMAP satellite.
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Learn more about WMAP education.
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For kids 14 and up, check out investigations into the destiny of our universe.
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NASA’s Astronomy Picture of the Day Web site contains images and links to exciting astronomical discoveries and observations. It also includes a searchable directory and glossary of astronomical phenomena.
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Similar to Astronomy Picture of the Day, this site has weekly updates of news and images from telescopes observing in ultraviolet, X-Ray and gamma-ray light.
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How big is the universe?

Scientists don’t really know if the universe is finite or infinite, but here is the best of our knowledge

Our best estimates put the observable universe at about 93 billion light-years across 8.8×10 23 kilometers. The real size, however, is probably much greater.

Observing the universe — parallax and beyond

Let’s start our foray into the size of the universe with a very simple experiment: place your palm in front of your eyes. Look at it and focus on its position. Then close one eye, look at the palm again, and then switch eyes. Your hand appears to slightly move sideways, because of the different position of your eyes — this is called parallax.

By knowing the distance between your eyes and seeing the apparent displacement of your hand, we can calculate the distance to your hand. Now, imagine that instead of your eyes, we have two telescopes out in space, and instead of your palm we have a very distant object, say a star. We know how far apart the two telescopes are so we can calculate the distance to the star through parallax.

Thanks to the Earth’s orbit (which we can calculate precisely), we have exactly that: the ability to observe the same thing from two different points (the same telescope, moved around by the Earth’s orbit). This approach is used routinely by astronomers to calculate the distance to celestial objects.

A simplified illustration of the parallax of an object against a distant background due to a perspective shift. When viewed from “Viewpoint A”, the object appears to be in front of the blue square. When the viewpoint is changed to “Viewpoint B”, the object appears to have moved in front of the red square. Image credits: Booyabazooka / Wikipedia.

However, after around 100 light years, the distance becomes simply too great and the parallax method starts to lose its efficiency. Still, through parallax, we know that the universe is at the very least 200 light years across (100 in both directions) — something which at one point, seemed inconceivably large.

The real size, however, goes far beyond that.

The observable universe — and a standard candle

This is where things start to get really interesting (and tricky). Let’s think about the age of the universe for a moment. When we look at something that’s 1 light year away, it took the light one year to get from that object to us, so we’re seeing it the way it was one year ago. In a way, we’re looking through time and seeing the past. We’ve seen galaxies that are over billions of years old, so the size of the universe must be at least a few billion light years across.

To finesse things, we know the age of the universe, within a pretty good margin, to be 13.7-13.8 billion years, and we know that from two crucial pieces of evidence.

The first one has to do with universal expansion. We know that the universe is expanding, and it’s expanding at an accelerating rate. Assuming that it’s expanding similarly in all parts of the universe (which most scientists agree), all the objects in the universe are moving apart from one another at a similar pace. Let’s take the galaxies, as incredibly massive “objects”: we know that they’re moving apart, and by knowing their current speeds and distances, as well as the rate at which the universal expansion is accelerating, we can calculate how long it took them to reach their current position. This method puts the age of the universe at around 14 billion years.

RS Puppis is one of the brightest known Cepheid variable stars in the Milky Way — which makes it one of the most important “standard candles”. Image credits: Hubble / NASA.

The second method relies on measuring the age of the oldest clusters we’ve been able to observe. This is not straightforward and makes extensive use of our knowledge of stellar formation, particularly a group of stars called “main sequence stars”, which are the most common type of stars. We know that these stars change color in time, becoming redder as they age. By measuring their color and brightness, we can calculate their age — they are a “standard candle”, an object whose brightness we can calculate mathematically. But for the very oldest stars, even this doesn’t really work, and this is where the work of Henrietta Swan Leavitt, an American astronomer, comes in. Back in 1908, Henrietta realized that there was a special class of stars called Cepheid variables. These stars have highly reliable brightness and pulsations, which enables astronomers to calculate just how old these stars are. Using this method, the age of the universe was calculated to be 13.7 billion years.

The fact that the two methods come up with such close values is encouraging, and subsequent studies and models have confirmed and refined this range. Currently, scientists are confident (99.1% accuracy) that the age of the universe is 13.81 billion years — meaning we have another important milestone in our quest to figure out the size of the universe.

So we have a smaller “yardstick” to measure things in our cosmic neighborhood, and a larger one to measure things in the observable universe. What’s next?

The size of the observable universe

We might think that the size of the observable universe is 13.7 billion light years in all directions, so 27.4 billion light-years across. Spoiler alert: that’s not true! That’s just what we can see now — during the time it took the light to travel to us, the universe has continued to expand. Keep in mind: space itself is increasing.

Visualization of the expansion of the Universe. Image credits: Eugenio Bianchi, Carlo Rovelli & Rocky Kolb.

[panel style=”panel-info” title=”Comoving and proper distances” footer=””]At this point, we should differentiate between the two distances.

Proper distance is essentially where a distant object would be at a specific moment of cosmological time. This can change over time due to the expansion of the universe.

Comoving distance factors out the expansion of the universe, giving a distance that does not change in time due to the expansion of space but can change, for instance, due to galactic movement.

The Universe’s expansion results in the proper distance changing, while the comoving distance is unchanged by this expansion.[/panel]

So how big has the observable universe become since its inception?

The best answer we have comes from something called redshift. When a source of light comes from very far away, its wavelength starts to shift towards the red side of the spectrum. This type of Doppler shift was a key indication that the size of the universe is increasing, and can help researchers estimate how much the universe has expanded.

Basically, if we were to find some really old photons and analyze their spectral shift, we’d have a good estimate of how old something is, and how far away it currently lies. The earliest photons we have come from the so-called cosmic microwave background (CMBR), faint cosmic background radiation filling all space which represents the earliest known electromagnetic radiation.

Some of our most accurate estimates of the CMBR come from the Wilkinson Microwave Anisotropy Probe (WMAP), which, along with other estimates, found that farthest observable photons come from 46.5 billion light-years away.

The Cosmic Microwave Background temperature fluctuations from the 7-year Wilkinson Microwave Anisotropy Probe data seen over the full sky as a celestial sphere. Image credits: NASA.

The comoving distance from Earth to the edge of the observable universe is about 46.5 billion light-years 14.26 (gigaparsecs or 4.40×10 26 meters) in any direction. So, although the light itself might have only traveled for 13.8 billion years, the distance from us to the point it came from is, at present, 46 billion light years away.

This would make the diameter of the observable universe about 93 billion light-years (the equivalent of 28 billion parsecs), assuming that the Earth occupies a relatively central position in the universe.

It should be noted that at the current time, the proper and the comoving distance between the Earth and the edge of the observable universe are defined as equal (for the sake of simplicity). This is merely a convention — at other times, the scale factor was different than 1.

The same measurements described above concluded that at the time the CMBR was emitted, the proper distance was only 42 million light-years.

Another visualization of the universal expansion. Image credits: NASA, Goddard Space Flight Center.

So, to the best of our knowledge, the size of the observable universe is 93 billion light-years across. It is almost certainly bigger than that, but we don’t have any substantial evidence to judge its size outside of that.

However, one statistical estimate carried out by Oxford researchers found that the universe might be 251 times larger than the observable universe, which would put it at 23343 light-years across. That’s truly humbling, and some studies go even beyond that. Estimates for the total size of the universe, reach as high as megaparsecs, as implied by one resolution of the No-Boundary Proposal. Just so you can get an idea of how big that number is, it doesn’t even matter what units of measure you express it in — whether it be nanometers or megaparsecs, the difference would simply get lost in the irrelevant final digits.

[panel style=”panel-default” title=”Universal expansion ” footer=””]Universal expansion can be very difficult to wrap your head around, but here’s an easy analogy to help you visualize things.

Think of the universe as a muffin dough. Think of matter inside this space as poppy seeds inside this dough. As the dough is baked, it expands, and the space between all poppy seeds increases — similarly, universal expansion drives matter apart, though the process is only detectable at cosmological scales.[/panel]

The shape of the universe

Now, we have some idea of how big the universe is — or rather, we have a lower limit to how big the universe is — but what does it look like?

Most people would probably imagine the universe to be somewhat spherical in shape. Although intuition is hardly reliable in cosmology, a spherical universe is entirely plausible. In General Relativity, space-time is curved, which would imply that there are three possible shapes of the universe:

Three possible shapes of the Universe: closed, open and flat from top to bottom. Image credits: NASA.

There are also other, more complex shapes which have been proposed, such as a Moebius Strip or its 3D correspondent, a Klein Bottle — where there is no inside or outside, only one surface.

However, more recent evidence suggests that the universe is essentially flat. Temperature measurements of the above-mentioned CMBR would exhibit substantial variations if the universe was curved, but to the best of our ability, we haven’t been able to spot any such variations, which indicates that, to an acceptable range, the universe is essentially flat.

If the universe is indeed “flat”, the math behind General Relativity and universal expansion indicates that it will continue to expand forever, though it’s not clear if this expansion will continue to accelerate indefinitely or will slow down.

However, this doesn’t really tell us anything about how big the universe really is, and there’s an even more puzzling possibility: perhaps the universe is so big that the fraction represented by our observable universe isn’t big enough to exhibit its curvature, much like from our personal perspective, the Earth seems flat, but if you zoom out sufficiently, its curvature becomes evident.

This leaves another important question to discuss.

Is the universe infinite?

Since we can’t exactly figure out how big the universe is, another possibility emerges: that of an infinite universe.

The two possibilities (of a finite or an infinite universe) raise equally puzzling situations: if the universe is finite, then what could possibly be outside of it, and what exactly is the universe expanding into? Is the universe creating space? Does that question even make sense?

If the universe is infinite, things get even weirder. How can something that’s not infinitely old be infinitely vast? Can an infinite universe expand? In theory, yes — although it’s very difficult to visualize (and makes the math and physics much trickier). Again, think of the universal expansion not as an “expansion”, but rather a “stretch”, in which all parts of the universe, from the very middle to the periphery, are being pulled apart from each other. But does an infinite universe contain all possible configurations of matter? Is there another you somewhere in the universe? Or even better, is there a version of you that’s immortal, doesn’t need sleep and has cat ears? That is the kind of problem which might emerge from an infinite universe.

[panel style=”panel-default” title=”Pi and an infinite universe” footer=””]For the sake of precision, we should say that an infinite universe doesn’t necessarily imply all possible matter combinations — just like, contrary to popular belief, the number Pi doesn’t necessarily include all possible number combinations.[/panel]

A more straightforward issue with an infinite universe is represented by Olbers’ paradox, which states that the darkness of the night sky conflicts with the assumption of an infinite and eternally static universe: if it were truly infinite, then every single bit of the night sky would eventually fall on to a star and would light up, until all the night sky is lit up. Since that doesn’t happen, then the universe isn’t infinite.

As more distant stars are revealed in this animation depicting an infinite, homogeneous and static universe, they fill the gaps between closer stars. Since the night sky is mostly dark, this seems to suggest that the universe is not infinite. Several alternative explanations have been proposed, but the fact that Olbers’ paradox has not been decisively proven for 300 years is telling. Image credits: Kmarinas86 / Wikipedia.

The truth is, we don’t know if the universe is finite or infinite, and we may never know. The complexity of the problem seems, at least now, insurmountable. But here’s the good thing: it might not really matter.

Even if the universe isn’t infinite per se, there’s a good chance it is practically infinite. This means that some areas might lie so far away from us that we could never reach them. Since according to our current understanding of physics nothing can go faster than the speed of light, considering the accelerating expansion, some areas might simply be mathematically unreachable — we can never interact with them in any way.

The size of the Universe is difficult to define. Because we cannot observe space beyond the edge of the observable universe, we can’t know for sure if it is infinite or not. We have a good idea of how big our observable universe is, but that’s probably just a tiny piece in a much larger puzzle. How big that puzzle is remains an ongoing matter of research — and will likely remain so for years to come.

Update: edited for typos in age of the universe.

How Big is the Universe?

The Universe is big, but how big is it? That all depends on whether the Universe is finite or infinite. Even the word “big” is tough to get clear. Are we talking about the size of the Universe we can see, or the Universe’s actual size right now?

The Universe is big, but how big is it? And what the heck kind of question is that? Are elephants big? Trucks? Dinosaurs? Cheese? Is cheese big? How big is cheese? How big is big?

The word “big” is tough to get clear. Are we talking about the size of the Universe we can see, or the Universe’s actual size right now? This becomes even more complicated when we are trying to work under assumptions of either the Universe is finite or the Universe is infinite.

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One difficulty with talking about the size, is that the Universe is expanding. Light takes time to travel from distant galaxies, and while that light travels, the Universe continues to expand. So our problem with talking about how big it is, is that there is no single meaning to distance when it comes to the universe. For this reason, astronomers usually don’t worry about the distance to galaxies at all, and instead focus on redshift, which is measured by z. The bigger the z, the more redshift, and the more distant the galaxy.

As an example, consider one of the most distant galaxies we’ve observed, which has a redshift of 7.5. Using this, we can determine distance by calculating how long the light has traveled to reach us. With a redshift of 7.5, that comes out to be about 13 billion years. You might think that means it’s 13 billion light years away, but 13 billion years ago the universe was smaller, so it was actually closer at the time the light left that galaxy. Using this, if you calculate that distance, it was only a short 3.4 billion light years away.

Now the galaxy is much farther than that. After the light left the galaxy, the galaxy continued to move away from us. It is now about 29 billion light years away. Which is definitely more than 13, and quite a bit more than its original 3.4.

Usually it is this big distance that people mean when they ask for the size of the universe. This is known as the co-moving distance. Of course, we can only see so far. So, how far can we see? The most distant light we are able to observe is from the cosmic microwave background, which has a redshift of about z = 1,000.

This means the co-moving distance of the cosmic background is about 46 billion light years. Sticking us at the center of a massive sphere, the currently observable universe has a diameter of about 92 billion light years. Even with this observed distance, we know that it extends much further than that. If what we could see was all there is, we would see galaxies tend to gravitate towards us, which we don’t observe.

Artist concept of the multiverse. Credit: Florida State University

In fact we don’t see any kind of galaxy clumping to a particular point at all. So as far as we know the universe could extend forever. It could be even stranger than that. Despite some media controversy, if the BICEP2 detection of early inflation is correct, it is likely the Universe undergoes a type of inflation with the intimidating moniker of “eternal inflation”. If it is the case, our observable universe is merely one bubble within an endless sea of other bubble universes. This is otherwise referred to as… the multiverse.

So, in the immortal words of Douglas Adams, “Space,” it says, “is big. Really big. You just won’t believe how vastly, hugely, mindbogglingly big it is. I mean, you may think it’s a long way down the road to the chemist’s, but that’s just peanuts to space”

What do you think? Does the Universe go on for ever? Tell us in the comments below. And if you like what you see, come check out our Patreon page and find out how you can get these videos early while helping us bring you more great content!

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