Our deepest galaxy surveys can reveal objects tens of billions of light years away, but there are more galaxies within the observable Universe we still have yet to reveal. Most excitingly, there are parts of the Universe that are not yet visible today that will someday become observable to us. (SLOAN DIGITAL SKY SURVEY (SDSS))

How Much Of The Unobservable Universe Will We Someday Be Able To See?

As more time passes since the Big Bang, more of the Universe comes into view. But how much?

Ethan Siegel
8 min readMar 12, 2019

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Even though it’s been billions of years since the Big Bang, there’s a cosmic limit to how far we can observe the objects that occupy our Universe. The Universe has been expanding all this time, but that expansion rate is both finite and well-measured. If we were to calculate how far a photon emitted at the instant the Big Bang occurred could have traveled by today, we come up with the upper limit to how far we can see in any direction: 46 billion light-years.

That’s the size of our observable Universe, which contains an estimated two trillion galaxies in various stages of evolutionary development. But beyond that, there ought to be much more Universe beyond the limits of what we can presently see: the unobservable Universe. Thanks to our best measurements of the part we can see, we’re finally figuring out what lies beyond, and how much of it we’ll someday be able to perceive and explore.

On a logarithmic scale, we can illustrate the entire Universe, going all the way back to the Big Bang. Although we cannot observe farther than this cosmic horizon which is presently a distance of 46.1 billion light-years away, there will be more Universe to reveal itself to us in the future. The observable Universe contains 2 trillion galaxies today, but as time goes on, more Universe will become observable to us. (WIKIPEDIA USER PABLO CARLOS BUDASSI)

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Ethan Siegel

The Universe is: Expanding, cooling, and dark. It starts with a bang! #Cosmology Science writer, astrophysicist, science communicator & NASA columnist.