# 1.1.1 The Edge of the Universe 15

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What is the edge of the Universe?  Where is the surface? Where does the universe end and what is beyond that end.  What defines the boundary of the Universe?  And does that question even make sense?

NOTE: many vCalc equations are embedded throughout vCalc descriptive pages like this page.  Even though they may not stand out in the text, if you hover over the name of an equation it will likely be linked to an actual, pop-up executable equation. For example: [Could not locate page MichaelBartmess.Force of Earth's Gravity]

Here's what we know about the extent of the universe:

The observable universe is defined by energy emitted from any matter, which can be observed from Earth today, where that matter might have emitted light or other signals that have had time to reach Earth.

Floating in this mostly empty void, we on Earth can observe energy coming to us from all directions.  The longest possible time this energy could have spent traveling to us, traveling to the "eye" of whatever sensor we are using to "observe", is the time since the universe began.

This means the edge of the observable universe is as large (or larger) as the distance light could have traveled since the universe began.

## Equations

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• Astro Travel Time