Evolution of the Universe

This page is designed to illustrate the relationship between the energy content and evolution of the universe, and explain the concept of the Ultimate Fate of the Universe.

  • Adjust the sliders below and observe how they affect the universe's evolution as shown in the line graph.
  • Watch the universe evolve in the animation panel.
  • Use the button panel to jump to certain pre-set scenarios. The Benchmark scenario is the best estimate for our universe!
  • Hover over the
    symbols to learn more about a specific topic.
  • This assumes that you're familiar with the energy density concept described here, in the tooltip next to the slider.

This panel depicts a graph of the size of the universe versus time. Change the selected series by using the sliders below, and click Add to add a new series.

Click the 'Animate' button to switch to an animation of how this universe evolves.

The size of the universe is described by a unitless value called the Scale Factor. This is used because the absolute size of the universe is unknown! A scale factor of 1 corresponds to the current size of the universe. For reference, the current Observable Universe is roughly 93 billion light-years (5.5 x 1023 miles) in diameter.

The evolution of the universe is entirely determined by the amount and type of stuff (energy) it contains at present. It can be described by the Friedmann Equations.

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These panels are meant to visualize how the universe will evolve under the conditions described by the sliders below.

The panel on the left depicts a graph of the size of the universe versus time. Change the selected series by using the sliders below, and click Add to add a new series.
The panel on the right depicts an animation of the universe evolving, with a few galaxies added for illustration. Note, the galaxies are not depicted to scale with the entire universe.

The size of the universe is described by a unitless value called the Scale Factor. This is used because the absolute size of the universe is unknown! A scale factor of 1 corresponds to the current size of the universe. For reference, the current Observable Universe is roughly 93 billion light-years (5.5 x 1023 miles) in diameter.
The galaxies shown in the universe should stay the same size for the entire evolution of the universe. Although space may be expanding, the self-gravity of these galaxies keeps them at the same size, while the distance between them increases. The size change shown here is a result of the blown up scale used for visualization.

The evolution of the universe is entirely determined by the amount and type of stuff (energy) it contains at present. It can be described by the Friedmann Equations.

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This panel depicts an animation of the universe evolving, with a few galaxies added for illustration. Note, the galaxies are not depicted to scale with the entire universe.

Click the 'View Chart' button to return to a graph of the size of the universe versus time.

The galaxies shown in the universe should stay the same size for the entire evolution of the universe. Although space may be expanding, the self-gravity of these galaxies keeps them at the same size, while the distance between them increases. The size change shown here is a result of the blown up scale used for visualization.

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Radiation

Omega r

0.0

Matter

Omega m

0.3

Dark Energy

Omega Lambda

0.7

This panel allows you to manipulate the amounts three distinct types of stuff (energy) in your toy universe. Play with the sliders and observe how the universe's evolution changes.

Remember, each type of energy is described in units of the critical energy density, and the sum of all forms of energy dictates the curvature of the universe (as described here).

Radiation describes all the energy in the universe in the form of light (photons). Most of this energy is in the Cosmic Microwave Background, an all present low energy field of microwave energy. It won't cook your food, but you can see it on the static on an old TV.
Matter is all the energy in the universe that has mass. This consists of two parts: first, all the stuff you usually consider matter, most of which is Baryonic Matter, and second, a mysterious form which doesn't interact with light, called Dark Matter. Most matter in our universe is dark.
Dark Energy is a hypothesized form of energy about which almost nothing is known except that it causes the universe to expand at an accelerating rate. We only know of it through its effect on the expansion rate of the universe, which we have measured.

Different forms of energy are described mathematically by their Equation of State, and in particular, the equation of state parameter, w. The value of w dictates the effect a particular kind of energy has on the evolution of the universe, and when in the universe's history that kind of energy dominates the evolution. For each kind of energy, the equation of state paramter, w, and relation between scale factor (a), and time (t) when that energy dominates in a flat universe are:

Matter
Radiation
Dark Energy*

*This represents only the most commonly considered form of dark energy. Technically anything within -1 < w < -1/3 is considered dark energy.

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This panel allows you to manipulate the amounts three distinct types of stuff (energy) in your toy universe. Play with the sliders and observe how the universe's evolution changes.

Remember, each type of energy is described in units of the critical energy density, and the sum of all forms of energy dictates the curvature of the universe (as described here).

Radiation describes all the energy in the universe in the form of light (photons). Most of this energy is in the Cosmic Microwave Background, an all present low energy field of microwave energy. It won't cook your food, but you can see it on the static on an old TV.
Matter is all the energy in the universe that has mass. This consists of two parts: first, all the stuff you usually consider matter, most of which is Baryonic Matter, and second, a mysterious form which doesn't interact with light, called Dark Matter. Most matter in our universe is dark.
Dark Energy is a hypothesized form of energy about which almost nothing is known except that it causes the universe to expand at an accelerating rate. We only know of it through its effect on the expansion rate of the universe, which we have measured.

Different forms of energy are described mathematically by their Equation of State, and in particular, the equation of state parameter, w. The value of w dictates the effect a particular kind of energy has on the evolution of the universe, and when in the universe's history that kind of energy dominates the evolution. For each kind of energy, the equation of state paramter, w, and relation between scale factor (a), and time (t) when that energy dominates in a flat universe are:



Matter
Radiation
Dark Energy *

*This represents only the most commonly considered form of dark energy. Technically anything within -1 < w < -1/3 is considered dark energy.

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This panel offers distinct pre-set scenarios for you to chose, all of which represent an interesting case for the universe's evolution.

Click a button to set your universe to that scenario and check out the energy contents.

Of particular note here is the Benchmark scenario. This represents the best estimate we have for how our real universe has evolved and will continue to evolve. Here, the amount of radiation, matter, and dark energy have all been measured experimentally. Note that they sum to 1, meaning our universe is flat!

A 'Crunch' universe starts out with a big-bang as in the benchmark scenario. Here though, the universe will reach a maximum size before the force of gravity causes it to contract back into a single poing in a big-crunch. This is a plausible scenario for our universe.

It is possible for the universe to start without a big-bang. In a so called 'Bounce' universe, space begins as large and contracts under the force of gravity. At some point, the dark energy takes over and the universe begins to expand once again.

The 'Loitering' universe is of note as it is the boundary between a bounce scenario and one that begins with a big-bang. Here the amount of energy is delicately balanced to allow the universe to stay the same size for a considerable amount of time. Here dark energy is set to 1.7134. This precision is necessary to make the universe loiter.

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