Segments in this Video

Dark Energy Overview (02:31)


Physicists struggle to understand what is causing galaxies to fall apart. The dark energy phenomenon questions Einstein's Theory of General Relativity, and may be evidence that the physics is flawed.

Saul Perlmutter's Research (03:12)

Dark energy seems to serve no useful purpose. In 1998, the astrophysicist studied whether the universe will expand infinitely or collapse. He observed "standard candle" supernovae and calculated relative distances to determine their age. He expected to find them slowing down.

Accelerating Universe (04:05)

Perlmutter observed supernovae that were fainter than previously imagined, indicating increased expansion rates. His colleagues named the phenomenon "dark energy" to reflect their ignorance. Bob Nichol recalls disbelief among the scientific community at his discovery.

Theory of General Relativity (03:09)

In 1915, Einstein's thought experiments led him to understand that Newton's gravity laws were conceptually wrong. Gravity was a consequence of mass interacting with space time distorted by planets— allowing physicists to predict how objects should be in the universe.

Testing General Relativity (02:13)

In 1919, Arthur Eddington observed starlight bent by distorted space time created by the sun's mass— proving Einstein's equation.

Cosmological Constant (02:16)

Einstein's original General Relativity equation predicted an expanding universe. Against his judgment, he included a lambda term to keep the universe static during calculations.

Expanding Universe (03:16)

In 1929, Edwin Hubble discovered our galaxy is one of millions moving apart from each other— introducing the notion of a beginning and an age. Einstein rejected the cosmological constant, simplifying his equation again. General Relativity is the most successful scientific theory yet.

Dark Energy Mystery (02:31)

General Relativity cannot explain accelerated expansion. Although the universe's volume increases, density remains constant— suggesting dark energy is being created from nothing. Physicists have re-added the cosmological constant to allow for accelerated expansion; either Hubble or Einstein was mistaken.

Quantum Mechanics and Dark Energy (03:17)

Dr. Clare Burrage explains that particles can come in and out of existence in the vacuum, adding tiny amounts of energy and mass to space time that could drive the universe's acceleration. However, calculations turn out wrong, indicating a missing physics law.

Dark Matter (03:32)

Dr. Vera Rubin plots a rotation curve of the solar system. In 1975, she observed Andromeda and discovered outer stars do not expand, suggesting unseen mass provides extra gravity holding spiral galaxies together.

Universe Composition (02:02)

Calculations showed that there was insufficient dark matter to make the universe operate as it does. Plugging dark energy into Einstein's mass-energy equation accounts for the missing mass. There is 4% baryonic matter, 26% dark matter, and 70% dark energy.

Euclid Satellite Consortium (02:01)

Dark matter may be a new particle, or Einstein's General Relativity equation may be incomplete. Scientists hope taking pictures of the universe will explain how it has expanded over its lifetime.

Euclid Space Telescope Technology (03:28)

U.K. Engineers build and test a camera that will capture the equivalent of Hubble's lifetime data each day. It will measure historic acceleration of stars and galaxies, and provide information about how dark matter has expanded over time. Learn about gravitational lensing.

Possible Euclid Satellite Outcomes (02:24)

The space telescope will stream unprecedented data from space, using statistics to point scientists in the right direction for dark energy. It could be the cosmological constant, an incomplete gravity theory, or that dark matter and dark energy are unified.

Mapping the Expansion of the Universe (02:22)

At Kitt Peak in Arizona, Risa Wechsler hopes to use the proposed dark energy spectroscopic (DESI) to check the validity of computer simulations of hypothetical universes. Without hard data, many theories try to provide a global solution to the dark energy problem.

Waiting for a Genius (02:42)

Curiosity and persistence drives cosmologists and physicists. Euclid Conference delegates discuss dark energy on a Lake Geneva cruise; they hope for a scientific breakthrough.

Next Einstein (02:59)

Observations are critical in understanding the universe. Watching stars brings ideas about dark energy and dark matter, but a team of scientists or a unique perspective is needed to solve the mystery.

Credits: The Dark Energy Mystery (00:39)

Credits: The Dark Energy Mystery

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The Dark Energy Mystery

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Einstein's Theory of General Relativity is still one of the pillars of modern physics. But 100 years after Einstein's theory, there's something that seems to undermine everything we thought we knew - Dark Energy. This mysterious cosmic force is not only causing our universe to expand, but this expansion is also accelerating. It makes up 70% of the universe. But no one can see it, and there is still great debate over what it actually is. This BBC Horizon program celebrates the anniversary of General Relativity - and looks at the latest experiments to try and understand Dark Energy.

Length: 50 minutes

Item#: BVL124886

ISBN: 978-1-64023-022-4

Copyright date: ©2016

Closed Captioned

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