The science of expansion: Andromeda, gravity, and the ‘Big Rip’

If the universe is expanding in all directions, why is Andromeda hurtling toward the Milky Way?

  • The Andromeda Galaxy and our Milky Way are on a collision course that will obliterate life on Earth 4.5 billion years from now.
  • The universe is expanding in all directions, all at once – so why are Andromeda and the Milky Way drawing nearer? The gravity between them is a stronger force than expansion.
  • The rate of expansion is accelerating. If it continues to speed up, its force may become strong enough pull things apart that are currently held together by superior forces: Our galaxy, the solar system, and even the atoms in our bodies. That possible ending to the universe is known as the 'Big Rip'.

Great scientific discoveries hide in boring places

NASA's Michelle Thaller explains how an accidental discovery led to the 1978 Nobel Prize in Physics.

  • In 1964, two American radio astronomers, Arno Penzias and Robert Wilson, discovered the Cosmic Microwave Background by accident. Their resulting work earned them the Nobel Prize in Physics in 1978.
  • They had long been trying to get rid of the annoying "noise" in their data (even thinking it was all the pigeon poop in their telescope) only to realize the noise was the treasure. They had stumbled upon the oldest light in the universe, and some of the strongest evidence to support the Big Bang theory. (What is the Cosmic Microwave Background?)
  • That's why space and science are never boring, explains NASA astronomer Michelle Thaller. One scientist's junk data can be another's Nobel Prize.

How kugelblitz black holes could power future spacecraft

In theory, we could use high-energy lasers to make our own artificial black holes, potentially capturing the enormous energy they emit.

Movie still from J.J. Abrams' 2009 film "Star Trek."
  • We think of black holes as traditionally being formed when matter is packed so densely that the gravity they exert prevents even light from escaping their event horizon.
  • However, Einstein showed that energy and matter are equivalent; rather than taking the enormous amount of matter required to make a sufficiently sized black hole, we could make one using light, known as a kugelblitz.
  • If we had the technology to capture it, the energy from a kugelblitz would be extraordinarily useful.
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It's embarrassing, but astrophysicists are the first to admit it. Our best theoretical model can only explain 5% of the universe. The remaining 95% is famously made up almost entirely of invisible, unknown material dubbed dark energy and dark matter. So even though there are a billion trillion stars in the observable universe, they are actually extremely rare.

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The universe is dying, new study confirms

Star production peaked three billion years after the Big Bang.

This map of the entire sky shows the location of 739 blazars used in the Fermi Gamma-ray Space Telescope's measurement. Brighter areas have stronger gamma rays. Image source: NASA/DOE/Fermi LAT Collaboration
  • Scientists track gamma rays across the universe's extragalactic background to calculate all of the starlight ever produced.
  • For 10.8 billion years, star production has been decelerating.
  • The research team measured nine years worth of data from the universe's 739 known blazars.
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