THE EXPANSION OF OUR UNIVERSE

1.Galactic Redshift

Redshift is a term used to describe the movement of astronomical objects away from us and the stretching of light coming from those objects. Light coming from objects moving away from us has a longer wavelength. This was discovered by astronomer Vesto Silpher through his spectrograph and was later shown to support the Big Bang Theory by Edwin Hubble. Astronomers measure this by comparing spectral lines of distant galaxies to those from nearby sources, finding the further a galaxy, the greater its redshift, meaning it recedes faster as space itself stretches. Redshift can be explained by the Doppler effect, which states that if a light source moves away, its wave gets stretched. Cosmological redshift is a term used when the space between galaxies expand.

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 2.Discovering dark energy

In 1998, two groups of researchers found that cosmic expansion was accelerating which implies the existence of a force counteracting gravity. That force is dark energy. Unlike dark matter, dark energy pushes galaxies apart. This was discovered by studying Type Ia supernovae, bright explosions of white dwarfs. Scientists compared their brightness to Earth to measure the distance and redshift of their light. This discovery led to Saul Perlmutter,Brian Schmidt, and Adam Riess winning the 2011 Nobel Prize in Physics.

3.What could dark energy possibly be?

Dark energy is thought to be an effect of a negative pressure that is pushing space outward by some people. Some people believe dark energy is the cosmological constant which is vacuum energy causing negative pressure. Other theories include that of a dynamic energy field filling space known as quintessence, while some think it could be an effect of a modified cosmic gravity.

Image credits:science.nasa.gov