How do you find the hubble constant

In theory, the constant's value is calculated by combining the velocity of distant galaxies as they appear to move away from us, along with an estimate of their distance.

Carrying out this measurement in practice has been easier said than done. Different methods for determining the Hubble Constant's true value have produced subtly - but significantly - different answers, much to the frustration of physicists.

One effective way of measuring the velocity of a retreating object is to look at its colour and then compare it with what you think its colour should be. Just as a siren's tone has a lower pitch as it moves away from your position at high speed, an object's colour will have a 'lower pitch', or redder hue, as its light waves are stretched by its relative motion. When this ' redshift ' phenomenon was applied to distant galaxies early in the 20th century, it appeared as if many more were retreating from us than we might otherwise expect.

The American astronomer Edwin Hubble took a closer look at this claim of runaway galaxies in , paying closer attention to their distances. He determined the further away the galaxy, the faster it appeared to retreat, establishing the groundwork for a theory on the Big Bang and the accelerated expansion of the Universe. In , American astronomer Edwin Hubble announced his discovery that galaxies, from all directions, appeared to be moving away from us.

This phenomenon was observed as a displacement of known spectral lines towards the red-end of a galaxy's spectrum when compared to the same spectral lines from a source on Earth. This redshift appeared to have a larger displacement for faint, presumably further, galaxies. Hence, the farther a galaxy, the faster it is receding from Earth. However, obtaining a true value for H o is very complicated. The Hubble Constant is the unit of measurement used to describe the expansion of the universe.

The cosmos has been getting bigger since the Big Bang kick-started the growth about The universe, in fact, is getting faster in its acceleration as it gets bigger. What's interesting about the expansion is not only the rate, but also the implications, according to NASA.

If the expansion begins to slow down, that implies that there is something in the universe that is making the growth slow down — perhaps dark matter, which can't be sensed with conventional instruments. If the growth gets faster, though, it's possible that dark energy is pushing the expansion faster.

As of January , measurements from multiple telescopes showed that the rate of expansion of the universe is different depending on where you look. The nearby universe measured by the Hubble Space Telescope and Gaia space telescope has a rate of expansion of A megaparsec is a million parsecs, or about 3. Hubble was an American astronomer who studied galaxies, particularly those that are far away from us. In — based on a realization from astronomer Harlow Shapley that galaxies appear to be moving away from the Milky Way — Hubble found that the farther these galaxies are from Earth, the faster they appear to be moving, according to NASA.

While scientists then understood the phenomenon to be galaxies moving away from each other, today astronomers know that what is actually being observed is the expansion of the universe.