What Is Hubble's Law?

Hubble's Law: Speed and distance are indirect observations. The relationship of speed-distance and speed-magnitude are based on the observation of the redshift-magnitude relationship and some theoretical assumptions. Hubble's law, originally derived from observations of normal galaxies, has now been applied to quasars or other special galaxies. Hubble's law is often used to calculate the distance of distant galaxies.

Hubble's Law

In 1929, the EP Hubble discovered that the receding velocity v of the extragalactic galaxy is proportional to the distance d, that is, the farther away the greater the apparent velocity.

Hubble's law is a statement of physical cosmology: light from distant galaxies

The apparent receding speed of extragalactic galaxies is proportional to the distance, that is, the longer the distance, the greater the apparent speed. This speed-distance relationship was discovered by the American astronomer Hubble in 1929, known as Hubble s Law or

As early as 1912,

In the process of deriving his famous law, Hubble must obtain two basic observational measurements of the same target galaxy, namely the apparent velocity v and distance r of the galaxy, and determine the Hubble constant H0 = v / r from this. The apparent velocity can be determined by measuring the Doppler shift of the spectral lines in the galaxy spectrum, which is relatively simple. The key issue is how to measure the galaxy's distance. Because the galaxy's distance is extremely far, the triangle parallax method "cannot reach this point", so we must find another way. Astronomers have found multiple measurements distant

Using Hubble's law v = H0 r, as long as the Hubble constant H0 can be determined, the distance r of the celestial body can be obtained from the apparent velocity v of the celestial body, which is called the cosmological distance. Speed. In this way, r = v / H0 may be the simplest gauge relationship to determine the astronomical cosmological distance, but only if the Hubble constant must be known.

as one of the branches of astronomy

Accelerated acceleration model

In 1998, the q value from the standard candlelight measurement of the Ia supernova was negative, which surprised many astronomy is that the expansion of the universe is still "accelerating" (although the Hubble factor will decay over time, see dark matter and CDM models ).