Hubble's law or Lemaître's law is the name for the astronomical observation in physical cosmology that: ( 1 ) all objects observed in deep space ( intergalactic space ) are found to have a doppler shift observable relative velocity to Earth, and to each other ; and ( 2 ) that this doppler-shift-measured velocity, of various galaxies receding from the Earth, is proportional to their distance from the Earth and all other interstellar bodies.

In effect, the space-time volume of the observable universe is expanding and Hubble's law is the direct physical observation of this process.

After confirmation of the Hubble's law by observation, the two most popular cosmological theories became the Steady State theory of Hoyle, Gold and Bondi, and the big bang theory of Ralph Alpher, George Gamow, and Robert Dicke with a small number of supporters of a smattering of alternatives.

Along with the explanation provided for the Hubble's law and for the cosmic microwave background, this observation has proved very difficult for alternative theories to explain.

The idea comes from a perceived need to reconcile Edwin Hubble's observation of an expanding universe ( which was also predicted from Einstein's equations of general relativity by Alexander Friedmann ) with the notion that the universe must be eternally old.

This fact is now known as Hubble's law, though the numerical factor Hubble found relating recessional velocity and distance was off by a factor of ten, due to not knowing at the time about different types of Cepheid variables.

Given the cosmological principle, Hubble's law suggested that the universe was expanding.

Hubble is generally mistakenly known for Lemaître's law or " Hubble's law " which was discovered by Georges Lemaître.

The primary source of verification of this expansion was provided by Edwin Hubble who demonstrated that all galaxies and distant astronomical objects were moving away from us (" Hubble's law ") as predicted by a universal expansion.

At the time of the initial publication of Hubble's galaxy classification scheme, the existence of lenticular galaxies was purely hypothetical.

Later observations ( by Hubble himself, among others ) showed Hubble's belief to be correct and the S0 class was included in the definitive exposition of the Hubble sequence by Allan Sandage.

The Friedmann – Lemaître – Robertson – Walker metric that is necessary for the Big Bang and Steady State models emerged in the decade after the development of Einstein's general relativity and was accepted as a model for the universe after Edwin Hubble's discovery of his eponymous law.

It was decided that the target should be in Hubble's ' continuous viewing zones ' ( CVZs )— the areas of sky which are not occulted by the Earth or the moon during Hubble's orbit.

The HDF was located in Hubble's northern Continuous Viewing Zone, as shown by this diagram.

The idea was that the cosmological redshift might be showing evidence of periodicity which would be difficult to explain in a Hubble's Law universe that had the feature of continuous expansion.

He was also the first to derive what is now known as the Hubble's law and made the first estimation of what is now called the Hubble constant which he published in 1927, two years before Hubble's article.

The burst happened approximately 13 billion years ago, so a distance of about 13 billion light years was widely quoted in the media ( or sometimes a more precise figure of 13. 035 billion light years ), though this would be the " light travel distance " ( see Distance measures ( cosmology )) rather than the " proper distance " used in both Hubble's law and in defining the size of the observable universe ( cosmologist Ned Wright argues against the common use of light travel distance in astronomical press releases on this page, and at the bottom of the page offers online calculators that can be used to calculate the current proper distance to a distant object in a flat universe based on either the redshift z or the light travel time ).

Another scaling jump of 10 < sup > 9 </ sup > was required to extrapolate to galactic conditions, and a third jump of 10 < sup > 9 </ sup > was required to extrapolate to the Hubble's law # Hubble length | Hubble distance.

His result was in good accordance with other estimates of these days ( 100 to 1000 kpc ) and were closer to recent estimates ( 778 kpc ) than Hubble's result ( 275 kpc ).

After the servicing mission was completed, all of Hubble's scientific instruments are of Ball Aerospace manufacture.

In August and September 2009, the Hubble's Deep Field was expanded using the infrared channel of the recently attached Wide Field Camera 3 ( WFC3 ).

One of Hubble's four Reaction Wheel Assemblies ( RWA ) -- part of the telescope's Pointing Control Subsystem -- was replaced with a refurbished spare.

One of Hubble's solar arrays was unexpectedly disturbed by a gust of air from Discovery's airlock when it was depressurized, but was not damaged.

Image: Core of Messier 100. jpg | Core of Messier 100 taken with the high resolution channel of Hubble's Advanced Camera for Surveys.

Hubble's ACS / HRC captures Mars during its 2003 opposition, yielding the sharpest visible-light color RGB color model | ( RGB ) photo yet taken from Earth.

Picture of small section of the Carina Nebula created from images taken with Hubble's Wide Field Planetary Camera 2.

The planet could be seen clearly on images taken by Hubble's Advanced Camera for Surveys ' coronagraph in 2004 and 2006.

Protoplanetary nebula known as IRAS 20068 + 4051 taken by Hubble Space Telescope | Hubble's Advanced Camera for Surveys.

Since there is a correlation of distance and redshift as expressed in Hubble's Law, redshift quantization would either indicate a quantization of the distances of galaxies from the Earth or a problem with the redshift-distance correlation, either of which would have serious implications for cosmology.

The star spectral classification and discovery of the main sequence, Hubble's law and the Hubble sequence were all made with spectrographs that used photographic paper.

where is defined above, H < sub > 0 </ sub > is Hubble's constant and Ω < sub > m </ sub > is the present value of the density of all the matter in the universe.

When combined with Hubble's law, the implication of the redshift is that the quasars are very distant — and thus, it follows, objects from much earlier in the universe's history.

The dramatic improvement in Hubble's imaging capabilities after corrective optics were installed encouraged attempts to obtain very deep images of distant Galaxy | galaxies.

Hubble's initial value for age was very low, as the galaxies were assumed to be much closer than later observations found them to be.

Even light itself does not have a " velocity " of c in this sense ; the total velocity of any object can be expressed as the sum where is the recession velocity due to the expansion of the universe ( the velocity given by Hubble's law ) and is the " peculiar velocity " measured by local observers ( with and, the dots indicating a first derivative ), so for light is equal to c (- c if the light is emitted towards our position at the origin and + c if emitted away from us ) but the total velocity is generally different than c .( Davis and Lineweaver 2003, p. 19 ) Even in special relativity the coordinate speed of light is only guaranteed to be c in an inertial frame, in a non-inertial frame the coordinate speed may be different than c ; in general relativity no coordinate system on a large region of curved spacetime is " inertial ", but in the local neighborhood of any point in curved spacetime we can define a " local inertial frame " and the local speed of light will be c in this frame, with massive objects such as stars and galaxies always having a local speed smaller than c. The cosmological definitions used to define the velocities of distant objects are coordinate-dependent-there is no general coordinate-independent definition of velocity between distant objects in general relativity ( Baez and Bunn, 2006 ).

Once Hubble's corrective optics were shown to be performing well, Robert Williams, the then-director of the Space Telescope Science Institute, decided to devote a substantial fraction of his DD time during 1995 to the study of distant galaxies.

However, due to Hubble's law regions sufficiently distant from us are expanding away from us much faster than the speed of light ( special relativity prevents nearby objects in the same local region from moving faster than the speed of light with respect to each other, but there is no such constraint for distant objects when the space between them is expanding ; see uses of the proper distance for a discussion ), and the expansion rate appears to be accelerating due to dark energy.

In 1924 Edwin Hubble's measurement of the great distance to the nearest spiral nebulae showed that these systems were indeed other galaxies.

On the largest scale, the universe is continually expanding, resulting in an average increase in the separation between individual galaxies ( see Hubble's law ).

File: Edwin Hubble with pipe. jpg | Edwin Hubble ( 1889-1953 ): discovered of the existence of galaxies other than the Milky Way and galactic red shift, found that the loss in frequency — the redshift — observed in the spectra of light from other galaxies increased in proportion to a particular galaxy's distance from Earth: Hubble's law

Subsequently, Edwin Hubble discovered an approximate relationship between the redshifts of such " nebulae " ( now known to be galaxies in their own right ) and the distances to them with the formulation of his eponymous Hubble's law.

In 1929, Hubble and Milton L. Humason formulated what is now known as Hubble's Law by combining Cepheid distances to several galaxies with Vesto Slipher's measurements of the speed at which those galaxies recede from us.

* Edwin Hubble publishes his discovery that the speed at which galaxies recede positively correlates with their distance, which becomes known as Hubble's law, the basis for understanding that the universe is expanding.

Hubble's contribution was to show that the magnitude of the redshift correlated strongly with the distance to the galaxies.

Among other types in Hubble's classifications for the galaxies are: spiral galaxy, elliptical galaxy and irregular galaxy.

Among his contributions are the observational proof that many nebulous objects are actually galaxies beyond our own Milky Way galaxy, the classification of galaxies according to the Hubble sequence, and the development of Hubble's Law relating a galaxy's observed red shift to its distance away.