Edwin Hubble And The Expanding Universe

The two keys to Edwin Hubble‘s breakthrough discovery were forged by others in the 1910s.

The first key, the period-luminosity scale discovered by Henrietta Leavitt, allowed astronomers to calculate the distance to variable stars from Earth.

Hubble had already used this knowledge in his 1924 discovery that the Andromeda nebula, containing a variable star, was more than 900,000 light years from Earth — way beyond our own galaxy — a surprise to everyone at the time.

With this scale and other tools, Hubble had found and measured 23 other galaxies out to a distance of about 20 million light years.

The second key was the work of Vesto Slipher, who had investigated the spiral nebulae, before Hubble’s Andromeda discovery.

These bodies emit light which can be split into its component colors on a spectrum.

Lines then appear in this spectrum in particular patterns depending on the elements in the light source.

Yet if the light source is moving away, the lines are shifted into the red part of the spectrum.

Analyzing the light from the nebulae, Slipher found that nearly all of them appeared to be moving away from Earth.

Slipher knew that a shift toward red suggested the body was moving rapidly away from the observer. But he had no way to measure the distances to these reddish bodies.

Hubble’s brilliant observation was that the red shift of galaxies was directly proportional to the distance of the galaxy from earth.

That meant that things farther away from Earth were moving away faster. In other words, the universe must be expanding.

He announced his finding in 1929. The ratio of distance to redshift was 170 kilometers/second per light year of distance, now called Hubble’s constant.

The numbers were not exactly right, and refinements in measuring techniques and technology have changed all of Hubble’s early figures. But not the basic principle. He himself kept working on the problem and collecting data throughout his career.

Some view Hubble’s discovery as the most important event in astronomy in the century.

It made the most basic change in our view of the world since Copernicus 400 years ago.

His results showing that the universe was expanding supported a theory that had been proposed by Georges LeMaitre in 1927.

A universe expanding, much like the aftereffect of an explosion, must have once been “unexploded,” a single mass in time and space.

In other words; the Big Bang.

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Comments (8)

  • Avatar

    Herb Rose

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    As Jason Verbelli pointed out in a comment to “Listen to this epic Big Bang debate (PSI) Einstein stated that if the motion of a source of light affect the light in any way his theories were wrong. To attribute the red shift and blue shift to the motion of the star emitting the light is to admit that relativity and a constant speed of light are wrong.
    The spectral shift is due to the velocity of light changing as it moves, as a wave, through electric and magnetic fields of changing strengths. A red shift is a result of the light traveling further in decreasing field strength and its wavelength getting longer. A blue shift is a result of light traveling further in a field of increasing strength. Light with both a red and blue shifts travels through multiple varying fields and is not a result of a star moving both towards and away from the observer when it emits the light. The shifts do not indicate an expanding universe, just one with changing electric and magnetic fields.

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  • Avatar

    Ken Hughes

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    There are two possible causes of this red shift and one of them has been totally ignored.
    The first, (and more obvious) is that the galaxies are indeed receding.
    The second, is that time was passing more slowly in the distant past.

    Either one of these causes will result in the observations we make, or even a combination of the two.

    General relativity does show that as time slows, then space shrinks, and as time speeds up, then space expands, and this is the only known causality for cosmic expansion,….the speeding up of time. There has never been any other proposition put forward for the expansion of the universe and it has simply been accepted without question, without any known cause.

    It’s a one way causality too. I mean, we can see how and why space expands if time speeds up, but there can be no effect on time if space expands. In fact, the very idea of space, or nothing expanding, is ludicrous. It can have no sensible meaning,….unless time passes faster.

    Taken to the limit, if time does not pass at all, then you might get anywhere you like, any distance, in no time at all. In other words, space has no meaning, no existence without the passing of time. Time “creates” space.

    And so we arrive at the singularity before the universe sprang into existence, with no time and no space, but that’s another story.

    The point is, that time is a fundamental process but space is nothing physical, just an effect of the passing of time.

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  • Avatar

    Guido FORRIER

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    I’ve always had my doubts about the so-called Doppler effect. This effect is certainly valid for sound waves. These “waves” are a variety of air pressure. But to translate that into light “waves” just doesn’t make sense to me. By the way : we actually do not see those stars but only the light that arrives at us after a long and protracted journey . ” Big bang ” is always presented as a true event and try to have a different vision !
    https://www.cloudynights.com/topic/813273-red-shift/
    Your theorie looks more sound to me :
    “The shifts do not indicate an expanding universe, just one with changing electric and magnetic fields.”

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