UK United Kingdom

Expand into 2013 by toasting 100 years of modern cosmology

As 2012 comes to a close and you toast the New Year, be sure to also raise a glass to one Vesto Melvin Slipher. My intent is to describe what Slipher did 100 years ago in Flagstaff, Arizona and why this…

When you’re celebrating the New Year, be sure to spare a thought for Vesto Slipher and the birth of cosmology. Nuwandalice

As 2012 comes to a close and you toast the New Year, be sure to also raise a glass to one Vesto Melvin Slipher.

My intent is to describe what Slipher did 100 years ago in Flagstaff, Arizona and why this event can be regarded as the birth of modern cosmology.

The Lowell Observatory was founded in Flagstaff in 1894 to continue the work of American astronomer Percival Lowell who had a real interest – or rather a fixation – in Mars … and Martians.

In 1903 Lowell hired a young astronomer, Vesto Melvin Slipher. Slipher became well known by astronomers (for reasons that will become clear shortly), but he certainly wasn’t a household name like Edwin Hubble, of Hubble Space Telescope fame.

In fact many astronomers would argue that Slipher helped make Hubble famous. Slipher’s results transformed our understanding of our place in the universe, in the same way Copernicus, Kepler and Galileo transformed our understanding of our place in the solar system.

Slipher detected a fundamental property of space, not intuitive to us – the fact that the universe is expanding. Ultimately, Slipher’s results provided an observational framework for Einstein’s General Theory of Relativity and its description of our universe.

But Slipher didn’t start out to help Einstein. Far from it.

He began observations from 1909 of so-called “spiral nebulae” that Lowell believed to be young evolutionary stages of solar systems, like ours. We now know that these “spiral nebulae” are galaxies like our own. But at the time many believed our galaxy was the entire universe.

Others were waiting for definitive evidence that our galaxy was one of many similar objects – the so-called “island universe” theory introduced by the German philosoper Immanuel Kant in 1755.

The problem was that the nebulae were too faint for Slipher to initially record a spectrum. Spectra, or light dispersed into its constituent wavelengths, can reveal an object’s elemental make-up. It’s also possible to detect the velocity of the object by measuring the induced shift in features in the spectrum.

The advent of photographic emulsions allowed even such small “Doppler” velocity shifts to be detected. Slipher toiled away, only having access to the relatively small Lowell Observatory 24-inch telescope.

Yet the difficulty he faced in getting good data strangely related more to the design of then-current-day instruments than the light gathering ability of his telescope.

From 1906-1912, through ingenious modifications, and trial and error, Slipher improved his data collection. He found that faster (small f/ ratio) camera lenses in his spectrograph could greatly improve his ability to record useful spectra. By late 1912 he had made his spectrograph an incredible factor of 200 times more efficient.

This dome contains the 24-inch telescope Slipher used to make his observations. Crunchy Footsteps

On the night of September 17, 1912, Slipher observed the Andromeda nebula, for a total of six hours and 50 minutes. Later, he made even lengthier observations including two over consecutive nights, and one over the last three nights of 1912. It was a cosmic breakthrough.

Slipher had finally recorded useful spectra. In 1913 he announced that the Andromeda nebula was moving toward us at an astonishing rate of 300 km/s.

At the time, the majority of stars had much smaller velocities, measured in the tens of km/s. Sliphers' velocity was quite startling.

This observation is arguably the starting point of modern cosmology. Yet the results appeared quietly, almost hidden, in volume 2 of the 1913 Lowell Observatory Bulletin. Slipher had no media liaison or public relations officer at his disposal.

At the August 1914 American Astronomical Society meeting at Evanston, Illinois, Slipher presented his results and received, quite rightly, a standing ovation.

It was argued by some that the nebulae were just high-velocity components of a larger all-encompassing galaxy. But as Slipher increased his sample of nebulae it was very apparent that the majority had very high velocities of recession (i.e. moving away from Earth).

The universe was revealing a long-held secret to Slipher. In 1917 he wrote to Lowell, only five years on from his discovery observation, that Kant’s “island universe” theory “gains favor in the present observations”.

In 1921 he published a then-amazing recession velocity of 1,800km/s, derived from a 28-hour exposure, for a nebula in the constellation Cetus.

So, modern cosmology is turning 100. Through ingenuity and perseverance, Slipher’s results displaced our galaxy from any preferred, central location in the universe.

The few galaxies that are approaching us, such as Andromeda, are doing so because they are close and gravity wins a cosmic tug of war.

Einstein published his General Theory of Relativity in 1915, and presented it to agree with a static universe, then the preferred model.

Slipher’s results made a static universe untenable. Space was not a fixed entity that galaxies were moving into. The velocities are not telling us how fast galaxies are moving away from us, but tell us how space itself is expanding.

Galaxies are the ultimate cosmic test particles. From 1915 onwards a variety of models using Einstein’s theoretical framework were proposed.

Yet as early as 1917 Slipher had intuitively informed Lowell that his results showed the Kantian island universe theory to be valid, and thus, exposed the expanding universe.

Vesto Slipher

Slipher deserves much greater recognition than he normally gets. It was his efforts, with detection methods improved over numerous, long nights, that led to the greatest overhaul of cosmology to that time.

He was not one to promote himself or his discoveries. His publications were short and to the point.

History is more likely to mention the flamboyant Edwin Hubble before Vesto Slipher. Yet Hubble would not have found his later fame without first using Slipher’s velocities.

Related discussions about the historical legacies of other astronomers such as Knut Lundmark, Georges Lemaitre and H.P. Robertson are best left for another day!

So when you are welcoming in the New Year be sure to include a toast to one Vesto Melvin Slipher, astronomer extraordinaire, and wish modern cosmology a happy 100th anniversary.

Cheers Vesto!

Sign in to Favourite

Join the conversation

9 Comments sorted by

  1. Kim Peart

    Researcher & Writer

    Thanks for tossing this gem into the pond Glen, to set the lights of the nebula flickering.

    It is amazing to have one's awareness of cosmology expanded beyond Hubble.

    And all this led to contemplation of the multiverse.

    What mystery waits next?

    Kim Peart

    1. Glen Mackie

      Senior Lecturer in Astronomy & Astrophysics, Coordinator of Swinburne Astronomy Online at Swinburne University of Technology

      In reply to Kim Peart

      Hi Kim,

      If I only had a crystal ball! If I had to guess I think HST still has some surprises left. HST will deeply image clusters of galaxies to detect gravitationally produced "arcs" (distorted background galaxies at very large distances). I reckon the galaxy redshift record may tumble! I also think LHC will uncover much more about the properties of the Higgs boson in 2013/14, (there could be others) and the physics of the (very) early universe and perhaps dark matter may need some re-thinking! Just guesses but it is a great time in this field.

      regards, Glen

    1. Don Gibbons


      In reply to Giles Pickford

      Hi Giles. Apparently the galactic collision is not a sure thing at the moment, and is contingent on Andromeda's transverse velocity. If we do collide, it will be around 4 billion years hence. The chance of stellar collisions during the galactic merger is thought to be remote. I was fortunate to take a brief peek through the 24 inch telescope at the Lowell Observatory some years ago. It is fitting that Mr Slipher's talent and diligence was able to be realised in such a beautiful place as the Lowell Observatory.

    2. Glen Mackie

      Senior Lecturer in Astronomy & Astrophysics, Coordinator of Swinburne Astronomy Online at Swinburne University of Technology

      In reply to Giles Pickford

      Hi Giles, and thanks Don

      van der Marel et al. (2012b) (the e-print is at have used the transverse velocity of M31 (van der Marel et al. 2012a based on HST proper motion measurements to determine that the Galaxy and M31 will merge in 5.9 Gyr, after a first pericenter passage 3.9 Gyr from now, to ultimately resemble an elliptical galaxy. The exact timing comes down to accurately knowing the absolute space motion and orbit(s). Give or take a Gyr I reckon the above time scales are right.

      By the way the velocity reported by Slipher, -300 km/s, is still accurate, but it is a heliocentric velocity. If you take into account the Suns (Earths) motion around our Galaxy then the better velocity to think of is the Galactocentric velocity of -120 km/s. So we are still on a collision course, but somewhat slower.

      regards, Glen

  2. Ivan Quail


    Thanks for that. Yet more evidence that great men stand on the shoulders of even greater and apparently unsung men. I will surely be thinking of him as the new year begins.

  3. Comment removed by moderator.

  4. Rick Ryals

    logged in via Facebook

    The funny part though is that Einstein doesn't appear to be wrong, rather, he just didn't know about the real, massive particle potential of the quantum vacuum, since matter generation in his static model *causes* expansion while holding the universe "flat" and stable.

    In General Relativity's most natural universe, the vacuum has negative density when,


    In this static state, pressure is proportional to -rho, but pressure is negative in an expanding universe, and so energy density…

    Read more
  5. Geoff Taylor


    Well like Hubble with Slipher, Einstein may well have stood on the shoulders of de Pretto in coming up with the mass-energy equation.
    Perhaps someone can explain why they are so confident in ascribing red shift to velocities of distant objects.
    After all, the EM radiation which reaches us does so we are told through a dark energy field containing dark matter. Could there not be phenomena in "space" reminiscent of Rayleigh scattering of visible light in the atmosphere giving us blue sky, or of solar gamma to visible transition as EM energy works its way up from the solar core through sequential absorption and
    reradiation? The radiation is subject to gravitational drag in some cases as well as other gravitational effects, including lensing.