When was the expansion of the universe discovered

The stars at that edge can then serve as standard candles. Riess says that the red-giant study still relies on assumptions about the amount of dust in galaxies — particularly in the Large Magellanic Cloud, which the study used as an anchor point. They could beat Cepheids in the near future, Kolb says. The needle could shift towards one of the other values. Or it could stay put, and the other techniques might eventually converge to it.

For now, cosmologists have plenty to puzzle over. Freedman, W. Riess, A. Download references. News 09 NOV News 17 SEP Obituary 06 AUG Albert Einstein College of Medicine Einstein. Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily. Advanced search. Skip to main content Thank you for visiting nature.

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. How matter top , radiation middle , and a cosmological constant bottom all evolve with time in Note, at right, how the expansion rate changes; in the case of a cosmological constant which is effectively what it does during inflation, or in the presence of a cosmological constant , the expansion rate does not drop at all, leading to exponential expansion.

For generations, this simple rule — that the average speed a distant object appeared to move away from us was proportional to its distance from us — was known as Hubble's Law, after Edwin Hubble. The constant that relates the recession speed to the apparent distance, even today, is known as the Hubble constant.

But the problem, in terms of history, is that Edwin Hubble himself wasn't the first to figure this out. But the story behind just who discovered the expanding Universe is even murkier. The mathematics governing General Relativity is quite complicated, and General Relativity itself But it's only through specifying the conditions that describe our Universe, and comparing the theoretical predictions with our measurements and observations, that we can arrive at a physical theory.

You can start with Albert Einstein, who first put forth his theory of General Relativity in Einstein's theory of gravity reduced to Newton's laws when distances were large and masses were small, and provided unique predictions that agreed with experiments and observations — in contrast to Newton's — when they weren't.

The orbit of the planet Mercury was the first puzzle to yield, followed by the prediction of bent starlight during a solar eclipse. Where Newton failed, Einstein succeeded. Yet Einstein realized that his theory predicted that a static Universe was unstable, and that it must expand or contract.

Rather than accept this robust prediction, though, Einstein instead rejected it, assuming the Universe must be static. Instead, he introduced his cosmological constant to compensate, leading to what he later referred to as his "greatest blunder" in all of physics. First noted by Vesto Slipher, the more distant a galaxy is, on average, the faster it's observed to For years, this defied explanation, until Hubble's observations allowed us to put the pieces together: the Universe was expanding.

Even before Einstein, there were the observations of Vesto Slipher, which were instrumental in the actual discovery of the expansion of space. In the early s, Slipher was observing what were then known as "spiral nebulae" with a new device on his telescope: a spectrograph. By breaking the light from these galaxies up into their individual wavelengths, he could identify spectral lines coming from the atoms inside. Since we knew how atoms worked, we could measure a systematic shift of those lines to different wavelengths: redder ones if they were moving away from us, bluer if they were moving towards us.

These spirals had speeds that were too great to be bound to our own galaxy; most were redshifted; some were moving much faster than others.

His results implied that these nebulae were galaxies of their own, and were mostly receding from us. But Slipher never put the whole puzzle together. Possible fates of the expanding Universe. Notice the differences of different models in the past; The next person to make a significant contribution was Willem de Sitter, who in showed that if you imagined a general relativistic Universe dominated by Einstein's cosmological constant, it would expand.

What was more alarming were the properties of the expansion: it would be relentless, continuing forever, and exponential, meaning the farther away an object was from us, the faster it would be pushed away from us.

Although there was not yet sufficient observational evidence to prove that the Universe was expanding, de Sitter showed that General Relativity, even as Einstein imagined it, should lead to an expansion.

And perhaps more remarkably, the type of expansion de Sitter described seems to be present in our Universe today: in the form of dark energy. The first Friedmann equation, as conventionally written today in modern notation , where the left