Cecily Zamora
Edwin Hubble is credited with discovering Hubble's Law, which states that galaxies are moving away from Earth at speeds proportional to their distance. Hubble's 1929 paper on the relationship between distance and recession velocity of galaxies unveiled the expanding universe and changed our understanding of the cosmos. However, some claim that the law should be attributed to Georges Lemaître, who demonstrated its validity two years before Hubble's publication. Hubble's Law, also known as the Hubble-Lemaitre Law, remains a fundamental concept in cosmology, allowing scientists to calculate the age of the universe and its expansion rate.
| Characteristics | Values |
|---|---|
| Name of the Law | Hubble's Law |
| Year of Publication | 1929 |
| Discoverer | Edwin Hubble |
| First to Publish Research | Georges Lemaître |
| Year of First Publication | 1927 |
| Profession of Georges Lemaître | Belgian priest, astronomer, and academic |
| Hubble's Law Basis | First observational basis for the expansion of the universe |
| Hubble's Law Application | Used to calculate the age of the universe |
| Hubble's Law Formula | v = Hd |
| Hubble Constant | Tells us how fast the universe is expanding |
| Hubble Constant Value | Remains up for debate |
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What You'll Learn
Edwin Hubble's 1929 paper
The paper focused on determining the distances of extra-galactic nebulae by applying absolute-luminosity criteria to specific types of stars, including Cepheid variables, novae, and blue stars involved in emission nebulosity. By doing so, Hubble established a correlation between radial velocities and distances, marking a significant step forward in understanding the universe.
Hubble's key contribution in this paper was the discovery of a linear relationship between redshift and distance, coupled with a presumed linear relationship between recessional velocity and redshift. This led to what became known as Hubble's Law, which describes the fundamental relation between recessional velocity and distance. In simpler terms, Hubble's Law states that the farther a galaxy is from Earth, the faster it moves away.
Hubble's work built upon previous research by astronomers such as Alexander Friedmann, who derived equations in 1922 suggesting the possibility of an expanding universe, and Georges Lemaître, who in 1927 published a paper demonstrating that Einstein's theory of general relativity implied an expanding universe. Hubble's 1929 paper provided observational evidence for these theoretical concepts, solidifying the idea of the expanding universe and revolutionizing the field of cosmology.
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Georges Lemaître's 1927 paper
In 1927, Georges Lemaître, a Belgian priest, astronomer, and academic, published a report in the Annales de la Société Scientifique de Bruxelles ("Annals of the Scientific Society of Brussels"). The report, titled "Un Univers homogène de masse constante et de rayon croissant rendant compte de la vitesse radiale des nébuleuses extragalactiques" ("A homogeneous Universe of constant mass and growing radius accounting for the radial velocity of extragalactic nebulae"), presented the first explanation of the observations on the recession velocities of galaxies. This phenomenon is now known as Hubble's Law, or the Hubble-Lemaitre Law.
In his report, Lemaître independently developed and built upon the work of Alexander Friedmann and Albert Einstein. He argued that the equations of Einstein's general theory of relativity implied that the universe is not static, contrary to Einstein's own beliefs at the time. Lemaître connected this prediction to a simple relation of proportionality between the average recessional velocity of galaxies and their distance from Earth. This relation became known as the Hubble constant.
Lemaître's 1927 paper had little initial impact as it was published in a relatively obscure Belgian journal that was not widely read by astronomers and physicists outside Belgium. In 1929, Edwin Hubble published a paper in the Proceedings of the National Academy of Sciences of the United States of America, presenting similar findings based on more abundant data. Hubble's work gained wider recognition, and the discovery of the law was attributed to him.
Lemaître's 1927 report was translated into English and published in 1931 in the Monthly Notices of the Royal Astronomical Society. However, the translation was not perfectly faithful to the original text and omitted Lemaître's estimate of the Hubble constant. Despite this, Arthur Eddington, a leading astronomer and theorist, characterised Lemaître's work as a "brilliant solution" to the outstanding problems of cosmology.
Lemaître's work on the expanding universe and the subsequent discovery of the Hubble-Lemaitre Law had a significant impact on modern cosmology. It provided the first observational basis for the expansion of the universe and is often cited as evidence for the Big Bang model.
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Hubble's career
Edwin Hubble is credited with the discovery of Hubble's Law, also known as the Hubble-Lemaître law, which is the observation that galaxies move away from Earth at speeds proportional to their distance. Hubble's work in this area was published in 1929, although he was predated by astronomer Carl Wilhelm Wirtz, who made similar discoveries in 1922 and 1924, and Georges Lemaître, who published his research in 1927.
Hubble's work has had a significant impact on the field of astronomy and cosmology. His law is considered the first observational basis for the expansion of the universe and is often cited as evidence for the Big Bang model. Additionally, Hubble's work allowed scientists to calculate the age of the universe.
Today, there are several companies named Hubble, including a platform that helps organisations manage their workspace needs and a financial services company. These companies are unrelated to Edwin Hubble, the astronomer.
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The Hubble constant
Edwin Hubble is credited with the discovery of Hubble's Law, also known as the Hubble-Lemaître law, in 1929. Hubble's Law is the observation that galaxies are moving away from Earth at speeds proportional to their distance. In other words, the farther a galaxy is from Earth, the faster it moves away.
Edwin Hubble, an astronomer at Mount Wilson Observatory, Southern California, first calculated the Hubble constant in 1929 using his measurements of stars. His original estimate was 500 km/s/Mpc, about seven times the current value. The Hubble constant has been refined over the years by generations of astronomers who have improved Hubble's methods and developed new ones. Despite these advancements, there is still no consensus on the exact value of the Hubble constant.
The true value of the Hubble constant remains a topic of debate among scientists. While fundamental physics suggests a value of around 68 km/s/Mpc, observations of stars and galaxies have yielded values ranging from 69.8 to 74 km/s/Mpc. This discrepancy implies that there may be gaps in our understanding of physics, and accurately determining the Hubble constant is a significant challenge in modern astronomy.
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Hubble diagram
Edwin Hubble's 1929 article, "A relation between distance and radial velocity among extra-galactic nebulae", was a turning point in our understanding of the universe. In this report, Hubble presented evidence for one of the most significant discoveries in 20th-century science: the expanding universe. He demonstrated that galaxies move away from us in all directions, with more distant ones receding faster in proportion to their distance. This relationship is depicted in the original Hubble diagram, a graph of velocity against distance. The equation describing this linear relationship is Hubble's Law, with the slope of the line being the Hubble constant.
The Hubble diagram is a visual representation of Hubble's Law, where the velocity of an object is plotted concerning its distance from the observer. A straight line with a positive slope on this diagram illustrates the law. The Hubble diagram has been extended with modern technology, allowing for extensive mapping and exploration of the universe's matter arrangement. These advancements have revealed that cosmic expansion has accelerated over the last 5 billion years, indicating the presence of "dark energy", which comprises most of the universe.
The Hubble diagram is a fundamental tool in cosmology, providing evidence for the Big Bang model. It measures the expansion of the universe and, when combined with other observations, supports the success of the Big Bang paradigm. The diagram also reveals the distribution of galaxies, showing that they are embedded in an expanding fabric of space and time. This distribution is further classified using the Hubble sequence, a morphological classification scheme for galaxies.
The Hubble sequence, published by Edwin Hubble in 1926, categorises galaxies based on their visual appearance. It includes three broad classes: ellipticals, lenticulars, and spirals. Galaxies with irregular appearances fall into a fourth category. The sequence is often represented as a tuning fork, with elliptical galaxies on the left and spiral galaxies on the right, divided into two parallel branches. The Hubble sequence is widely used in both professional and amateur astronomy for galaxy classification.
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Frequently asked questions
The discovery of Hubble's Law is attributed to Edwin Hubble, who published his work in 1929.
Yes, Georges Lemaître, a Belgian priest, astronomer and academic, predicted Hubble's Law and demonstrated its validity two years before Hubble published his work. Alexander Friedmann also derived the Friedmann equations in 1922, showing that the universe might be expanding at a calculable rate.
Hubble's Law, also known as the Hubble-Lemaître Law, states that galaxies are moving away from Earth at speeds proportional to their distance. This means that the further a galaxy is from Earth, the faster it is moving away.
