Similar disks can be seen around other nearby stars and are thought to provide the (more.) Over the past few decades, measurements of the Hubble expansion have led to estimated ages for the universe of between 7 billion and 20 billion years, with the most recent and best measurements within the range of 10 billion to 15 billion years.Ī disk of dust and gas, appearing as a dark band in this Hubble Space Telescope photograph, bisects a glowing nebula around a very young star in the constellation Taurus. The velocities of distant galaxies can be measured very accurately, but the measurement of distances is more uncertain. The age of the universe can be derived from the observed relationship between the velocities of and the distances separating the galaxies. The ages of the universe, our galaxy, the solar system, and Earth can be estimated using modem scientific methods. The rocky planets, including Earth, were near the sun, and the gaseous planets were in more distant orbits. In successive stages these planetesimals coalesced into the nine planets and their numerous satellites. In the case of our sun, the gas and dust within this disk collided and aggregated into small grains, and the grains formed into larger bodies called planetesimals ('very small planets'), some of which reached diameters of several hundred kilometers. Some proportion of stars, including our sun, formed in the middle of a flattened spinning disk of material. If the mass of material in the cloud was sufficiently compressed, nuclear reactions began and a star was born. In some of these clouds, where there was sufficient mass and the right forces, gravitational attraction caused the cloud to collapse. Within galaxies, including our own Milky Way galaxy, changes in pressure caused gas and dust to form distinct clouds. In fact, the Cosmic Microwave Background Explorer (COBE) satellite launched in 1991 confirmed that the background radiation field has exactly the spectrum predicted by a Big Bang origin for the universe.Īs the universe expanded, according to current scientific understanding, matter collected into clouds that began to condense and rotate, forming the forerunners of galaxies. Observations showed this deduction to be correct.

One such deduction was that the temperature in deep space today should be several degrees above absolute zero. This Big Bang hypothesis led to more testable deductions. A huge explosion, known as the Big Bang, then sent matter and energy expanding in all directions. From this deduction came the suggestion that all the currently observed matter and energy in the universe were initially condensed in a very small and infinitely hot mass. One is that the universe was more condensed at a previous time.

Hubble's hypothesis of an expanding universe leads to certain deductions. The implication of these findings is that the universe is expanding. Moreover, the velocities of recession increase in proportion with distance, a discovery that has been confirmed by numerous and repeated measurements since Hubble's time.

Hubble made observations that he interpreted as showing that distant stars and galaxies are receding from Earth in every direction. In the late 1920s the American astronomer Edwin Hubble made a very interesting and important discovery. But the processes by which planets, stars, galaxies, and the universe form and change over time are also types of 'evolution.' In all of these cases there is change over time, although the processes involved are quite different. The term 'evolution' usually refers to the biological evolution of living things.

Space phenomena facts