It includes living things, planets, stars, galaxies, dust clouds, light, and even time.
A historical perspective
Before the birth of the Universe, time, space and matter did not exist. The Universe contains billions of galaxies, each containing millions or billions of stars.
The space between the stars and galaxies is largely empty. However, even places far from stars and planets contain scattered particles of dust or a few hydrogen atoms per cubic centimeter. Space is also filled with radiation e. Then those atoms grouped together.
Over lots of time, atoms came together to form stars and galaxies. The first stars created bigger atoms and groups of atoms called molecules.
The universe is expanding even faster than we thought
That led to more stars being born. At the same time, galaxies were crashing and grouping together.
As new stars were being born and dying, then things like asteroids, comets, planets, and black holes formed! How long did all of this take? That is a very long time.
What an Idea!
Because it got so big and led to such great things, some people call it the " Big Bang. Have you heard the name Hubble before? He has a spacecraft named after him: the Hubble Space Telescope. With current technologies, these types of planets are easier to detect. With that in mind, scientists are still trying to estimate how many rocky and Earth-like planets are out there.
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By one estimation, for every grain of sand on Earth, there could be as many as 10 Earth-like planets in the universe. That's according to Peter Behroozi, a Hubble fellow at the University of California, Berkeley, who presented during the same session as Stanley. Of course, it is important to remember that the universe is a very big place, and at the moment scientists can search for life only on planets within the Milky Way galaxy. Behroozi is working to link galaxy formation with planet formation.
In a paper published in in the Monthly Notices of the Royal Astronomical Socity, he and his co-author showed that larger galaxies produce a greater number of Earth-like planets than do smaller galaxies such as, for example, the Milky Way.
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But because there are many more Milky Way-size galaxies in the universe, that's where most Earth-like planets in the universe should be found. Thus, Earth's location in a Milky Way-size galaxy is not unique. This work not only helps scientists make estimations about how many planets are currently in the universe, but how many will form, assuming the universe continues to grow and evolve in the same way it has in the recent past. In the paper, Behroozi and his colleague look far ahead into the future and estimate that "the universe will form over 10 times more planets than currently exist.
hackricouca.tk During his talk, Stanley re-traced the history of humanity's search for life beyond Earth, and showed how people are influenced by their own times and experiences when trying to predict what lies beyond this planet. William Herschel, an extremely influential 18th century astronomer, believed that intelligent beings lived on the sun.
In the 19th century, mainstream astronomers thought they saw artificial canals built by intelligent creatures on Mars and Venus. Observations of those two planets and the sun by space-based probes have disproved those ideas, but new research has also given rise to updated ideas about how and where life could exist elsewhere in the universe. For example, Stanley said, in the last 40 years, scientists have adopted a broader view of the conditions under which life can exist.
So-called extremophiles are organisms that live in environments that were previously thought inhospitable, like at the bottom of the ocean, under the ice in Antarctica and in areas that receive high doses of radiation.
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Stanley said many aspects of the Drake equation need updating not only with new scientific evidence, but also with new perspectives.