Big History Project
- ACTIVITY: Planet Card Sort
- WATCH: Unit 4 Overview
- ACTIVITY: Unit 4 Vocab Tracking
- WATCH: Threshold 4 — Earth & Solar System
- ACTIVITY: Threshold Card —Threshold 4 Earth & the Solar System
- WATCH: How Did Earth and the Solar System Form?
- READ: How Our Solar System Formed
- READ: The Rocket Scientist - Mary Golda Ross: Graphic Biography
- READ: Gallery — Earth & Solar System
- Quiz: Earth & the Formation of Our Solar System
WATCH: Threshold 4 — Earth & Solar System
Clouds of diverse, chemical matter spun around our Sun, coming together to form our Earth and Solar System. Created by Big History Project.
Want to join the conversation?
- What are the small organisms pictured in the end screen? Tardigrades?(3 votes)
- Since the video ends with "... more complex entities. Such as, the first living organisms" he's probably referring to the very first forms of simple life such as single-celled prokaryotes and basic, multi-celled eukaryotes. Tardigrades are much more complex forms of life than these very early living organisms. This video talks about these early forms of life: https://www.khanacademy.org/partner-content/big-history-project/life/what-is-life/v/bhp-minithresholds-of-life(6 votes)
- What are matter and molecules(4 votes)
- Is the universe still growing or is it gonna stay the same?(3 votes)
- The universe is still growing, and faster than light!(2 votes)
- will the universe continue to grow?(3 votes)
- Yes, the universe is expanding as we speak. However, the exact rate, called the Hubble constant, hasn't been determined with precision yet because there are different methods to measure it.(2 votes)
- this question is somewhat out of topic
is every planet a sphere or a geoid(1 vote)
- Yes, that is part of the definition for determining planet-hood. From the IAU website:
(1) A "planet" is a celestial body that (a) is in orbit around the Sun, (b)
has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape,and (c) has cleared the neighbourhood around its orbit.(5 votes)
- why does the cloud forms a disk by flattening out ? shouldn't it form a sphere around the Star ? and why doesnt the remaining cloud also just get accreted into the star itself ? How do mere dust clouds manage to resist the star's gravity ?(2 votes)
NARRATOR: Today, about 98% of the atomic matter in the Universe consists of hydrogen and helium. But thanks to threshold three, that other 2% is made up of all the other elements in the periodic table. That makes some amazing things possible because these different elements can combine to form an almost infinite number of different types of matter. Objects that are much more complex than stars could now form. Objects like planets, and that was the work of threshold four. Here's how it works. When new stars are formed, they're surrounded by huge clouds of chemically rich matter our ingredients for this threshold. These clouds spin in different orbits around the newly forming star, creating Goldilocks conditions that are just right for elements to combine. Some atoms combine chemically to form a variety of different molecules, but also, atoms and molecules often clump together to form bigger and bigger lumps of matter. This process is called accretion. And eventually it goes on to form entire planets. Now, since lighter elements are much plentiful in the Universe many planets consist mainly of hydrogen and helium like Jupiter and Saturn. But because hydrogen and helium atoms are so light, intense radiation sometimes blasts them away from regions close to the new star. Those regions then contain a relatively high concentration of other heavier elements. And eventually, these elements may clump together through accretion to form solid planets such as our Earth. In our planet's crust for example, the most common elements are oxygen, silicon, aluminum, and iron, not hydrogen and helium. Our earth formed about 4.5 billion years ago, but the very first rocky planets may have formed within a billion years or so of the Big Bang. These planets represent new forms of complexity because they contain a much greater diversity of chemical substances that had ever existed before, and that could create even more complex entities such as the first living organisms.