We'll Say Goodbye To Our Planet In 1,000 Years, Says Stephen Hawking
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Humans have been on Earth for hundreds of thousands of years. So far so good, right? Well, according to famed physicist Stephen Hawking, things around here are about to get ugly for us. It's time to start poking around the neighborhood for a better place to call home. And by place, we mean planet.
Earth May Have Entered A New Epoch
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We may be in a new epoch. Like the humans that survived the last glacial period to move from the Pleistocene to the Holocene, modern humans may have left the Holocene to enter the brand-new Anthropocene—the "age of humans." To delineate these stretches of time, geologists must identify individual boundaries in layers of rock known as strata. If a boundary is found in rock all over the world, the International Commission on Stratigraphy (ICS) appraises it for entry in the International Chronostratigraphic Chart, which defines geologic time in terms of eons, eras, periods, epochs, and ages. Often, these rock boundaries are caused by natural events such as ice ages and volcanic activity. The Anthropocene is not yet an official epoch, but if it becomes one, it will be defined by human activity—specifically, the significant changes we've made to the land, air, and water. The date of the epoch's start is up in the air, but it will most likely be 1945, the date of the first nuclear bomb detonation. There's another thing that's unusual about the Anthropocene beyond its human influence: geologic time is usually captured in rock, and it's too early to see human influence in the geologic record. If the ICS adds this epoch, it will be the first of its kind. Explore the science of strata with the videos below.
70% Of Earth's Fresh Water Is Frozen
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About 71% of the Earth is covered in water. Most of that is in oceans, rivers, and lakes, but some is frozen in the Earth's two ice sheets. Those ice sheets, which cover most of Greenland and Antarctica, only contain 2% of the world's total water supply, but a whopping 70% of the Earth's fresh water. Scientists estimate that if the Antarctic Ice Sheet—the larger of the two—melted, sea level would rise by around 60 meters (200 feet). Not only that, but it could affect the weather: a study showed that less sea ice in the Arctic causes rainier summers in western Europe, and another study suggests that it's causing more extreme heat waves in the United States and elsewhere. And counterintuitively, melting ice also causes more melting ice. A 2016 study found that a shrinking in the Greenland Ice Sheet causes what are known as "blocking events," where high-pressure systems park themselves on top of one area for days or even weeks. This brings warm, moist air that heats the surface below and causes even more ice to melt. Explore the relationship between polar ice and climate change in the videos below.
Last Time Earth Was At This Spot in the Galaxy, Dinosaurs Existed
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You're always moving because the earth is always rotating. It's also revolving around the sun, making a complete orbit once a year. Our sun, likewise, revolves around the Milky Way galaxy, taking our entire solar system with it. It takes the sun approximately 225-250 million years to make a full trip around the galaxy, a period known as a "cosmic year." This means that at any given moment, our planet is in roughly the same spot in the Milky Way it was 250 million years ago. Today, that point in history coincides with the Permian-Triassic extinction, the most catastrophic of our planet's five mass extinction events, when 90% of marine species and 70% of land species died out. After the extensive decimation, the Triassic period began, bringing with it Archosaurs, early grasshoppers, and eventually the first mammals, all of which lived on the supercontinent known as Pangaea. In another 250 million years, we'll arrive back at this spot in the Milky Way. Find out more about the movement of the universe in these videos.
Key Facts to Know
As the Earth rotates, the Equator moves the fastest while the poles move the slowest. 1:06
The Milky Way Galaxy is headed toward the Andromeda Galaxy at approximately 405,500 kph (252,000 mph). 2:40
Here's a breakdown of humanity's celestial speed: 3:58
Where Is Earth In The Universe?
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Before the Laniakea Supercluster was outlined in 2014, most astronomers placed the Milky Way inside the Virgo Supercluster. The Laniakea Supercluster is much bigger, containing about 100,000 galaxies and spanning 520 million light-years. Its name is an homage to Polynesian explorers who navigated the Pacific ocean by looking at the stars, and means "immeasurable heaven" in Hawaiian. The definition of "supercluster" is an evolving one, however, and scientists think that our place in the universe may alter yet again as research continues to advance.
from Nature Video Channel
Key Facts to Know
The Milky Way galaxy is nested on the outskirts of the Laniakea Supercluster. 0:39
Most galaxies in the Laniakea Supercluster are being pulled toward a dense area of space called the Great Attractor. 1:54
Scientists defined the boundaries of the Laniakea Supercluster at points where the "flows" of galaxies diverged. 3:09