The Future | Crash Course Pods: The Universe #10

30 Aug 2024 (19 days ago)

Future Threats to Earth

The future of Earth is uncertain, but scientists can make predictions based on trends such as climate change and the burning of fossil fuels.
Asteroid impacts are a threat to Earth, but scientists are developing technology to deflect them, such as the DART Mission.
Surveys of near-Earth objects are conducted to identify potential threats, and while there are objects being monitored, none are currently considered a major threat.
In the long term, the impact of a near-Earth object is extremely likely, though not imminent.
Technological advancements may eventually help mitigate the threat of near-Earth objects.
Solar flares and coronal mass ejections from the Sun can cause significant disruptions on Earth, such as the Carrington event in 1859.
Random astronomical events like supernovae or gamma-ray bursts could potentially affect Earth, though none are expected to occur soon.

Geological changes on Earth, such as glaciation events, axial tilt changes, and plate tectonics, will continue to occur, altering the planet's layout and magnetic field.
The Earth and its celestial environment will undergo significant changes over time, both predictable and unpredictable.
The Moon is gradually moving away from Earth, which will eventually result in the loss of total solar eclipses.
The Moon is moving away from Earth at a rate of 3.78 centimeters per year.
The Earth's rotation is slowing down, causing the length of a day to increase by 1.8 milliseconds per century on average.
Eventually, total solar eclipses will no longer occur due to the Moon moving farther away from Earth.

The Sun, a middle-aged star, is currently fusing hydrogen into helium, a process that defines its lifespan.
As the Sun burns through its hydrogen, it will gradually become brighter and expand, eventually becoming a red giant star.
In approximately one billion years, the Sun's increased brightness will cause a runaway greenhouse effect on Earth, boiling the oceans and making the planet's surface uninhabitable.
The habitable zone in the solar system will shift as the sun's brightness increases, but Mars will still lack sufficient atmosphere for liquid water even with increased warmth.
Eventually, Mercury and Venus will become pollution in the Sun's white dwarf, and Earth might also fall into the Sun.
The Sun will lose its outer atmosphere after becoming a red giant, leaving a dense core called a white dwarf, which will be about the size of Earth but much denser.
In a billion years, the Sun will be 10% brighter, which could have drastic effects on Earth, such as boiling oceans.
In approximately 7 billion years, the Sun will enter its red giant phase and potentially engulf the inner planets, including Earth.
As the Sun transitions into a white dwarf star, its outer layers will create a planetary nebula.

The Andromeda Galaxy, currently 2.5 million light-years away, is moving towards the Milky Way at a speed of 110 km per second and is expected to collide with it in about 4 billion years.
When the Andromeda and Milky Way galaxies collide, the stars within them will not collide, but the gravity of the event will cause stars to be thrown around, creating tidal forces and long streamers of stars.
The collision of the Andromeda and Milky Way galaxies will cause bursts of star formation due to the collision of gas within the galaxies, and the merging of the supermassive black holes at the center of each galaxy could eject or tear apart stars.
If a star, such as our sun, is ejected from a galaxy, it is possible that the gravitational forces of the ejection could disrupt the orbits of planets in the star's solar system, but it is also possible for the star to continue to exist outside of a galaxy.
The Andromeda Galaxy and the Milky Way will collide and merge to form a new galaxy called Milkdromeda. This collision will trigger some new star formation, but not as much as in the early universe due to the reduced availability of gas.
Over time, Milkdromeda will become dimmer and redder as existing stars die out and fewer new stars are born. The remaining stars will primarily consist of low-mass red dwarfs, which have extremely long lifespans. It is estimated that 90-95% of all stars that will ever exist have already formed.

In the distant future, billions of years from now, the Sun will transition into a white dwarf and gradually cool down over an extremely long period, potentially evolving into a black dwarf, although the universe is not yet old enough for any black dwarfs to exist.
In about 100 billion years, the universe's expansion will make it impossible to observe anything outside the Milkdromeda galaxy, even with advanced telescopes like the JWST.
This expansion will also stretch and obscure the cosmic microwave background radiation, eliminating evidence of the Big Bang and leaving future civilizations with no observational data about the universe's history or expansion.
In 100 billion years, any remaining humans will not know about the history of the universe, other galaxies, or the Big Bang.

A study analyzed the light spectrum from a polluted white dwarf star, revealing the presence of heavy elements like silicon and iron.
The presence of these heavy elements in the white dwarf's spectrum suggests that the star had consumed planets, as these elements are not typically found in a star's core.
A star consumed its rocky planets, leaving only pollution in the white dwarf's spectrum as evidence.
White dwarfs are a type of degenerate matter, specifically electron degenerate matter.
In the distant future, Earth will be pollution inside degenerate matter.
If the Sun were more massive, it could collapse into a neutron star, a very compact object with the mass of the Sun but the size of a city.
The Sun is currently in the middle of its lifespan and will become brighter, puffier, and redder as it burns through its hydrogen.