Earth is our home. It is an intricate and fascinating world and the only planet in the Solar System that’s covered in liquid water and provides a habitable place for life to exist.
Our planet is surrounded by an atmosphere, protecting us from heat and harmful ultraviolet rays while regulating Earth’s temperature.
While this blanket of gases provides us with some level of defence from exterior factors, we are not completely sheltered from the influence of the physical Universe beyond Earth’s atmosphere.
Our planet has a complex relationship with space, resulting in an intricate bond between the two.
Here are some of the biggest ways in which the Universe affects Earth and life on our planet.
Rocks, dust and hunks of junk
One of the simplest ways to watch Earth’s protective atmosphere defend us from what space throws our way is to look for a shooting star.
These bright white lights, streaking through the darkness are not stars at all, but meteors, tiny specks of space dust or rocks called meteoroids that have broken off from larger bodies in the Solar System.
Fabulous meteor showers like the Perseids or Geminids are attributed to debris from comets or asteroids left in Earth’s path.
This enters our atmosphere at speeds of around 150,000km/h (90,000mph). At those speeds, even a meteoroid the size of a grain of sand can punch through metal plates and cause significant injury if it were to hit a person.
Fortunately, friction in Earth’s atmosphere causes the space rock to heat up and harmlessly vaporise, producing a bright meteor.
Not all streaks of light in the night sky are created from rocks and dust.
Whizzing above our heads is an incredible amount of space junk – human-made objects that include parts of spacecraft, defunct satellites and even flecks of paint.
Space junk or orbital debris is the by-product of over 60 years of space exploration.
The US Space Surveillance Network has tracked around 56,450 pieces of junk.
Just like dust and rocks, pieces of junk can re-enter Earth’s atmosphere, burning up in the process and creating bright, fast streaks of light like a meteor.
Sometimes, there is a very small chance that space junk makes it through our atmosphere intact.
In 1997, a 250kg (550lb) fuel tank from the second stage of a Delta II rocket survived re-entry through Earth’s atmosphere and landed near Georgetown in Texas.
Space weather
Not only is Earth blanketed under a protective atmosphere, but our planet is also surrounded by a colossal magnetic field that extends out into space, a region known as the magnetosphere.
It’s created by Earth’s molten iron outer core, which is constantly churned around by the planet’s rotation and convection currents within the red-hot liquid.
This constant movement generates large, fast-moving electrical currents which in turn create Earth’s magnetic field. It is as if Earth has a huge magnet at its centre.
The magnetosphere shields us from a constant barrage of charged particles called the solar wind and particle radiation from coronal mass ejections, massive ejections of plasma and magnetic fields emitted from the Sun.
Most of this solar energy is trapped within the Van Allen belts, two belts of radiation located within the inner region of Earth’s magnetic field that surround the Earth like two big space doughnuts.
But our magnetosphere isn’t entirely particle-proof.
Variations in the solar wind can lead to disturbances within the magnetosphere, generating space weather or geomagnetic storms that can penetrate our atmosphere and produce the wonderful dancing red, purple and green lights of the aurora.
While beautiful to watch, the storms can negatively impact GPS systems, satellites, power grids and telecommunications.
Electromagnetic radiation
At the heart of our Solar System lies the Sun, a massive yellow dwarf that has a diameter of 1,392,000km (864,950 miles) and sits 149,597,870km (92,955,807 miles) away from Earth.
The electromagnetic radiation that we receive from the Sun comprises infrared radiation, visible light and ultraviolet radiation, all of which are produced by nuclear fusion at the star’s core.
It is the most important energy source for our planet, providing us with the heat and light we need to survive, driving our ocean currents, seasons and weather.
Earth’s atmosphere acts as an insulating layer, helping to stop that heat escaping, but it also plays an important role in keeping us safe from some of the most harmful rays, including gamma rays and some ultraviolet radiation waves.
Our atmosphere absorbs and reflects electromagnetic radiation through the presence of several gases, including carbon dioxide, water and ozone gas.
Without Earth’s protective atmosphere shielding life from these harmful rays, organic matter would be seriously damaged, altering its atoms and molecules.
Wildlife and the night sky
The Sun and Moon play a crucial part in the existence of life on Earth. The natural world is connected to the Moon and stars.
Almost all animals on Earth have a circadian clock, an internal clock regulated by light that helps us navigate the 24-hour day.
But there are some animals that depend on the lunar cycle too.
Many marine animals rely on the tides, and so their feeding and reproductive cycles are tied to the Moon.
Coral, for instance, uses the waning Moon as a signal to spawn, while reef fish forage for food more intensely around the full Moon.
Terrestrial life also relies on our celestial satellite. Insect activity has long been shown to fluctuate in step with the phases of the Moon.
Ephedra foeminea, the Werewolf plant, takes advantage of this fact by secreting a sugary substance when the Moon is full, to attract passing nocturnal pollinating insects.
Some animals even look beyond our Solar System and use the stars to navigate, just as humans have done for millennia.
A study in the 1960s found that indigo bunting songbirds of North and South America were able to identify Polaris, the North Star, and used it to navigate during migration, becoming disorientated when the region around the star was blocked from view.
There were even suggestions the birds could relearn how to navigate using Betelgeuse instead.
Even creatures that can’t make out individual stars are known to follow them.
The humble dung beetle’s compound eyes are sensitive but have a low resolution, meaning while bright stars are all but invisible, they have a much better view of the Milky Way.
The insects are known to use the bright swathe of light to keep themselves on track and moving in a straight line.
Gravitational pull
Gravity is all around us, not just here on Earth, but throughout the Solar System.
It holds the planets in their orbits, keeps the Moon in its circuit around Earth and even helps new stars to form.
The proximity of the Moon to Earth – on average 384,400km (238,855 miles) away – creates a gravitational pull on our planet’s oceans, creating the tides.
Tides are the regular rise and fall of the oceans caused by the gravitational pull of the Moon and to a lesser extent, the Sun
As Earth spins on its axis each day, the oceans are affected by two forces.
The side of Earth closest to the Moon experiences a high tide caused by the gravitational pull of the Moon.
On the opposite side of Earth, furthest from the Moon, a second high tide of the day is created by the centrifugal force of the Moon and Earth orbiting each other.
Twice a month during the Moon’s full or new phase when the Moon, Earth and Sun are in alignment, spring tides occur.
These tides are higher than normal because the Sun’s gravitational pull is added to the gravitational pull of the Moon.
Seven days after a spring tide, when the Moon and Sun have moved along their orbits and are at right angles to each other, neap tides occur.
Simply speaking, the effects of the Moon and Sun cancel each other out, producing a tide that is lower than usual.
Cosmic rays and ghostly neutrinos
We’re being blasted by invisible rays. But don’t be alarmed – they’re not from some alien, they’re cosmic particles.
Discovered in 1912 by physicist Victor Hess, harmless cosmic rays (known as cosmic particles) are fast-moving charged particles produced by the Sun, black holes and exploding stars, that travel across the great expanse of the Universe.
Once upon a time, they started out as atoms, but as their outer electron layer was stripped away, they remained as nuclei.
Earth is bombarded by trillions of rays every day, but our protective atmosphere shields us from them.
Studying cosmic rays can tell us a lot about the chemical and physical properties of space and the Universe, how our Universe is changing and even helped to discover antimatter.
Neutrinos or ghost particles, on the other hand, share similarities with cosmic rays but are uncharged particles travelling through space in a straight line, making their way to Earth at the speed of light all day, every day.
They are the most abundant particle in the Universe and because they are uncharged, are not affected by powerful magnetic fields and rarely interact with matter – which is particularly problematic for scientists, as they can’t use electric or magnetic forces to ‘catch’ and study them easily.
In 2005, construction of the IceCube Neutrino Observatory began in Antarctica and was completed six years later.
The detector comprises a cubic kilometre of ice with digital optical modules buried to a depth of 2,500 metres (8,200ft), designed to detect particles from cataclysmic events in the Universe.
The first gigaton neutrino detector ever built, it observes 100,000 neutrinos a year.
Human perspective
Many astronauts have experienced incredible views of our Blue Planet suspended against the blackness of space, a sight that most of us can only dream of.
Two of the most famous and inspiring photographs that capture that moment are ‘Earthrise’, taken in 1968 by Apollo 8 astronaut William Anders as he orbited the Moon, and the ‘Blue Marble’, a photograph of Earth taken aboard the Apollo 17 spacecraft in 1972.
Capturing the vulnerability of our planet against the vastness of space, they influenced the birth of environmentalism.
Viewing Earth from space has resulted in astronauts reporting a change in their emotions, an overwhelming sense of beauty and stronger connections to people and to Earth as a whole.
This phenomenon is known as the Overview Effect, a term coined in the 1980s by the space philosopher Frank White.
The spiritual and sometimes religious feelings that astronauts have felt during missions have been a focus of studies in psychology and ethics.
Just imagine how you would feel in their place!
This article appeared in the December 2024 issue of BBC Sky at Night Magazine
