快猫短视频

WHEN I was 4, my favourite book was Balloonia by Audrey Wood. It tells the story of a little girl who realises that balloons have an afterlife when they float away. Wielding a sharp pin, she takes a balloon hostage, demanding that it take her to Balloonia. There, she experiences a world where everything is made of balloons, including the animals and the landscape they populate.

It is a wonderful tale. It is only later in life that I have come to worry it might be predicated on the continued availability of the second most abundant element in the universe: helium. Trouble is, helium is running out on Earth.

When we fill a balloon with helium, it floats because helium is lighter than air. Sound also travels through helium faster than it travels through air, which is why inhaling helium makes people鈥檚 voices sound temporarily more high-pitched.

Beyond its entertainment value, helium is also a crucial coolant in its liquid form. It pops up in diverse technologies, from fancy medical equipment like MRI machines to big physics toys such as space rockets and the Axion Dark Matter Experiment, which searches for axion particles, my favourite candidate to make up the universe鈥檚 missing dark matter.

On a day-to-day basis, we rarely give much thought to the origins of helium, but they are fascinating. Almost all of the helium in the universe was produced when space-time as we know it was only a few minutes old. This period is called big bang nucleosynthesis, an era that began when the universe became cool enough that radiation could no longer prevent protons and neutrons coming together to form the first atomic nuclei.

During that time, the first element in the periodic table, hydrogen, formed in great quantities, making up 75 per cent of the luminous matter in the universe. Nearly all the rest is the second lightest element 鈥� helium. These two elements make up most of the gas clouds that hang around the universe. Along with a small amount of lithium made at the same time, they formed the foundation for the first generation of stars.

Stars aren鈥檛 just made from helium; they are also a site for making it. Stars are collections of tightly packed hydrogen and helium atoms whose high density causes the initiation of nuclear explosions. These explosions are extremely bright, producing light across the electromagnetic spectrum, including at visible wavelengths. That is what we have to thank for every sunrise and the beauty of the night sky.

鈥淭he existence of a world of floating balloons is predicated on the availability of helium鈥�

But these explosions also smash and glue elements together to make heavier ones. In our sun, hydrogen nuclei fuse into helium, producing high-energy radiation in the form of gamma rays. In more massive stars, this stellar nucleosynthesis is more complex, leading to the production of heavier elements like the carbon that is the basis for human life. We really are made of star stuff!

There is an irony in this cosmic abundance, however. All the helium we have on Earth, from the stuff we put in balloons to the stuff we put in MRI machines, originates not directly in stars, but in radioactive decays in Earth鈥檚 crust. Over time, the heavy elements uranium and thorium 鈥� themselves made when stars explode at the end of their lives or when neutron stars collide 鈥� break down. The products include alpha particles consisting of two protons and two neutrons bound together, otherwise known as helium nuclei.

Unfortunately for Earth (and Balloonia), helium isn鈥檛 endlessly abundant. In fact, we are currently facing a global shortage. More than 90 per cent of the world鈥檚 helium supply 鈥� the US, Qatar and Algeria 鈥� with most of it a byproduct of natural gas extraction.

Current sources are running low and efforts to tap new ones have been delayed. 快猫短视频s have tried to get the US Congress to improve the management of existing supplies, but political challenges have got in the way.

The link between natural gas and helium supplies is one reason this is complicated: accelerating global warming demands that we move away from fossil fuels as energy sources, not look for more of them. But unlinking helium from fossil fuels raises difficult-to-address questions given current economic structures.

Changing how we do things often seems like an impossibility. The case of helium reminds us that the universe is a vast and wonderful place, but also how we need to make do with 鈥� and cherish 鈥� what we have on Earth.