Aug 5th. Cambridge, UK. 16:00.
She hasn’t cancelled. That’s a good sign, surely.
Well, unless the unimaginable happened. No, I refuse to give in to more dreadful thoughts. She’ll be here any minute now.
Signed into the Zoom call, I waited for my friend and Lebanese chemist Martine Abboud to show up for the chat we had scheduled few weeks earlier. Martine is based in Oxford UK, but she had been in Lebanon, visiting.
16:05. I waited with my heart in the palm of my hand. Then a message came…
After a calamity hits Lebanon whether it’s an explosion, air raid or assassination, what we Lebanese people do first is a head count. Then funerals and fury follow. We bury our dead, sweep away our shattered dreams and the rubble, and ponder how to start again with whatever is left.
Except that at times, nothing is left.
Martine lost a relative. A wild range of emotions swept her in less than 24 hours; shock, disbelief, anxiety, sadness, surrender, hopelessness, heartbreak, guilt, and anger. Having returned to the UK only the day before, already missing Beirut’s simplicity and authenticity, she had lost track of the days and our e-meeting.
What was supposed to be friends catching up, a week later became two scientists trying to make sense of their country and their realities.
Shock waves and shocking realities
In a warehouse in the port of Beirut on the 4th of August, an explosion released a tremendous amount of energy generating a high-pressure wave.
The thin, spherical front washed over the city within seconds, giving off a huge amount of heat. This high-pressure wave was travelling at few thousand metres per second, as estimated by analysing the videos of the explosion. That’s much faster than the speed of sound, 343 m/s. So, you could see it first, then hear the noise, a shuddering sonic boom.
You also hear a sonic boom when you crack a whip for example. Because the tip of the whip moves faster than the speed of sound, it creates weak shockwaves.
A white dome over the clouded city
Like sound waves, shockwaves are as transparent as the air in which they travel. This gives them a mystique that Hollywood uses for dramatic effects as heroes get slammed down and dive for cover after explosions. However, in Beirut explosion, the shockwave was clearly visible, like its unfolding tragedy.
Beirut is very humid during summertime, especially near the sea, so the air has a lot of water vapor. Above the explosion’s compressed air, there is a region of lower pressure. Consequently, the compressed air expands quickly and cools down, and so the water vapor in the humid air condenses and forms a white cloud. Once the pressure equalises, it evaporates and disappears.
We see this condensation around planes flying near or above the speed of sound, as a cloud with the shape of a cone.
Besides sheer negligence, what’s behind the blast? The chemist weighs in…
Footage of the explosion helps estimate the energy released by the detonation. A quick and very simplified calculation gives the TNT equivalent, a unit to measure the destructiveness of explosions. This calculation comes with a wide margin of error but suggests it would require hundreds of tons of TNT to cause the blast.
There were reports of 2,750 tons of ammonium nitrate (AN) stored in the port for 6 years. AN is a white powder that looks like table salt. It is used as a fertiliser and, by itself, is not explosive. Being a strong oxidiser, it requires a source of ignition to cause an explosion. An initial fire around the region, whose cause awaits further investigation, would have led to the massive explosion.
Poor storage conditions have undoubtedly exacerbated the detonation. AN is hygroscopic, which means that if its surrounding environment contains moisture it will absorb it. The storage conditions were not fully disclosed but it looks like AN was stored in adjacent bags and was not coated with special agents to reduce its tendency to absorb moisture. In Beirut’s very humid environment, this would have facilitated the powder to come together as a ‘cake’, a solid mass, and hence, making the velocity of detonation greater.
The accurate quantity of AN that exploded remains debatable. In comparison with previous explosions like Toulouse and Texas, the radius of the blast wave, around 9 km, would have been expected to be larger had all the 2750 tons been there and exploded. However, many factors could have influenced the blast – including the landscape, temperature and the presence of the sea nearby.
Strong blasts are devastating, causing houses and buildings to collapse. Shrapnel, or fragments from the explosion, can shoot by like supersonic bullets, reaping more lives and livelihoods. About 177 people died, more than 5,000 were injured and an estimated 300,000 became homeless.
A hopeless country?
On Wed Aug 5th, Martine got two emails. One from an 18-year-old student who started an initiative, Simply Youth, to highlight how the youth of Lebanon can contribute and create opportunities. Another also from a student who started a platform, Volunteer Beirut, to map and mobilise volunteers to help with the crisis.
We are angry but not defeated. Many volunteered, helped, contributed, and donated.
We will create the Lebanon we deserve and need, and until then, stay tuned for an initiative or two.
Artwork is by Irene Salinas Akhmadeeva.
