What the World’s Largest Dump Truck Can Tell Us About the Physics of the Sun
Behold the mighty Liebherr T 282B dump truck!
It is one of the two or three largest dump trucks in production. By many measures, it’s the largest dump truck in the world. The Leibherr T 282B is 14.55 metter long (48 feet), 8.7 meters wide (29 feet) and stands 7.4 meters tall—a towering 24 feet! Unloaded, the truck itself weighs a staggering 600 short tons! (A “short ton” is 2,000 lb; a “metric ton” is 2,205 lb.)
The T 282B can carry a maximum of about 400 short tons. It’s 3,500 horsepower engine can propel this monster truck to an astonishing 40 mph, fully loaded and weighing 1,000 tons!
Now, here is how the T 282B can help us understand in a physical way what’s going on in the Sun. Consider this: our Sun converts approximately 600 MILLION tons of hydrogen into helium every second! Every second!
That number is virtually impossible to conceive of in physical terms, but maybe the Liebherr T 282B can help gives an idea of what that much mass might mean. Let’s imagine that instead of the gas hydrogen, the Sun’s nuclear fusion “burned” something the T 282B could carry — say, coal.
Now imagine 1.5 MILLION of these T 282Bs fully loaded with 400 tons of coal, roaring past you every second. That’s the equivalent mass of how much hydrogen is being converted to helium every second at the core of our sun!
Of course, the hydrogen to helium conversion isn’t one-to-one, a very small fraction of the mass of the hydrogen is converted to energy according to Einstein’s famous equation, E =MC squared:
Here’s a fuller explanation of the Sun’s fusion process from Wikipedia :
The proton–proton chain occurs around 9.2×1037 times each second in the core of the Sun. Since this reaction uses four free protons (hydrogen nuclei), it converts about 3.7×1038 protons to alpha particles (helium nuclei) every second (out of a total of ~8.9×1056 free protons in the Sun), or about 6.2×1011 kg per second. Since fusing hydrogen into helium releases around 0.7% of the fused mass as energy, the Sun releases energy at the mass-energy conversion rate of 4.26 million metric tons per second, 384.6 yotta watts (3.846×1026 W), or 9.192×1010 megatons of TNT per second. This mass is not destroyed to create the energy, rather, the mass is carried away in the radiated energy, as described by the concept of mass-energy equivalence.
Kind of blows the mind, no? Our Earth actually intercepts an infinitesimal percentage of the Sun’s energy—maybe about one one-billionth of the Sun’s total energy output actually reaches the Earth.
Of all the Sun’s energy that does reach Earth, about 30 percent is immediately reflected back to space by clouds and the Earth’s atmosphere and surface. Most of the energy that is aborbed by the land, oceans, clouds, and atmosphere is subsequently radiated back into space. Less than one percent of the total energy that reaches Earth is used by plants for photosynthesis.
It’s amazing to consider that every second a little more than 4 million metric tons of mass is converted to energy at the Sun’s core! Using the Leibherr T-282 B as our “measuirng cup” again, that’s a conversion of mass to energy of more than 10,000 T 282B dump truck loads of mass every second!
Or, put another, perhaps even more inconceivable way, the fusion reaction at the core of the Sun releases the energy equivalent of 9.192×1010 megatons of TNT per second! That’s the energy of over 90 billion one megaton bombs every second! No wonder the Sun is so hot, even though it’s incredbily massive compared to the (relatively) small amount of hydrogen being converted to helium.
Again, even with the help of our monster truck, it’s almost impossible for our minds to grasp the scales and magnitude of the masses and energies involved.
But maybe now, with some imagination and the help of the mighty (by human scale!) Leibherr T 282B, we have a better grasp of the monumental physical processes going on in the Sun—the processes that make life here on Earth possible.
Now, who wants to test drive one of these big brutes? I would love to give it a try! Just don’t ask me to parallel park one!