The near-miss asteroid last week raised questions regarding how these space rocks move in orbit. Astronomers are studying the “Yarkovsky Effect”– a subtle force caused by the uneven heating of an asteroid’s surface. University of Arizona astronomer Ed Beshore [excerpt below] likens the force of the Yarkovsky Effect to the pressure you feel when holding two grapes in your hand– an almost negligible force for the duration of a moment, but which, accumulated over millennia, has appreciable influence on an asteroid’s orbit. Over time, the Yarkovsky Effect can “move mountains.” (Beshore)
This is a reminder of how many and varied are the powers at work in the world– and a reminder that power is not just big and loud. Small pressures, applied patiently and relentlessly, can shift seemingly irresistable objects. So it is good to pause and recollect these small pressures, these soft powers: the powers of love and commitment; the powers of prayer and trust; the powers of truthful words and good deeds. They don’t move asteroids, but they can move the human heart.
“The force that through the green fuse drives the flower drives my green age” is Dylan Thomas’s poetic rendition of another power: the life-force, pulsing and moving, in flower and human alike. For some of us, Christ is the fullest expression of this life-force: the willing renunciation of domination (power over), and the willing embrace of suffering love/compassion (power with). Even death, we affirm, is not stronger than this force for life.
The asteroid story from The Christian Science Monitor follows:
For instance, when sunlight hits the surface of an rotating asteroid, the asteroid returns that energy to space in the form of heat.
“The heat acts like a tiny rocket thruster that can push asteroids out of otherwise harmless orbits,” he says. The reason: A rotating asteroid sheds the heat unevenly across its surface, in effect sloughing it off in the direction of “dawn” on the asteroid. This direction may or may not coincide with the direction the asteroid is traveling along its orbit.
Indeed, this force, known as the Yarkovsky effect, is thought to help resupply the inner solar system with asteroids that otherwise might have stayed in the main asteroid belt, which lies between Mars and Jupiter.
A year ago, Dr. Beshore says, one of the mission’s team members performed “a really exquisite set of measurements using radar data and came up with a preliminary estimate for the kinds of forces” this effect imposes on OSIRIS-Rex’s target asteroid.
It’s about the same as “the force that you feel when you hold a couple of grapes in your hand,” he says, adding “that force, applied over millions of years, can literally move these mountains of rock around.” [Emphasis added]
Since the force also plays a role in shaping and reshaping the orbits of near-Earth asteroids, “it’s really quite important for us to make sure we understand this force much better.”