“Unlike the Sun, the Moon’s surface is made of mostly heavier elements, while the Sun is mostly hydrogen and helium. When cosmic rays (high-energy particles) from throughout the Universe collide with heavy atoms, nuclear recoil causes gamma-ray emission. With no atmosphere or magnetic field, and a lithosphere rich in heavy elements, cosmic rays produce gamma-rays upon impacting the Moon.”
When you view the Moon with your eyes, you’re not seeing it shine so brightly because it’s emitting its own light. Rather, it’s reflecting sunlight on its illuminated phase and reflecting light emitted from Earth (known as “Earthshine”) on the darkened portion. If you look at the Moon in many different wavelengths, from radio to infrared to ultraviolet to X-ray energies, you’ll find that the Sun is much brighter, and the Moon primarily emits light due to reflection.
But in gamma-rays, that entire story changes. The Sun emits virtually no high-energy gamma-rays, with only minor bursts during solar flared. The Moon, on the other hand, emits high-energy gamma-rays constantly; for almost 30 years we know that it outshines the Sun in this particular wavelength range.
Astronomers Debate: How Many Habitable Planets Does Each Sun-Like Star Have?
“We know that there are between 200 billion and 400 billion stars in the Milky Way galaxy. About 20% of those stars are Sun-like, for about 40-to-80 billion Sun-like stars in our galaxy. There are very likely billions of Earth-sized worlds orbiting those stars with the potential for the right conditions to have liquid water on their surfaces and being otherwise Earth-like, but whether that’s 1 or 2 billion or 50 or 100 billion is still unknown. Future planet-finding and exploring missions will need better answers than we presently have today, and that’s all the more reason to keep looking with every tool in our arsenal.”
Most of the time, in science, the quality of our data drives the size of our uncertainties. When we have very little data and it’s only of poor quality, our uncertainties tend to be large; when we have lots of very good data, our uncertainties shrink. NASA’s Kepler mission has provided astronomers with an unprecedented suite of data on exoplanets, revealing thousands of new worlds beyond our Solar System. And yet, despite all it’s found, if you ask the simple question of “how many Earth-like planets orbit a typical Sun-like star,” answers disagree by a factor of 100: from about 1% of stars have them to there’s between 1 and 2 for each and every such star.
This Is Why We Don’t Shoot Earth’s Garbage Into The Sun
“Considering that the United States alone is storing about 60,000 tons of high-level nuclear waste, it would take approximately 8,600 Soyuz rockets to remove this waste from the Earth. Even if we could reduce the launch failure rate to an unprecedented 0.1%, it would cost approximately a trillion dollars and, with an estimated 9 launch failures to look forward to, would lead to over 60,000 pounds of hazardous waste being randomly redistributed across the Earth.
Unless we’re willing to pay an unprecedented cost and accept the near-certainty of catastrophic environmental pollution, we have to leave the idea of shooting our garbage into the Sun to the realm of science fiction and future hopeful technologies like space elevators. It’s undeniable that we’ve made quite the mess on planet Earth. Now, it’s up to us to figure out our own way out of it.”
As human beings continue to lead the technologically advanced lives we’re presently leading, we’re also producing waste of many different types. Biohazards, dangerous chemicals, nuclear waste and other pollutants must be kept out of drinking water, agricultural regions, the oceans, atmosphere, and away from populated areas. You might wonder why, now that we’re well into the space age, we haven’t considered shooting Earth’s most difficult-to-deal-with garbage into the Sun?
“During the red giant phase, Mercury and Venus will certainly be engulfed by the Sun, while Earth may or may not, depending on certain processes that have yet to be fully worked out. The icy worlds beyond Neptune will likely melt and sublimate, and are unlikely to survive the death of our star.
Once the Sun’s outer layers are returned to the interstellar medium, all that remains will be a few charred corpses of worlds orbiting the white dwarf remnant of our Sun. The core, largely composed of carbon and oxygen, will total about 50% the mass of our present Sun, but will only be approximately the physical size of Earth.”
Looking forward in time, the death of our Sun is easy to envision, as we’ve seen Sun-like stars in their dying phases and immediately afterwards plenty of times. But what happens after that, in the far future? Will our Sun’s corpse remain a white dwarf forever? Will it simply cool down, radiating heat away? Or will something exciting happen?
Maybe we’ll get ejected from the galaxy. Maybe we’ll get devoured by a black hole. Maybe we’ll merge with another object, or experience an interaction that forever changes us from what we were. Maybe we’ll even experience a cataclysm that destroys our stellar corpse entirely!
This Is How The Sun Moves In The Sky Throughout The Year
“It’s easy to see that the topmost point corresponds to the summer solstice, while the lowest point corresponds to the winter solstice, but there is no special astronomical significance to the “crossing-point” in the Sun’s analemma as seen from Earth. Occurring approximately on April 14th and August 30th, those dates are only determined by the way our seasons, determined by axial tilt, align with our planet’s orbit around the Sun.
If our perihelion and aphelion were aligned with the equinoxes, rather than the solstices, we’d have a teardrop-shaped analemma, rather than a figure-8, which is how the Sun appears from Mars! The analemma is the beautiful, natural shape traced out by the Sun over time, creating a figure-8 as both our orbit and axial tilt dictate. Enjoy the Sun’s motion through our skies, as its unique cosmic pirouette is due to our planet’s one-of-a-kind motion through space!”
You might notice that the Sun is changing its position in the sky, while sunset and sunrise times also change. But did you know that you’d get this bizarre, pinched, figure-8-like shape if you took a picture of the Sun every day throughout the year at 24-hour intervals? It’s true! The shape is known as Earth’s analemma, and it’s determined by a variety of factors that you must consider all of in order to get the explanation right.
“If it weren’t for the quantum nature of every particle in the Universe, and the fact that their positions are described by wavefunctions with an inherent quantum uncertainty to their position, this overlap that enables nuclear fusion to occur would never have happened. The overwhelming majority of today’s stars in the Universe would never have ignited, including our own. Rather than a world and a sky alight with the nuclear fires burning across the cosmos, our Universe would be desolate and frozen, with the vast majority of stars and solar systems unlit by anything other than a cold, rare, distant starlight.
It’s the power of quantum mechanics that allows the Sun to shine. In a fundamental way, if God didn’t play dice with the Universe, we’d never win the Powerball three times in a row. Yet with this randomness, we win all the time, to the continuous tune of hundreds of Yottawatts of power, and here we are.”
In the core of our Sun, where temperatures cross the threshold of 4 million K (and rise all the way up to 15 million K), nuclear fusion occurs, driving the energy output of our Sun. Yet if you looked at what was going on at a particle level, that first step towards fusion is where two protons collide to form a deuteron. Only, there are two immediate problems: a deuteron is made out of a proton and neutron, not two protons, and that the two protons don’t even have enough energy to overcome the electrostatic repulsion between them! Thankfully, the Universe is quantum in nature, meaning weak interactions do occur, changing a quark’s flavor type, and particle positions are defined by quantum wavefunctions, which can overlap.
The Sun Will Someday Die, And That’s Why You’re Alive
“It’s true: death comes for us all. It comes for everyone we know and don’t know; it comes for everyone that will ever live. After we’re all dead for billions of years, the Sun will die, too.
But that’s not the full story, and it leaves out the best part. A star’s death brings a remarkable story of cosmic rebirth and possibilities for life to the Universe. It is a story of creation that goes hand-in-hand with destruction, and it follows just below. Give it a shot. It just might be the most remarkable, wonderful story an elementary schoolchild could hope to hear.”
It was a few years ago that I got one of those questions that has stuck in my mind ever since. In particular, it was a message from an elementary school teacher who had a distraught child. The teacher asked me:
“I need a good explanation for a third grader, whose Mom tells me is deeply concerned, that the sun will blow up.”
This is one of the toughest truths about the Universe that many of us will ever learn. The answers to it can make you feel small, inconsequential, and meaningless at times.