You'd be forgiven for thinking the afternoon sun looks yellow — but the light it gives off is technically white.
The Earth's atmosphere makes the star appear yellow. The gases bend the light in an effect called Rayleigh scattering, which is what also makes the sky appear blue and causes sunsets to blaze into brilliant oranges and reds.
It also doesn't help that astronomers classify the sun as a yellow main-sequence G-type star, or "yellow dwarf" — which has nothing to do with color.
Movie scenes of spaceships flying through a dense field of tumbling, colliding rocks are not realistic.
The asteroid belt — a zone 200 million to 300 million miles from the sun — is an incredibly lonely and desolate void.
In fact, if you pulled all the asteroids in that belt together, they'd be only about 4% of the mass of Earth's moon.
Most scientists agree that space begins 62 miles up, where the Earth's atmosphere is more or less a vacuum.
Yet going past this point does not magically make you weightless. If you were in an accelerating rocket, you would feel many times Earth's gravity. It's only when you start falling that you'd feel weightless.
To orbit something is to fall forever around that object. The moon around the Earth, the Earth around the sun, the solar system around the Milky Way — they're all falling toward one another in a crazy cosmic dance.
If you were 250 miles above the Earth, you'd have to travel 17,500 mph around the planet to experience continuous free-fall — the same speed as the International Space Station and its inhabitants.
Most asteroids are heaps of rubble, so a powerful blast would probably just break everything apart further. That's like turning a single bullet into a shotgun blast — not a good idea if you're trying to save the planet.
However, some researchers think a well-directed, smartly designed nuclear attack could irradiate an asteroid's surface, vaporize some of the rock, and shoot off gases that'd push an asteroid on off-course. Phew.
Wouldn't it be nice to get a glimpse of tomorrow based on something as simple as where the sun, planets, and moon were located when you were born?
Yet thorough scientific investigations of astrology have repeatedly failed to back up any predictions from an astrological sign or horoscope.
In a seminal 1985 study published in the journal Nature, scientists used a nonbiased, double-blind protocol and worked in conjunction with some of the top astrologers in the US to test the predictive power of astrological signs.
Mobile phones broadcast a wireless radio signal and constantly look for, ping, and relay data to and from land-based cellular towers.
When you make a call, the nearest tower connects you to another phone via a vast network of tower-to-tower connections and buried cables.
A satellite might be involved in an international call — but 99% of worldwide communications data travels through undersea cables.
From the International Space Station, 250 miles up, you can see the Great Wall and many other man-made structures. Tiny satellites that orbit even closer than that can see objects like Apple's spaceship campus.
This is only partly true, as the science behind Earth's ocean tides is anything but straightforward.
The moon does affect ocean water, but that force at any one point is about 1/10,000,000th Earth's gravity. It's really the interplay of gravity among the moon, Earth, and the sun that creates a tidal force — and it's more of a squeeze than a pull.
Each molecule of water is pulled by the moon's gravity. But alone, that gravitational acceleration is so weak it isn't noticeable. Because ocean water covers about 71% of Earth's surface and connects as one liquid body, however, all of those tiny forces add up to form a significant pressure — what we call the tidal force.
Molecules of water near the poles are forced mostly straight down by Earth's gravity. Those on the face of Earth closest to the moon experience the strongest force toward the moon, and those on the opposite side of Earth feel the weakest acceleration.
Together, these interactions form a pressure on seawater that generally directs it away from the poles and toward the equator, where it's just strong enough to fight gravity to form two bulges: the high tides.
High tides stay put as the Earth rotates underneath them every day, and they follow the moon as it orbits Earth every 28 days. Low tides occur where the tidal force (or water pressure) is weakest, and dramatic tides can result where land and seafloor terrain funnel more seawater into one spot.
The sun's gravity also affects the tides, accounting for roughly one-third of the phenomenon. When the sun's gravity counteracts the moon's, it leads to lower-than-average "neap tides." When the sun lines up with the moon, it triggers larger "spring tides."
Smaller bodies of water, like lakes and pools, don't have noticeable tides because they lack enough liquid to create a pressure that can visibly overcome Earth's gravity.
When a small object orbits a big object in space, the less massive one doesn't travel in a perfect circle around the larger one. (In fact, no object in space has a perfectly circular orbit.) Rather, both objects orbit in ellipses around a combined center — or halfway point — of gravity, called a barycenter.
For a puny, fragile planet like Earth, which is 1/332,949th the mass of the sun, the barycenter is so close to the center of the sun that we don't even notice the slightly off-kilter orbit. It seems as though we circle the very center of the star.
But Jupiter is the largest planet in the solar system, weighing more than twice the mass of all the other planets, moons, asteroids, and comets combined. This moves its barycenter with the sun some 1.07 solar radii from the star's center, or about 30,000 miles above the sun's surface.
Earth is slightly flattened at the poles and bulges at the equator, giving it an oblong 3D shape called a spheroid.
This is because the planet rotates, and its rock behaves kind of like a merry-go-round: The closer you are to the edge of the merry-go-round, the stronger you have to grip a bar to not be flung off because of a greater centrifugal force.
At the equator, Earth's rotational speed is about 1,037 mph, which is about 60% of the speed a bullet travels after it shoots out of the muzzle, typically. But farther north or south, it's slower — New York City, for instance, moves at 786 mph.
Rock is somewhat gummy and plastic beneath the Earth's crust. So unlike the stiff metal of a merry-go-round, the forces of rotation and gravity create a bulge along the equator. In fact, if you were to stand at sea level on the equator, you'd be more than 13 miles farther away from Earth's center than if you were at sea level on either pole.
Because of climate change and the melting of glaciers (and less weight pushing down on the crust), scientists think that bulge is growing — even though it should be decreasing as the Earth's rotation slows by a fraction of a second each year.
It's easy to think the far side of the moon is dark, since we never see it. But it goes through the same lunar phases as the near side, which faces the Earth — in reverse.
When there's a new (and very dark) moon on the near side, for example, that means there's a full moon on the far side. We just can't see it from our vantage point.
So yes, there is a "dark side" of the moon — but it's always moving and sometimes faces Earth directly.
When it is summer in the Northern Hemisphere, the Earth is not closer to the sun. In fact, it's quite the opposite: The planet is at its farthest point from the sun during the summer.
It is warmer during the summer because Earth is tilted. During its orbit, our home planet's tilt allows the sun's energy to hit us more directly.
In reality, the moon orbits about 239,000 miles from Earth. If you could somehow hop in a Boeing 747 and cruise to the moon at full speed, the journey would take about 17 days.
Unimpeded, light can move at 299,792,458 meters per second in a vacuum. But it slows down when it travels through different substances. For example, light moves 25% slower through water and 59% slower through diamond.
Particles like electrons, neutrons, or neutrinos can outpace photons of light in such materials — though they have to bleed off energy as radiation when they do.
What about light in a vacuum? Even then, the expanding fabric of space once exceeded light-speed during the Big Bang.
Physicists also think two quantum-entangled particles might be able to "move" or teleport their states instantly, no matter how much distance separates them.
If you're in total darkness at the coldest spot in the known universe, the vacuum of space can get down to -454 degrees Fahrenheit. Brr!
But in sunlight near Earth, temperatures can swing to a boiling 250 degrees Fahrenheit. That's why astronauts wear reflective white spacesuits.
The physicist Enrico Fermi once famously asked "Where is everybody?" after seeing a cartoon featuring a flying saucer in 1950. Many people believe Fermi's question — now known as the Fermi paradox — was about the existence of aliens. If other intelligent life exists, the logic goes, why haven't we found any proof of it?
But Fermi was questioning the feasibility of travel between stars — not the outright existence of aliens, something he was said to have never doubted.
The Fermi paradox as we know it does question alien existence, but it's not named after the people who advanced this concept. That honor belongs to the astronomer Michael Hart and the physicist Frank Tipler, who refined the idea in the 1970s and 1980s.
"The Fermi paradox might be more accurately called the 'Hart-Tipler argument against the existence of technological extraterrestrials,' which does not sound quite as authoritative as the old name, but seems fairer to everybody," Robert Gray, an astronomer, wrote for Scientific American.
It's easy to assume solids are the most abundant form of matter in the cosmos, since we all live on a giant rock. But plasma is vastly more abundant — stars, including our sun, are gigantic orbs of glowing plasma.
There are many more phases of matter as well, like supercritical fluids, which occur on Venus' surface. But solid, liquid, gas, and plasma are the main ones.
MAPLE GLEN GARDENS