Astronauts orbiting Earth aboard the International Space Station feel weightless as they experience microgravity. Do you experience gravity walking around Earth?
That’s right! Gravity may be the weakest of the four fundamental forces, but it’s still strong enough to keep you tethered to Earth! Even though you don’t consciously feel the pull of Earth’s gravity in daily life, you are subject to it.
In 2006, the International Astronomical Union voted to revoke Pluto’s status as one of the classic planets of the solar system. Which definition of “planet” do some planetary scientists still push for that would reinstate Pluto’s status as a planet?
Nice one! According to this definition, Earth’s moon and many other moons would also be planets.
How is a star born?
Perfection! This accumulation can happen for many reasons: because of random fluctuations of density within the cloud of dust and gas or because of an external influence like a collision with another molecular cloud, a supernova or even other stars forming close by.
Liu Cixin’s novel, The Three-Body Problem, was recently turned into a hit Netflix show by the same name. The three-body problem is a real physics concept — and so is the star system that is referenced in the TV series. Which star system is that?
You got it! At 4.2 to 4.4 light-years from Earth, the Alpha Centauri system is our closest neighboring star system. It comprises three stars: Alpha Centauri A, B and C. Alpha Centauri C, often called Proxima Centauri, is orbited by a small, rocky exoplanet that some scientists think could be habitable. We don’t know much about it yet, since our telescopes aren’t powerful enough to image it.
The majority of matter in the universe isn’t observable matter, like you or me or the device that you’re reading this on. It’s DARK matter — which seemingly doesn’t interact with normal matter! How much of the universe is made up of normal matter?
You got it, dude! Even though normal matter makes up everything we see in the universe, scientists believe that there must be more than five times as much dark matter as normal matter hanging around to fit their observations.
The universe is expanding — and it’s accelerating as it expands. Scientists call the force driving that accelerating expansion dark energy, and they measure it with cosmic probes. What’s one example of a cosmic probe?
Stellar (no, literally)! Scientists use many things to measure dark energy — supernovas, the distribution of galaxies and the cosmic microwave background, to name just a few. Cosmologist Brian Nord likens these probes’ movement in space-time to buoys in the ocean: As we look at their movement over time, we learn more about how space-time is expanding.
Astronauts can face multiple health hazards while living in space. On the list below, which is NOT a risk presented by spaceflight to the human body?
Correct! While time dilation is a real principle of physics that affects astronauts, its effects on the human body in orbit would be minimal. The five primary hazards of human spaceflight, according to NASA, are space radiation, isolation and confinement, distance from Earth, gravity (and the lack of it) and closed or hostile environments.
If you fell headfirst into a stellar-mass black hole, astrophysicist Priyamvada Natarajan says, the difference in the strength of gravity between your hair and the tips of your toes would be so strong that it would rip you apart — yikes! What’s the technical term for that?
Oh, the pasta-bilities! As you approached a black hole (theoretically, we’re hoping), you’d be stretched in the direction of the black hole and compressed perpendicular to it, making you a long, noodle-y shape. And while we haven’t observed this happening to humans, researchers have observed the spaghettification of stars.
In 1964, two radio astronomers in New Jersey were trying to track satellite signals when they picked up a strange hum — one that could be heard everywhere they pointed their antenna. What did that hum turn out to be?
Yep! Even though scientists Arno Penzias and Robert Wilson weren’t looking for it, the hum that their antenna kept picking up turned out to be the afterglow radiation of the big bang. Today, it’s what we call the cosmic microwave background, and it’s critical to our understanding of the early universe.
Astrophysicists like Katie Mack have theorized about potential endings to our universe! One of them is aptly named “heat death.” But what does that mean?
It might be trillions of years in the future, but the heat death ending of the universe is based on what we’ve observed about dark energy in the present. In this hypothetical ending, eventually galaxies would be so spread out and far away that the light from one could never reach the other. That’s one long-distance relationship!
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