What is that? Archives – Page 2 of 2

Quick and easy explanation of ASTEROIDS

By Matthew Cross July 22, 2020 July 21, 2020 What is that?

Image Headline: What is that Asteroid--A tiny planet, a rock, a lump of metal--any one of these--floating in space without gravitry and without air

Asteroid – lump of rock or metal that orbits the sun

An asteroid, a word also meaning “like a star,” is a lump of rock or metal–and sometimes ice–that orbits the sun. Some orbit the sun directly, some orbit other planets, and some orbit our entire solar system.

Asteroid Belt

What is the Asteroid Belt and where is it located?

Millions of asteroids orbit the sun just like the Earth and the planets do. Most of the asteroids scientists have found are located in the Main Asteroid Belt, which is a band of asteroids 140 million miles wide. The Main Asteroid Belt starts just outside the orbit of Mars and is well inside the orbit of Jupiter, which is the next planet out from Mars.

Image of the asteroid Bennu and other asteroids in the distance — The asteroid Bennu likely formed in the Main Asteroid Belt, maybe two billion years ago, but its path brings it much closer to Earth now. Source: NASA.

See an amazing image of the Main Asteroid Belt here at Space.com. (The Main Asteroid Belt is shown in green.)

If you have ever seen a model of the solar system, you know the eight planets all travel in the same plane around the sun. Their orbits–the paths they take–look like a disc (or flat plate) of rings around the sun. The Main Asteroid Belt creates a thick ring on this same plane, like its part of the same disc or plate. The asteroids in the Main Asteroid Belt also travel in the same direction around the sun as all the planets of our solar system.

What are asteroids made of?

Most asteroids in the Asteroid Belt are made of rock. Some asteroids are made of metal–mostly iron and nickel. These metal asteroids are shiny and reflect the sun’s light. Some asteroids are made of a mix of rock and metal. And some more distant asteroids are made of ice. Some asteroids may even contain ice made from water, which could be useful to support astronauts if we colonize the Asteroid Belt.

Image of the asteroid Psyche showing two large craters — Artist’s concept of the asteroid 16 Psyche, a metallic asteroid composed of iron and nickel, like the Earth’s core. Psyche may be the stripped core of an ancient planet. Image credit: Maxar/ASU/P. Rubin/NASA/JPL-Caltech.

Some asteroids are solid. Some asteroids are just “piles of rubble held together by gravity,” according to an article by Nola Taylor Redd on Space.com. “Most asteroids aren’t quite massive enough to have achieved a spherical shape and instead are irregular, often resembling a lumpy potato.”

How big are asteroids?

Asteroids range from the size of specks of dust to moonsize. The largest asteroid in the Asteroid Belt is the dwarf planet Ceres. It is almost 590 miles across (diameter). That is small compared to Earth’s moon, which has a diameter of 2,158 miles. But it’s much bigger than one of Mars’s moons, Deimos, which is only seven miles across.

Ceres comprises 25 percent of the mass in the Main Asteroid Belt.

There are a number of other asteroids that are 100 and 200 miles long.

What about other asteroids?

Image of the asteroid Arrokoth, which looks like a sphere stuck to a slightly larger sphere, giving the impression of a two-ball snowman — Here is a photo of Arrokoth taken by the New Horizons spacecraft. Image grabbed from NASA’s website.

Beyond Neptune is an even wider ring of asteroids called the Kuiper Belt. The Kuiper Belt includes the dwarf planet Pluto, which astronomers once used to count among the nine planets in our solar system. There is even a snowman-shaped asteroid in the Kuiper Belt named Arrokoth.

NASA has a great interactive web page dedicated to the Kuiper Belt.

Eros

The asteroid Eros has made history both in astronomy and science fiction.

Discovery of Eros

Two astronomers discovered Eros independently on the same day, August 13, 1898–Gustav Witt in Berlin, Germany and Auguste H.P. Charlois in Nice, France. It was the first near-Earth asteroid ever discovered.

Image of the asteroid Erros, which looks like an oblong shape with a crater near the center — This image of Eros was created from four images taken by NEAR on February 14, 2000, immediately after taking orbit. The crater in the center is four miles wide. Source: NASA/JPL/JHUAPL.

NASA’s visit to Eros

Eros was also the first asteroid on which we have landed a spacecraft. Eros, named after the Greek god of love, was first orbited by a spacecraft, the NEAR spacecraft, on Valentine’s Day, February 14, 2000. After nearly a year orbiting and studying Eros, the NEAR spacecraft landed on Eros on February 12, 2001.

Astronomers have also used Eros to determine the distance between the sun and the Earth and to determine the combined mass of Earth and the Moon.

See a NASA’s 3-D rendering of Eros that you can move and manipulate on your own screen.

Ender’s Game

Eros also entered the annals of Science Fiction in the novel Ender’s Game, which won both the Hugo and Nebula awards.

In Ender’s Game, the hero Ender Wiggin travels to the asteroid Eros, which has been turned into I.F. Command, a military base and training center, to finish his military training.

“The tug reached Eros before they could see it. The captain showed them the visual scan, then superimposed the heat scan on the same screen. They were practically on top of it–only four thousand kilometers out–but Eros, only twenty-four kilometers long, was invisible if it didn’t shine with reflected sunlight.”

“The captain docked the ship on one of the three landing platforms that circled Eros. It could not land directly because Eros had enhanced gravity, and the tug, designed for towing cargoes, could never escape the gravity well.”

. . . .

“Ender hated Eros from the moment he shuttled down from the tug. He had been uncomfortable enough on Earth, where floors were flat; Eros was hopeless. It was a roughly spindle-shaped rock only six and a half kilometers thick at its narrowest point. Since the surface of the planetoid was entirely devoted to absorbing sunlight and converting it to energy, everyone lived in the smooth-walled rooms linked by tunnels that laced the interior of the asteroid. The closed-in space was no problem for Ender–what bothered him was that all the tunnel floors noticeably sloped downward. From the start, Ender was plagued by vertigo as he walked through the tunnels, especially the ones that girdled Eros’s narrow circumference. It did not help that gravity was only half of Earth-normal–the illusion of being on the verge of falling was almost complete.

[E]veryone lived in the smooth-walled rooms linked by tunnels that laced the interior of the asteroid.
Ender’s Game

“There was also something disturbing about the proportions of the rooms–the ceilings were too low for the width, the tunnels too narrow. It was not a comfortable place.”

By the end of Ender’s Game, we learn the secret of the unusual construction of the base inside Eros. But I won’t spoil author Orson Scott Card’s surprise. So read Ender’s Game and find out for yourself.

Design your own asteroid!

Image: Artist's concept of an asteroid. — Artist’s concept of an asteroid. Source: NASA.

As we’ve seen, asteroids can be any shape you want. What shape would you make your asteroid? Would you create a military base or a shopping mall inside it? Or would you make a theme park or a factory on the outside?

Would you add your own gravity–like I.F. Command did in Ender’s Game? Or would you let visitors enjoy the fun of zero-grav?

What would you name your asteroid?

Please post your comments below.

Be stellar!

Matthew Cross

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What is that?–LIGHT YEAR-a measure of distance–not a measure of time

By Matthew Cross July 15, 2020 July 16, 2020 What is that?

Image: Prism refracting white light into a rainbow. Text: LIGHT YEAR--A measure of distance--not a measure of time--the light year helps astronomers describe the vast distances between the stars.

Today is Wednesday, so it’s time for our regular feature What is that? Here’s today’s term:

Light Year – a unit of length used to measure great distances in space

Light Year is a confusing term. We all know what a year is. A year is the length of time from your birthday to your next birthday. It is also the length of time it takes the Earth to travel around the sun one time. That idea may help us.

A year measures time. It is how long the Earth takes to travel around the sun. We could make up a term called an Earth Year. It would mean how far the Earth travels in one year — or how far that trip around the sun is. By the way, that is about 584,000,000 miles. (If you live anywhere besides the United States, then that is about 940,000,000 kilometers.)

If an “Earth Year” (my made up term) is how far the Earth travels in one year, then a Light Year is how far a beam of light travels in one year. Light travels very, very fast. It can travel from the sun to the Earth in about 8 minutes. That is about 92,960,000 miles (149,600,000 kilometers). It takes me more than 8 minutes just to run one mile.

According to scientists, light is the fastest traveler in the universe. In fact, there is a rule of physics that says nothing in the universe can travel faster than light.

Light travels slower through glass and water than through air or a vacuum. Source: NASA.

Light also travels at a constant speed in the vacuum of space. (It does slow down when it passes through air, a window, or water. But even then, it travels super fast. Michael Phelps is fast in water, but light is still faster.) In the vacuum of space, light does not get tired and stop flying along.

A digital version of the Sun’s spectrum created from observations captured by the Fourier Transform Spectrometer at the McMath-Pierce Solar Facility at the National Solar Observatory on Kitt Peak, Arizona. Source: N.A.Sharp, NOAO/NSO/Kitt Peak FTS/AURA/NSF.

Because light travels so fast, it travels very far in one year. That makes a Light Year–a measure of distance–very useful for measuring the vast distances between stars. For example, the nearest star to our sun is Proxima Centauri. It is about 25,000,000,000,000 miles away (40,000,000,000,000 kilometers). It’s much easier to say (and to write) 4.25 light years.

So, when someone says “That is light years away,” they mean it is very far. They are not talking about time or how quickly a human could travel that distance. They are just talking about how large the distance is.

Invent your own measurement!

Let’s invent our own measurement of distance.

First, decide what you will use to set your measurement length. Will it be the length of an object? (To measure small distances, we could use the length of a twig we found.) Will it be the distance that something travels? (Like how far you can ride your bike in five minutes?)

What will you use your new measurement length to measure? The length of your hand? Then length of a car? The length of your neighborhood?

Finally, what will you name your measurement length? An “twig unit”? A “bike in 5”? Will you name it after yourself? (A “Matthew Mile”?) Or create a shiny, brand-new name you made up yourself? (A “plenth”?)

Please post your comments below.

Be stellar!

Matthew Cross

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What is that?–ANSIBLE-Science fiction writers create fictional devices–like the ansible–to allow characters to communicate quickly across the vast reaches of outer space. Let’s explore ansibles and physics.

By Matthew Cross July 8, 2020 July 7, 2020 What is that?

Image: Radio telescope dish beneath a starry sky. Text: What is that?–ANSIBLE-Science fiction writers create fictional devices–like the ansible–to allow characters to communicate quickly across the vast reaches of outer space. Let’s explore ansibles and physics. — Photograph by VM_Quezada (unsplash.com@vm_quezada).

Ansible — a machine used for instant communication across vast distances of space.

Sci Fi writers have created many fictional devices that allow people to talk, write, or send messages instantly or very quickly across the vast empty stretches of space.

This is a phonograph. It plays records or discs. But for some reason, I always picture one of these when I hear the word “ansible.” Photo by Sudhith Xavier (www.unsplash.com@sudhithxavier).

The legendary Ursula LeGuin created the word “ansible” in her 1966 novel Rocannon’s World. She described a device that could be used to send instant text messages to anyone else with an ansible.

LeGuin used the ansible in later books as well. By the way, “ansible” is a shortening of the word “answerable,” so-named because the device allowed a person to type a question that could get an “answerable” reply in a reasonable amount of time.

Why do Sci Fi writers need a fictional device?

Why did Le Guin need a fictional communication device? Why couldn’t her characters just send messages using an antenna that sends radio waves?

The problem is the speed of radio waves and the great distances between solar systems.

The Speed of Light

In empty space, radio waves travel at the speed of light. According to the great physicist Albert Einstein, nothing can travel faster than the speed of light. Even though his theory is more than 100 years old, it is still hard for most people to understand. That’s probably because in our daily lives, the only thing we see traveling at those speeds is light itself. And individual light particles–called photons–are too small and too fast for us to detect with our eyes.

Photo by Jon Geng (unsplash.com/@colourlife).

Light has no mass. It is pure energy. That’s why it can reach such a high speed. But for things with mass–things made out of atoms like you and me and everything we own–we gain mass the faster we travel. At the fastest speeds that humans and machines can travel, the change is barely noticeable. But if you send a ship rocketing through space, the closer it gets to the speed of light, the more its mass grows.

A spaceship floating in space has no weight. But it still has mass. To push it forward faster than it is already traveling requires more energy. Einstein’s law says that the faster you make the ship fly, the more mass it has. That means each time you try to add speed, you need more energy than the last push. Before the ship could ever reach the speed of light, you would run out of energy.

Radio telescope antennas capture radio waves. They can pick up a radio signal, but not send one. Photo by Matheo_JBT (unsplash.com@Matheo_JBT).

What does the speed of light have to do with communication across space?

In science fiction, we often write and read about people traveling to planets in far away solar systems. It takes years for light–even traveling as fast as light does–to reach a planet in another solar system. That means that a communication system that uses radio waves, light or lasers to send messages to a planet outside our solar system would take years. More than a lifetime, if the planet is not near one of our neighboring stars.

Why don’t Sci Fi writers use something real–some technology that we know–other than light or radio waves to send messages then? Well, because nothing travels faster than the speed of light.

Photograph by VM_Quezada (unsplash.com@vm_quezada).

Long distance communication in Sci Fi

It’s hard to write a gripping Sci Fi story if the heroes on a distant planet send an urgent message back home to Earth and then must wait 20, 50 or even a 100 years to receive the reply. Sometimes Sci Fi writers want to tell stories where humans living on different worlds or in spaceships far apart can still talk to each other or communicate in some way.

That’s why LeGuin created the fictional ansible. So her heroes could send messages back home and receive orders from their superiors.

Create your own device!

What kind of fictional device can you imagine to instantly communicate between Earth and a space ship light years away? What would you call it? How would it work?

Please post your comments below.

Be stellar!

Matthew Cross