What Do You Know About the


Light tells the story of the universe . Since light takes time to travel, the farther out into space we look:


the further back in time we see


the further into the future we see


we see things that happened just recently

You got it!

ANSWER: the further back in time we see

When we flip a switch we see the light almost instantly. But sunlight is 8 minutes old, and light from galaxies can be millions or even billions of years old! Light that is 13.8 billion light years away (13.8 billion ly old) has reached Earth from every direction. Astronomers call this sphere the observable universe.

Question 1 of 10

What is the most distant thing in space that we can see without a telescope ?


the Orion Nebula, a stellar nursery in our Milky Way


the Andromeda galaxy, our closest neighbor


the Virgo cluster, a collection of about 2000 galaxies

You got it!

ANSWER: the Andromeda galaxy, our closest neighbor

Andromeda is over 2.5 million light-years away. But compared to the size of the universe, that distance is tiny.

Question 2 of 10

In the 1920s, Edwin Hubble and fellow astronomers at Mount Wilson Observatory were the first to discover galaxies beyond the Milky Way . What else did they discover?


distant galaxies move farther and farther away from us


distant galaxies look like the Milky Way


distant galaxies give off light

You got it!

ANSWER: distant galaxies move farther and farther away from us

It seemed the universe was stretching or expanding. This was the first evidence for the Big Bang theory.

Question 3 of 10

According to the Big Bang theory, the universe was born about 13.8 billion years ago. At the moment of the Big Bang, the universe was:


hot and dense like the center of a star


hot and dense like the center of Earth


scientists have no idea

You got it!

ANSWER: hot and dense like the center of a star

The very early universe was very hot, very dense, and very bright, like the center of a star. Everywhere was starlight!

Question 4 of 10
Bellhorn telescope and night sky

In 1964, astronomers working with a radio telescope in New Jersey accidentally discovered something that came to be known as the cosmic microwave background. What was it?


a bright white light from the Big Bang


low energy radiowaves from the Big Bang


a loud noise from the Big Bang explosion

You got it!

ANSWER: low energy radiowaves from the Big Bang

The astronomers thought the faint signal might have been pigeon poop on their telescope. But they actually detected the afterglow of light from the early universe — the oldest light ever seen. Only a radio telescope could pick up the longer wavelengths of the cosmic microwave background.

Question 5 of 10
Planck Satellite in space with Earth in the background

In 2009, the Planck satellite was launched into space to measure light in the microwave band. It orbits:


the Moon




the Sun

You got it!

ANSWER: the Sun

Planck orbits the Sun about 1.5 million km (1 million mi) from Earth, at a point where Earth and the Sun's gravity balance each other exactly. Their combined gravity means that anything near this location orbits the Sun in exactly one year, and stays in the same place relative to Earth.

Question 6 of 10
Albert Einstein

Albert Einstein's famous equation E=mc2 shows the relationship been an object's mass (m) and its energy (E). What does 'c' represent?




the speed of light



You got it!

ANSWER: the speed of light

The 'c' stands for the speed of light, or 670 million miles per hour. Since 670 million squared is a huge number, this means that an object with just a little mass holds a huge amount of energy! The letter 'c' comes from the Latin word celeritas, which means 'swiftness.'

Question 7 of 10

Normal matter is everything we can touch and see, including dogs, trees, planets, stars, and galaxies. It makes up how much of the total mass-energy in our universe?


less than 5 percent


about 25 percent


more than 70 percent

You got it!

ANSWER: less than 5 percent

More than 95% of the universe is made up of stuff we can't see; Dark matter, an invisible substance, makes up about 25%. A mysterious pressure called dark energy makes up about 70%.

Question 8 of 10

Dark matter is invisible, so how do scientists know it exists?


its gravity affects stars and galaxies


it emits light in otherwise dark regions of space


it absorbs light like a black hole

You got it!

ANSWER: its gravity affects stars and galaxies

We can't see dark matter because it does not emit or absorb light. Scientists know it's there because its gravity affects things we can see. Dark matter's gravity holds galaxies together.

Question 9 of 10

How did dark energy get its name?


it's related to dark matter


light cannot escape it


astronomers don't know much about it

You got it!

ANSWER: astronomers don't know much about it

In 1998, astronomers discovered that a mysterious pressure was working against gravity and causing the expansion of the universe to speed up, or accelerate. Scientists called it 'dark energy.'

Question 10 of 10
Nice try! Not bad! Out of this galaxy! Out of this universe! You got out of 10 right on the first guess.
Image Credits:
dark matter background image, © AMNH; Andromeda Galaxy, courtesy of NASA/JPL-Caltech; Bellhorn Telescope, © AMNH; Planck Satellite and Earth, courtesy of JPL/NASA; Albert Einstein, courtesy of AMNH.