WEBVTT FILE

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The Hubble Space Telescope is 
many things. It’s an observatory,  

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a satellite, and an icon of cultural 
and scientific significance – but  

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you might be surprised to find out 
that Hubble is also a time machine!

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No, no, no, not like that!

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With Hubble’s position just above Earth’s murky 
atmosphere, its clear view literally lets us  

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witness our universe’s past. It allows us to 
travel back in time and see things as they were…

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1.3 seconds ago…

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33 minutes ago…

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An hour ago…

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Or even a little bit older than that!

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But how does that work? After all, Hubble 
doesn’t travel beyond our solar system,  

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or even our home planet’s gravity. 
So how can it “see” the past?

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The answer is light. The term “light-year” 
shows up a lot in astronomy. This is a measure  

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of distance that means exactly what it 
says – the distance that light travels  

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in one year. Given that the speed of 
light is 186,000 miles per second,  

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light can cover some serious ground over the 
course of 365 days: almost 6 trillion miles worth!

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Hubble works by gathering light from objects 
in our universe – some as close as our Moon  

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or comets coming into the inner solar system, 
and some as distant as galaxy clusters that  

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are billions of light-years away. All that 
light takes time to reach the telescope,  

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just as it takes time for light to 
travel from its source to our eyes.

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For example, our Sun is located about 93 
million miles from Earth. That means that  

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it takes roughly eight minutes for its 
light to reach us here on our planet,  

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so when we look at the Sun we see it 
exactly as it was eight minutes in the past.

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Cosmically speaking, the 93 million miles 
between us and the Sun are nothing. We  

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orbit around just one of billions 
of stars in the Milky Way Galaxy,  

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which is one of countless trillions of 
galaxies in the universe. With that in mind,  

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time travel gets more intense when Hubble 
observes objects beyond our star system.

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Think about what you were doing four years ago 
today. What type of sandwich you were eating,  

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what song you were listening to, what work or 
school assignment you had, or the car you drove. 

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Keep those images in your head as you now think 
about the next closest star to us named Proxima  

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Centauri. It’s about four light-years away, which 
makes it a close neighbor on a universal scale.

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So right when you ate that ham, tuna, and peanut 
butter sandwich four years ago, the light from  

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Proxima Centauri just left the surface of that 
star and began zooming out towards us. And here  

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we are, four years and many, many sandwiches 
later, and that light has finally arrived.

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Now, think about what you were up to 700 
years ago. Or… at least imagine what your  

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great great great great great great… add 30 
or so more “greats” and you’ll get the point,  

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great great Grandparents were doing in the 1300s.

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If they were in Europe they might have been a 
brave knight fighting for their king and country. (Or money.)

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If they were in Japan they might have  

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been an early samurai helping to 
overthrow the Kamakura shogunate.

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If they lived in Africa, they might have 
been collecting gold from Mansa Musa,  

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or maybe your ancestor even WAS Mansa Musa, 
arguably the richest human of all time.

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During all of those events, the light from 
the giant star Betelgeuse left its surface.  

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And all that time from the 1300s up until 
today that light was traveling at 186,000  

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miles per second towards us. This means 
that when Hubble looks at Betelgeuse,  

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the star appears exactly as it was 700 years ago.

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Wanna go even further back in 
time? Well our next stop is the  

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Andromeda Galaxy! The Andromeda Galaxy is 
a whopping 2.5 million light-years away,  

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but that’s just the closest major 
galaxy to us here in the Milky Way.

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Things were so much simpler back during the 
Paleolithic period, weren’t they? Dinosaurs  

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had only been extinct for 62.5 million years 
as opposed to 65 million years ago. Sandwiches  

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weren’t even invented yet, let alone peanut 
butter for sandwiches, let alone sliced bread  

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for peanut butter sandwiches on sliced bread, 
and the very earliest humans were just figuring  

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out how to be… human. Smartphone technology 
was still quite a few years away though.

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Perhaps some of Hubble’s most legendary 
observations are its deep field images,  

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which collect light from thousands of galaxies 
that are billions of light-years away.

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With this type of imagery, we can better 
understand how our universe changes over  

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time by puzzling out how galaxies evolve. The 
farther back we look with Hubble, the closer we  

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get to the big bang, when the universe began – 
so the most distant galaxies observed by Hubble  

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often appear to us as the “youngest” ones – giving 
us a sneak peek at the universe in its infancy.

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Because these galaxies emitted 
their light when they were young,  

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we get to witness them in their early stages.

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These young galaxies are actually old 
galaxies now as they have evolved over  

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the time this light has taken to reach us. 
Hubble has observed galaxies as far back as  

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13.4 billion years in the past! That’s just 400 
million years away from the big bang itself!

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So hopefully you’ve enjoyed this time 
traveling trip with the Hubble Space  

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Telescope. But remember, you can time travel 
all on your own without a fancy space telescope  

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as well. The next time you’re outside at 
night, remember to look up at the stars;  

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you’re seeing those stars as they were 
hundreds, if not thousands of years ago.  

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Those photons of light have been traveling very 
far and very fast over a very long period of  

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time to reach your eyes at that one special 
moment, so don’t blink or you’ll miss it!