How Can a Satellite See the Past?
- ByVanguard Team
- Apr 10, 2025
- 2 min read
The idea of “seeing the past” might sound like science fiction... but in astronomy, it’s a daily reality.
And the ones making this possible are our satellites and space telescopes. These are humanity’s most powerful eyes — looking so far that they end up looking back in time.
How is this possible?
It all comes down to the speed of light.
Light travels at about 300,000 kilometers per second, but the universe is massive. So massive, in fact, that the light from many galaxies takes millions or even billions of years to reach us.
In other words:
When a satellite like the James Webb Space Telescope observes a galaxy 13 billion light-years away…
…it’s seeing what that galaxy looked like 13 billion years ago — not what it looks like today.
It’s as if light were a delayed message, carrying records from the cosmic past.
When we look into deep space, we are also looking back in time.
James Peebles, Nobel Prize in Physics
The role of satellites in time exploration
James Webb Space Telescope
Captures infrared light stretched by the expansion of the universe. It can observe galaxies that formed shortly after the Big Bang — making it a true space-time machine.
Hubble Space Telescope
For decades, it provided some of the deepest views of the universe, including the iconic Hubble Deep Field, which revealed thousands of galaxies in a tiny patch of sky.
Radio telescopes and other space observatories
Capture different wavelengths (like microwaves and radio waves), revealing hidden structures and ancient cosmic events such as supernovae and black holes
Seeing the past to understand the present
These observations help us:
Study the formation of the first stars and galaxies
Understand the expansion of the universe
Explore the composition of the early cosmos
Search for chemical signatures of life on distant planets
When we look into space with a satellite, we’re not seeing the “now.”
We’re accessing a deep cosmic record, etched into light.
Want to keep exploring ideas that challenge time and expand our view of the universe? Stick with us on the ByVanguard blog.
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