how can we see planets that are like 100s of 1000s light years away? And when we do, aren’t we looking in the past?
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If you [watch this video of the 2015 Tianjin explosions](https://youtu.be/iv5g2MhPT5I) and pay attention to the sound, in many viewpoints, the explosion happens 2 or 3 seconds before you hear anything…
In this instance, you’re actually hearing the past because the energy released takes time to be transmitted through space.
In the same way, light also takes time to be transmitted through space… It just travels immensely quicker and can be immensely further away.
Also, you can see in those videos that the further away the explosion, the quieter the explosion.
The same is true with light as well.
In order to see a planet that is 1000s of light years away, we’re looking throught the most powerful telescopes for just a handful of photons (or actually a lack thereof because we don’t see the planet itself, but a dimming of the star that hosts the planet as it eclipses it.)
So that light is indeed coming from the past and it takes a couple of cool tricks and some well-tuned observational equipment to see that far out.
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