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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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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Simple answer is light travels until it hits something. Space is pretty empty so it keeps going until you see it. Then that bit of light stops.

And, yes, whatever we are seeing happened long ago. Even the light from our sun is 8 minutes old before we see it.

We’ve never yet seen a planet outside the Solar System. What we see are indications of their existence. They pass in front of their star, causing a tiny but measurable dip in brightness. Or big ones cause the star’s position to wobble in a periodic fashion.

Yes we are looking in the past. We see their star and by observing we found that parts of the stars have a dot like point when looking at them. Research later we could confirm that these points we saw were indeed planets moving on their lanes. The bigger and closer the planet is to it’s star, the ‘easier’ it gets to observe it.

Technically we can’t prove the looking into the past thing because we cant prove that light moves the same speed in all directions

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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