When we see the Sun, do we actually see its past?

  • The Sun's rays hit our eyes around 8 minutes after they are emitted from the Sun.
    Does this mean that the Sun that we see is always the Sun as it was some 8 minutes before? I strongly think this must be happening; is it really a fact? Do we always see the Sun's past?


    Down vote? I was just curious if i was thinking right. Anyway Thank you bro!

    The speed of light is finite. How could the answer be anything but yes?

    Hmm.. Well that is true but it is hard to digest that we are watching an object's past. When i had this argument with my pal and a teacher they made my fun. So i tried to verify. Now i can convince them n even have a debate. Thanks for answering!

    Light only travels about 11.8 inches per nanosecond. You have to be *very* close to an object to get real time information about it.

    If you look at the person next to you, you also see an image of the past

  • Joan.bdm

    Joan.bdm Correct answer

    7 years ago

    Yes, you are right. We don't only see the Sun 8 minutes in the past, we actually see the past of everything in space. We even see our closest companion, the Moon, 1 second in the past.



    The further an object is from us the longer its light takes to reach us since the speed of light is finite and distance in space are really big.


    In fact we see *everything* in the past, whether it's in space or not. If you see an object, say, 30 cm (~ 12 inches) away, you're seeing the light that left it about 1 nanosecond ago. At that scale, though, the delay in your own visual processing is *much* longer than the speed-of-light lag.

    If we want to get even more complex, the photons from our sun that reach our eyes are actually much, much older than ~8 mins. They were created at the core of the sun something like 100,000 YEARS ago (I can't remember the exact estimate–someone pls correct me). It takes that long for the photons to travel from the immense pressure/gravity of the Sun's core and other layers before the light/photons finally escapes the Sun's corona on it's 8-minute journey to us.

    @iMerchant Your latter point isn't true. The photons emitted in the core of the Sun were absorbed in the core of the Sun. The radiative energy takes a long time to diffuse outwards. The photons we see were emitted from the solar photosphere 8 minutes ago.

    @RobJeffries Good point indeed. We would not want the photons emitted in the core to hit us.

    I suppose one could add that most simple statements about space and time are to some degree bogus, if one fully considers general relativity. Fast moving objects -- say, neutrinos with mass -- would think that not much time passed since they left the sun. For the photons surely no time passed at all (and they didn't travel at all spatially, either). In a way one could probably say that *everything* we see at a given point in time, including GN-z11 and the microwave background, is almost contemporary -- from the view point of a very fast observer.

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Content dated before 7/24/2021 11:53 AM