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?
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1$\begingroup$ Down vote? I was just curious if i was thinking right. Anyway Thank you bro! $\endgroup$– DeepeshkumarCommented Feb 26, 2015 at 3:52
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4$\begingroup$ The speed of light is finite. How could the answer be anything but yes? $\endgroup$– ProfRobCommented Feb 26, 2015 at 9:04
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$\begingroup$ 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! $\endgroup$– DeepeshkumarCommented Feb 26, 2015 at 10:23
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1$\begingroup$ 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. $\endgroup$– Wayfaring StrangerCommented Mar 23, 2017 at 19:49
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$\begingroup$ If you look at the person next to you, you also see an image of the past $\endgroup$– planetmakerCommented Apr 28, 2020 at 5:22
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6 Answers
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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.
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13$\begingroup$ 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. $\endgroup$ Commented Feb 25, 2015 at 23:27
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2$\begingroup$ 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. $\endgroup$ Commented Sep 22, 2016 at 15:26
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7$\begingroup$ @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. $\endgroup$– ProfRobCommented Mar 19, 2017 at 19:16
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$\begingroup$ @RobJeffries Good point indeed. We would not want the photons emitted in the core to hit us. $\endgroup$ Commented Sep 19, 2017 at 12:27
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$\begingroup$ 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. $\endgroup$ Commented Sep 19, 2017 at 12:35
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The speed of light in a vacuum is 299,792,458 meters per second, not infinite. Let's say, for example, particle of a beam of light, the photon, is emitted. It takes ~8 minutes to get to us; when it hits our eyes, we see it. This means that we see a photon that was emitted from the sun 8 minutes ago. We aren't, per se, looking "back in time", but we're looking at a photon that is ~8 minutes old.
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Answer is Yes. Not only to sun and moon, we are seeing each and every distant object we are ever experiencing with certain delay. For example, if you are reading this text on a computer screen at 50 centimetres distant from your eyes, you are actually experiencing the past version of 1.66777852e-9 seconds.
One interesting thing to know is, in reality past, present and future exist all together as spacetime in the fabric of cosmos. For example, when you say, we are seeing 10 years past version of a star which is 10 light years away from our planet, similarly an alien right now is watching 10 years past version of our earth seating on that star.
An excellent explanation can be found here presented by Brian Greene to understand how mind boggling reality we are living in.
answered Mar 19, 2017 at 13:53
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$\begingroup$ This does not prove that future is an illusion. $\endgroup$– AnixxCommented Mar 25, 2017 at 13:12
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$\begingroup$ @Jim what did you mean? Very old video link? $\endgroup$ Commented Apr 29, 2020 at 5:00
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1$\begingroup$ Oh sorry, typo. I meant a very cool video. $\endgroup$ Commented Apr 29, 2020 at 9:06
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$\begingroup$ Yes. That’s actually a cut piece of original longer documentary which is about 50 minutes. Sharing for interested people youtu.be/Zuedaptw73w $\endgroup$ Commented Apr 29, 2020 at 9:38
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It is better to speak here of sensing light generated by, or reflected from a body that reflects light. Seeing, as such, involves cognitive processes wherein sensed light is information. Our seeing eyes are causally affected by a total array of photons arriving at different times according to how they are distributed in the experienced world. The sun, or a high-flying jet are identified and recognized by acquaintance which is the ground of knowledge by experience for a particular person. What we learn from experience of the sun generally is understood as having little use for the factual knowledge that the sun is 8 minutes and 20 seconds behind our observation. But, an astronomer looking at distant objects in the night sky may need to take the delay factor into account.
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1$\begingroup$ Not exactly the same thing, but helioseismologists need to worry about an even smaller effect: Are there any ways in which the light time difference between the center and the edge of the solar disk is noticeable? $\endgroup$– uhohCommented Dec 30, 2021 at 0:59
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TL;DR:
Yes
Long Answer:
Yes, We see the Sun's past and every object in interstellar space
Because the Sun is 8.317 light-minutes away (more precisely 8.3167464 light-minutes) and the speed of light is finite not infinite i.e 299792458 m/s in vacuum and space is a vacuum thus it also takes time for light to reach the Earth from the Sun (and this is the same for every other celestial and non-celestial oobject)
These same effects are everywhere for example if you are watching a movie in a theater then ideally the ideal distance would be 1.5 times the screen width and the width would be let's say 22 meters (IMAX Theater) then using the formula given below you can calculate the time taken which would be: 110.108073 nanoseconds.
These effects are given by a simple equation:
$P = Distance/C$
We use also the same effect to watch a few million years after the Big bang to see what the Primordial Universe looked like which JWST is also currently doing.
Kindly note that the 8.3167464 light-minutes is the semi-major axis of the "Goldilocks" orbit we are in and not the entire orbit since our Orbit is a eclipse due to Kepler's laws so the time we see in the past may vary as we are moving season to season
Also The speed of light is the same everywhere so there are no chances of it being slowed down sometimes and it speeding up other times (unless you flow it through some material like Air) because of time dilation and Space is a vacuum unless there is something called Lumniferous Ether (which was denied by the Michaelson-Morely Experiment).
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$\begingroup$ A downvote. Why is there a downvote (-1), so that I can improve upon my answer $\endgroup$– user47732Commented Jan 6, 2023 at 4:57
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3$\begingroup$ I didn’t downvote this, but a couple of recommendations for improving your answer: a) about a third of the way through, your answer starts to stray outside the scope of the question; try to be a bit more concise b) this is a rather old question that has been answered pretty well; your answer is functionally equivalent to the others. Perhaps try focusing on unanswered questions or ones that have been answered only partially. $\endgroup$– Justin TCommented Jan 6, 2023 at 8:36
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1$\begingroup$ Thanks a lot @JustinT. It helped me to improve the answer and I will try to keep it more Concise $\endgroup$– user47732Commented Jan 6, 2023 at 8:53
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Yes. It's 8 and a half minute old sunlight. When you look at stars you're viewing hundred. Thousands, millions year old pics
