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Hobbes's avatar

If we are looking into the past when we look at distant stars, doesn't that mean that when we look at objects in everyday life we see them as they were a moment ago?

Asked by Hobbes (7368points) September 24th, 2010

If I understand this correctly, it’s a good example of how our perception of the world is constructed by our minds.

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21 Answers

Fyrius's avatar

Strictly speaking, yes, that’s true. Light is a physical stuff that takes time to travel.
Of course, the delay is so small it’s only worth taking into account with things as insanely far away as stars, and maybe the other planets.

poisonedantidote's avatar

yes, there is a delay. but only a tiny one. with every day stuff the differences are not really worth mentioning. its only worth mentioning when you are talking about millions of miles.

the sun, 8 minutes.
jupiter, 4 hours (if i remember correctly, that sounds like a lot)
our nearest star, 4.5 years


Rarebear's avatar

Well, the world isn’t constructed by our minds. The world is there whether our minds are there or not.

earthduzt's avatar

I suppose that would be correct, but lets see light travels at 186,000 mps so if I’m standing 4 feet from someone looking at them you’d pretty much see them in real time because the amount of time light would take to travel it would not even matter, we are talking planck time here. It only starts to show an affect when we are talking about gigantic distances (millions of miles to light years)

Hobbes's avatar

I just think its interesting that there is a delay, however small it might be. I think it’s interesting because it shows how our perceptions are a model of reality, and a very thin slice of reality at that.

@Rarebear – True, but from birth to death our perceptions are all we experience.

jaytkay's avatar

The speed of light was first accurately measured in the 1920s, by the delay of a light beam bouncing back from a mirror 22 miles away.

It’s amazing what people can do with simple equipment and immense imaginations. It was done at the Mt Wilson observatory above Los Angeles.

Michelson’s Speed of Light Experiment

poisonedantidote's avatar

@Hobbes there is probably a bigger delay from your eye to the brain than there is from the object to the eye.

robmandu's avatar

“Light travels faster than sound. That’s why some people appear bright until you hear them speak.” —author unknown

Rarebear's avatar

@Hobbes But the world doesn’t change based upon our perspectives. This may seem like its splitting hairs, but this is, in essence the dividing line between postmodernism and realism. Postmodernists believe that the reality of the world and universe is based upon what we perceive it to be. Realists reject this argument and say that the world is what it is, no matter how we perceive it.

But the essence of your question is correct. Everything has its own personal space-time, and time will run differently for every person. This is the essence of Special Relativity.

gasman's avatar

Yes, however briefly. We are already accustomed to hearing sounds of distant events arriving late. With light it’s similar, but about a million times faster.

Hobbes's avatar

@poisonedantidote – That’s true, and that’s another delay before you actually experience the perception. Sound travels even slower than light, so there’s an even bigger delay between the thing making the sound and the perception of it.

I’m not denying the existence of a reality beyond our senses, I’m just saying that the sensory experiences we have are representations of reality and not reality itself.

When a tree falls in a wood it doesn’t make a sound if nothing is around to hear it. It makes waves in the field of air molecules around it, but if nothing perceives those waves and processes them they never become “sound”.

CMaz's avatar

You can see the delay when watching a live broadcast from the other side of the world.
Minor account for Time Base delay.

iamthemob's avatar


I think the more interesting side of that is not the fact that what we perceive as the present is really the past…but that what we perceive is the world as interpreted by the limited ability we have to sense it (e.g., the visible light spectrum, the audible frequencies…etc.).

What would the world look like if we could perceive signals into the ultraviolate and infrared? What if we could hear radio waves?

txinkman's avatar

Everybody knows the earth is round, but nobody wears arc-shaped shoes.

iamthemob's avatar


Sure we do. It’s just that the ark has a zero-degree curvature.

Hobbes's avatar

@iamthemob – I think the two ideas are related. We experience what is actually the past because of our limited ability to sense reality.

iamthemob's avatar


Yeah…I was just kind of being a jackwagon. ;-)

robmandu's avatar

Personally, I subscribe to the definition that sound is “mechanical vibrations transmitted by an elastic medium” regardless if there exists a witness present to actually hear them.

I think it useful to have a simple one-word label to use other than “waves in molecules of air”. Nor have I found it to be confusing conversationally to explain that there might be circumstance in which sound was present, but persons to hear it not.

That’s my perception of it anyway. ;-P

CyanoticWasp's avatar

That’s true unless you’re Charles Dickens inventing The Ghost of Christmas Yet to Come. In that case, you’re looking at the world as it will be. Maybe. Of course, given the light delay, you’re looking at the world as it “will have been” at some point a little farther in the future than your view of the event would permit.

anartist's avatar

If so, it is less than one of Grace Hopper’s “nanoseconds.”

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