# Proof we can see the past? **URL:** \ **Category:** Factual Questions\ **Created:** [July 23, 2000, 10:40pm UTC](https://boards.straightdope.com/t/proof-we-can-see-the-past/26577 "2000-07-23T22:40:34Z")\ **Posts on this page:** 13\ **Page:** 2
**Author:** ![Abe](https://avatars.discourse-cdn.com/v4/letter/a/f1d935/32.png) [@Abe](https://boards.straightdope.com/u/Abe)\ **Post date:** [July 24, 2000, 8:53am UTC](https://boards.straightdope.com/t/proof-we-can-see-the-past/26577/21 "2000-07-24T08:53:08Z")
I think **tcburnett** may be right as regards “the stronger the telescope, the further back in time you can see”. This does not apply to our own solar system, which is quite small on the general scale of things. If you train a powerful telescope as far as you can in the universe, however, you are seeing objects as they appeared billions of years ago. That is because the light itself has taken billions of years to reach us, and the message carried by that light is old. You can examine quasars and other mysterious objects on the edge of our universe with very powerful telescopes. An ordinary telescope won’t show you very much of the outer reaches, whereas a serious mama telescope can focus on a point in the sky and bring you an image that you wouldn’t otherwise see. So, in a sense I think it is a question of the definition of the image, but in another sense a more powerful telescope allows you to see light and other electromagnetic radiation that you could not possibly detect. The farther away you’re looking, the older the information will be (in the sun’s case, since it is 8 light-minutes away, the information we receive is 8 minutes old). To look farther away with reliable definition, you need better telescopes. Better telescopes allow you to observe older information with higher definition. So it is correct to say that bigger and better telescopes allow you to see further into the past. ---
**Author:** ![tcburnett](https://avatars.discourse-cdn.com/v4/letter/t/c5a1d2/32.png) [@tcburnett](https://boards.straightdope.com/u/tcburnett)\ **Post date:** [July 24, 2000, 9:06am UTC](https://boards.straightdope.com/t/proof-we-can-see-the-past/26577/22 "2000-07-24T09:06:23Z")
You are 20 minutes too late, Abe. I already conceded the point. I didn’t care whether it was technically accurate or not, I was just trying to convey a concept. It was easier to drop it than lose the whole idea of the OP by making the answer so complicated that handy won’t have any idea what is going on. ---
**Author:** ![VarlosZ](https://avatars.discourse-cdn.com/v4/letter/v/d78d45/32.png) [@VarlosZ](https://boards.straightdope.com/u/VarlosZ)\ **Post date:** [July 24, 2000, 9:07am UTC](https://boards.straightdope.com/t/proof-we-can-see-the-past/26577/23 "2000-07-24T09:07:47Z")
This is purely a question of semantics, but even semantics has a certain logic to it. When we look at the sun, we’re not seeing anything from the past. We’re seeing the **present** state of the light that happened to have left the sun 8 minutes ago. As for the telescope being able to let people see **further** into the past, I think you’ve got it backwards. If you train a telescope at a distant star, aren’t you in effect bringing your vision closer to the star, thus decreasing the time it takes for the light to travel to you, thereby transporting you less far into the past (that’s the best way to put it, I guess)? ---
**Author:** ![Demigod\_5](https://avatars.discourse-cdn.com/v4/letter/d/ecd19e/32.png) [@Demigod\_5](https://boards.straightdope.com/u/Demigod_5)\ **Post date:** [July 24, 2000, 9:12am UTC](https://boards.straightdope.com/t/proof-we-can-see-the-past/26577/24 "2000-07-24T09:12:53Z")
> [@](#): > > Since you wish to show your particular abilities I will abandon my attempt to encourage a potential new scientist and leave the mentoring to you. You seem to have the advantage of being a mindreader, moderator and teacher. You take it from here. Can you do something constructive? I’m sorry tcburnett, I never thought you would be so offended by that simple remark. Since you seem to have emotional ties to this thread, and since this thread has seemingly already been run into the ground, I will thank you for stepping out of my way, and I will keep this brief. Handy, light is evil. Don’t listen to these people. Use common sense. This subject doens’t seem too difficult, so I guess you’ll catch on fairly quickly. ---
**Author:** ![Liberal](https://avatars.discourse-cdn.com/v4/letter/l/848f3c/32.png) [@Liberal](https://boards.straightdope.com/u/Liberal)\ **Post date:** [July 24, 2000, 10:04am UTC](https://boards.straightdope.com/t/proof-we-can-see-the-past/26577/25 "2000-07-24T10:04:05Z")
When you say “stronger telescope”, do you mean greater magnification or larger arpeture? ---
**Author:** ![Phobos](https://avatars.discourse-cdn.com/v4/letter/p/3d9bf3/32.png) [@Phobos](https://boards.straightdope.com/u/Phobos)\ **Post date:** [July 24, 2000, 12:37pm UTC](https://boards.straightdope.com/t/proof-we-can-see-the-past/26577/26 "2000-07-24T12:37:55Z")
I consider myself an amateur astronomer. But I think the OP has been answered. The further away something is, the longer it takes the light to get here…so, the older the image is. We see the past. > [@](#): > > \*Originally posted by VarlosZ \* > \*\*As for the telescope being able to let people see **further** into the past, I think you’ve got it backwards. If you train a telescope at a distant star, aren’t you in effect bringing your vision closer to the star, thus decreasing the time it takes for the light to travel to you, thereby transporting you less far into the past (that’s the best way to put it, I guess)? \*\* No. You’re still capturing the same photons at the same point (your telescope/eye). The distance between the source and your eye is not changed by the telescope. The telescope increases the effective size of your eye so you can capture and resolve/focus more light. > [@](#): > > When you say “stronger telescope”, do you mean greater magnification or larger arpeture? With telescopes, the primary thing is larger aperature. Magnification helps only a little (in fact it can often reduce clarity). ---
**Author:** ![Phobos](https://avatars.discourse-cdn.com/v4/letter/p/3d9bf3/32.png) [@Phobos](https://boards.straightdope.com/u/Phobos)\ **Post date:** [July 24, 2000, 12:43pm UTC](https://boards.straightdope.com/t/proof-we-can-see-the-past/26577/27 "2000-07-24T12:43:46Z")
2 more cents… Seeing the past helps us understand astronomy/cosmology. But for all **practical** purposes, it’s the present, because we cannot interact with the past (speed of light limitation). (didn’t mean to confuse the OP…yes, we see the past…the moon is actually how is was over 1 second ago, the sun over 8 minutes ago, the closest star over 4 years ago, the closest large spiral galaxy about 2 million years ago) Conversely, astronomers 4.5 billion light years away can watch the formation of the Earth. ---
**Author:** ![MadHatter](https://avatars.discourse-cdn.com/v4/letter/m/f6c823/32.png) [@MadHatter](https://boards.straightdope.com/u/MadHatter)\ **Post date:** [July 24, 2000, 1:15pm UTC](https://boards.straightdope.com/t/proof-we-can-see-the-past/26577/28 "2000-07-24T13:15:03Z")
That’s like saying watching re-runs of MASH is looking at the past. ---
**Author:** ![handy](https://avatars.discourse-cdn.com/v4/letter/h/b5a626/32.png) [@handy](https://boards.straightdope.com/u/handy)\ **Post date:** [July 24, 2000, 2:46pm UTC](https://boards.straightdope.com/t/proof-we-can-see-the-past/26577/29 "2000-07-24T14:46:17Z")
tcburnett, guess you’ve been waiting for me to catch up here so let’s see. A bigger telescope won’t get you any nearer to the sun & thus, shouldn’t change the time part. However, it can make things more visible & sharper [not that you should look at the sun] so you get a clearer image of what happened in the past 🙂 Im no young scientist, I already have a BA from UCSD a long time ago. ---
**Author:** ![handy](https://avatars.discourse-cdn.com/v4/letter/h/b5a626/32.png) [@handy](https://boards.straightdope.com/u/handy)\ **Post date:** [July 25, 2000, 3:06pm UTC](https://boards.straightdope.com/t/proof-we-can-see-the-past/26577/30 "2000-07-25T15:06:14Z")
tcburnett, if you look in the other side of a 1000mm telescope, how far into the future can you see? ---
**Author:** ![CheapBastid](https://avatars.discourse-cdn.com/v4/letter/c/8baadc/32.png) [@CheapBastid](https://boards.straightdope.com/u/CheapBastid)\ **Post date:** [July 25, 2000, 5:05pm UTC](https://boards.straightdope.com/t/proof-we-can-see-the-past/26577/31 "2000-07-25T17:05:02Z")
You’ve got it all wrong, you don’t need a _stronger_ telescope, but a **longer** one. If you had one that was a few light years long you could see right into those stars instantly! =) ---
**Author:** ![John\_Kentzel-Griffin](https://avatars.discourse-cdn.com/v4/letter/j/ccd318/32.png) [@John\_Kentzel-Griffin](https://boards.straightdope.com/u/John_Kentzel-Griffin)\ **Post date:** [July 25, 2000, 5:35pm UTC](https://boards.straightdope.com/t/proof-we-can-see-the-past/26577/32 "2000-07-25T17:35:15Z")
To convert from units of distance to units of time, we use the speed of light as a conversion factor. Let’s see 1000 mm is one meter, so we want see how far in the future one meter is. c = 299896943 m/sec. We divide 1 m by c and we get: 3.33447880460722135470383904513e-9 secs or approximately 0.00000000334478 secs. I hope this helps. ---
**Author:** ![Padeye](https://avatars.discourse-cdn.com/v4/letter/p/a9a28c/32.png) [@Padeye](https://boards.straightdope.com/u/Padeye)\ **Post date:** [July 25, 2000, 9:03pm UTC](https://boards.straightdope.com/t/proof-we-can-see-the-past/26577/33 "2000-07-25T21:03:44Z")
> [@](#): > > \*Originally posted by CheapBastid \* > \*\*You’ve got it all wrong, you don’t need a _stronger_ telescope, but a **longer** one. If you had one that was a few light years long you could see right into those stars instantly! > > =) \*\* There is never a chunk of fire hose handy to bludgeon someone with when you really need one. On a serious note that telescope could make the image take _longer_ to get to your eye. A Newton reflector or cassegrain increases the distance the light has to travel. Massive thick lenses in a refrector slow the light. [Previous page](https://boards.straightdope.com/t/proof-we-can-see-the-past/26577.md?page=1)