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Looking Back in Time
Transcript of Looking Back in Time
Light travels at 186,000 miles per second, it takes it 8 minutes to get from the Sun to Earth. So, we are actually looking at what happened on the sun 8 minutes ago, because that's how long it took the light to get to our eyes. Anyway, if we wanted to look back in time at ourselves, we would have to see the light again. Say there's an event on Earth. The light from the event will escape in every direction. If we had a mirror on a planet, for example, 10 light minutes away, it would take the light 10 minutes to get to the mirror on the planet, where the mirror would reflect it, then 10 minutes to get back to Earth. If we saw the light that has been reflected back at us, we would see 20 minutes back in time. -Problems- The biggest question is: Is the technology we have now suffecient enough to be able to reflect the light in such a precise angle that it comes to directly the point we want it to on Earth. After all, it would have to come to an observation center, so the light would have to be reflected at a perfect angle. Would it work if that mirror was precise enough? Yes. Are mirrors precise enough? By what I have researched, I think so. During an Appolo mission we put mirrors on the moon to calculate how far away the moon is from Earth. We shined a laser at the moon's mirror, and it reflected back to a given point on Earth. So, if lasers can do it, why couldn't light? Next question: Would the telescopes be able to see 20 light minutes away? After all, that is the distance they would need to see if we want to look at the light coming from Earth. The answer, yes. Easily. Ten light minutes is 11,600,000 miles away. Twenty light minutes is 223,200,000 miles away. We can see supernovas that are 190,000 light years away with our telescopes. To give you an idea on how far away that is, one light year is 5,865,696,000,000 miles. Now take that number and multiply it by 190,000. This is about what my model would look like: Earth Planet with mirror (for example 10 light minutes away) Light (10 minutes) Light (another 10 minutes) You'd be seeing back in time by 20 minutes. Another big problem is: If an event happens on Earth and we want to see that event again, the mirrors would have to be ready at an angle to reflect it to the specific point on Earth. So, we would have to send up a signal to tell the mirrors to change to the presice angle fit for the reflection. However, nothing is faster than light, by theory. Nothing we have now is, that's for ceartain. So, if we sent the signal, it would already be behind the light, and it would reach the mirror after the light, and we would miss the event. I know this idea is complicated so here's a diagram: So let's say an event happened, and we want to look at that event again. The problem is, unless we were expecting the event, the mirror would be at a different angle, not suited for reflecting the light back to the given point on Earth. So, we want the light to go from the event, hit the mirror, and come back to an observation center. Observation center Event we want to see Mirror Planet (10 light minutes away) Earth Light (from the event) Signal (that's going to change the direction of the mirror so the light reflects to a given point) But, we have a huge problem here. The light's going to get to the mirror before the signal. And, the mirror isn't ready for the light, because the signal hasn't gotten there. So, the light will reflect off in a meaningless direction, and we'll never be ready to observe it. -Solution to this problem- So, the signal needs to catch up to the light and pass it in order to get to the mirror first, and change the angle so it's ready for the incoming light. Only problem, nothing goes faster than the speed of light, so hows that signal going to pass it? We'd have to slow down the light. How are we going to do that? We're going to have the light go through a substance. Light slows down in denser substances. In space, light travels 186,000 miles per second. In glass, light travels 120,000 miles per second. So, that's a significant decrease in speed. We could have the light go through the substance, where it would slow down, and let the signal catch up. One problem with this: There's something called 'refraction' in substances. Refraction causes the light to bend, or change direction. So, when the light goes through the substance, it could change the direction it's going. Planet (10 light minutes away) Mirror Substance (to slow down light) Incoming light Light hitting the substance and changing direction The light would get to the mirror, but the mirror would have to account for refraction for the light to go in the ceartain direction we want it to go in. Another solution to this problem is having a substance that has little to no refraction. However, most substances that have little refraction also have little density, so it wouldnt slow down the light as much. If we could find a substance fit for this position, it would make it all possible. Of course, there's another challenge: If the mirror is on a planet ten light minutes away the face of that planet will be rotating, just like Earth. But, the mirror won't always be facing Earth because it's rotating along with the planet. So, the mirror would have to be constantly adjusting to face Earth. If that was to be done, there would be nothing we could do when the other planet was facing away from Earth, or when the vision is blocked by the sun or platet. There are several solutions to this problem: Have several
mirrors and each one can have a different veiw of Earth, so if one mirror is blocked by another planet or the sun, we'll have other mirrors that will probably have a veiw of Earth. Or, another solution (and personally my preference), have the mirror within Earth's gravitational pull, or orbiting the Earth, like the moon. This way, it will always be facing Earth (like one face of the moon is always facing Earth). Another option is putting it on the moon. That will make it more stable, and might provide more protection from astroids or other space debris. However, If there was an astroid heading for the mirror that was stationed on the moon there would be nothing we could do. The mirror would potentially be a sitting duck, unable to move out of harms way. If the mirror was orbiting like other artificial sattelites it could maneuver, and get out of harms way. So, if we do this we will have one other problem. No matter what the sattelites angle it will only be able to see half of the Earth, because of the sphere shape. So, we could have one mirror orbiting on each side of the planet, and we could have vision of the whole planet. But here's another problem... The time for light to get to the moon is 1.2841774 seconds. So, if the mirrors were placed as far away from the Earth as the moon we would be looking back in time about 3 seconds, which is lame. Also, even if we do slow down light for a signal to catch up and get to the mirror before it, the margin wouldn't be enough. We might slow it down from 186,000 miles per second to 120,000 miles per second, but that's still extremely fast, and it would have a major headstart over the signal, which would be sent probably minutes after a ceartain event. So, we would have to find a substance that drasticly changes the speed of light. But, if we do, who wants to look back in time 3 seconds??? However, there's a way to fix that problem. Every problem has a solution. We could have the light reflect back and forth from the mirror to Earth. So, once the light is reflected from the mirror in space it could come back to Earth, where it would be reflected again, and again, and again, however many times you want. Each time it is reflected you see back in time farther by 1.2841774 seconds. If you saw back to the reflected thousandth time (so just the image reflected 1,000 times) you'd be seeing back in time 21.402957 minutes. Try reflecting one mirror into another sometime. If you look into the mirrors you see everything reflected again and again, an infinate amount of times if the mirrors hare precisely parallel with eachother. Each time you see a reflection you're looking back in time. It might not be much at all, it depends on the distance the mirrors are apart. If they are less that a couple hundred thousand miles apart, you probably won't be able to tell the difference. However, in this case, each time you see another reflection you are seeing a little over one second farther back in time. How far you can see back in time depends on how well alined the mirrors are, and how big the mirrors are. --Credibility--
A bit about me. I'm a couple of months away from entering highschool as a freshman. That's right, I'm 14. I explained this whole idea to my parents (who are both rocket scientists/aerospace engineers) and they both said it theoritically works. I got the same answer from my science teacher. I live in Denver, Colorado, too. Sources
Ewert, Micheal. "Looking Back in Time." Looking Back in Time. Web. 28 May 2011. <http://csep10.phys.utk.edu/astr162/lect/cosmology/lightspeed.html>.
Cain, Fraser. "Distance to the Moon." Universe Today — Space and Astronomy News. Universe Today, 10 Oct. 2008. Web. 28 May 2011. <http://www.universetoday.com/19426/distance-to-the-moon/>.
Swafford, Jamie. "Astronomy - Science." Spike's Home Of The Grate! Web. 28 May 2011. <http://spikesworld.spike-jamie.com/science/astronomy/c421-20.html>.
Eric, John, and Paraag. "Refraction." Light Refraction Rays. The Visual Percep Zone. Web. 28 May 2011. <http://library.thinkquest.org/27066/lightrays/nlrefraction.html>. --Tests--
The smaller scale you get on this kind of idea, the more precise you have to be. So, I can not time the speed of light, considering it goes 186,000 miles per second. However, I can test substances that have refraction, and I can reflect light with mirrors into ceartain directions. I can also use two mirrors to reflect light back and forth. All this is helpful. I've learned that the substances I have tested (water, maple syrup, glass) all have refraction. Some more than others. I figured out that the larger the mirror, and the more alined the mirrors are, the farther back you can see. Most of the other components to the process are untestable. Thanks for considering! Questions? Input? Comments?
At this point any input is helpful. Email me at 'firstname.lastname@example.org'