Why does an observer see  distance and time smaller at horizon.?
151900
It's simple geometry. Let's say your field of view is 180 degrees. The amount of your field of view covered by an object is related to its size, and its distance from you. The relation is: d=rΘ, or Θ=d/r, where Θ is the angle in radians, r is the distance from you (radius), and d is the length of the object. As objects get further away from you, r increases and d remains the same, so Θ gets smaller. The amount of your field of view covered by the object decreases as its distance from you increases.\n\nFor the same reason, things in the distance appear to move slower. They are covering the same real distance (d), but that movement is across a smaller portion of your field of view (Θ). So they take longer to cross the same amount of your field of view as something closer, so they appear to be moving slower.
752656
The size of an object you can resolve with an optical system has a theoretical limit given by the wavelenght of the light you're using divided by the diameter of the optics multiplied by 1.22. If you plug the numbers in you find for a 1 foot diameter optical system at visible light (~400 nm) at an altitude of 100km, the smallest thing you could see is on the order of a foot, give or take (rough calculation). You could definitely not read a postage stamp or a wrist watch. Maybe a license plate with some bigger optics, but this is ignoring all sorts of atmospheric scintillation which screws things up.
359864
when u fire a rocket at high speed when u r moving at near speed of light relative to an observer, from the observer point of view, the rocket would never reach the speed of light due to relativistic effects of time dilation and length contraction. The observer would observe a flat rocket that is moving in slow motion.. the closer it is to the speed of light, the slower it moves, when it reach the speed of light, the observer would see the rocket as frozen and not moving. And from your point of view, u cannot accelerate the rocket to the speed of light RELATIVE to u.\n\nThe crucial point here is, RELATIVE. Everything has to be discussed relative to something else. There is no meaning in talking about ultimate speed since physical laws r invariant under translation and there is no prefered point of reference in the universe. When u talk about speed, u have to specify, with respect wo what.\n\nThere is no simultaneity in Einstein's relativity theory. The time u observe for a rocket to travel 1 mile is different from the time observed by the observer observing from somewhere else which is moving with some speed relative to u. This is relativity.\n\nAnd when u r moving near the speed of light, relative to an observer, u will not disintegrate and burst into some x-ray. As mentioned already, speed is relative. You are stationary with respect to your desk. But from the point of view of an alien observing from a planet a distance away, u r moving due to the motion of the Earth and sun and everything. Does that mean u or the alien would disintegrate and vanish into thin air???? no, of coz not. Pls do not think about friction.. that when u rub with air or other particles as u move thru space, u give off energy. no, that's not relativity.\n\nWe observe stars becoz they give off light from the nuclear reactions that is happening constantly in their core. We observe differing wavelengths due to the intensity of energy emitted, and also due to Doppler's effect due to expanding universe.\n\nThe centre idea of Einstein's relativity is that, there is no absolute space and time anymore. Space and time r different manisfestation of the same thing and they r interwoven into a connected flexible piece called the spacetime... instead of space and time in Newtonian physics. Relativity must not be understood in terms of theories of Newtonian physics. Relativity is not a new play on the stage of physics. Relativity is itself a new stage, literally.
1118162
If we imagine this all happening on in 1 dimension, a line, (i.e. no up/down or side to side movement possible), then the only way something can travel is toward or away from the observer.\nEven if this is not the exact case as in your example, this effect is easily done by merely turning one's head in order to align one's reference frame to the direction of the car's motion and thus would have the same effect.\n\nIn this case, our observer sitting at some location on the line and in his reference frame, everything else is moving either toward him or away from around him.\nIn his reference frame, he sees a car heading Straight towards him at relativistic speeds in the opposite direction he is facing.\n\nA length contraction occurs only in the direction of motion as observed by the observer.  In other words, if the car is moving toward/away from the observer, the car's length shortens, not its width or height.\nThe length contraction is in the same direction as the relativistic motion.  Since we defined this to be a single dimensional system with only one direction of travel possible, the approaching car would not get thinner or shorter (less tall), but rather, its length would contract.\n\nThe effects of the car appearing wider and taller as it got closer and closer would still apply as normal since the car is not traveling in either of those directions.\n\n\nIn your own frame of reference, taking a measurement and finding that the car has experienced a length contracting still makes that measurement every bit as real and valid as a measurement taken from the other car's frame of reference (v = 0) where there is no length contraction.
66085
Earth is around, you know that. An aero plan has to fly around and it would be flying thousands of kilometers away from you.\n\n It would appear that the plane is flying so slowly. But if you see an aero plane that is flying on low altitude that would appear to be faster.\n\nSky is so wide, you can see larger area if you look further and further you can see more wide angle. \n\nIt is not same as if it is closer to you, the distance would be very small. If it is far distance is greater.
418592
We can see backwards in time by looking into the night sky. Light from stars and galaxies takes a physical amount of time to get to us. When we look at the Sun we can only see it as it was 8 minutes ago 'cos that's how long it takes for light from the Sun to reach the Earth. It takes 4.3 years from the nearest star, so we see it as it was 4.3 years ago. It takes 2.5 million years from the nearest galaxy in Andromeda, so we see it as it was 2.5 million years ago. The furthest objects are around 15 billion light years away so when we are observing them we are looking backwards in time 15 billion years this is 10 billion years before the Earth and Sun even existed! We are close to witnessing creation itself. Light travels at 186,262 miles per second in a vacuum or 7 times around the world in a second. Jules.
301180
Also, we only see it when it is above the horizon.\n\nDuring the day, the sun is obviously above the horizon.  But the moon sets an hour or so later each day, so sometimes it is below the horizon in the day, and sometimes not.
113023
It is just an optical illusion. Your brain apparently compares the moon (and the sun) with familiar objects around it and that makes it appear larger. If you took pictures and measured, you would see that there is no difference (we had to do this in school in grade 8, and there definitely is no size difference). \n\nThere are refraction effects when the moon and the sun is low in the horizon that distort their shape so they do not look spherical, or are no longer simply connected, or exhibit green flashes etc. But the size does not vary appreciably if they are high enough in the sky to be seen as circular disks.
168351
Same answer, different explanation.\n\nWhen you look at something, you see light coming from the object (either reflected or generated).  Light takes time to move through space (or air, or any distance through any medium).  So the light you are seeing has come from the object some amount of time ago, and you are looking into the past.\n\nExample:  Light takes 8 minutes to reach the Earth from the Sun.  So anytime you look at the Sun (which you shouldn't do), you are seeing it as it existed 8 minutes ago!  In the past!  If it were to dissapear, we would not know for a full 8 minutes, as there is still light on the way to us from it!\n\nOnce you start looking outside our solar system, the time it takes light to get to us changes from hours/mintes, to years/centuries/melinia!  Then you are truly looking into the distant past, seeing things as they were thousands of years ago.
10953
well yeah... \nwell we dont have any definitive start or end point, so it's only relative to itself meaning that you can only measure a change in time, not how much of it you actually have. \nyour actual question is a little ambiguous, if this isnt what you meant, you can add some to the question,  are you looking for an explanation of how high velocities distort time or something, because I can explain that if you would like, just add it onto the question or make a new one or something.
170084
The correct formula for calculating tiem dilation is t'=t/gamma where t' is the new time, t is the time in the rest frame and gamma is the inverse square root of (1 - v^2/c^2)\n\nAs a result of this, if v (velocity) tends towards c (the speed of light), then the gamma factor tends towards infinity (because 1/sqrt(0) goes to infinity). So actually, if you do travel at the speed of light, you do not experience time at all - a photon is one such example; however anything with mass cannot travel at the speed of light, so unfortunately you cannot 'freeze' time for any object with mass. But if you are travelling at a velocity only slightly greater than 0 with respect to the rest frame, you actually experience less time than a person who is in the rest frame, albeit by a tiny tiny factor.\n\nNot sure what you mean by splitting space time in half :S
457317
Remember Einstein, It is all relative to the observer. You and the mirror would be traveling at the same speed so your observational world would be the same. Now if somebody was traveling with you slightly less than the speed of light, they would see a empty mirror. It is a paradoxical question just as if you where to travel the universe for 5 yrs at the speed of light, then return to earth, you would have only aged the 5 years, but all of your friends would have long ago died of old age waiting your return.Interesting, No? Good luck and happy perplexing.
239445
This is due to relative velocity. It's a great concept...it's the same concept which applies to you sitting at your desk..believe it or not...the earth you are situated on is revolving at the rate of once everyday..but do you feel it?? Nope...that is because you are revolving with it at the same speed. The formula for relative velocity is Vu-Vo where Vu is your speed and Vo is the speed of the other car..since they are the same, you subtract and voila..you get zero..therefore the car appears to be moving at zero speed in your vision. Check out relative velocity on GOogle..its a fun topic and your question is the fundamental base to relativity...Wow huh??\n\nGood luck.\n\nAyerhs\n\nPS: it is most definitely not because they have it on cruise control..I mean they could if they wanted but thats not the reason that they seen stationary to you.
24853
There are many ways to approach this problem. First, a quick and easy way:\n\nLet's agree that Alice is in frame A and Bob is in frame B.\n\nIf they both go on a trip and come back at the same time, as measured by Chuck who stayed home, then based on special relativity we can all agree that whomever was traveling closer to the speed of light on their trip will have a clock that's behind everyone else's (ignore accelerations for simplicity). So, if Alice traveled faster then her clock would be behind even Bob's clock. Based on this you must logically conclude that Alice would have observed Bob's clock ticking FASTER, not slower THAN HER OWN if she somehow viewed him in transit. Of course, Chuck would have seen both their clocks running slowly, but Alice's more slowly than Bob's.\n\nSome things are relative but you have some invariants, namely spacetime and the speed of light. Even if observers don't agree when things happened, the events are still fixed, in one position in spacetime. Einstein said that individually space and time are relative but you still have an absolute from which to measure, and that's spacetime. All entities are moving through spacetime at the speed of light (c). That's right, even you, but most of that velocity is directed through time. If an object were to have a zero velocity in space then its speed through time (the 4th dimension) is c. As you increase your speed through space some of your speed through time is diverted (but the vector total is always c) and thus time appears to slow down for you as observed by someone at rest in space.\nThe point being that there IS an absolute from which to measure so if Bob were traveling slower than Alice then Alice would see Bob's clock ticking faster than hers but slower than the stationary clock.\n\nI didn't quote any sources but most of my current conception of relativity came from an excellent book: "The Fabric of the Cosmos" by Brian Greene.
68749
Rabid_Scientist is entirely correct.  Both you and your home see time in the other place as speeding up.  I do have something to add to that though.  If you maintain a constant velocity, it can only be measured relative to some other point of reference, so there is no way to determine which is faster, and consequenty it cannot be determined whose time is actually going faster.  However, if you are accelerating it's a whole different story.  As you speed up to that super fast speed where the time differental starts to be noticable, you will see time on your home planet speed up and they will see your time slow down. (Sorry, I'm not going to try to explain this, I'm not sure I entirely understand it myself).  If you were to go back to your home planet, far more time would have passed for them than for you.  This effect will be greater with greater acceleration and greater speed so in that regard time will pass on your home planet more quickly the faster you go.
523034
The first answer *edit* was modified so now what I say here makes no sense - but her website confirms that I am right (5km = ~3 miles)*. If we want to know the distance to the horizon from a vantage point on a sphere, the only thing that matters is the radius of the sphere and the height of the vantage point.\n\nSo, assume you are standing with your eyes at 5'5" looking out at a calm ocean. You will typically be able to view the sea surface at 3 arcminutes, or roughly 5 kilometers, out to sea. Beyond that you would still be able to see ships and whatever else sticking above the water quite easily, but upon close inspection realise they appear deeper in the water than they actually are.\n\nAlso note that light bends around mass, so you might be able to "see" farther than your actual vantage point, but I'm not doing that calculation.\n\nI assume that people who have values higher than mine are thinking about higher vantage points than mine, because I think my estimations are close and I'm positive that my logic is right. Correct me if my numbers are off, but I'd like to know why.
188637
I'm actually studying this right now. Ok, I need you to consider "Time and Space". You've probably heard these terms used together quite often. Here's the story: Think of our Solar System as a bed mattress. If you put something heavy on it, like a bowling ball, then smaller objects (like a marble) placed next to it will be drawn to it, correct? This is basically the concept of gravity, and why we're on the ground and why Earth is revolving around the Sun instead of wandering off in space. Now, time is irrelevant because things revolving around the sun have different timeframes, for example, Mercury has a year of 88 Earth days, whereas a day on Venus is actually longer than it's year. Now, if something moves quicker, it is therorized to move slower in "Time". Therefore, if the Earth spun around the Sun faster, we would then live longer lives. Now Einstein understood that light is the fastest known thing in the universe, because it travels at 186,000 miles per second (300,000 km/sec). Now everything that we know of, that we can see, that does exist would be invisible unless there were light to see it, and for this reason, things are "relative" to the speed of light. Do you follow? Everything that moves, moves in a speed compared to light. It's kinda hard to grasp, but consider this; when there's a T-storm, and lightning strikes, you see the lightning, and then you hear the thunder. That's sound trying to catch up to the speed of light. Now, Einstein theorized that the faster you move, the slower time goes, because you are approaching the speed of light, and because light is the fastest thing in the Universe, there's nothing to compare it to, therefore time, in a sense, STOPS once you reach that speed. And If you exceed the speed of light, Time may very well move in reverse. Now do you see why time truly does not exist? Here's my favorite example: Let's say you have two identical twin brothers, and one of them is an astronaut, and goes on a space voyage in a spaceship travelling at the speed of light for a really long time. Long time? To who? To the astronaut? Nope. according to the Theory of Relativity, no matter how long he is gone, as long as he is moving at the speed of light, time will not pass for him at all. The astronaut could return after 50 Earth years to discover that his brother is an old man whereas the astronaut is still young enough to do backflips, not aging one bit. I hope that helps you, as You can tell I take a great deal of interest on the topic.