how to measure distance in space?

Question

if some thing happens in universe,immideatly telescopes finding it.at the same time it says the distance of incident in hundreds of light years ,how this is posssible

Answer 1

Your question is really good.

But, I'll object your statement "if some thing happens in universe,immideatly telescopes finding it".

No!!! Any happening in the universe will be propagated with the speed of light. For e.g. If in our solar system, we know that light takes around 8 min to reach from sun to earth. so imagine a condition If somehow you take off sun from solar system, it will take 8 mins to let you know that sun has disappeared even though you are looking at sun (through a proper filter) continuously.

Astronomical objects are so distant that whatever object you see today, light has emerged from those objects 100's of years back...

Its not possible to communicate any incident faster than the speed of light. This was highlighted in Special theory of relativity by Einstein.

Now if your question is how to measure a distance between object just by looking at a light coming from it, it may done by looking at half-life time of photons. Somebody technical at particle physics may give a detail answer on this.

Answer 2

It all depends.... if the target is pretty close, we use triangulation, based on multiple telescopes at the same time or a single telescope at different times, often using the far star fields as landmarks for the measurement. This is often referred to as Parallax, when the angle is measured from two different points on earth's orbit.

For certain kinds of stars (mostly Cephid variables) we know their absolute brightness because we've found that it depends on the period of the variability of the star. Knowing its absolute brightness and its relative brightness, we can calculate the distance (farther away stars of the same absolute brightness are dimmer appearing). This even works for some nearby galaxies because this type of star has been identified in them.

For farther away objects (far galaxies) we use red-shift measurements to estimate the distance. This is least accurate, but Fred Hubble figured this one out.

For some solar system objects, we've used radar (1946 to the moon, 1956 to Venus, later to some other objects. Another thing that was done was to send a probe and time the radio delays, but that is radar with an active transponder.

Hope this helps

Answer 3

Suppose a star goes nova in a nearby galaxy (say, one of the Magellanic Clouds). Telescopes on earth will see the event at the same time, even though the event happened thousands of years ago and thousands of light-years away. The light from the explosion has been traveling for all that time, and eventually reaches the earth.
The distance to galaxies is measured using a particular kind of star called a Cepheid variable. If you want to know how, try Google or Wikipedia.

Answer 4

A light-year is a unit of distance. It is the distance that light can travel in one year. Light moves at a velocity of about 300,000 kilometers (km) each second. So in one year, it can travel about . 9,500,000,000,000 kilometers.

on Earth, a kilometer may be just fine. It is a few hundred kilometers from New York City to Washington, DC; it is a few thousand kilometers from California to Maine. In the Universe, the kilometer is just too small to be useful. For example, the distance to the next nearest big galaxy, the Andromeda Galaxy, is 21 quintillion km. That's 21,000,000,000,000,000,000 km. This is a number so large that it becomes hard to write and hard to interpret. So astronomers use other units of distance.

Answer 5

Parallax.

The earth moves from one side of the sun to the other. When that distance is known, and the angle can be measured from one position to the view of the same star 6 months later, the distance can be calculated. A larger angle is a closer star, a narrow angle is a farther star.

You can see the same affect by measuring the angle of your view from the top of a tree to the bottom. Walk back a few hundred feet and do it again, the angle decreases. Get it?

Answer 6

I do not understand your question exactly. Light years means the distance light travels in space in one year. What I have read is that when we see something in space happen it possibly happened long ago and it took this length of time to reach earth in regards to light such as the explosion of a star etc.

Answer 7

good question.......space.....space between to things or more ?man has always measurd things.......how long , tall,wide heavy..at what speed?.....what amount? what size shirt do you wear....shoes..? i'm starting here because you started measuring too...at an early age.........many of these measurements were already decided....yr mom made pancakes with so much flour...milk salt,butter etc using teaspoons, cups and a time for cooking at a certain temperature [more measurin].....if you enjoy
d breakfast..you may have b gone and weighed yourself to see if you are heavier...yr mom may have stopoped eating at two pancakes because v she counts calories[amount of heat] and has that mixed up with weight...........so you learned that you can take a cardboard box and measure how high/wide/or long it is.....you can even find out how much it will hold...and how much it weighs empty or full....that box could be plastic/wood or even steel...you can see if more than one box was made of the same material...and you compared it to others...they would nearly be the same....not including temperature or altitude..or the time it took to measure..or the time of day.....or humidity...if there was differences....you would wonder why .
congratulations...so do scientists...now if you had ten full boxes all the same size and had to ship them to different places in the world...you can see that they would not arrive at the destinations at the same time if they are to arrve at the same time you would send them at different times,,right?...so distance and time come into play...or rate....one other measurement....if some of ther boxes perished/ evaporated or just plain dissapeard....they would no longer be measureable but yet could be considerd as duration.....so you could say.....it takes less time by flying then by boat or by truck or train......so what we call space can be solid/liquid or gaseous...and the measurements can be the same anywhere by who ever measures...if they all use the same system of measuring and whats being measured .. amount of / quality of ....and the medium its being measurd through..............all of these i use to explain what and how scientists...use telescopes to learn about the space outside of our atmosphere.....and they COMPARE...a form of measuring with each others findings...so if you tell me wow the moon sure looked big last night...i say what time did you look at it and where r you located......and even though it is 24 hours diofferent...i could look at the same time tonight....except daylight savings...and cloud cover....and see what you mean by..big....and most people could do the same...if theyre location was withn a certain position of the earth where the moon was visable... not all telescopes work the same...and the methods used vary....but since the speed of light is considerd as a reliable guide for measuring.....it travels at 186000 miles per sec every second in empty space....but it slows in different materials....in water ..any gravitational field absorbs some of its energy....in a diamond it is slowd to nearly 50- %......... but generally light radiates out in all directions from its source and is only slowd by what it passes through...remember the plane can travel faster than the boat or truck....so when a new sighting of an event occurs...others can view it from their location...if they know the location of that event....we have never seen two stars the same...identical....we groupe them into catagories....some are smaller and some much larger than our star the sun...and some are not only younhger or older but are of a different generation.....hope this helps because we measure....we can predict when a box could arrive in or somewhere on the earth......and because light b travels inthe same speed...we realize some of the stars we see now....sent out their light thousands or millions of years ago....,have a nice breakfast

Answer 8

It isn't. You must have heard wrong, perhaps, or read something by someone who didn't know their basic astronomy, but it does, in fact, take years for light to cross between the stars to us.

Astronomers routinely observe stars and other objects millions, even billions of light-years away. This means they are looking at those stars as they were millions and billions of years ago.

As for how we determine distance over such long distances, that involves several different methods. For stars of up to a few thousand light years away we use trigonometry. The observation of special kinds of stars, called "Cepheid variables", as "benchmarks" for more distant observations. Much more than this and someone who knows more than I will have to explain how it all works.

Hope this helps.

Answer 9

The unit of measurement of distance in space is the distance that light could travel over a period of one year at the rate of 186000 mile per second . because distances of such immense magnitutude are very long and difficult to write and pronounce in terms of figures ,as tromers have adopted such a scale . I none year lgiht will be travelling a distance of 186000* 365*24*60*60 . just multiply and see the length of this figure . This is for one year - one light year . suppose the distnce is so vast tha it takes light a million years , just mutiply the figure you get for one light yer by a million . in cosmology , we very freely and frequently come across distances that are immensely and nimaginably great . So the distance that light travels in a period of one year is taken as a Light year for measuring the distnces in space.
So ,if ,even the light tkes so many million years to reach the earth from some distant object how is that tghe atronoimers calculate the distances in their life time ? That they do by obeserving the spectrum of the light and the shifting of the colour componets of the spectrum , particularly the red colour of the spectrum. They have determined that the red colur at the end of the the spectrum of light received from objects shift thier positon as the distance from the object to the place to which the light isreceived and that ther is an uniform pattern in that shift by which the distance can be calculated . by observing the rate of the shift , they sem to calculate the rate of movenmnet of th source of the light also . it seems that tey use the strength of the X-ray and other radio active waves also to measure the rate of movement of the source of the waves .Specific informationon these mattters will be avilable in th websites like wikipedia on astronomy etc. What we to day observe something in respect of some distant objets today may be the position of the object concerned some millions of years ago and most of them do not indicate the current position at all. the curent position or conditon os is only assessed or guessed with reference to the observationand the the assessment of the changes that
could have occured in relation to the factors or laws that are expected to have come into play during the time lapse etc .So most of what we see to -day in the distant sky is not what is .; but what was some millions or billions of light years ago .
But still it is open to one question . Is light continuint to trvel fo millions of years even after the the source of light is put out?will not light get dissipated or absorbed by other objcts in space once it starts travelling on space ? Will light travelling in vaccum (assuming that it travells in vaccumonly in space) will not die out once the source id put out ? If so why not we conserve /save light and keep the light ,at least te unused portion of it after we switch of the light in our homes?
The light travelling for millions of light years and reaching the earth from some distnt source whinc might perhaps by now could have turned into a black itself is intriquing .
The astromers may be comming accross many more surprises . They are really doing a tremendous job to unravel in thier short span of life, the mystries of the universe .in trying to unfold th secrets that nature has taken billions and billions of years to accomplish.
In fact it is nature that is doing the job as the human brain is also part of the wonderful nature itself .

Answer 10

To figure this out lets check out how astronomers measure the distance to planets . The planets look like pinpoints of light to our unaided eyes, and we can't simply look up at the sky and tell how far they are from Earth or from each other, or even see that Earth and the other planets actually revolve around the Sun. But astronomers have come up with some brilliant ways to discover their distances.

Until less than 500 years ago, most people thought Earth was the center of the solar system. By the time Johannes Kepler was born in 1571, people were starting to get the idea that the planets revolve around the Sun. Kepler was the first to explain the puzzling movements of the planets by realizing that their orbits around the Sun are not perfect circles, but instead are ellipses, like elongated circles. Kepler discovered that the motions of the planets could be described very accurately by some simple mathematical formulas. The closer a planet is to the Sun, the faster it travels, and Kepler found a method to connect the average distance of a planet from the Sun to the time it takes the planet to make a complete orbit around the Sun.

Kepler's discoveries allowed him to figure out how much closer or farther all the planets are to the Sun than Earth is, even though he could not figure out the actual distances. For example, he knew Mars is closer than Saturn, because one Mars orbit takes less than 2 years, while one Saturn orbit takes about 29 years. Although he couldn't use that to calculate their real distances, he did figure out that Mars is about 1.5 times farther from the Sun than Earth is, and Saturn is 10 times farther away than the Sun.

If only astronomers could determine the distance from Earth to any other planet or the Sun, they could use that to find the distances to all the planets, and their understanding of the arrangement of the solar system would be greatly improved.

One of the first people to make a good measurement of the distance to a planet was the great astronomer Gian Domenico Cassini. In 1672, Cassini used a technique called parallax to measure the distance to Mars.

You can understand parallax by holding your thumb up at arm's length and looking at it first with one eye, and then your other. Notice how your thumb seems to shift back and forth against the objects that are farther away. Because your two eyes are separated by a few inches, each views your thumb from a different position. The amount that your thumb appears to move is its parallax. When astronomers measure the parallax of an object and know the separation between the two positions from which it is observed, they can calculate the distance to the object. Using observations on Earth separated by thousands of miles -- like looking through two eyes that are very far apart -- parallax measurements can reveal the great distances to planets.

Although he didn't get quite the right answers, Cassini's results were very close to the correct values. The Sun is about 93 million miles from Earth. As Earth and Mars move in their separate orbits, they never come closer than 35 million miles to each other. Saturn, the most distant planet known when Cassini was alive, is around 900 million miles away. Imagine how exciting it must have been for him to discover that the solar system is so fantastically big!

Astronomers can use parallax to find distances to objects much farther even than planets. To calculate the distance to a star, astronomers observe it from different places along Earth's orbit around the Sun. If they measure the object's position several months apart, their "two eyes" will have a separation of well over 100 million miles!

Now astronomers have technologies to measure distances to other planets more directly. When we have a spacecraft at another planet, we know the time it takes a radio signal to travel between Earth and the spacecraft. We can also send a powerful radar signal toward a planet and time how long it takes for the echo to return. Astronomers know how fast these signals travel (the speed of light), so measuring how long they take makes it easy to calculate the distance very accurately.

You can get a feel for the distances between the planets with a fun activity right in your driveway or other big, flat area. To learn more , go to The Space Place web site at spaceplace.nasa.gov. Click on Goodies for Teachers, then scroll down to Make a Scale Model of the Solar System. Just like Cassini must have been, you may be amazed to discover how large the solar system really is, and you might take the time to think about how impressive it is that we can measure such vast distances from our home here on little Earth.