If light is the fastest means of travel, how can scientist measure an object 100 or 1,000 light years away?

Answer 1

Because the light has taken that long to get here.

When we look at a star 100 light years away, we see it not as it is but as it was 100 years ago. That star might have exploded 80 years ago, but we won't see that for another 20 years.

The effect is even measurable with the Sun. The light from there takes about 8 minutes to get here, so we see the sun as it was 8 minutes ago.

You seem to know what a light year is, but anyway, check the link.

Answer 2

Usually a star's, or other object out there, distance is determined by parallax measurement. A star is located and graphed,charted,mapped, whatever and then six months later-when the earth has moved to the other side of the sun in its orbit, the same star is graphed again. This creates a "triangle" whose base is the diameter of the earth's orbit, and the two legs are derived using the angles the star was from the earth at the two different times. So, taking that base line, and drawing two lines from it at the proper angles used in charting the star, they will intersect where the star is. Now, through trig and geometry the distance can be determines. Sort of like a survey crew on the side of the road shooting distances to objects from two different locations to get measurements.
But, like everyone else has mentioned, the stars we see aren't really where we are seeing them. With a star that is say approx 5 light years away, like Alpha Proxima, the light that we see left it 5 years ago. It has since moved in that 5 years. So, it isn't really there at our "now" when we look at it. Because, as you look out across space, you look back through time. That is why Einstein called it space-time, correcting Newton's term absolute space.

Answer 3

One possible way of estimating the distance of an object many light years away is by the light echo method. For example, when a supernova explodes, it will illuminate surrounding clouds. Now if you subtract an image of this illuminated cloud with another image where the cloud is not illuminated by the supernova, only the illuminated part of the cloud would stand out.

We can measure the angle of this illuminated cloud to the supernova. We also know how long it took for light to travel from the supernova to the cloud. For example, if the photo was taken 100 days after the initial supernova explosion, the distance of the illuminated cloud to the supernova is given by time taken (100 days) * speed of light

Since you know the angle between the SN and the illuminated cloud, and the distance of the cloud from the SN, it becomes a triangulation problem.

Answer 4

Scientist know the speed of light and they know the distance in miles to an object in space, which is millions or billions of miles away. To show the distance in miles the number would be very large. So they express the distance in light years so that the number is not so large.

Answer 5

Ur question has contradiction,speed of light has nothing to do with light years.

To measure an object such as star's distance,we use parallax method (direct method) or candle light method (indirect approach)

For parallax method,its juz the same as using simple trigonometry.

Candle light method is a bit complicated..with the use of spectroscopy.

So in short...your question is a bit wrong (misconception i guess)

It's just like you are asking " my father's car speed is 100 miles/hour...so how do i measure the distance of 2000 km? "

its juz...dont mix...try to grab the concept,i pretty sure you can!

Best of luck!

Answer 6

Light year is a measure of distance, not time. A light year is how FAR light can travel in one year.

Answer 7

Of course, they are not seeing the object as it now is, but as it was a century or a millennium ago. Measuring interstellar distances is a complex task, as described in the first link below. Besides light years, distances in space can be measured in astronomical units (for relatively nearby objects) or parsecs, as described in the second link below.

Answer 8

we measure the object as it was 100 or 1000 years ago

who knows what happened to it after that....we'll only come to know later.

information cannot travel faster than speed of light even though entangled particles (quantum physics) can "act on" each other instantaneously.

Answer 9

i think they use some kinf of scientific scale, they only measure a small distance and compare it with some fixed measurement that they already have

Answer 10

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