Calculating distance to object?

  • Thread starter Sock
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In summary, astronomers use various methods to calculate the distance to an object. The most common method is to use the sun as the object, and other methods are used for more distant objects.
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Sock
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First I would like to say sorry for registering just to ask this question. I tried searching but its kind of a long search term. If there is another thread you know of just linking it is fine.

How do astronomers calculate the distance to an object? You can use the sun as the object. It can be a simple explanation, I just want to know the basics.
 
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  • #2
There are several ways.

First, for close objects stick your finger close to your face and blink your eyes, one on and one off and then the other on and the first one off. Note how far your finger moves. Now move your finger out as far as your arm will go and blink your eyes again. Note how far your finger moves. It didn't move as far did it? This same technique can be used in a grand scale with stars. When the Earth is on one side of its orbit, the location of the target star is noted against the background. Then on the other side of the orbit, it is noted again. Some simple trig and wola! The answer pops out. This is good for a few thousand light years.

Out further, they use Cepheid variable stars. These stars vary in a cycle and the length of the cycle is related to the brightness of the star. This can be used out to the near by galaxies.

Finally, how much the objects are red-shifted (which is dependent on how fast the objects are moving away from us) shows very distant distance. The older the object the greater the red-shift because the universe is expanding.
 
  • #3
If general relativity is correct, then this is a difficult and subtle problem in theory.

In practice, distances are often calculated by comparing the amount of detected starlight with the total quantity of light which that type of star is thought to emit (same as guessing the distance of a car by the brightness of its headlights), but you're relying on the models for the different types of star.

Another important method is to look at the object from different positions, just like the parrallax between your two eyes let's you judge distances.

In the case of the moon (or separations on earth), these days we can simply time laser signals to measure its distance.

I think the distance to the sun was found using the length of the year and the weight of the earth.
 
  • #4
Alright, thanks.
 
  • #5
There are a lot of different methods that astronomers use to measure distances. Ned Wright has a nice summary:

Distance Ladder
 
  • #6
One word: Trignometry
Two words: Trignometry, and Angular Size

These topics are covered in most Trig textbooks. It is explained in the first few chapters of: Barons Guide to Trignometry, which to this date is one of my favorite books.

The first one, Paralax, is used to determine the distance of an object if it is close to Earth, but at large distances, this technique does not work at large distances.

http://en.wikipedia.org/wiki/Cosmic_distance_ladder

Has some information on the topic you are seeking.
 
Last edited:

1. How do you calculate the distance to an object using trigonometry?

To calculate the distance to an object using trigonometry, you will need to measure the angle between the ground and your line of sight to the object, as well as your distance from the object. Then, you can use the tangent function to find the object's distance from you. The formula is distance = height / tan(angle).

2. What is the difference between using the Pythagorean theorem and trigonometry to calculate distance?

The Pythagorean theorem and trigonometry both involve calculating distances, but they use different approaches. The Pythagorean theorem uses the lengths of sides in a right triangle to find the hypotenuse, while trigonometry uses angles and ratios to find a side length. In most cases, using trigonometry will give a more accurate distance measurement.

3. How can you calculate the distance to an object without using any tools?

If you do not have any tools to measure angles or distances, you can use the concept of similar triangles to estimate the distance to an object. First, measure your height and the length of your shadow. Then, measure the object's shadow. By setting up a proportion with the similar triangles, you can find the object's distance from you.

4. Can you use the same method to calculate distance for objects at different heights?

Yes, you can use the same method for objects at different heights. As long as you measure the appropriate angles and distances, you can use the tangent function to find the distance to any object at any height.

5. What should you do if the object you are trying to measure distance to is not in line with your height?

If the object is not in line with your height, you can use the concept of horizontal and vertical angles to find the distance. Measure the angle between your line of sight and the ground, as well as the angle between the ground and the object's location. Then, you can use trigonometry and the given angles to find the distance to the object.

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