# Calculating Distance: What Am I Doing Wrong?

• B
• Discman
In summary, the conversation is discussing the calculation of the standard ruler, specifically the sound horizon shell, used in the Baryon Acoustic Oscillations (BAO). The person is questioning why the standard ruler is 2 times longer than expected and the expert explains that the calculation was done using conformal time instead of actual time, which explains the discrepancy.
Discman
What I'm doing wrong?
speed X time = distance
0,6 c X 380000 jr = 228000 ly
times expansion of 1000 gives 228.000.000 ly
This is equal to about 72 Mpc
Why is the standard ruler 2 times as long: about 150 Mpc
What is wrong, or do I forget in my calculation?

What exactly do you want to calculate? Where do those numbers come from?

A (!) standard ruler is any object of known size.

With these numbers I am pointing of course at the cosmic standard ruler which is used in the BAO.
Speed fundamental tone of acoustic waves 0,6 c, time to sound horizon 380.000 yrs
And the calculated standard ruler is the radius of the sound horizon shell (not the diamater)
So, again, why 2 times so long?

Thank you very much. By coincidence I was just beginning to think into that direction when your answer arrived.

## 1. How do I calculate distance?

To calculate distance, you need to know the distance formula, which is d = √((x2-x1)^2 + (y2-y1)^2). The x and y values represent the coordinates of two points, and the distance formula will give you the distance between those two points.

## 2. What units should I use for distance calculation?

The units used for distance calculation depend on the units of the coordinates you are using. For example, if you are using coordinates measured in meters, the distance will be in meters. If you are using coordinates measured in feet, the distance will be in feet. It is important to use consistent units for accurate calculations.

## 3. How do I know if my distance calculation is correct?

You can check the accuracy of your distance calculation by using a known example or by double-checking your work with a calculator or math software. Make sure you are using the correct formula and units, and that your calculations are done accurately.

## 4. Can I calculate distance between more than two points?

Yes, you can calculate the distance between any number of points as long as you have their coordinates. You can do this by finding the distance between each pair of points and then adding them together to get the total distance.

## 5. What are some common mistakes when calculating distance?

Some common mistakes when calculating distance include using the wrong formula, using inconsistent units, and making calculation errors. It is important to double-check your work and make sure you are using the correct formula and units for accurate calculations.

• Cosmology
Replies
1
Views
1K
• Cosmology
Replies
11
Views
3K
• Cosmology
Replies
12
Views
4K
• Cosmology
Replies
111
Views
10K
• Cosmology
Replies
8
Views
1K
Replies
11
Views
394
• Introductory Physics Homework Help
Replies
5
Views
1K
• Cosmology
Replies
6
Views
1K
• Cosmology
Replies
4
Views
2K
• Special and General Relativity
Replies
25
Views
716