Length Contraction Calculator

Objects appear different to observers when they are moving, especially at a high rate of speed. Calculate how small they seem to be with this length contraction tool.

Required Information

Observed Length:

What it is

What is Length Contraction?

Create Date: September 26, 2024

Last Modified Date: November 17, 2024

Length contraction is a phenomenon where an object that is moving at a high rate of speed will appear shorter, or contracted, to an observer who is standing still.

How do you Calculate Length Contraction?

When calculating length contraction of an object, you will use two variables:

  • Normal length of object

  • Object velocity
Once you have the value of these variables you can utilize this formula to find the length the object would appear to standstill observer:
An image showing the formula for finding the length of an object from a standstill observer which would be influenced by length contraction.
Where:
  • CL = Contracted Length of the object

  • NL = Normal Length of the object

  • C = The speed of light

Understanding Your Results

When you use this tool you will get a single number back which is the new perceived length of the object from a standstill observer. This is not the length that the object will contract by, it is the new perceived length post-contraction of the object, by someone who is not moving. This is shown in feet by default but can be converted into other units of length measurement by choosing them from the dropdown menu.

How to Use the Length Contraction Tool

Length contraction is an interesting concept in the universe. It can be calculated with just a few steps when using this tool. The steps include:

  1. Enter the normal length of the object.

  2. Enter the velocity at which the object will be moving at when it is being observed. By default, we have entered a rate of 125,000 miles per second.

  3. Ensure your entries are correct and the unit associated with them are aligned with your desired entry.

  4. Hit calculate and get the new perceived length of the object instantly!

Example Calculation

Let's say we are evaluating an asteroid that is moving through space. We know that it is about 50 feet long and is moving at a speed of 115,000 miles per second. We can use this tool to find its perceived length after experiencing length-contraction. We will enter 50 into the normal length field, then change the object velocity value to be 115,000.

We are now ready to hit calculate. Once we do, we learn that to a standstill observer, the 50-foot asteroid will appear to be only 39.335 feet long due to the effects of length contraction.

Length Contraction - Frequently Asked Questions

The effects are simply visual and not truly physical. For example, if you have a 12-inch ruler, it would not look like it was actually 12 inches depending on the speed at which it is moving.

Length contraction only affects the length at which the object is moving. If it is moving up or down then yes, length contraction would be applied to height.

No, they are independently measured phenomena. Time dilation refers to time while length contraction relates to the length and size of an object.

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