Number 7 in Science & Technology

A page of the Numeropedia - the Special Encyclopedia of Numbers

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The number of rainbow colors: red, orange, yellow, green, blue, indigo and violet. Sometimes, the indigo is ignored from the list.

 

There are seven magic numbers in nuclear physics: 2, 8, 20, 28, 50, 82 and 126. They are the numbers of nucleons such that they are arranged into complete shells within the atomic nucleus.

 

Theoretically, the maximum duration for a solar eclipse is about 7 minutes 31 seconds. The longest duration recorded was 7 minutes 28 seconds, over the Philippines on June 20th 1955.

 

Apollo 7 is the first Apollo spaceship to carry a crew into orbit successfully, on 11 October 1968. It spent 10 days 20 hours in space and orbited the Earth 163 times.

 

The first (number system) digit in the 12-digit UPC Version A (Universal Product Code for North America) barcode is 7 or 0 for groceries, (followed by 5-digit manufacturing code, 5-digit product code and 1 check digit at the right end).

 

An average person’s eyes are approximately 7 cm (centimeters) or 2¾ inches apart. This is also the width between the side-by-side left-eye and right-eye cameras used to record 3-D movie pictures.

 

The standard 7-segment electronic display of numbers, using digital circuit technique. Other: 10 or 16-segment…

 

7.5

The powers of commercial incandescent light bulbs: 300W, 100W, 75W, 60W, 40W, 30W, 15W, 7.5W and 3W.

 

The inner radius of a typical compact disk (CD) is 7.5 mm (millimeters), with outer radius 60 mm and thickness 1.0 mm. It mass is 16 grams.

 

Sterling silver is an alloy containing at least 92.5% silver (and at most 7.5% other metal, such as copper).