RSS iconTwitter iconFacebook icon

The Trek BBS title image

The Trek BBS statistics

Threads: 141,536
Posts: 5,513,014
Members: 25,140
Currently online: 442
Newest member: themagicman

TrekToday headlines

Two New Starships Collection Ships
By: T'Bonz on Dec 26

Captain Kirk’s Boldest Missions
By: T'Bonz on Dec 25

Trek Paper Clips
By: T'Bonz on Dec 24

Sargent Passes
By: T'Bonz on Dec 23

QMx Trek Insignia Badges
By: T'Bonz on Dec 23

And The New Director Of Star Trek 3 Is…
By: T'Bonz on Dec 23

TV Alert: Pine On Tonight Show
By: T'Bonz on Dec 22

Retro Review: The Emperor’s New Cloak
By: Michelle on Dec 20

Star Trek Opera
By: T'Bonz on Dec 19

New Abrams Project
By: T'Bonz on Dec 18


Welcome! The Trek BBS is the number one place to chat about Star Trek with like-minded fans. Please login to see our full range of forums as well as the ability to send and receive private messages, track your favourite topics and of course join in the discussions.

If you are a new visitor, join us for free. If you are an existing member please login below. Note: for members who joined under our old messageboard system, please login with your display name not your login name.


Go Back   The Trek BBS > Entertainment & Interests > Science and Technology

Science and Technology "Somewhere, something incredible is waiting to be known." - Carl Sagan.

Reply
 
Thread Tools
Old July 18 2013, 11:32 PM   #1
Lt. Uhura-Brown
Lieutenant Commander
 
Location: New Zealand
Confused about E=mc²

I was thinking about the famous equation E=mc² the other day, when I realised I didn't actually understand it, or rather, the units used.

It seems to me that Joules = (volume multiplied by density) multiplied by (300 million meters divided by 1 second) multiplied by (300 million meters divided by 1 second)?

I know there's something I must be missing, but I can't wrap my head around how it all fits together.
Lt. Uhura-Brown is offline   Reply With Quote
Old July 19 2013, 12:47 AM   #2
Christopher
Writer
 
Christopher's Avatar
 
Re: Confused about E=mc²

Mass is a basic quantity that doesn't have to be broken down; kilograms are generally the preferred unit. A joule is a newton-meter, and a newton is a kilogram-meter per second squared; so that means joules are (kg x m/s^2) x m = kg x m^2/s^2 = kg x (m/s)^2, which is mass (kg) times velocity (m/s) squared, with the velocity being the speed of light.

So a mass of 1 kg, if converted to energy, would come out to 1 kg x (3 x 10^8 m/s)^2 = 9 x 10^16 J.
__________________
Christopher L. Bennett Homepage -- Site update 11/16/14 including annotations for "The Caress of a Butterfly's Wing" and overview for DTI: The Collectors

Written Worlds -- My blog
Christopher is offline   Reply With Quote
Old July 19 2013, 08:04 AM   #3
Asbo Zaprudder
Rear Admiral
 
Asbo Zaprudder's Avatar
 
Location: On the beach
Re: Confused about E=mc²

^What Christopher says. Also, in particle physics and astrophysics, the units commonly used are electron volts (eV) for energy and eV/c² for mass -- the latter usually being abbreviated to eV if natural units are used which set c=1.

One volt (V) is defined as being the potential difference when one coulomb (C) of charge crosses that potential resulting in a change of one joule (J) of energy. One electron volt is defined as the magnitude of the energy change of an electron moving through an potential difference of one volt. So 1 eV = 1.602x10^−19 J given that the magnitude of the charge on the electron is 1.602×10^−19 C (the charge is actually a negative quantity for electrons and positive for positrons, of course).

Last edited by Asbo Zaprudder; July 19 2013 at 08:22 AM.
Asbo Zaprudder is offline   Reply With Quote
Reply

Bookmarks

Thread Tools

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump



All times are GMT +1. The time now is 02:15 AM.

Powered by vBulletin® Version 3.8.6
Copyright ©2000 - 2014, Jelsoft Enterprises Ltd.
FireFox 2+ or Internet Explorer 7+ highly recommended.