Lecture 1: Powers of Ten - Units - Dimensions - Measurements - Uncertainties - Dimensional Analysis - Scaling Arguments

author: Walter H. G. Lewin, Center for Future Civic Media, Massachusetts Institute of Technology, MIT
recorded by: Massachusetts Institute of Technology, MIT
published: Oct. 10, 2008,   recorded: September 1999,   views: 172727
released under terms of: Creative Commons Attribution Non-Commercial Share Alike (CC-BY-NC-SA)

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1. Fundamental Units:

The fundamental units are length, time and mass.

2. Powers of Ten:

"The Powers of Ten" (© Charles &amp; Ray Eames and Pyramid Media) movie, covering 40 orders of magnitude, has been removed from the video for reasons of copyright.

3. Dimensions:

Dimensions are denoted with brackets; some examples are given.

4. The Art of Making Measurements:

A measurement is meaningless without knowledge of its uncertainty. The lengths of an aluminum rod and the length of a student are both measured standing straight up and lying down horizontally to test whether the student's length is larger when he is lying down than when he is standing straight up. Within the uncertainty of the measurements, the difference between standing and lying is substantial for the student (NOT for the aluminum rod).

5. Was Galileo Galilei's Reasoning Correct?

Why are mammals as large as they are, and not much larger? The argument suggests that if they become too heavy, the bones will shatter. Galileo Galilei suggested that material properties of our bones impose a natural limit on the size of things. Professor Lewin brings this to a test by presenting Galilei's scaling arguments, and he compares them with actual measurements.

6. Dimensional Analysis:

The dimensions of both sides of the equation must be the same; this is non-negotiable in physics. Using this idea, Professor Lewin reasons that the time for an object to fall from a certain height is independent of its mass and proportional to the square root of the height from which it is dropped. He confirms this conclusion by dropping an apple from 3.000 m and 1.500 m with an uncertainty in each of 3 mm. He then shows why his "prediction" was a cheat.

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Reviews and comments:

Comment1 Peter, November 27, 2008 at 12:34 a.m.:

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Comment2 Patrick Yoon, January 22, 2009 at 9:16 a.m.:

wow now i can download the lectures??

Thanx guys~ :) it's been a pain in the neck to go to the computer lab everytime i wanted to check on the lectures :)

Comment3 xavier, April 4, 2009 at 1:46 a.m.:

I think more homework links would do wonders.

Comment4 Simon Beaumont, April 24, 2009 at 11:01 p.m.:

Fabulous first undergrad lecture - jeez if that didn't get one engaged you're taking the wrong degree -- deep and meaningful physics for the the neophyte - our science education is in good hands! Natural philosophy is alive and well. Bravo!

Comment5 C P RAJESH, December 3, 2009 at 9:10 a.m.:

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Comment6 Ryan, February 17, 2010 at 3:03 p.m.:

These videos will certainly help those who fall asleep in lectures lol. It will also help those who are trying to grasp concepts to better understand the subject matter. all in all, a very helpfull resource!!

Comment7 thi, April 4, 2010 at 5:11 a.m.:

direct introduction!short and simple~

Comment8 hassaan, May 26, 2010 at 8:48 p.m.:


Comment9 Dan Yi, June 7, 2010 at 12:04 p.m.:

it's a little difficult to understand the whole lecture with the dictionary,anyway, the lecture is really great.perhaps i should swot up my English.^-^ thanks~

Comment10 lry, June 15, 2010 at 4:21 p.m.:

I think I must study my Engglish hard...I can not understand what he say....This is very sorry!

Comment11 omer rahim, August 21, 2010 at 10:17 p.m.:

Thanks for this lecture

Comment12 Liu Fengwei, October 4, 2010 at 11:39 a.m.:


Comment13 George, October 11, 2010 at 3:59 p.m.:

brings back lost memories form the early '60s

I'll be catching other lectures this way

Comment14 Steve Hamm, October 13, 2010 at 11:18 a.m.:

Here's a new homage to Powers of Ten created by IBM


Comment15 Ozgur, June 17, 2011 at 1:49 p.m.:

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Learn more about physics.

Comment16 Zhang Junxian, August 22, 2011 at 8:08 a.m.:

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Comment17 Ashwathi Meethan, May 14, 2013 at 6:12 p.m.:

Can we say that the ratio t1/t2 is proportional to the square root of (h1/h2) when the mass for objects 1 & 2 are the same?

Comment18 Awais Amjad, March 7, 2014 at 4:06 p.m.:

Good Lecture

Comment19 SUBHADEEP DAS, January 2, 2015 at 7:57 a.m.:

How to download eng sub of this video

Comment20 Alexis Escobar, February 19, 2015 at 4:30 p.m.:

Hello. I can´t download subtitles for this video. Please, can you provide us a link for them?

Comment21 sss ss, March 12, 2015 at 6:46 p.m.:

Hello. I can´t download subtitles for this video. Please, can you provide us a link for them?

Comment22 ss ss sss, March 18, 2015 at 12:40 a.m.:


Comment23 sepideh, September 25, 2015 at 6:09 p.m.:

The subtitle doesn't work! Can you help me?

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