Walter Isaacson Quote
One way to understand that Einstein was talking about invariance, rather than declaring everything to be relative, is to think about how far a light beam would travel in a given period of time. That distance would be the speed of light multiplied by the amount of time it traveled. If we were on a platform observing this happening on a train speeding by, the elapsed time would appear shorter (time seems to move more slowly on the moving train), and the distance would appear shorter (rulers seem to be contracted on the moving train). But there is a relationship between the two quantities—a relationship between the measurements of space and of time—that remains invariant, whatever your frame of reference.62 A
Walter Isaacson
One way to understand that Einstein was talking about invariance, rather than declaring everything to be relative, is to think about how far a light beam would travel in a given period of time. That distance would be the speed of light multiplied by the amount of time it traveled. If we were on a platform observing this happening on a train speeding by, the elapsed time would appear shorter (time seems to move more slowly on the moving train), and the distance would appear shorter (rulers seem to be contracted on the moving train). But there is a relationship between the two quantities—a relationship between the measurements of space and of time—that remains invariant, whatever your frame of reference.62 A
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About Walter Isaacson
Isaacson attended Harvard University and Pembroke College, Oxford as a Rhodes scholar. He is the co-author with Evan Thomas of The Wise Men: Six Friends and the World They Made (1986) and the author of Pro and Con (1983), Kissinger: A Biography (1992), Benjamin Franklin: An American Life (2003), Einstein: His Life and Universe (2007), American Sketches (2009), Steve Jobs (2011), The Innovators: How a Group of Hackers, Geniuses, and Geeks Created the Digital Revolution (2014), Leonardo da Vinci (2017), The Code Breaker: Jennifer Doudna, Gene Editing, and the Future of the Human Race (2021) and Elon Musk (2023).
Isaacson is a professor at Tulane University and an advisory partner at Perella Weinberg Partners, a New York City-based financial services firm. He was vice chair of the Louisiana Recovery Authority, which oversaw the rebuilding after Hurricane Katrina, chaired the government board that runs Voice of America, and was a member of the Defense Innovation Board.