July 15, 2019

On the 100th anniversary of the theory of relativity, a rabbi talks with an Einstein expert

This month marks the 100th anniversary of Albert Einstein’s theory of general relativity. To understand its implications and the role of Einstein’s Jewishness in developing the theory, Rabbi Naomi Levy interviewed professor Hanoch Gutfreund, the director of the Einstein Center at the Hebrew University of Jerusalem and the university’s appointee responsible for Einstein’s intellectual property.

Rabbi Naomi Levy: Can you please explain the theory of relativity in a nutshell?

Professor Hanoch Gutfreund: We are talking about the general theory. I think it may be the most sophisticated, intellectual factor that has been produced in a single human brain. Einstein himself tried to explain it, very often. When he came to the United States for the first time in 1921, journalists asked him to explain. He told them, “This is very simple. Matter tells space how to curve — and this is all it is about.” Of course, the journalists were stunned. They turned to Mrs. Einstein and asked her, “Do you understand the theory of relativity?”

And she said, “He tries to explain it to me all the time, but I do not think that understanding the general theory of relativity is essential to my happiness.”

But I do think that understanding it brings happiness.

In Newton’s theory, the universal law of gravitation, the mass is attracted by the gravitational pull. That’s why an apple falls from a tree, that’s why the moon revolves around our planet Earth.

In Einstein’s theory of general relativity, gravitation is not a force. Gravitation is a property, a geometry of space, and what this theory tells us is that space itself is a dynamic entity. It is affected by mass. Space is curved.  And other masses then move in curved space. So this geometry of space is a new, innovative idea. Things are much more complicated because we have also time, and time and space are not independent of each other. They are combined into a full dimensional space-time. This is very difficult to imagine.

Now, how do we know that it is true? We know because there are a number of empirical tests. This theory predicts the bending of light from a distance, which was actually confirmed. Most people do not know that if we did not know general relativity, we would not have GPS technology, because general relativity tells us that the pace of clocks — time — moves slower in a strong gravitational field than in a weak gravitation field. That means that the clock on Earth is slower, is delayed with respect to a clock in a satellite because the gravitational field is weaker.

The GPS system depends on recent signals from our GPS device in the car, or wherever, to satellites. Then they are reflected back. We measure the time it took for the signal to go back and forth. We would not calculate the time correctly if we didn’t know that on the way the time moves slower.

We have a very good reason to celebrate.

NL: Are there other very common things in our lives today besides GPS that we need to celebrate Einstein for?

HG: Every electronic device today depends on something that Einstein did already in 1905.

You know, this photoelectric effect, for which he got a Nobel Prize, because he understood the mechanism by which light may generate electricity. That is the photoelectric effect. All the photovoltaic devices that use solar energy are based on that. If you stand in the doorway of the elevator and the door doesn’t close, do you know why? It’s because you block a ray of light from one side to the other. If you would not block, that ray of light would activate a photoelectric device there. It generates some electric current to close the door.

NL: Do you think that there is something specific about being a Jew or being an outsider that contributed to Einstein’s thinking that helped him to think outside the box?

HG: For him, according to his own testimony, his Jewish identity was a choice based on his observation. He came back to Germany and faced anti-Semitism. And then, slowly, he developed this Jewish identity. His biographers tell us that outside of physics, this became his strongest commitment that grew, evolved and intensified with time.

According to Einstein, there are three stages in the evolution of a religious concept. The first is based on fear. The second is what you call the Judeo-Christian tradition, based on moral values. He identified with the values, but did not identify with the anthropomorphic aspect of God in religion. His concept then is the third one: cosmic religion. And cosmic religion is the one where he identified with Spinoza. God is nature, and God is reflected in the harmony of nature and does not care about what we do or do not do. This is our own responsibility.

NL: I know you wanted to talk about the university and the importance of the Einstein Archive.

HG: It is important that the Hebrew University is in possession of this immense asset, this treasure, this cultural, scientific treasure. It’s about 80,000 documents that shed light on everything that he did — his science, his political activity. And it’s here because he wanted it to be here, because he was one of the founders of the Hebrew University. That puts us in this unique position that when the whole world celebrates, nobody can do anything without us.

NL: Will Einstein’s unified field theory ever turn out to be true?

HG: Yes. It is, maybe, Einstein’s greatest intellectual legacy. He persevered to the end of his life. He obsessively pursued this goal. His greatest legacy is that today this problem is at the frontier of physics, and thousands of young people, the brightest minds of mankind, are pursuing this goal.

There is hope … but it’s not there yet. 

Naomi Levy is founder and rabbi of Nashuva, a spiritual community. This interview was edited and condensed.