My mother knew Einstein’s stepdaughter when all three were at Princeton during the mid forties. They did tea with Einstein at his house (112 Mercer St.) on Sunday afternoons. Einstein waited until he heard the tea kettle whistling before coming down the stairs to the kitchen to join them. He was invariably disheveled.

He was usually in deep thought and not very sociable and would soon politely excuse himself to return to work. But when he dallied it was because he had a chance to discuss things of interest that had previously escaped his notice and thought. And this, despite my mother’s efforts, was not talking about physics. Her field was what today we would call molecular biology but he resisted her efforts to have him explain physics to her.

But occasionally, Einstein would pick up on a discussion that the animated younger women were having for which Einstein had questions. Politely, and with a cool intellectual demeanor, he would ask my mother questions. And he would bore in to a deeper point. One example she related was on her plans on hosting a Jewish religious meal (Seder). My mother was from Italy and hence Sephardic Jewish. Einstein, though German and hence Ashkenazi Jewish, had lived for a time in Italy and knew some of the differences in customs. Though not interested in the religious parts, he queried her understanding of these different customs and their meaning. Like an anthropologist, he tried to calculate where and when the Jewish traditions had diverged.

Einstein was, according to my mother, genuine and gentle but persistent and occasionally impatient. He was inquisitive. He didn’t make small talk. He tried to understand things, and only spoke to ask a question or clarification. He never patronized or disrespected these two young women. And, according to my mom, when asked on the IRS tax forms for his occupation, Einstein wrote in “student”. I’ve tried to do the same.

BTW, my younger brother was born 5 days after Einstein died, April 18, 1955, and was named Albert.

Said
Alfredo A. Sadun
Professor at University of California

Multiplication of vectors

When two vector quantities are multiplied, the product is sometimes a scalar quantity and sometimes a vector quantity. Based on this characteristic of the product, the product of the vector equation is divided into two parts.

1. Scalar multiplication or dot multiplication
2. Vector multiplication or cross multiplication

Scalar multiplication or dot multiplication
If we multiply two vector quantities and the product is a scalar quantity, this product is called a scalar product. To denote scalar multiplication we use the dot symbol as the symbol of multiplication, so scalar multiplication is also called dot multiplication.

Eg: Both force and displacement are vector quantities. By multiplying them scalar we get work, which is a scalar expression.

Vector multiplication or cross multiplication
If we multiply two vector quantities and the product is a vector quantity, we call it vector multiplication. Vector multiplication is also called cross multiplication because we use the cross sign as the sign of multiplication to denote vector multiplication.

For example, the radius of gyration and linear momentum are both vector quantities. By vector multiplying them we get angular momentum which is a vector quantity.

Renewable sources of energy are very potential and sound alternatives of the present energy crisis and global warming.

Renewable energy resources; such as solar, wind, rain, tides, waves etc. energy are constantly replenished and will never run out.

Renewable energy technologies can produce heat and electricity with very low carbon dioxide emissions for all in everywhere.

Clean and will improve the quality of the environment of our shared HOME and save us to be survive & healthy stay with longer life

The world faces two energy problems: most of our energy production still produces greenhouse gas emissions, and hundreds of millions of people lack access to energy, 91%.

We still now lack of safe, low-carbon, and cheap large-scale energy alternatives to fossil fuels. Until we scale up those alternatives the world will continue to face the energy problems of today. The world has another global energy problem that is just as big: hundreds of millions of people lack access to sufficient energy entirely, and they got to use….with terribly: to themselves and to the environment.

In nature, the same element is found in different mass numbers, called isotopes.

Since the elements are the same, they have the same atomic number or proton number. For example, the hydrogen element is found in three different mass numbers. They are-
Protium (atomic mass = 1)
Deuterium (atomic mass = 2)
Titrium (atomic mass = 3)
Here their atomic number or proton number is the same.
Isotopes can be remembered by the last letter “p” – the number of protons is the same.