Introduction:
Among the options provided, Albert Einstein and APJ Abdul Kalam worked in the field of science. Rabindranath Tagore, on the other hand, was primarily known as a poet, philosopher, and musician. Let's discuss the contributions of Albert Einstein and APJ Abdul Kalam in the field of science.

Albert Einstein:
- Albert Einstein was a renowned physicist who is best known for his theory of relativity, which revolutionized our understanding of space, time, and gravity.
- His famous equation E=mc², which describes the equivalence of energy and mass, is one of the most well-known formulas in science.
- Einstein also made significant contributions to the field of quantum mechanics, particularly with his explanation of the photoelectric effect, for which he was awarded the Nobel Prize in Physics in 1921.
- His work laid the foundation for modern physics and had a profound impact on the development of technologies such as nuclear energy and the development of atomic weapons.

APJ Abdul Kalam:
- APJ Abdul Kalam, also known as the "Missile Man of India," was a prominent scientist and the 11th President of India.
- He played a crucial role in the development of India's space and missile technology. He was one of the key scientists involved in the development of India's first indigenous satellite launch vehicle, the SLV-III.
- Kalam also played a pivotal role in the development of India's nuclear weapons program and was instrumental in the successful testing of nuclear weapons in 1998.
- He was a strong advocate for the use of technology in addressing social and economic issues and emphasized the importance of scientific research and education in the country.

Conclusion:
In conclusion, both Albert Einstein and APJ Abdul Kalam made significant contributions in the field of science. Einstein's theories revolutionized our understanding of the universe, while Kalam's work in space and missile technology propelled India's scientific advancements.