Tag: science & technology

Willem Kolff invented the first practical dialysis machine (kidney machine) in the Netherlands during World War II (1943). His invention saved countless patients with kidney failure and pioneered the field of artificial organ replacement.

Alexander Fleming discovered penicillin in 1928 at St. Mary's Hospital in London when he noticed that mold (Penicillium notatum) killed bacteria in a petri dish. This discovery revolutionized medicine and earned him the Nobel Prize.

Jonas Salk developed the first successful polio vaccine in 1955. His inactivated virus vaccine was tested in massive clinical trials and dramatically reduced polio cases worldwide. Salk became a medical hero for refusing to patent the vaccine.

Willem Einthoven invented the electrocardiograph (ECG) in the Netherlands and received the Nobel Prize in 1924 for it. His string galvanometer could accurately record the electrical activity of the heart, revolutionizing cardiology and heart diagnosis.

The average distance from Earth to the Moon is approximately 240,000 miles (384,400 km). This distance varies because the Moon's orbit is elliptical, ranging from about 225,000 miles at perigee to 252,000 miles at apogee. Option C is the closest to the average.

Twelve American astronauts walked on the lunar surface during the Apollo program (Apollo 11, 12, 14, 15, 16, and 17). Each mission had two astronauts who landed, while one remained in lunar orbit. No other nation has yet landed humans on the Moon.

Mare Imbrium (Sea of Showers) is the largest lunar mare, covering approximately 829,000 square miles. It was formed by a massive asteroid impact around 3.9 billion years ago and later filled with basaltic lava, creating the dark plain we see today.

True soil requires organic matter from living organisms. The moon's surface material is called regolith - crushed rock and dust from meteorite impacts, not soil. Option A describes fossil-based soil on Earth, B incorrectly claims similarity to Earth sand, and C describes hardened magma, not lunar surface material.

The moon's density is about 3.34 g/cm³, while Earth's average density is about 5.51 g/cm³. This difference exists because the moon lacks Earth's large iron core. Option A is incorrect - the densities differ significantly, and B/C are wrong as the moon is LESS dense, not more.

In nuclear physics, beta radiation (β) consists of high-energy electrons or positrons emitted during radioactive decay. Alpha particles are helium nuclei, gamma rays are electromagnetic radiation, and theta is not used for this purpose.