Explanation

• O⁻ (O Negative) is the universal donor blood group.
• It can be transfused to A, B, AB, and O blood groups.
• O⁻ blood lacks A, B, and Rh (D) antigens.

Additional information:

• Universal Recipient: AB⁺ (AB Positive)
• ABO Blood Groups: A, B, AB, O
• Rh Types: Positive (+) and Negative (−)
• Total Common Blood Groups: 8 (A⁺, A⁻, B⁺, B⁻, AB⁺, AB⁻, O⁺, O⁻)

Last verified on 14-07-2026

Explanation

• Nicolaus Copernicus proposed the heliocentric model.
• Heliocentric means the Sun is at the center.
• Earth and other planets revolve around the Sun.
• Proposed in the 16th century.
• Ptolemy supported the geocentric model (Earth-centered).

Explanation

• Ice is less dense than water, so it floats.
• Archimedes’ Principle explains the buoyant force acting on floating ice.
• The buoyant force acts upward against gravity.
• Formula: FB = p Vg
• Key point: An object floats when buoyant force = its weight.

Explanation

• Light Year is the distance that light can travel in one year.
• The distance light travels in one year is known as light year.
• 1 light year is equal to 9.5 x 10¹²km.

Last verified on 30-03-2026

Explanation

Uranus is the planet in our solar system that rotates on its side

• Rotates on its side (axial tilt ~98°), appearing to spin sideways
• 7th planet from the Sun
• 3rd-largest planet in the solar system
• Very cold and windy
• Has faint rings and more than two dozen small moons

Last updated by NS on 06-09-2026​

Explanation

• Red blood cells lack a nucleus to maximize space for hemoglobin, which carries oxygen.
• More hemoglobin means more oxygen transport.
• This makes RBCs highly efficient for gas exchange.
• Lack of nucleus also gives them a flexible shape.
• This helps them pass through narrow blood capillaries.

Last verified on 14-06-2026

Explanation

• Pressure cookers cook food faster due to Gay-Lussac’s Law.
• This law states that pressure increases when temperature increases in a closed container.
• In a pressure cooker, steam is trapped, increasing pressure.
• Higher pressure raises the boiling point of water above 100°C.
• Food cooks at a higher temperature, so it cooks faster.

Last verified on 14-06-2026

Explanation

• Jabir ibn Hayyan, known as the "father of chemistry."
• He was an Arab Chemist.
• Composition of Alchemy was written by Jabir Bin Hayyan.

Notable ideas:

• Use of organic substances in chemistry
• Sulfur-mercury theory of metals
• Science of the balance
• Science of artificial generation

Last verified on 07-02-2026

Explanation

• Penicillin, the first true antibiotic, was discovered by Alexander Fleming.
• He made this discovery in 1928 at St. Mary’s Hospital, London.
• He found that a mould (Penicillium) killed bacteria in culture dishes.
• His findings were officially published in 1929.
• First patient treated: Albert Alexander (12 February 1941)

Last verified on 01-06-2026

Explanation

• Allergy is an abnormal immune response to harmless substances like dust or pollen.
• It occurs when the body reacts excessively to an allergen.
• This reaction involves the immune system producing antibodies.
• Thus, allergy is mainly due to an antigen–antibody reaction.

Last verified on 23-04-2026