Tag: science & technology

A red blood cell actually takes about 20-60 seconds to complete one full circulation through the body, not one minute. The heart pumps approximately 5 liters of blood per minute, and each red blood cell makes thousands of trips through the circulatory system in its 120-day lifespan. The one-minute estimate is close but not precise enough.

The cornea is indeed avascular (has no blood vessels), making it the only part of the human body without a direct blood supply. It receives oxygen directly from the air and gets nutrients from tears and the aqueous humor (fluid inside the eye). This transparency is essential for vision - blood vessels would scatter light and impair vision.

The human heart can generate enough pressure to squirt blood much farther than 1 foot - up to 30 feet or more. Normal systolic blood pressure can reach around 120 mmHg, which is sufficient to propel blood vertically against gravity. The '1 foot' distance is a significant underestimate, making the False statement correct.

Carbon dioxide is the primary greenhouse gas responsible for global warming through the greenhouse effect. It traps heat in the Earth's atmosphere by absorbing infrared radiation. While other gases like methane and water vapor also contribute, CO2 from burning fossil fuels is the main driver. Nitrogen is inert and noble gases do not trap heat.

The 2009 United Nations Climate Change Conference (COP15) was held in Copenhagen, Denmark. This summit produced the Copenhagen Accord, a significant international agreement on climate change mitigation. Dubai, New York, and London have not hosted UN climate summits in 2009.

The ozone layer in the stratosphere absorbs most of the Sun's harmful UV radiation. When this layer is depleted by chemicals like CFCs, more UV rays reach Earth's surface. Oxygen, carbon dioxide, and clouds do not perform this protective UV-filtering function.

The Maldives held an underwater cabinet meeting in 2009 to highlight the threat of rising sea levels from climate change. As a low-lying island nation, the Maldives faces existential danger from global warming. This dramatic publicity stunt drew international attention to their vulnerability.