Finding the stuff that dreams are made of

R Stickgold1

  • 1Harvard Medical School, Boston, MA 02115, USA. robert_stickgold@hms.harvard.edu

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Collisions in Multiple Dimensions: Problem Solving

In multiple dimensions, the conservation of momentum applies in each direction independently. Hence, to solve collisions in multiple dimensions, we should write down the momentum conservation in each direction separately. To help understand collisions in multiple dimensions, consider an example.
A small car of mass 1,200 kg traveling east at 60 km/h collides at an intersection with a truck of mass 3,000 kg traveling due north at 40 km/h. The two vehicles are locked together. What is the...
Finding the Center of Gravity01:03

Finding the Center of Gravity

The center of gravity of a body is an imaginary point where the body's total weight is assumed to be concentrated, and the body is perfectly balanced. The center of the mass of a body is a point at which the whole of the mass of the body appears to be concentrated. If the acceleration due to gravity, g, has the same value at all points on a body, its center of gravity is identical to its center of mass. The center of gravity of homogeneous bodies such as a sphere, cube, or rectangular plate is...
Sleep-Wake Cycles01:24

Sleep-Wake Cycles

Sleep is an essential physiological process vital to maintaining overall well-being. The reticular activating system (RAS), a network of neurons in the brainstem, regulates wakefulness and sleep. While it may seem passive, sleep consists of distinct cycles, each with its unique characteristics and functions. Two key sleep phases are non-rapid eye movement (NREM) and  rapid eye movement (REM).
NREM Sleep
NREM sleep comprises four progressive stages that seamlessly merge:
Castigliano's Theorem: Problem Solving01:14

Castigliano's Theorem: Problem Solving

The deflection of a simply supported beam that carries a central point load can be analyzed using structural mechanics principles, particularly by applying Castigliano's theorem. This theorem relates the displacement at the load application point to the partial derivatives of the strain energy in the structure. The simply supported beam with a point load at its center has symmetric reaction forces at the supports, each bearing half of the load. The bending moment at any point along the beam is...
Dreaming01:30

Dreaming

Sigmund Freud revolutionized our understanding of dreams by proposing that they are a window into the unconscious mind. According to Freud, dreams are not mere stories our minds create while we sleep but are profoundly meaningful narratives about our hidden desires and fears. He introduced two key concepts: manifest content and latent content. The manifest content is the actual content and imagery of the dream — what we remember when we wake up. The latent content, however, represents the...
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Lucid Dreaming

Lucid dreaming is a unique state of consciousness where an individual realizes they are dreaming while still in the dream. This awareness allows them to manipulate their dream environment consciously. Researchers like Stephen LaBerge have significantly contributed to the understanding of lucid dreams, highlighting that during these dreams, certain areas of the brain, such as the prefrontal cortex, that involve self-awareness and thought evaluation show increased activity.
Studies have shown...