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  2. Dynamical friction - Wikipedia

    en.wikipedia.org/wiki/Dynamical_friction

    The effect of dynamical friction explains why the brightest (more massive) galaxy tends to be found near the center of a galaxy cluster. The effect of the two body collisions slows down the galaxy, and the drag effect is greater the larger the galaxy mass. When the galaxy loses kinetic energy, it moves towards the center of the cluster.

  3. List of unsolved problems in astronomy - Wikipedia

    en.wikipedia.org/wiki/List_of_unsolved_problems...

    Why is the Sun's corona so much hotter than the Sun's surface? Why is the magnetic reconnection effect many orders of magnitude faster than predicted by standard models? Space weather prediction: How does the Sun produce strong southward-pointing magnetic fields in solar coronal mass ejections that lead to geomagnetic storms?

  4. Space physics - Wikipedia

    en.wikipedia.org/wiki/Space_physics

    Space physics, also known as space plasma physics, is the study of naturally occurring plasmas within Earth's upper atmosphere and the rest of the Solar System. It includes the topics of aeronomy , aurorae , planetary ionospheres and magnetospheres , radiation belts , and space weather (collectively known as solar-terrestrial physics [ 1 ] ).

  5. n-body problem - Wikipedia

    en.wikipedia.org/wiki/N-body_problem

    In physics, the n-body problem is the problem of predicting the individual motions of a group of celestial objects interacting with each other gravitationally. [1] Solving this problem has been motivated by the desire to understand the motions of the Sun, Moon, planets, and visible stars.

  6. Vacuum energy - Wikipedia

    en.wikipedia.org/wiki/Vacuum_energy

    Using the upper limit of the cosmological constant, the vacuum energy of free space has been estimated to be 10 −9 joules (10 −2 ergs), or ~5 GeV per cubic meter. [3] However, in quantum electrodynamics , consistency with the principle of Lorentz covariance and with the magnitude of the Planck constant suggests a much larger value of 10 113 ...

  7. Quantum fluctuation - Wikipedia

    en.wikipedia.org/wiki/Quantum_fluctuation

    3D visualization of quantum fluctuations of the quantum chromodynamics (QCD) vacuum [1]. In quantum physics, a quantum fluctuation (also known as a vacuum state fluctuation or vacuum fluctuation) is the temporary random change in the amount of energy in a point in space, [2] as prescribed by Werner Heisenberg's uncertainty principle.

  8. Free response question - Wikipedia

    en.wikipedia.org/wiki/Free_response_question

    Free response questions typically require little work for instructors to write, but can be difficult to grade consistently as they require subjective judgments. Free response tests are a relatively effective test of higher-level reasoning, as the format requires test-takers to provide more of their reasoning in the answer than multiple choice ...

  9. Two-body problem - Wikipedia

    en.wikipedia.org/wiki/Two-body_problem

    The two-body problem is interesting in astronomy because pairs of astronomical objects are often moving rapidly in arbitrary directions (so their motions become interesting), widely separated from one another (so they will not collide) and even more widely separated from other objects (so outside influences will be small enough to be ignored safely).