Lecture 9: Relativity

These flashcards cover key concepts regarding relativity, interstellar travel, and critical thinking as learned in Lecture 9.

What are the fundamental ideas of special relativity?

The laws of nature are the same for all observers, and the speed of light in a vacuum is constant for all observers.

What is time dilation?

Time dilation is the phenomenon where moving clocks run slow compared to stationary clocks.

What is length contraction?

Length contraction is the phenomenon where moving objects appear shorter in the direction of motion compared to stationary observers.

What is the cosmic speed limit according to general relativity?

The speed of light (c = 3 x 10^8 m/s) is the ultimate speed limit that cannot be exceeded.

What is gravitational time dilation?

Gravitational time dilation is the effect where clocks in stronger gravitational fields run slower compared to those in weaker fields.

What was the first observational test of general relativity?

The perihelion precession of Mercury's orbit.

What notable prediction does general relativity make regarding light?

Light is bent when it passes near a massive object, such as the Sun, which causes gravitational lensing.

What did the radar observations of asteroids demonstrate in testing general relativity?

They showed the effects of time delay due to the gravitational field of the Sun.

Define UFOs as discussed in the lecture.

Unidentified Flying Objects (UFOs), recently rebranded as Unidentified Aerial Phenomena (UAPs), are sightings that have not been conclusively linked to known entities or phenomena.

What are some examples of cognitive biases mentioned in the lecture?

Confirmation bias, availability bias, and egocentric bias.

What is a thought experiment?

A thought experiment is a hypothetical situation used to explore the consequences of a theory or principle logically.

What is the effect of gravity on light, according to the lecture?

Gravity can bend light, a phenomenon observed as gravitational lensing.

How does relativistic velocity addition differ from classical velocity addition?

At high speeds, the observed velocities combine differently, not simply by addition as in classical physics.

What is the significance of gravitational waves?

Gravitational waves are ripples in spacetime caused by accelerating masses and were predicted by general relativity.

What did Einstein's theory of general relativity predict about gravitational redshift?

Light escaping a gravitational field is redshifted, meaning it loses energy and increases in wavelength.

Why is critical thinking important in evaluating claims about UFOs and other anomalies?

Critical thinking allows individuals to assess the quality of evidence and discern between extraordinary claims and the ordinary explanations.