Which of the following is true? Group of answer choices 1. The grandfather paradox is a paradox about whether someone can kill their own grandfather 2. The grandfather paradox is a paradox about whether someone kills their own grandfather 3. The grandfather paradox shows that no time travel is consistent 4. The grandfather paradox shows that time travel is impossible

From earth a spaceship traveling at a velocity close to the speed of light will appear to be: a) shorter than the size of a spaceship traveling at non-relativistic speeds.                                                                                                    b) the same size as a spaceship traveling at non-relativistic speeds.                                                                                                     c) longer than the size of a spaceship traveling at non-relativistic speeds.                                                                                                    d) all of the above

Topic: Theory of relativity Instructions: Answer the problem. Show complete solutions. View Image.

Scientists claim that empty space has an undetectable form of energy known as “dark energy.” This theory is needed to explain wich of the following? * A) The galaxies in the universe are getting brighter. B) The universe is heating up. C) The universe is expanding at an increasing speed. D) The stars and planets in the universe are getting louder.

Just answer question 4 please

Challenges to Space Exploration a) We can round numbers to say light (and all electromagnetic radiation: radio waves, infrared, ultraviolet, etc.) travels at approximately 3x108 m/s. At its closest approach, Mars is about 0.5 au of the Earth. At this distance, how long would it take for an astronaut on Mars to communicate with Mission Control on Earth? Give your answer in minutes. Explain why Mars rovers have entire sequences for travel pre-programmed and uploaded all at once rather than being driven around in real time with a joystick. For the Earth-Moon distance in 5b, you can use 384,400 km b) The boosters that launched Apollo 11 allowed the astronauts to reach a speed of 25,000 miles per hour. At that speed, about how long did it take for the astronauts to reach the Moon? At that speed, how long would it take to reach Mars, assuming the closest approach distance given above? Give your answers in days.

Which axiom of set theory is used to define the constructible universe L? A. Axiom of Infinity B. Axiom of Power Set C. Axiom of Choice D. Axiom of Constructibility

Which of the following can be concluded from the two premises below: 1.  Whatever begins to exist has a cause 2. The universe began to exist some 14 billion years ago a. the universe must have a cause b. nothing c. the universe caused itself d. there must be a multiverse

Please solve the following special relativity question. Please explain each step with details and concepts. This is review for an exam