The most significant validation of Einstein’s Theory of General Relativity required the observation of stars that appear near the Sun in the sky. Due to the predicted curvature of space caused by the Sun, what were the stars expected to do when the Sun appeared near them in the sky? Why couldn’t astronomers just go out at any time and take pictures of this effect? So what did they have to wait for?  Did astronomers validate Einstein’s prediction?

According to the tiny world experiment, there are only 5.2 intermediates between any two people on Earth (thus 6-degree of separation). This is a remark that has been made for well over half a century. The Internet may be useful in this regard. Let's pretend that everyone on Earth doubles their friend count on Facebook, Twitter, and every other social network they participate in (2x). Calculate the relative distance between us now. What do you think it is?

Science homework. Having trouble

I don't understand the question. Please help. This is for my astronomy lab assignment.

How do we define the time interval of one "second" now, and keep track of elapsed time accurately enough to navigate spacecraft through the solar system, or place you on Earth with a GPS receiver? What place in space is our absolute reference point from which we measure distances in physics? If I climb a ladder more than a few feet  I am clearly in danger if I fall.   Being foolish, I think I can react fast enough to not hit the ground hard if I have more than 1 second to react.  How high would that be when a fall to the ground takes 1 second?  Hint:  The distance of fall is (1/2) a t2, where a is the acceleration  of a falling body and near Earth it is about 10 m/s2 for anything.

Speed of light is just a theoretical concept: it cannot actually be measured in practice because light travels too fast. True or False?

I’ve gotten 3 different answers each time I’ve worked #4 out. I have no idea what to do.

Can someone help with this?

Please explain the theory also. I need to understand the concept. Thank you in advance. A light of wavelength 620 nm is emitted from 5 Schwarzschild radii from a 20 solar mass black hole. What wavelength is observed for this light by an observer a long distance away? (The objects are not moving with respect to the observer)

A star is 80 light years from Earth. How fast does a spacecraft have to be for the journey to last the 70 years of an astronaut's life? The answer is 0,7526c. Show a complete approach on how to get to the answer by using the necessary equations.