responding to a claim that the number of grains of sand was infinite, calculated that the number of grains of sand needed to fill the universe was on the order of 1063. Our understanding of the size of the universe has changed since then, and we now know that the observable universe alone is a sphere with a radius of 1026 m. Estimating the size of a grain of sand, A) Approximately how many grains of sand would fill the observable universe? B) How many times larger or smaller is this number than Archimedes' result?

What is meant by the critical density of the universe? Why is this quantity important to cosmologists?

The total mass of a single stage rocket as it sits on the pad ready for launch is 3.20 × 106 kg. If fuel is consumed at the rate of 2.30 x 104 kg/s and the speed of the exhaust is 2.82 x 10° m/s, determine the following. (a) thrust produced by the engine (b) magnitude of the acceleration of the rocket just as it lifts off the launch pad 7m/s2

With the aid of one or more diagram, explain how observations of the CMB can be used to determine whether or not space is flat, positively curved or negatively curved. Describe two pieces of evidence that have led to the suggestion that the Universe contains Dark Energy.

Does it make sense to ask, “If the universe is expanding, what is it expanding into?”

In the reading, you were told that there were roughly 10,000 galaxies in the image of the Hubble Ultra Deep Field alone. The image is roughly 10 square arcminutes and there are roughly 1.5*10^8 square arcminutes composing the entire sky. With that in mind and assuming that the Hubble Ultra Deep Field represents an average part of the sky, roughly how many galaxies may exist in the observable universe? (Please include commas for every factor of 1,000; for example 2,343,567,890)

How many times longer than the length of recorded history is the age of the universe? I was also given that the length of recorded history is 10E11 s, and that the age of the universe is 10E18 s. But, when putting 10E18/10E11 = 10E7, I get the wrong answer.

Assume that a typical galaxy contains about 200 billion stars and that there are more than 150 billion galaxies in the known universe. Estimate the total number of stars in the universe.

The critical density of a universe is around 5×10-27 kg/m³. Estimate the Hubble constant for this universe.

For the graph shown above, a) what quantity would you label the y-axis with if the distance is between galaxies and the Earth? Explain your answer. Think through what we know is happening, motion-wise, out there in the galaxy. b) Also explain why you think there are dots and a solid line, on the graph.