Question

10. Assume there is a certain type of celestial object in the universe that is born, matures, ages, and eventually dies. All of these objects were born at essentially the same time in the life of the universe and we can tell something about their age from their photographs. With our telescope we photograph two of them: Object A, 20 million light-years away and Object B, 200 million light years away. The light from which object took the longest time to get to our telescope? ___________ Which object appears younger? ____________ Explain your answer. ___________________ ____________________________________________________________________________

11. In 2007, Iris attempts to communicate with intelligent beings on a planet four light-years distant by sending radio signals. When is the earliest she might expect to hear a response? ______________

12. How many years would it take Mark to make a round trip to the Centauri system, four light-years distant, if his spaceship traveled at 10% of the speed of light? ______________________________

Answer 1

Que 10

The light from which object took the longest time to get to our telescope?

Answer: As we can see that object A is 20 million light years while object B is 200 million light years away and both the objects took different times to reach our telescope and according to theory of relativity speed of light remains constant so the object B is 200 million light years away so it will took 200 million years to reach at us while object A took only 20 million to reach us so object B took longest time to reach at us .

Which object appears younger?

As we can see that the light emitted by object B and which reaches us will be 200 million years old while the light emitted by object A is 20 million light year old so according to earth frame of reference what we ll see at object B is 200 million years old and what we will see at object A is 20 million years old and both the objects born , matures , eventually dies at the same time but we are looking 200 million year old at object B so it appears younger to us as compare to the object B.

Que 11 In 2007, Iris attempts to communicate with intelligent beings on a planet four light-years distant by sending radio signals. When is the earliest she might expect to hear a response?

In 2007 , iris attempts to communicate with intelligent beings on a planet which is 4 light years distant by sending radio signals . As we know that radio signal is an electromagnetic wave so it will travel at the speed of light so 1 light year ( It is defined as the distance travelled by light In 1 year when it is moving with a speed of 3 * 10 ^8 m/s is known as 1 light year) . So it will send the signal at 2007 and it is 4 light years away from earth and this will take 4 years to reach the signal at earth and if we transmit back at the same speed again it will take 4 years to reach our signal at the iris so total it will take 8 years to she hear a response so the earliest possible time will be when she hear a response is 2015 from the reference of earth.

Que 12 How many years would it take Mark to make a round trip to the Centauri system, four light-years distant, if his spaceship traveled at 10% of the speed of light?

This problem is solved on a paper of which I uploaded a pic which is shown below:

It takes 40 years for 1 side trip and total it will take 80 years for round trip.

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